Northeast Weather Blog

Nor'easter on the way

By: sullivanweather, 10:09 AM GMT on February 28, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings
Fig.1 - Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.

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Forecast Discussion


Synopsis - Issued - 2/28/09 @5:15am


A 500mb low will drop from the Central Plains into the Southeast over the next 24 hours into a sharpening trough over the eastern third of the country. Prior to the main event, a wave of low pressure will ride northeastwards off the Delmarva coast tonight, providing the coastal plain/southeastern interior with mainly light precipitation. As the 500mb low over the Southeast opens, low pressure at the surface will intensify and head up the coast, partially phasing with a 500mb trough diving into the eastern Great Lakes out of the northern stream. The result will be a rather prolonged winter storm moving up the coast from Sunday evening into early Tuesday morning. Cold follows Tuesday though Thursday before another trough approaches by Friday.


Short-term - Issued - 2/28/09 @5:15am


The cold front to blow through much of the region yesterday afternoon and last night is currently pushing offshore southeastern Massachusetts and Downeast Maine, accompanied by scattered rain showers. Ahead of the front temperatures are still in the upper 30’s to mid 40’s but behind the front temperatures drop sharply, with much of western and northern New York in the teens with 20’s elsewhere across the interior or New York and Pennsylvania. This has lead to formation of black ice on area roadways during the overnight and will pose a travel hazard during the early morning hours. Lake effect snow showers and flurries are also scattered about western/central New York and the northern tier of Pennsylvania. These shouldn’t add up to much more than an inch before winding down as drier air advects into the region. Otherwise expect partly cloudy to mostly sunny skies over the western interior with more in the way of cloud cover to begin the day in the eastern half of the region with the cold front still in the vicinity.


The front continues to march further offshore today with skies gradually clearing over eastern areas by the noon hour. Meanwhile, to the south, the cirrus shield ahead of the next system will already be advancing into the region. This will be in response to the development of low pressure at the tail end of the cold front over the Lower Mississippi Valley region. This low will move a tick east of northeast, moving into the Carolinas by evening and off the southern Delmarva Coast overnight. On this track, most of the heavy precipitation will skirt by to the south of the region, leaving mainly light precipitation on the northern periphery of the storm to move over south-central Pennsylvania and the coastal plain. 0°C isotherm @850mb lies just southeast of the I-95 corridor with thermal profiles to the immediate northwest of this region indicating a mixture of snow/sleet and freezing rain. Further northwest the precipitation will be in the form of snow but QPF will be much lighter, around a tenth of an inch. There are a few rouge models that spit out a bit more QPF but with best forcing moving offshore early in the overnight and cold dry air filtering into the region thanks to large dome of Canadian high pressure to the north of ~1038mb, the light end of the spectrum should do. To the areas southeast of the 0°C isotherm precipitation will be in the form of sleet and freezing rain away from the immediate coast, where primarily liquid rain should fall. A light glazing on exposed colder surface of up to a tenth of an inch can be expected in areas that receive freezing rain. To the far northwest skies will be mainly partly cloudy with basically no precipitation to speak of outside of a few thin lake bands. Temperatures will be in the single number and teens to the northwest with 20’s to low 30’s under the thicker clouds and precipitation.

The low moves southeast of Cape Cod late Sunday morning, with precipitation ending as snow showers in all but perhaps Cape Cod and the islands, where thermal profiles suggest rain. Accumulations will be on the light side, generally an inch or two to the northwest of the I-95 corridor and around an inch along it. To the northwest, high pressure will be in control with mainly fair skies and chilly temperatures, in the teens and 20’s. Highs along the coastal plain should climb into the 30’s. Winds will begin to increase out of the northeast to around 10-15mph, higher along the coast.




Mid-term - Issued - 2/28/09 @5:15am


Many factors are starting to come together, signaling a major winter storm from Georgia to Maine. The main action occurs in the midterm as 500mb closed low over the Southeast begins to open and head northeastward. Surface low pressure will form along the southern tip of a strengthening baroclinic zone along the coastal plain of the East Coast and adjacent western Atlantic waters and head up the coast as a significant winter storm. The storm doesn’t start at the higher latitudes either. Under the pocket of the cold air aloft associated with the upper low, dynamic cooling will allow precipitation to changeover to snow over the Southeast, possibly coming down heavy at times. Frontogenic forcing combined with modest instability aloft under the upper low will lead to CSI banding and thundersnow which could produce several inches of snow in a short period of time. Very similar to the system that brought snow over Louisiana and Mississippi in December, accumulations won’t be widespread due to the convective nature of the snow, with some locations getting as much as 3-6” while others get very little. Where the snow will be widespread will be in a developing deformation band from the Piedmont of North Carolina to the northern Mid-Atlantic into the eastern half of the Northeast. As mentioned, a strengthening baroclinic zone will set up right along the coast acting as a conduit for copious amounts of Atlantic moisture as a 50kt low-level jet moves along it. Deep-layer ascent will precipitate this moisture out aided by strong frontogenic forcing, upper divergence, and great jet dynamics with coupled jet structure noted. Banded precipitation, mainly in the form of snow, will break out across the Piedmont Sunday afternoon, as dynamic cooling changes any leftover rain to snow here. By Sunday evening snow will break out over much of New Jersey, eastern Pennsylvania, southeast New York and southern New England, save the immediate coast where rain or a wintry mix will fall. The snow will start to become heavy around midnight and remain as such through Monday morning. With cold dry air draining down from the northwestern periphery of the storm, there will be a sharp cutoff to the precipitation shield, likely just east of the I-81 corridor. How much snow will fall where is still uncertain and will be determined in a snowmap, likely tomorrow, but most areas along and to the northwest of I-95 should expect at least 6 inches. Winds will continue to increase out of the northeast around 20-30mph with higher gusts leading to blowing and drifting of snow.

Precipitation associated with the low moves into New England on Monday with deformation axis/trowal extending back into eastern New York State, eastern Pennsylvania and northern New Jersey. Significant accumulations of snow will be found over New England, mainly within 100 miles of the coast, as the storm pulls through. Strong northeasterly winds will shift to the north and northwest as the day progresses and the storm moves by. These winds should be in the 15-30mph range, with higher gusts. Bitterly cold air will dive into the region behind the departing low Monday night and Tuesday with 850mb temps dropping to –15°C to –20°C region wide and 1000-500mb thicknesses dropping below 510dm. Pretty cold airmass for early March. Snow showers will linger across the higher terrain of northern New York and New England with scattered lake snows in the snowbelts. Temperatures will run some 10-20 degrees below normal.





Long-term - Issued - 2/28/09 @5:15am


Cold air sticks around for Wednesday as northwest flow regime dominates. Embedded within this flow may be a minor disturbance or two that will kick up snow showers across the interior and enhance any lake activity. Otherwise expect mainly fair skies lasting into Thursday as temperatures slowly begin to moderate. By Friday, low pressure will be tracking towards the region from the west. Residual airmass over the region still appears cold enough for snow or a wintry mix across at least the northern half of the region with mainly rain to the south. Active pattern of weather may continue into next weekend and beyond as a very stormy beginning to March looks to be in store.



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Radar: Northeast Region Loop

NE radar
Fig.3 - Radar loop of the Northeast region. Courtesy of Weather Underground.

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Current snowcover

Northeast Snowcover
Fig.4 - Snow cover as of February 26th, 2009 over the Northeast. Courtesy of NOAA.


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Local SST's

Northeast SST's
Fig.5 Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


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2008-09 Winter Forecast


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Updated: 5:25 PM GMT on February 28, 2009

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March lion to roar? (update)

By: sullivanweather, 10:16 AM GMT on February 25, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings
Fig.1 - Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.

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Forecast Discussion


Synopsis - Issued - 2/25/09 @5:15am


High pressure will slide offshore during the day on Wednesday, giving way to a much stormier pattern, each with more complexities than its predecessor. The first system, a weak shortwave, arrives late tonight and Thursday. The next system arrives quickly on its heels late Thursday night dragging a strong cold front through the region on Friday. This cold air may set the stage for a widespread significant snowfall as low pressure over the Southeast potentially phases up with a northern stream trough resulting in a nor’easter by late in the weekend.


Short-term - Issued - 2/25/09 @5:15am


Sprawling 1030mb surface high pressure will provide a fair day across the Northeast this Wednesday. Sun will be filtered by clouds of varying thickness that will increase from the west ahead of an approaching shortwave. The winds will be noticeably lighter over New England and eastern New York today as well and temperatures will be several degrees warmer than yesterday. Highs will range from the low to mid 40’s along the coastal plain of New Jersey and the Philadelphia metro area, with upper 30’s to near 40°F along the remainder of the coastal plain and Long Island into southern New England. Across the interior temperatures will climb into the mid 30’s to low 40’s across the southern half with upper 20’s to mid 30’s across the north.

Shortwave moves into the Northeast tonight, with precipitation moving into western Pennsylvania and the Niagara Frontier by midnight. Thicknesses indicate that snow should be the dominant precipitation type across New York at the start with more of a wintry mix of snow sleet and freezing rain across northern Pennsylvania. To the south of I-80, west of the Appalachians precipitation should be primarily liquid rain but east of the mountains some cold air damming will present a threat for light freezing rain or freezing drizzle. Precipitation should reach western New England by daybreak and progress eastward on Thursday and fall apart as forcing weakens. There may be a few breaks of sun, especially along the coastal plain but skies should remain mostly cloudy throughout much of the region with areas of fog and drizzle. Max QPF is two-tenths of an inch from this system, mainly in New York, so a coating to a couple inches of snow could fall across upstate New York, while a thin coating of ice accretion may occur across Pennsylvania into southeastern New York where QPF should be under a tenth of an inch. After the precipitation end temperatures will steadily climb into the 40’s across much of Pennsylvania and the coastal plain, where there may even be a scattering of low 50’s. From upstate New York into central and northern New England highs will climb into the mid 30’s to near 40°F.


Mid-term - Issued - 2/25/09 @5:15am


Warm advection gets cranking Thursday night with the 850mb 0°C isotherm moving north of the Canadian border across all but northern Maine. This is in response to a strengthening southwesterly low-level jet ahead of low pressure moving out of the Midwest and into the lower Great Lakes. Temperatures will fall during the evening to near freezing across the interior then slowly rise after midnight. Along the coastal plain temperatures should remain above freezing all night.

Low pressure moves up the St.Lawrence Valley on Friday, dragging a cold front through the region. With much of the Northeast in the warm sector this looks like a rainstorm. The exception will be far northern Maine where there may be enough cold air for a wintry mix of precipitation types. The cold front moves offshore Friday night with any leftover precipitation changing to snow showers. As high pressure builds north of the region on Saturday, drying things out and bringing seasonable temperatures, attention turns south and west as a couple of systems may combine over the eastern US for a messy end of the weekend into early next week.


Long-term - Issued - 2/25/09 @5:15am

Update!! - Issued 2/27/09 @6:05am

There remains tremendous spread regarding the upcoming coastal storm(s) Saturday night into Tuesday. After many model twists and turns a loose consensus has started to form, though, any mention of consensus is a stretch. Timing and track differences remains but models have settled on a two-part system. The first wave will form along the tail end of the cold front in the Lower Mississippi Valley Friday afternoon and lift northeastwards to the Carolina Piedmont by Saturday afternoon. Models have already begun to diverge at this point and proceed further apart with some tracking the system off the coast of Delmarva Saturday night and others taking it offshore the Tidewater area. For the Northeast, the difference in either solution is vast. Rather than discuss the southern solution, which would yield little to nothing through Sunday night, I’ll discuss the northern solution. The northern path takes the storm about 150-200 miles north and emerges off the Delmarva Coast late Saturday night. A solid shield of snow would develop from south-central Pennsylvania, northeastward, across the interior, to southern New England. There may be a brief period of rain at the onset due to some residual boundary layer warmth, but strong lift and evaporational cooling will adequately cool the column for snow to become the predominate precipitation type. In this area, advisory level snowfall is within reach. Further southeast, within the I-95 corridor, temps aloft and vertical profiles suggest a mixing of precipitation types. With strong high to the north oozing down a shallow colder and drier airmass, freezing rain and sleet are a definite concern. Closer to the immediate coast temperatures aloft and within the boundary layer are just warm enough for liquid rain. The cold, dry air mentioned above will also serve in maintaining a rather sharp cut-off line to the precipitation on the northwest side of the storm. In a line from State College, PA to Utica, NY to Caribou, ME, most areas to the northwest will see very little from this storm, even with the northerly route. Low moves 50-100 miles southeast of Cape Cod on Sunday, racing northeast, out to sea. Snow will spread northeastwards, across interior regions of New England within 100 or so miles from the coast. Along the immediate coast there may be some mixing with rain, as will there be pockets of freezing rain or sleet within several miles of the coast, but across Maine, most of the precipitation will be in the form of snow. In areas of snow, the potential exists for several inches, likely in the advisory range as well. A few places, such as Downeast Maine, may even get warning criteria snowfall.

The snow from the first system winds down Sunday afternoon into Sunday night from southwest to northeast. However, attention will still be focused to the south as the 500mb low over the Southeast begins to open and lift north. Low pressure will once again travel up the coast and, once again, the question is a coastal hugger, or out to sea? It’s far too early to tell at this stage what will become of this second low, but recent trends in the ECMWF/GGEM/SREF suggest that it will be close enough to the coast to deliver snowfall to much of the same region to receive snow from the first storm. This second system would potentially arrive as early as Sunday night and potentially last to as late as Tuesday night, ultimately depending on timing. It won’t be in a rush to move up the coast either, so should the storm effect the region there may be a solid 18-24 hour precipitation event. Stay tuned!

Behind the departing low additional northern stream energy is suggested my models to move over the Northeast, aiding in the formation of a closed low in the general vicinity. The result would be continued unsettled weather with below normal temperatures, lasting into Thursday and perhaps Friday.







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The benchmark ‘5-day forecast’ will be quite the elusive standard to achieve to open the long-term portion of the forecast. Sunday falls on day five and there’s much uncertainty regarding a couple shortwave disturbances moving into the eastern half of the nation, one in the southern stream and another, potentially two, in the northern stream. Initially, a wave of low pressure will be over the Southeast on Saturday as a northern stream trough moves out of the Northern Rockies into the Northern Plains. Closer to the region, surface high pressure will be moving eastward, across central Ontario and into Quebec, building behind Friday’s cold front. However, unlike most areas of high pressure this winter, which have been transient in nature, this one will hold its ground over northern Quebec and merge with high pressure dropping into the Midwest, forming a ‘banana high’. In addition, deep-layer ridging will be building over the North Atlantic, signaling that the storm would run into some trouble trying to escape out to sea. With the phasing of jets over the East Coast, the banana high wrapped around the northern and western peripheries of the storm and the building heights over the North Atlantic, a classic set-up for a major East Coast storm. Had I been looking at this set-up during a different winter my confidence might be higher. However, this is already the umteenth time this winter we’ve seen this set up and I can count on one finger how many times a coastal was the result. There’s still uncertainty in timing, track and even how many shortwaves ultimately become involved. At this juncture, the three suspects are the usual: inland, coastal and offshore. Should the storm affect the Northeast in due course, it will likely stick around into Monday and be slow to leave Tuesday as a vertically stacked low over Quebec. Behind the storm much colder air will invade the region with medium range models indicating 850mb temps of –20°C moving in. March may come in like a lion but may be more akin to a snow leopard.



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Radar: Northeast Region Loop

NE radar
Fig.3 - Radar loop of the Northeast region. Courtesy of Weather Underground.

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Current snowcover

Northeast Snowcover
Fig.4 - Snow cover as of February 26th, 2009 over the Northeast. Courtesy of NOAA.


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Local SST's

Northeast SST's
Fig.5 Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


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2008-09 Winter Forecast


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Updated: 11:08 AM GMT on February 27, 2009

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Maine continues to endure strong winter storm

By: sullivanweather, 9:34 AM GMT on February 23, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings
Fig.1 - Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.

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Forecast Discussion


Synopsis - Issued - 2/23/09 @4:30am


A strong winter storm in the Gulf of Maine will move into the Canadian Maritimes during the day on Monday with snow gradually tapering over Maine. Lingering upper trough and cyclonic flow will keep scattered to numerous snow showers over the interior, aided by the lakes and upslope flow. High pressure builds on in Tuesday as snow showers retreat to far northern New England and fair weather spreads over the region heading into Wednesday. Unsettled conditions return Thursday and Friday as a lead shortwave and secondary trough/cold front bring precipitation back into the region. Behind the front, an arctic airmass building over the Canadian Prairies will blast into the Northeast.


Short-term - Issued - 2/23/09 @4:30am



Fig.2 - Radar loop of Maine showing intense band of snow. Snowfall rates of 2-3"/hr can be found within this band this morning as it rotate into northern Maine. Courtesy of Weather Underground.


Strengthening low pressure, now at 990mb over the Gulf of Maine at the time of this writing, will move up the Bay of Fundy this Monday morning and into the Gulf of St.Lawrence by the evening. Heavy snow will be ongoing during the early morning across Maine, perhaps mixing with a bit of rain along the immediate coastal sections from Bar Harbor to Eastport. The ample moisture feed comes from a very strong 50-60kt easterly low-level jet, coming straight from Atlantic waters. This moisture is then being lifted by strong frontogenic forcing, PVA/DVA in the mid-levels and highly diffluent upper level winds in the left exit region of a 130kt jet streak rounding the trough offshore. Deep ascent intersects is intersecting the prime snow growth layer leading to very impressive snowfall rates of 2-3”/hr. This is all occurring in a band within the developing comma head of the storm extending from Houlton to Millinocket then curling back southwards into the greater Portland area. This band will slowly translate northward through the morning, reaching Caribou by dawn and the Canadian border by mid-morning. The southern end of the band will weaken and slide east-southeast as forcing decreases. Snowfall now through the remainder of the storm will range from 2-4” along the coast, 4-8” across central Maine and up to a foot from Caribou and points north, where the broth of the storm is yet to move in. In addition to the snow, strong winds will create blowing and drifting of the snow and near blizzard conditions at times. The snow will slowly taper off during the afternoon as the best forcing moves into Canada, leaving widespread snow showers in a lingering deformation axis. Temperatures will hold steady through the morning hours and fall during the afternoon into the teens and lower 20’s. Biting north to northwesterly winds will drop wind chill values below zero. Not a good day to be out today in Maine. Further southwest, conditions won’t be as bad as they are in Maine but a very winter-like day none-the-less. Cold cyclonic flow combined with a mid-level low pressure within the upper trough dropping through the region will work in tandem with lake moisture and orographics to make for numerous snow showers across the interior. In fact, the mid-level low dropping into the region is the original mid-level feature which formed the parent low pressure that moved into Ontario yesterday after bringing Michigan, Illinois and Wisconsin a good dumping of snow. With the secondary low taking over off the New England Coast, becoming the dominant feature within the trough, the old 500mb low is now incorporated within the larger circulation of the upper trough and will drop southeastwards into the region today. Temperatures aloft with this feature are quite cold, approaching –40°C @500mb. Despite lowering inversion heights this afternoon, a few snow squalls may result from this disturbance dropping through the region, especially across areas of enhanced orographic lift such as the Catskills and Berkshires. There will also be some lake effect to deal with but with veering winds, increasingly sheared flow aloft, decreasing synoptic moisture, lowering inversions and diurnal effects starting to have better influence in breaking up bands, amounts won’t be impressive by snowbelt standards, despite strong lake induced instability with >20°C deltaT’s. In favored areas on a 290-310° trajectory, 3-7” of snow should fall with lesser amounts outside of the favored areas. The coastal plain will escape much of the snow shower activity as winds downslope and cry off the higher terrain to the northwest but a few stronger snow showers may sneak down over the mountains. Skies will be mostly sunny to start the day with an increase of cumulus/stratocumulus by late morning and afternoon. Winds will be blustery throughout with northwesterly winds of 10-25mph with gusts to 40-45mph at times in strong cold advection pattern. Temperatures will struggle to climb at all today as cold air gets funneled into the region but the noticeably higher sun angle is beginning to offset the strong cold advective events and temperatures will rise several degrees into the mid to upper 30’s along the coastal plain. It will be a bit different over the interior will increased cloud cover will limit how much sun manages to break through and highs today will reflect this with most locations outside of the deeper river valleys remaining below freezing. 20’s for most areas will do with teens across the higher terrain of the Adirondacks, Greens and Whites.

High pressure is slow to build in from the west tonight and much of the lake effect/upslope activity will continue throughout the overnight. However, as inversions lower and moisture decreases the extent of the snow shower activity will pull back towards the lakes and remain secluded to the higher terrain of northern New York and New England. A few inches of snow may fall, especially downwind of Lake Ontario. With winds taking on a more northerly trajectory some bands of snow may develop off the Finger Lakes region of New York and Lake Champlain. Elsewhere across the region skies will gradually become mostly clear and the winds will start to relax some. With modified arctic air over the region temperatures will take a dive. Lows will bottom out in the low to mid 20’s along the coastal plain with teens and single digits over the interior. Winds will be from the northwest to north-northwest around 5-15mph with higher gusts, especially over northern New England, closer to the low center.

High pressure builds over the Northeast during the day on Tuesday, ending most of the lake effect activity during the morning hours and the wrap-around/upslope snows over New England by afternoon. Airmass over the region is still quite cold and temperatures will run some 5-10 degrees below normal, despite the increasing amounts of sun. Winds will kick up once again over New England as a fairly tight pressure gradient will still exist between the low over Atlantic Canada and the high building over Pennsylvania. However, strengthening subsidence inversion over New York and Pennsylvania will keep the wind a bit more subdued by the afternoon. High pressure continues to build over the region Tuesday night, leading to a night of ideal radiational cooling for much of the region, though some mid/high clouds may skirt into western sections after midnight. Lows will drop back into the 20’s along the coast with teens and single digits inland. Some of the colder valleys will have no trouble dropping below zero, especially given the fresh snow cover aiding in radiating heat from the boundary layer.


Mid-term - Issued - 2/23/09 @4:30am


Mid/high clouds ahead of a weak shortwave will filter into the Northeast on Wednesday as high pressure moves offshore but, for all intents, it will be a stellar day. Temperatures will begin to moderate as warm air moves in aloft and highs will approach normal for late February. The aforementioned weak shortwave will slide across the region Wednesday night and Thursday bringing light precipitation to the region. 850mb 0°C isotherm will have moved far enough north to bisect the region by daybreak Thursday. To the north mainly light snow showers will be found while to the south things will be a bit more tricky. Surface temperatures may still be near/below freezing as the precipitation moves in leading to a period of light freezing rain/drizzle. This should be a localized and limited threat, however, as temperatures should quickly warm above freezing during the day on Thursday.


Long-term - Issued - 2/23/09 @4:30am


A stronger system will organize over the Mid-Mississippi Valley region of the country Thursday night and move towards the region on Friday. Current indications are for this system to track into the lower Great Lakes and up the St.Lawrence River Valley. This puts much of the region on the warm side of the storm, though northern New England may remain cold enough for more wintry precipitation types. Rainfall should remain under two-thirds of an inch for most locations and temperatures don’t look to warm up fast enough or long enough for major hydrologic concerns. Localized ice jams/movement may occur but most river ice should remain frozen in place. As this system departs it will blast a strong cold front through the region with the airmass behind it of arctic origin. Once again, lake effect looks like a good bet for the snow belts. Arctic high pressure builds in on Saturday but then model consensus breaks down. The GFS is the more benign model, lingering high pressure over the region to close out the weekend then bringing a flat trough into the Northeast to start next week. However, the ECMWF and Canadian GGEM are much more ominous. Both of these models show a sharpening trough over the eastern US with significant East Coast cyclogenesis occurring late Sunday into Monday and Tuesday that would deliver a major winter storm. This hasn’t been the first time this year both of these models showed a similar solution of a major nor’easter in the long term only to back away as the time period in question approaches. In fact, the current storm blasting Maine with snow as shown by both of these models 7 days ago to effect the entire region with heavy snow and high winds; not just Maine. More will follow on this in the upcoming week should it still pose a threat.



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Radar: Northeast Region Loop

NE radar
Fig.3 - Radar loop of the Northeast region. Courtesy of Weather Underground.

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Current snowcover

Northeast Snowcover
Fig.4 - Snow cover as of February 22nd, 2009 over the Northeast. Courtesy of NOAA.


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Local SST's

Northeast SST's
Fig.5 Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


___________________________________________________________

2008-09 Winter Forecast


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Updated: 9:48 AM GMT on February 23, 2009

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More snow this weekend

By: sullivanweather, 1:56 PM GMT on February 20, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued - 2/20/09 @9:00am


Vertically stacked low pressure resides over northern Maine with cold cyclonic flow and several shortwave disturbances rotating around it to produce snow showers throughout the Northeast today. A brief break later tonight and tomorrow morning then a clipper system will move into the region for the remainder of the weekend. In the vicinity of Long Island a secondary area of low pressure will develop and tap into Atlantic moisture to give New England a significant snowfall, especially Maine. Lake effect snow will be left in its wake on Monday before high pressure builds in on Tuesday. This high will give way to the next trough approaching from the west, bringing unsettled weather back into the region to close out next week.


Short-term - Issued - 2/20/09 @9:00am


The winter storm that has plagued the Northeast over the last couple of days will continue to do so today. Now a vertically stacked low pressure system over northern Maine, several disturbances will rotate around this feature into the Northeast today, producing scattered snow showers. One of these disturbances, currently producing snow showers over Maine, moved through Pennsylvania, New York and southern New England yesterday afternoon and evening producing heavy snow squalls and dumping 3-6 inches of snow over the Catskills, Taconics, Berkshires and Litchfield Hills. A couple more 500mb vorticies will move through the Northeast over the next 12-18 hours, but they won’t be nearly as impressive as yesterday’s. With much colder skin temperatures today, less moisture and weaker disturbances aloft the low-level lapse rates won’t be nearly as steep as those seen yesterday, which lead to the impressive area of squalls. The first disturbance is currently diving into central New York and Pennsylvania, producing flurries and widely scattered snow showers. This feature will move through southeast New York into southern New England this afternoon with the highest concentration of snow showers over the higher terrain with some lighter snows sneaking down into the coastal plain. The second disturbance will take a similar path about 6 hours after the passage of the first. These disturbances will also enhance snow from the lake effect machine, which will continue to affect upstate New York and northwestern Pennsylvania. As these disturbances pass through they will veer the flow, changing the orientation of the bands, limiting persistent banding and accumulations as a result. Also, with the higher sun angle as we head into late February, the activity will become more cellular in nature during the afternoon. Despite some negatives, snowfall in favored snow belts will add up to an additional 3-6 inches. West facing slopes of the Adirondacks, Greens and White will also see light to moderate accumulations of snow today as orographic lift wrings out an additional 2-4 inches of snow over these areas. Temperatures will be well below normal with the core of a modified arctic airmass (-18°C @850mb) squarely over the region. Highs will struggle to climb to the freezing mark along the coastal plain while the interior of the Northeast remains in the 20’s and teens. Winds will still be quite blustery with 10-20mph sustained winds with gusts to 30mph, especially in exposed terrain.

Aforementioned shortwaves move offshore tonight, ending most of the snow shower activity over the region. The exceptions will be around the lakes and in upslope regions where snow showers will continue. An additional inch or two of snow may fall in these areas. There may also be a few scattered snow showers over Maine as moisture continues to wrap around the vertically stacked low over the Maritimes. A surface ridge axis will push in from the west after midnight, lowering inversion heights and diminishing the lake effect over western New York and Pennsylvania. Skies will clear from the west and winds will become light, leading to ideal radiational cooling conditions after midnight. Temperatures will drop into the low to mid 20’s along the coastal plain tonight with teens and single digits expected across much of the interior.


The low over the Maritimes will move away from the region on Saturday, with the lake effect winding down and the upslope snows ending in the morning. But as quickly as one system moves out the next will be moving in. High/mid-level clouds will increase from the west as the day progresses and snow may break out over western New York and Pennsylvania by dusk. Temperatures will continue to average 5-10 degrees below normal with highs in the mid to upper 30’s along the coastal plain with mid 20’s to low 30s inland. Across the higher terrain of northern New York and New England temperatures will likely hold in the teens.


Mid-term - Issued - 2/20/09 @9:00am


A fairly potent clipper system will rotate through the eastern Great Lakes region and into southern Ontario Saturday night into early Sunday. Snow will spread over western/central New York during the overnight as isentropic lift increases and the nose of a developing 40-50kt low-level jet impinges on the area, leading to light accumulations despite the system being somewhat moisture starved. Forcing along a cold front will also cause snow showers to develop over Pennsylvania in a band that will move east fairly rapidly during the overnight hours. The primary 500mb low pressure will track with the surface low into Canada but an additional shortwave rounding the base of the trough will tilt the trough negative and induce cyclogenesis along the coast early Sunday. Exactly where this occurs is still a bit uncertain but current indications are for secondary development to occur around Long Island. As it looks right now, this secondary development will occur late enough to spare most areas west of the Hudson Valley of significant accumulations but the same cannot be said for much of New England. As the secondary develops and the core of the low-level jet pushes offshore, Atlantic moisture will be tapped and thrown back over New England, greatly increasing the precipitation intensity. A warming boundary layer may change the snow over to rain along the South Coast of New England, including the Cape and islands. The low will also rapidly intensify from a 1010mb center noon Sunday to a 988mb low early Monday morning. Snow will become quite heavy from central Massachusetts into New Hampshire and Maine, with mesoscale banding features and increasing frontogenesis leading to fairly impressive snowfall rates of 1-2”/hr. By the time the snow lifts out of Maine Monday morning up to a foot of fresh snow may fall. Wrap-around snows and lake effect will be leftover on Monday as the storm pulls into Atlantic Canada. Temperatures will continue to average below normal and the winds behind the departing system will be quite blustery once again.





Long-term - Issued - 2/20/09 @9:00am


High pressure builds into the Northeast on Tuesday ending the lake effect snows and making for a rather pleasant day with fair skies, though temperatures will remain on the chilly side. A moderating trend begins on Wednesday as the high slides offshore and a return flow pumps milder air into the region. Moisture will increase Wednesday night and Thursday as a trough approaches from the west. This will translate into snow showers across the north with perhaps some liquid rain showers to the south, maybe beginning as some light freezing rain. Uncertainty in the long term increases thereafter as models struggle in their handling of a building arctic airmass over Canada and ridging in the Intermountain West breaks down allowing for a steady stream of Pacific moisture/energy to enter the North American pattern. This picture will likely become more clear in the coming days but the potential is there for more storminess late Friday into the beginning of next weekend.


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Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


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Local SST's

Northeast SST's


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Updated: 2:05 PM GMT on February 20, 2009

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Winter storm to affect Northeast

By: sullivanweather, 12:21 PM GMT on February 18, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

--------

Forecast Discussion


Synopsis - Issued - 2/18/09 @7:20am


A complex winter storm will affect the Northeast today through Friday bringing a variety of precipitation types with mainly snow to the north. Further south warm air will move in ahead of low pressure moving well northwest of the region to change initial batch of snow over to rain. As the storm pulls away colder air filters back into the region changing precipitation back over to snow by Thursday evening. A clipper then moves into the region this weekend, though, model trends will have to be watched as some runs have shown a much more significant event taking place. Upper trough lingers into Monday along with some lake effect before ridging builds east by Tuesday.


Short-term - Issued 2/18/09 @7:20am


A 994mb low pressure is located over southeastern Iowa early this Wednesday morning, heading for the Great Lakes, as a 500mb trough digs into the Upper Mississippi Valley. Ahead of this area of low pressure moisture is being transported from the Gulf into the region via a 40-50kt low-level jet and lifted over a warm front moving in from the south. This increase in isentropic lift will cause precipitation to blossom over Pennsylvania by mid-morning, moving into New York and New Jersey by the afternoon. From the central mountains of Pennsylvania and points north and east, including the Laurel Highlands and the Allegheny Front, precipitation will be mainly in the form of snow and should accumulate up to two inches, mainly on colder surfaces. To the south and west, and along the coastal plain, the precipitation may start as a brief period of snow but should change to rain quickly. With no blocking high to the north/northeast there will be very little resistance to the advancing warm air on the low-level jet. This will allow for the boundary layer to warm above freezing from south to north through the morning and into the afternoon, extending up to the I-80 corridor by sunset. Even further northeast, into northern New York and much of New England, much of the day will be spent precipitation-free under increasing cloudiness and temperatures in the mid 20’s to low 30’s.

The warm front makes steady progress north during the evening hours, changing snow to rain over the remainder of Pennsylvania, the southern half of New York and southern New England to the I-84 corridor. Here an additional inch to two inches of snow may fall, bringing total accumulations to 2-4 inches, with the highest amounts across the higher elevations of the Catskills. The higher terrain also stands a chance of seeing some freezing rain where cold air is tough to scour out. Rain showers will continue to be found to the south, through Pennsylvania and up along the coastal plain to the Big Apple but a quickly advancing dry slot/cold front should end precipitation from west to east by around midnight. Meanwhile, over the North Country, the action will just be getting started. Here is where a rather modest snow event will take place. A triple point low forms along the front in central New York overnight, halting the warm front’s northward progress around the I-90 corridor. Low-level jet also cranks up to about 55kts and gains more of a southeasterly component, tapping into Atlantic moisture. Strong isentropic lift will lead to a steady moderate to occasionally heavy snow across northern New York east into central Maine, especially where orographics aid in lift along southeast facing slopes. Snowfall rates of a half-inch to an inch per hour, occasionally heavier, can be expected over a 6-12 hour time span. Strongest omega (>-15microbars/sec) will be below the best snow growth zone, so snow ratios will be on the low side, around 10-11:1, as most isentropic lift events are. The rain/snow line may progress as far north as a Saratoga-Concord line but will likely stay just to the south as cold air becomes better locked in with the development of the triple point low. There may also be some shadowing that occurs north of the Adirondacks and in the Champlain Valley, limiting snowfall in these region overnight. Lows will range from the upper 20’s across the north to the mid to upper 30’s south. Along the warm front extending along the I-90 corridor temperatures will hover near the freezing mark.

Double barrel low slowly translates eastward during the day on Thursday, with the triple point low moving to the Gulf of Maine by afternoon and the primary over the St.Lawrence Valley. Best lift moves into northern Maine during the morning hours where several inches of snow will fall. Elsewhere across the North Country a surface trough extending between the two areas of low pressure will keep light snow/snow showers persistent over the region. As winds shift from the west by afternoon upslope flow will increase over west facing slops, bringing an additional 2-3 inches. The low never really consolidates during the day on Thursday, sharing power equally between each other, with MSLP’s of around 990mb. Despite the lack of intensification, a modest 25-35kt boundary layer wind from the west, combined with decent cold air advection (850mb temps dropping ~6°C between 18/12Z and 19/00Z) will help to make for a rather blustery day across New York, Pennsylvania, New Jersey and southern New England. The moist, cyclonic flow will also work in tandem with moisture added by the Great Lakes and a strong 500mb vortmax moving through the region leading to widespread snow showers, especially in the favored snow belts. Here several inches of snow will accumulate, including the west facing slopes of the Appalachians. Elsewhere across the interior snow showers will become more numerous during the late morning and afternoon hours as the upper disturbance pulls though. There may even be a few squalls as low-level lapse rates steepen during the day as the colder air moves in aloft. Also of note, the sun angle is higher now and the boundary layer is more readily heated. A few of these snow showers may survive the trip over the mountains into the coastal plain but for the most part downsloping will keep this area dry. Temperatures will hold nearly steady from their morning readings, perhaps rising a degree or two by noon before falling back off as the cold air deepens over the region.




Mid-term - Issued - 2/18/09 @7:20am


Cold, moist cyclonic flow continues over the Northeast Thursday night into Friday night as low pressure moves into the Canadian Maritimes, becomes vertically stacked and gradually fills. Upslope flow over the west facing slopes across the Northeast Kingdom will continue to produce numerous snow showers with additional moderate accumulations. The same can be said for areas southeast of Lake Erie and Lake Ontario. Elsewhere across the Northeast the snow showers will b more scattered about with light accumulations along the west facing slopes of the Berkshires and Catskills and little to none across the remainder of the interior. As one heads down to the coastal plain skies will be partly cloudy for much of the midterm. Temperatures across the region will average about 4-7 degrees below normal.


Long-term - Issued - 2/18/09 @7:20am


Low confidence forecast for the long term period, especially early. A rather potent shortwave trough/Alberta clipper will dive into the longwave trough carved out over the eastern half of the country. The surface low will track into the Mid-Mississippi Valley region to the northeast this weekend and that’s where model consensus starts to wane. Some models want to keep this trough progressive, bringing a light snowfall to the region. Other slow the trough down, develops low pressure in the Southeast, which works up the coast late Sunday into Monday bringing the region a significant winter storm. Out of phase MJO and a neutral to slightly positive NAO suggest the former and a nuisance event. However, these sharp shortwave trough sometimes have tricks up their sleeve and the more potent solution of a nor’easter developing from this low cannot be ruled out. This has become a very rare occurrence over these last couple winter seasons but this forecaster refuses to be asleep at the wheel and feels it’s worth a mention. As the trough pulls east lake effect snow showers will be left in its wake then high pressure builds down from central Canada bringing fair skies and seasonably cold temperatures to the Northeast by Tuesday. The next trough passage looks to occur at the end of next week.





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Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


___________________________________________________________

Local SST's

Northeast SST's


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Winter returns this week

By: sullivanweather, 5:30 PM GMT on February 16, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued - 2/16/09 @12:30pm


High pressure will settle over the Northeast during the next 36 hours as a powerful oceanic storm develops well out to sea. On Wednesday, a system of moderate strength will move into the lower Great Lakes spreading a variety of precipitation types across the region. This low will slowly pull through the region with secondary development occurring in the Gulf of Maine on Thursday that should help to bring colder air back into the region changing any leftover precipitation back to snow/snow showers. Cold cyclonic flow continues into Friday with scattered snow showers most concentrated around the lakes. Then a northern stream disturbance drops into the large trough carved out over the Eastern US bringing a threat of snow this weekend.


Short-term - Issued - 2/16/09 @12:30pm


The short term will feature rather quiet weather as a north-south surface ridge axis builds into the region. There are a few renegade snow showers and flurries scattered over the region today but these should be on the wane during the afternoon hours and shouldn’t amount to much. A weak upper disturbance lingering over Maine is helping to promote a few of these snow showers. There’s also a few snow showers to be found over central New York and central Pennsylvania thanks to some lake effect and weak orographc lift. Lowering inversion as high pressure builds in should bring an end to the snow shower activity off the lakes this afternoon while the activity over Maine will hang tough and last into the early evening. Elsewhere over the region skies are mostly sunny but temperatures aren’t as responsive to the sun thanks to the lowering inversion heights and a modified arctic airmass over the region. Highs today will reach into the mid 20’s to low 30’s across the interior with upper 30’s to near 40°F along the coastal plain. Tonight skies will continue to clear out as winds go calm leading to decent radiational cooling conditions. Lows will range from the low to mid 20’s along the coastal plain with teens and single digits inland.

More of the same tomorrow as surface ridge axis will be squarely over the region. Skies will be mostly sunny and temperatures will be within a few degrees of those experienced today – upper 30’s to near 40°F coastal plain, mid 20’s to low 30’s interior. Perhaps the most important development on Tuesday will be what’s going on over the North Atlantic as the pattern becomes increasingly blocked. The storm currently developing offshore the Carolinas will become a sub-970mb storm center located halfway between Bermuda and Newfoundland. The strength and position of this low will become critical in the mid term portion of the forecast as low pressure from the west moves into the lower Great Lakes on Wednesday. Mid/high clouds from this low will spread into the Pennsylvania and New York Tuesday evening, lowering and thickening during the overnight. By daybreak light snow may break out across the Niagara Frontier and areas west of the Appalachians as isentropic lift increases and the column moistens. Elsewhere skies will be mostly clear with a few high clouds moving in late in the overnight. Temperatures will be seasonably cold once again Tuesday night thanks to several hours of radiational cooling west and practically the entire night east.


Mid-term - Issued - 2/16/09 @12:30pm


Situation over the region becomes a bit murky in the midterm as complex area of low pressure moves into Michigan and occludes. A triple point low will form somewhere along the front, likely in New York State, then the double barrel low will slowly translate east, as a tertiary low develops in the Gulf of Maine on Thursday as the greatest baroclincy pulls offshore. This third low eventually becomes the dominant one by Friday morning, deepening in the neighborhood of 985mb over Nova Scotia. In terms of sensible weather, a wave of isentropic lift will rapidly move through the Northeast during the day on Wednesday, bringing light snows to the region that will transition to a wintry mix and eventually rain over the southern half of Pennsylvania and along the coastal plain. Precipitation amounts will be light with the initial batch of precipitation, generally under a quarter inch liquid equivalent leading to 1-3 inches of snow and under a tenth of an inch ice accretion in areas that transition to a wintry mix. Warm air aloft should continue to stream northwards Wednesday night lifting the transition zone into central New York and central New England. As the triple point low forms precipitation intensity will gradually increase over eastern New York and New England as greater inflow of Atlantic moisture moves into the region. To the west the dry slot will rapidly advance into western/central New York and Pennsylvania, tapering precipitation off to snow showers north and rain showers/light wintry mix south. The cold front will sweep offshore by Thursday morning as the third low pressure develops in the Gulf of Maine. Significant snowfall will occur over northern New England during the day on Thursday, except for the immediate coast of Maine where rain may mix in with the snow cutting back on accumulations, as the remainder of the interior sees widely scattered snow showers in cyclonic flow/wrap-around. Along the coastal plain some downsloping will lead to partly cloudy skies. Winds will start to become quite blustery as low pressure intensifies off the Maine Coast. This low lingers over the Canadian Maritimes Friday with cold cyclonic flow over the Northeast leading to widely scattered snow showers that will be most prevalent in upslope regions and around the lakes with lake enhancement.



Two possible scenarios Wed-Thurs. Scenario 1 will likely occur (discussed above) but cannot discount scenario 2 at this time (low track further south).







Long-term - Issued - 2/16/09 @12:30pm


The low pressure will slowly lift towards the Labrador Coast on Saturday leaving behind a rather deep trough carved out over the Eastern US. Scattered lake effect/upslope snow showers will continue into the Saturday as a new area of low pressure digs down the backside of the trough. Recent model runs have shown this to be a very potent, dynamic system as it cuts across the Ohio Valley into the central Appalachians. With cold temperatures entrenched over the region snow should break out late in the day on Saturday across Pennsylvania and spread eastwards Saturday night into Sunday. The track of this system is not set in stone but models have hinted at coastal redevelopment which could bring significant snows to the region, especially along the coast where snowfall as been hard to come by in recent weeks. As residents of the southern portion of the Northeast and along the coast can attest, these northern stream clippers systems have brought the above-mentioned regions their greatest snow this winter season as other southern stream system have moved north to transition precipitation over to a wintry mix and finally rain. Case in point being the system to move through midweek. Whether or not the clipper undergoes coastal redevelopment or the primary remains, the system will move into New England on Sunday bringing a new round of snow to those regions to close out the weekend. Lake effect snows and below normal temperatures will be left in the systems wake next Monday as a pattern change looks to occur as we head into next week across the country.




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Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


___________________________________________________________

Local SST's

Northeast SST's


___________________________________________________________

2008-09 Winter Forecast


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Updated: 7:08 PM GMT on February 16, 2009

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Quiet until midweek then major storm??

By: sullivanweather, 6:12 PM GMT on February 13, 2009


Current watches, warnings and advisories.


Eastern US current watches/warnings

--------

Forecast Discussion


Synopsis - Issued - 2/13/09 @1:10pm


A rather benign pattern is in store the next 4 or 5 days for the Northeast aside from some minor features. The first is a tightly would mid/upper level disturbance that will be dropping into Maine over the next 24-36 hours providing a few snow showers. The second will be a weakening low pressure moving through the Ohio Valley that will bring a light snowfall to the southwestern third of Pennsylvania on Saturday. Thereafter high pressure will slowly build into the Northeast with fair skies and seasonably cold temperatures lasting into Tuesday. Complex situation develops by midweek as a significant southern stream trough moves out of the western states towards the region. Phasing with a northern stream disturbance is possible that may yield a major winter storm for the region.


Short-term - Issued - 2/13/09 @1:10pm


Mostly sunny skies cover most of the Northeast early this afternoon with overcast skies and some flurries confined over Pennsylvania as minor shortwave disturbances ripple along the backside of the trough carved out over the region. These should gradually wane during the afternoon as drier air in the low level advects into the region. Temperatures are within a few degrees of their seasonal averages across the Northeast this afternoon with northern New England in the upper teens to low 20’s. The remainder of the interior is in the upper 20’s to mid 30’s with the coastal plain in the upper 30’s to low 40’s. Winds are out of the northwest around 10-15mph with gusts up to 25mph. Much better than yesterday’s widespread 40-60mph winds which caused several fatalities throughout the region.

High pressure slowly builds towards the region from Hudson Bay that will calm the winds over the western two-thirds of the region and provide mainly fair skies to these areas tonight. Low temperatures will show quite a variation as winds will decouple in some areas leading to ideal radiational cooling, especially in areas that still have some snow cover. Other areas won’t see winds decouple, leading to much warmer over night temperatures. The range in low temperatures will be from the mid and upper 20’s along the coastal plain, with mid teens to low 20’s over the western interior except for sheltered snow covered valleys where lows will drop into the single digits. The eastern third of the region will still be under the influence of the storm system that blew through the region on Thursday. Wrap-around moisture combined with a surface trough and mid/upper disturbance rotating around the larger trough over the Canadian Maritimes will provide clouds and snow showers to northern New Hampshire and Maine. A couple inches may accumulate in favored upslope areas but outside of these areas any accumulations will be light, generally under an inch. Here temperatures will remain in the teens with northwesterly winds around 10mph.


The upper disturbance/surface trough couplet over Maine will move east of the region on Saturday with gradually improving conditions by noon after morning snow showers that may bring an additional inch or two of snowfall. Mid/high clouds will be increasing from the west, lowering and thickening during the morning hours across New York and Pennsylvania as the remnants of low pressure moving in from the Ohio Valley spreads towards the region. Deep vertically stacked low pressure over the Canadian Maritimes will provide a good deal of confluence that will be shearing this system apart as it moves into the region but not before a general area of light snowfall moves across Pennsylvania, mainly the western half of the commonwealth. A couple inches may accumulate over the Allegheny Front and Laurel Highlands due to aid from orographic lift but this system will be rapidly weakening and moisture starved so the lower elevations, especially east of the Appalachians, will see very little, if any snowfall which may even mix with sprinkles given marginal boundary layer temperatures. Highs will range from the 20’s across the northern interior with 30’s across the southern interior and coastal plain.

The weak disturbance moving through Pennsylvania will be offshore and hardly noticeable by daybreak as confluent flow takes it’s toll on the system and secondary low pressure develops on the southern end of the trough offshore. A few snow showers may linger across the southern third of the state during the evening hours before all precipitation ceases. Only scattered clouds will remain after midnight. Temperatures will drop back into the 20’s south and teens/single digits north. Winds will be light from the northwest around 5-10mph.


Mid-term - Issued - 2/13/09 @1:10pm


A very quiet midterm period is in store as sprawling high pressure slowly builds into the Northeast from central Canada. Cold northwesterly flow may provide a few lake effect snow showers early in the period. In addition, minor shortwaves in the northern stream may also provide a few snow showers to northern New England. The most important weather feature during the midterm won’t directly effect the Northeast, in fact. A shortwave suppressed far to the south will move off the coast of the Carolinas and develop into a powerful system offshore as a blocking pattern develops over the North Atlantic. Position and evolution of this feature will be instrumental in the long-term period as the next disturbance works east from the Plains. Temperatures during the midterm period will average close to seasonal norms for mid February.


Long-term - Issued - 2/13/09 @1:10pm


The big weather story this upcoming week will occur in the long term portion of the forecast. A northern stream shortwave will slowly rotate eastward along the US/Canadian border, reaching the Northeast late Tuesday night. At the same time, a southern stream disturbance will be moving out of the Plains towards the Ohio Valley. These two systems will phase up in our general vicinity, providing the region with a major storm. Track/timing of this potential storm is still very uncertain with some models phasing the lows over the Ohio Valley and carrying it towards the interior of the Northeast, a pattern we’re all very familiar with this winter. This solution would lead to significant snows across the north with more of a wintry mix to rain scenario across the south. Other model solutions take a more southerly route with the above-mentioned features with cyclogenesis occurring along the East Coast, which will lead to a major nor’easter with significant snowfall extending down to the coast. Much to early to say which solution has a better chance of verifying but there are some indications that this system may have more of a coastal signature. As mentioned in the midterm section, high latitude blocking will be occurring in/around the Davis Strait and the storm track will be suppressed more to the south thanks in part to the recent stratospheric warming event. Also, the storm to develop over Atlantic waters from the shortwave to move off the Carolinas will provide a good deal of confluence over northern New England that should also make an attempt at holding the system closer to the coast. However, seasonal patterns are hard to break and for the previous two winters we’ve seen many potential coastal lows simply track straight into the heart of the Northeast, spoiling many-a-snowstorms. Models should have a better handle on the situation by the end of the weekend. Check back in then for a new blog with the latest forecast. Behind the departing storm the Northeast will be in a cold northwesterly flow regime with temperatures dipping below normal once again. The pattern also remains favorable for more storminess deeper into the extended forecast with a deep trough carved out over the Eastern US.



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Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


___________________________________________________________

Local SST's

Northeast SST's


___________________________________________________________

2008-09 Winter Forecast


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Severe thunderstorms this evening

By: sullivanweather, 10:43 AM GMT on February 11, 2009




URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 20...RESENT
NWS STORM PREDICTION CENTER NORMAN OK
555 PM EST WED FEB 11 2009

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

WESTERN MARYLAND PANHANDLE
NORTHWEST NORTH CAROLINA
NORTHEAST OHIO
WESTERN PENNSYLVANIA
WESTERN VIRGINIA
EASTERN WEST VIRGINIA

EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 555 PM UNTIL
1000 PM EST.

HAIL TO 0.5 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 70
STATUTE MILES EAST AND WEST OF A LINE FROM 75 MILES SOUTH
SOUTHWEST OF DUBLIN VIRGINIA TO 30 MILES NORTH OF DUBOIS
PENNSYLVANIA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

OTHER WATCH INFORMATION...CONTINUE...WW 16...WW 17...WW 18...WW
19...

DISCUSSION...NARROW LINE OF FORCED MOIST CONVECTION/THUNDERSTORMS
WILL CONTINUE RACING ENEWD ACROSS WW ALONG AND JUST NORTH OF 115 KT
H5 JET MAX. IMPRESSIVE PRESSURE FALLS AND INTENSE/DEEP ASCENT
SHOULD SUSTAIN LINE AND ASSOCIATED WIND DAMAGE THREAT THIS
EVENING...DESPITE LACK OF VERY LIMITED INSTABILITY. WIND DAMAGE MAY
BE WIDESPREAD WITH MORE PRONOUNCED BOWING SEGMENTS WITHIN THIS LINE.
IN ADDITION...EXTREME SHEAR MAY SUPPORT AN ISOLATED/BRIEF-LIVED
TORNADO ALONG LEADING EDGE OF THE LINE.



Current watches, warnings and advisories.


Eastern US current watches/warnings

--------

Forecast Discussion


Synopsis - Issued - 2/11/09 @5:45am


A spring-like storm will move through the Great Lakes and across the North Country today into tomorrow bringing rain across much of the region. Strong winds and snow showers will be left in its wake extending into Friday. This weekend another system moves towards the region from the Ohio Valley but will be met with a strengthening confluent flow over New England that will shear it out over New York and Pennsylvania. High pressure builds in from the Upper Midwest Sunday and Monday with temperatures gradually becoming colder.


Near-term - Issued 2/11/09 @5:45am


A cyclone over the Plains responsible for numerous severe weather reports, including tornados, and flooding rainfall will rapidly move to Lower Michigan by this evening, upstate New York by Thursday morning and be centered over Nova Scotia Thursday evening intensifying from a 997mb low currently to ~975mb tomorrow evening. This track puts much of the Northeast in the warm sector of the storm and temperatures early this morning are indicative of this. As of 4am, it’s a balmy 54°F at Erie, PA. 52°F in Pittsburgh, PA, 51°F in Dunkirk, NY and 47°F in Watertown, NY. Within the warm sector are pockets of very dense fog. This is especially true in the more sheltered valley locations but with cold, snow-covered ground over much of the region, pockets of dense fog can be found virtually anywhere. However, the warm front has yet to push through all of the Northeast, currently residing in a north-south line bisecting Vermont and then continuing east, just north of I-90, to the coast. North of this front temperatures are in the upper teens to mid 20’s. Winds this morning are light and variable.


Short-term - Issued - 2/11/09 @5:45am


Aforementioned warm front continues to slowly work northeastward during the course of the day, reaching central Maine by the late afternoon. Over northern Maine, where winter weather advisories are posted, a few passing snow showers or a light wintry mix can be expected with precipitation amounts totaling under a tenth of an inch liquid equivalent. But given that some of this precipitation will be in the form of freezing rain road conditions may become hazardous. Further south and west, in the warm sector, skies will be mostly cloudy and low clouds/drizzle will hang around the higher terrain for much of the day. Showers will develop during the afternoon across the St.Lawrence Valley as frontogenic forcing increases and some rain may skirt the Niagara Frontier as shield of rain pulls into Ontario but, for the most part, there should be an absence of any significant rainfall across much of the region today. The storm moving in from the Plains will remain far enough west of the region that we should be able to squeak out a decent day. Temperatures will be well above normal, with highs into the low 60’s along the southern coastal plain and 50’s stretching across the remaining southern two-thirds of the region. Closer to the warm front, in northern New Hampshire and central Maine, temperatures will rise into the low to mid 40’s with 30’s across northern Maine north of the warm front.

As the surface low pulls into the eastern Great Lakes tonight it will push a surface cold front towards the region. Southerly flow ahead of this front in the warm sector will have dragged up plenty of moisture from the Gulf, with strong moisture pooling noted in PW fields (1.00+) and in dewpoint temperatures (50°F+) just ahead of the front. Aloft, there’s a very good set-up for a winter time dynamically driven convective event across the state of Pennsylvania, New Jersey and western/central/southeast New York. There will be an elevated unstable layer in the low-levels, just above the boundary layer. Kinematic fields prog 45-55kts @850mb and 50-65kts @700mb at the time of the frontal passage. This region also finds itself under the left front quad of a 130kt jet streak rounding the base of the trough, crashing heights, strong PVA as the 500mb disturbance pulls through. There’s even a few hundred joules of CAPE showing up over the southern half of Pennsylvania. Convective potential is there and should it develop those stronger winds above the boundary layer over 50kts may mix down causing damaging straight-line winds. Set up calls for bowing line-segments and perhaps a bit more of an organized squall line to move across southern Pennsylvania, under the core of the best kinematic/thermodymanic couplet. Aside from the convective threat, a general area of showers will spread over this region with rainfall amounts of a quarter to a half an inch. This rainfall, combined with snow melt, will lead to some minor flooding concerns. On a more localized level, there may be some break-up/movement of ice that could lead to ice jam flooding. This threat may be exacerbated by heavy rain from convection where a lot of rain can fall in a short period of time leading to rapid changes in stream/river flow. Further north, increasing frontogenesis over northern New York and New England will lead to a steady stratiform rainfall developing during the overnight. Better, longer duration forcing will lead to higher precipitation amounts here, from a half-inch to an inch, but the very deep snowpack should be able to handle this amount of rainfall without too much concern. North of the front, in northern Maine, temperatures will be cold enough at the surface for more of a wintry mix of snow/sleet and freezing rain, however, precip amounts will remain light. Temperatures will begin the night very mild over much of the region ahead of the front. Mostly upper 40’s to mid 50’s can be expected, with a few spot locations remaining near 60°F along the coast. After the cold frontal passage temperatures will fall back into the upper 30’s. The front should reach the Hudson Valley by daybreak. Behind the front lingering rain showers will gradually turn to snow, especially across the higher terrain of the Allegheny Front and the Laurel Highlands. Cold air advection will alsop mix down quite a strong boundary layer wind, on the order of 40-50kts! These will occur in gusts, especially over the higher terrain but sustained winds will still howl around 20-30kts. Across northern Maine, north of the warm sector, temperatures will be near freezing or a couple degrees below with the wintry precip and winds will be light, out of the east.

Low pressure pulls across the North Country on Thursday, strengthening as it does so. The strengthening low, combined with a very steep pressure rise/fall couplet, tight gradient and continued cold air advection will make for a very windy day. 40-50kt boundary layer wind will be found over much of northern Pennsylvania, New York and western New England during the day on Thursday and this should be mixed down to the surface given a fairly well-mixed layer in cold advective pattern. The other concern will be warp-around/upslope/lake-enhanced snowfall developing by late morning into the afternoon. Across the favored snowbelts and the north/west facing slopes of the Adirondacks/Greens/Whites, the potential exists for 4-8” of new snowfall. Elsewhere across the interior a fresh coating to a couple of inches may whiten the ground with little if any snow making down to the coast during the day on Thursday. In fact, from the Hudson Valley east into the southern two-thirds of New England the morning will be fraught with rain and the chance for an embedded line of convection associated with the cold front before it pulls offshore by early afternoon. Northern Maine will see precipitation make a slow transition over to snow as colder air working into the system and a triple point low takes over in the vicinity of Nova Scotia. Temperatures will remain steady near their morning temperatures at daybreak or slowly fall throughout the day. As mentioned above, winds will be an issue that will spread northeast during the day.


Mid/long-term - Issued - 2/11/09 @5:10pm


Snow showers will linger Thursday night and early Friday morning over the northern interior, bringing a couple more inches to the higher terrain and around the snowbelts. Elsewhere skies will gradually clear as low pressure moves away from the region. Temperatures return to seasonable levels. High pressure builds in Friday afternoon and Friday night from the west as a tightly wound 500mb low drops down towards northern Maine, rounding the backside of Thursday’s storm over Newfoundland. This feature will play an intricate role in how far northeast snow from an approaching system from the Ohio Valley advances. Already a weakening system as jet energy passes it by, a strengthening confluent flow develops over New England Friday night and Saturday that will shear apart the low pressure moving out of the Plains and into the Ohio Valley. Snow will fall in a narrowing band along the north side of the low track from Iowa to Michigan then cutting east-southeastwards into Pennsylvania. There will be a sharp cut-off on the northeast side of this precip as it bucks against the confluence over New England. This confluence will eventually win out, shearing the system out Saturday night into early Sunday. Light to moderate snow amounts may fall with this system, with the highest amounts over the Allegheny Front and the Laurel Highlands likely in the advisory range. Elsewhere across Pennsylvania and perhaps extending up to the southern tier of New York only an inch or two at most will fall. Under the confluence there will be a shield of high/mid clouds but no precipitation while over northern Maine the tight circulation of the 500mb low may provide enough dynamics to squeeze out a couple inches of snow here as well.


High pressure builds into the Northeast on Monday and sticks around for Tuesday as a much larger trough begins to move out of the west. Cyclogenesis will occur in the Plains once again and head east but unlike the last system, won’t be moving into a hostile environment. This should allow this system to maintain and spread precipitation back into at least the southern half of the region by Wednesday. Model differences are apparent but this one has potential for a more significant QPF event. With cold air expected to be in place much of this precip may also fall as snow or a wintry mix. Lots of time to watch this one and our spring reprieve will be a distant memory should we be staring down the barrel of another major winter storm. Storm or no storm, with the jet stream far to the south and northwesterly flow from Canada behind the departing system temperatures will gradually drop below normal to close out next week.

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Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


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Local SST's

Northeast SST's


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2008-09 Winter Forecast


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Updated: 1:19 AM GMT on February 12, 2009

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February Thaw

By: sullivanweather, 3:53 PM GMT on February 07, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued - 2/7/09 @10:55am



A much milder day across the Northeast as warm air that originated in the Plains finally makes it into the region on deep southwesterly flow. It won’t last long as a cold front blasts through the region later tonight and tomorrow, bringing a few rain/snow showers. Modified arctic air moves into New England as warmth slowly builds under deep layer ridging to the west Monday into Tuesday. By midweek the next system affects the region bringing mostly rain as the primary moves well northwest of the region into Canada, changing to snow as triple point low forms over the Canadian Maritimes. Seasonably cold air follows to close out the week.


Short-term - Issued - 2/7/09 @10:55am


The heat is on! Strong warm advection has pushed the 850mb 0°C isotherm through the Northeast to the Canadian border or will do so by early afternoon! Clouds, deep snowpack and a few light showers will temper this mild air somewhat across the North Country where highs will struggle to reach freezing. Colder locations may get some freezing drizzle due to marginal air temperatures and cold ground but this should be mostly a nuisance. Further south where a few peaks of sun manage to break through, temperatures will climb into the upper 30’s to mid 40’s, even some upper 40’s along the southern New Jersey coastal plain. A much welcomed airmass for many in those winter doldrums.

As low pressure moves across Ontario into Quebec tonight a trailing cold front will drop into the region. Drizzle/freezing drizzle across the north will transition to snow showers by morning. Northern Maine and the higher terrain of the Adirondacks/Greens/Whites may pick up an inch or two of fresh snow. The front will drop south very slowly during the overnight as it will be aligned to the upper flow aloft. This delay in progress will allow the southern half of the region to remain precipitation-free for much of the overnight with partly to mostly cloudy skies. Temperatures across the north drop into the upper 20’s by daybreak with the southern locales remaining in the low to mid 30’s. The ground is still very cold and given the mild moist airmass there may be patchy black ice that develops after midnight. Snow melt will contribute to this but often times ground temperatures become colder than the dewpoint allowing for moisture to coalesce and freeze on sidewalks and roadways. This should mainly be a problem over the southern interior as coastal locales should have sufficiently warm air temperatures, around 40°F, to prevent ice buildup.

Upper trough axis reaches the Northeast on Sunday, turning the winds more from the north, which helps to blast the front through the region. Ultimately, the front crosses the coast by late in the afternoon but the initial delay leaves the southern half of the region in the ‘warm sector’ for much of the day. Under partly cloudy skies, temperatures will rocket up into the upper 40’s to mid 50’s by early afternoon then level off as thicker clouds move in and a few light showers develop from frontogenic forcing and increasing lapse rates as cold air arrives aloft first. Further to the north, from the NY/PA border and across the northern Catskills to Massachusetts, the front will move in much earlier in the day, likely before noon. Temperatures will warm during the morning hours before leveling off around 40°F as the front passes, then slowly fall through the afternoon. Light showers will accompany the front, then precipitation slowly transitions to snow showers by later in the afternoon. North of I-90 the front should be past the region by mid-morning with mainly snow as the precipitation type. An additional inch or two may fall across upslope regions of the higher terrain and a stronger squall or two may drop an inch or two elsewhere as well. Temperatures will begin the day in the mid to upper 20’s and slowly fall into the teens by late in the afternoon. Winds will also get quite gusty over New England as the pressure gradient increases between the developing storm over Newfoundland and the building high over the Great Lakes. Strong cold air advection will lead to a well-mixed boundary layer that will help to bring the 30-40kt boundary layer flow down to the surface on occasion.

High pressure slowly builds in Sunday night with gusty winds continuing over Maine. The core of the modified arctic airmass will also be squarely overhead with 850mb temps dropping to near –20°C. The combined air temperature (near/below zero) with the wind will make for some dangerously cold wind chills but nothing Maine hasn’t already seen this brutal winter! Further west, the high will be building in with winds slackening during the overnight. Some lake effect may continue to be found downwind of Lake Ontario with marginal deltaT’s of 15°C helping to induce some lake instability. Any accumulations will be light. Away from the lake effect, skies will be partly cloudy to mostly clear with temperatures falling into the teens and 20’s.


Mid-term - Issued - 2/7/09 @10:55am


High crests over the Northeast on Monday and despite the brilliant sunshine, strengthening inversion will help to keep things on the chilly side. Temperatures will range from the teens across New England to the 20’s across much of upstate New York and central New England and 30’s south of there. This high will translate offshore Monday night with return flow bringing milder air back into the region by Tuesday. Sharpening baroclinic zone running northwest to southeast across New England will be the focal spot for some wintry precipitation as isentropic lift increases. To the southwest, from central/southeast New York and all of Pennsylvania and New Jersey precipitation should mainly be in liquid form. Precipitation amounts will be a tenth of an inch of less, so no big deal, just more nuisance showers. Temperatures will climb several degrees above normal.


Long-term - Issued - 2/7/09 @10:55am


Low pressure approaches from the west on Wednesday but will move well northwest of the region into the Great Lakes and up into Canada. This puts the Northeast in the warm sector of the storm and should lead to mostly liquid precipitation from a cold frontal passage. The only exception will be far northern Maine where the warm front will get hung up and occlude leading to a wintry mix. Precipitation amounts look to range from a quarter to two thirds of an inch. This amount of rain should be absorbed into the snowpack will relatively little side effects across the north. Further south over Pennsylvania is where the exception may lie. The rainfall will be preceeded by some warmth that may ripen the snowpack enough for greater melting to occur. Will have to keep a close eye on temperatures as 2 or 3 days of average temps of ~42-43 degrees may start to break up river ice combined with the anticipated rainfall/melting snow. The saving grace may be a quickly moving dry slot and being displaced to the south of the warm front that would lead to precip amounts on the low side of the above mentioned range. Temperatures will drop back below freezing by daybreak on Thursday halting the melt. Triple point low forms by Thursday morning over the Canadian Maritimes with a surface trough extending back to the primary low over the St.Lawrence River Valley. That combined with cool, moist cyclonic flow within the upper trough axis will lead to widespread snow showers over the Northeast on Thursday. This continues into Friday then by the weekend a developing storm in the Plains may threaten the Northeast with more snow.



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Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


___________________________________________________________

Local SST's

Northeast SST's


___________________________________________________________

2008-09 Winter Forecast


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'Shadow' of a storm

By: sullivanweather, 7:14 PM GMT on February 02, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued - 2/2/09 @2:15pm

Low pressure will ride northeast out of the Gulf of Mexico this evening, passing several hundred miles offshore on Tuesday. Meanwhile an amplifying mid/upper level trough will move into the Northeast from the Ohio Valley, partially linking up with the offshore low through an inverted trough. This feature, working in tandem with deformation banding, will provide a light to moderate snowfall within 100 miles or so of the coastline but this is small potatoes compared to the blockbuster of a snowstorm earlier predicted amongst various computer models. Rather benign weather follows, lasting until the weekend when the next trough moves in. Temperatures will be cold following the passage of the upper level trough but will undergo moderation by the weekend as broad southwesterly flow develops across the eastern half of the country.


Short-term - Issued - 2/2/09 @2:15pm


A cold front has pushed through the Northeast over the previous 24 hours and currently rests along the immediate coastal plain. Behind this front the cooler air has been very slow to filter into the region as shown by surface temperatures which have risen into the 40’s and 50’s along the coastal plain with 30’s over much of the interior aside from northern New York and New England where temperatures remain in the 20’s. Behind this front precipitation is starting to blossom within an area of increasing 850-700mb frontogenesis combined with moisture streaming north along the mid-level thermal gradient. The boundary layer is still somewhat dry and it will take some time for this precipitation to reach the ground. Surface observations from Pennsylvania, where radar returns are strongest, show little in the way of this precipitation reaching the ground with Johnstown, PA reporting light snow and Selinsgrove, PA reporting light rain. As the atmosphere gradually moistens during the afternoon hours the precipitation aloft will eventually make it down to the surface across a more widespread area with rain below elevations of 1000’ and snow over the higher terrain. Towards the south low pressure is currently forming in the Gulf of Mexico and will take a track across Florida then northeastward, about 250-300 miles offshore. This low was to become a major nor’easter, however, a northern stream shortwave that was originally progged to phase with this low allowing it to deepen rapidly and hug the coast will be late in arriving. Hence, the Northeast will find itself on the northwest fringes of this system as it moves by offshore.

Swath of mid-level frontogenesis slowly pushes eastward tonight, weakening as it does so and moving to the coastal plain by morning. Precipitation amounts with this feature will be light, generally under a tenth of an inch. Along the coastal plain this precipitation will begin as rain but as colder air pushes southeastward tonight the rain will slowly transition over to snow with little if any accumulations during the overnight. Further inland, where temperature are colder, the predominate precipitation type will be snow. The snow will be light and only accumulate an inch or so overnight, mainly across the higher terrain. Further to the north and west skies will be mostly cloudy with little, if any precipitation. Lows will drop into the teens and 20’s across much of the interior with 30’s along the coastal plain.

Even though most of the Northeast will be missing on the storm moving towards the Canadian Maritimes over the open waters of the Atlantic, there will still be some issues to deal with. For one, an inverted trough will develop along the backside of the offshore low providing enough low-level convergence for precipitation to break out, mainly within 100 miles of the coast from eastern Pennsylvania to southern New England. Also, with the mid/upper level trough approaching from the west, broad ascent will be introduced over the region in addition to the convergence provided by the inverted trough and deformation axis extending back to the southwest of the departing offshore low. Several inches of snow may fall in the above-mentioned areas through Tuesday night before the inverted trough falls apart and the deformation band weakens. Further west under the upper trough itself scattered snow showers will be found with up to inch or so of accumulation, especially over the Laurel Highlands and the Allegheny Front in upslope areas. The offshore low may also skirt close enough to Cape Cod and Downeast Maine for these areas to get under the main shield of precipitation associated with the oceanic storm. Boundary layer temperatures over the Cape look too warm for much in the way of snow and rain should be the precipitation type over this region, including Nantucket and Martha’s Vineyard. This precipitation may gradually change over to snow by later on Tuesday night but by this time the main batch of precipitation will have moves past and the leftovers of the inverted trough will be moving in. So little in the way of accumulations here. Across extreme Downeast Maine temperatures do appear cold enough for snow and a few inches may accumulate here for precipitation ends by Wednesday morning. There will be cold air advection throughout Tuesday as the offshore low intensifies and drags down a colder airmass from the north into its tightening circulation. With this being the case there will be little diurnal rise in temperatures and they will likely hold right near their morning lows or fall some in precipitation as UVM helps to drag down colder air from aloft. Highs will be in the low to mid 30’s along the coastal plain with mid to upper 20’s over the interior. Clouds will keep temperatures from rapidly falling Tuesday night but with colder air filtering into the region temperatures will slowly fall throughout the night into the 20’s along the coast with teens inland.



Mid-term - Issued - 2/2/09 @2:15pm


The upper trough axis moves overhead during the day on Wednesday and offshore by Wednesday night. Scattered snow showers within the trough axis will dot the region with a higher concentration of snow showers downwind of Lake Ontario. Lake Erie, now frozen over, will provide little in the way of lake effect/enhanced snow given marginal temperatures aloft. Areas that do manage to see some breaks of sun during the morning will quickly see stratocumulus develop by afternoon as convective temperatures are reached. Highs will be several degrees below normal as 850mb temps drop to –14°C to 20°C from south to north. It will also be quite blustery given the cold air advection and a 15-20kt boundary layer flow. Core of the cold airmass moves overhead Wednesday night with 850mb temps around –18°C or lower across the entire region. North-northwesterly flow will continue with lake effect snow showers in multi-bands across central New York but these won’t amount to much more than a few inches given the short fetch across Lake Ontario. Elsewhere skies will be partly cloudy. Lows will run about 5-10 degrees below normal.

One more cold day on Thursday as the core of the modified arctic airmass settles over the Northeast. Skies will be fair, however, as high pressure builds to the south of the region with a surface ridge axis extending north into the region. With the flow becoming anti-cyclonic the lake effect snow showers should lift north and end by the afternoon with an inch or two additional accumulation, at most. High pressure to the south of the region continues on towards the Southeast Coast Thursday night with warm advection beginning. A weak trough moving well to the north of the region combined with the warm advection (weak isentropic lift) and weak left exit jet dynamics may provide a few scattered snow showers across the north. Low-level will be very dry so it remains to be seen how much, if any, precipitation actually makes it to the surface, though it should be nothing more than nuisance snow if it does so. Clear skies during the evening will make for ideal radiational cooling conditions so temperatures should plummet after dusk but high clouds filtering into the region should put a cap on the falling temperatures by midnight, perhaps a little later east.


Long-term - Issued - 2/2/09 @2:15pm


A pattern change begins to take effect here in the Northeast by Friday as building heights slowly propagate eastward from the Plains/Midwest. The flow turns west-southwesterly at all levels of the atmosphere helping to pump a much milder airmass towards the region. Temperatures return to seasonable levels by Friday and above by Saturday as the next trough of low pressure approaches. This trough will provide rain showers across the southern half of the region with a mix or snow towards the north. Trailing cold front moves through the Northeast on Sunday but the cold airmass behind the front is quickly eroded as the next trough back the flow back from the southwest to begin next week.



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Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


___________________________________________________________

Local SST's

Northeast SST's


___________________________________________________________

2008-09 Winter Forecast


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Updated: 8:26 PM GMT on February 05, 2009

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Numerical model rope-a-dope

By: sullivanweather, 1:11 PM GMT on February 01, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

--------

Forecast Discussion


Synopsis - Issued - 2/1/09 @8:15am

A clipper low, part of an amplifying trough over the Eastern US, will move across southern Canada on Sunday providing scattered snow showers to the North Country along with a brief moderation in temperatures as a warm front pushes into the southern half of the region. A cold front will quickly follow, pushing to the East Coast and stalling by Monday morning. This frontal boundary will provide a tightening baroclinic zone for low pressure moving northeast from the Gulf of Mexico to travel along. At the same time a potent northern stream shortwave will dive into the Upper Midwest, sharpening the trough over the eastern half of the country while providing plenty of upper support for cyclogenesis just off the East Coast. This developing storm will tap into Atlantic moisture and throw it back over the cold sector in the Northeast bringing the potential for a significant snowstorm. This low moves out of the picture by Wednesday with cold and windy conditions along with lake effect snow. Another clipper moves through the region on Thursday with, perhaps, a moderating trend by the weekend.


Short-term - Issued - 2/1/09 @8:15am


A clipper will move from the northern Great Lakes region to southern Quebec Superbowl Sunday, lifting a warm front into the region. Some weak isentropic lift will generate snow showers across northern New York and New England throughout the day, which may amount to an inch across the higher terrain. Otherwise, areas that receive snow on Sunday should see a dusting to a coating at most. Elsewhere, across southern New England, much of New York, Pennsylvania and New Jersey skies will be partly cloudy to mostly sunny during the morning and early afternoon hours with much milder temperatures than those of yesterday. Later in the afternoon, as the cold front approaches, cloudy skies wil return once again. Highs will reach the mid 30’s across the interior with low to mid 40’s along the coastal plain. To the north where the aforementioned clouds and snow showers persist temperatures will remain in the 20’s. Winds will be out of the south to southwest at 5-15mph.

The cold front presses through the Northeast tonight with little fanfare. Basically there will be some clouds lined up along it with little in the way of precipitation. These clouds, however, will help to keep overnight temperatures much warmer than any night during the last several. Lows should fall into the upper 20’s to low 30’s along the coastal plain with teens and 20’s across the interior, colder the further north one heads. Winds will shift from the southwest to the west behind the front around 5-10mph.

The cold front sliding through the Northeast becomes stalled out along the coast as it aligns to the upper flow aloft. Low pressure developing in the northern Gulf of Mexico will stream moisture northward along the front that will lead to an increase in clouds as the day progresses with perhaps a few flurries or sprinkles developing by afternoon. Northwest of this front, skies will be partly cloudy with seasonable temperatures. Really, the calm before the storm. Temperatures will range from the mid 20’s to low 30’s over the interior with mid 30’s to low 40’s along the coastal plain. Winds will be light and mainly from the north.


Mid-term - Issued - 2/1/09 @8:15am


Once again, extreme uncertainty in the mid-term as little consensus between the models remains. Seemingly, each model has its own solution as to what will develop and this is due to each model’s handling of a northern stream shortwave that will be dropping into the Upper Midwest during the day on Monday. Some models, namely the NAM/GFS, are much stronger with this feature causing a rapid sharpening of the trough over the eastern half of the country. In turn, the Gulf low heading up the coast, but slightly offshore, gets captured and pulled back towards the Northeast. The old stalled cold frontal boundary provides a ribbon of strengthening baroclincy allowing for the surface low to intensify as it reaches our latitude. Intense deformation band of snow in the cold conveyor flow develops on the backside of the low on Tuesday and Tuesday night bringing significant amounts of snow across the Northeast within 100-150 miles of the coast down to the northern Mid-Atlantic and extending north into much of New England. As the mid-level low pressure features aloft approaches the coast secondary development occurs later Tuesday night as the primary shears out keeping snow over the region until Wednesday morning. This solution has the potential to drop a foot or more of snow across a wide region of the Northeast. QPF’s range from three-quarters of an inch to an inch and a half in both the NAM/GFS. This snow would also be rather fluffy as cold air gradually incorporates itself into the circulation of the storm system from the north. Snow ratios should range from 12-16:1 or higher near the end of the storm as max omega intersects a moist snow growth region in the deformation axis. The SREF plumes also have decent support for this scenario as the SREF mean precip over the Northeast ranges from a half inch to an inch in the above mentioned areas with many plume diagrams showing an inch or more of QPF. Further to the northwest, from a State College, PA-Utica, NY-Berlin, NH line snow amounts taper quickly with generally a quarter inch or less of QPF expected translating to 1-4 inches of snow. West of the Appalachians little if any QPF is expected with mainly partly to mostly cloudy skies and gradually cooling temperatures throughout the midterm period.

Those are the snowy models. International models aren’t nearly as snowy beginning with the UKMET, which shows basically a non-event as the Gulf of Mexico low races quickly out to sea barely brushing Cape Cod and Downeast Maine with very light QPF.

In the middle of the very snowy American models and the out-to-sea UKMET lies the Canadian GGEM and the ECMWF. These models have trended west over their last couple of runs but not as extreme as the GFS/NAM or SREF’s. They take low pressure about 100-150 miles further offshore than the American models with some light to moderate QPF, generally under a half inch, in the deformation banding on the backside of the storm. This would still give areas within 50-75 miles of the coast a 2-6” snowfall, roughly a half to a third of the output of the GFS/NAM.


Long-term - Issued - 2/1/09 @8:15am


Cold, moist cyclonic flow continues on Wednesday as the storm system pulls away into the Canadian Maritimes. Scattered snow showers will be found throughout the region with the highest concentration of them downwind of Lake Ontario and across upslope area of northern New York and New England. Several more inches of snow may accumulate in the favored snowbelts on a northwesterly flow. Some models still hang back an area of snowfall from a secondary development along the coast trailing behind the main storm which may act to keep steady snow going over New England as well. A few more additional inches may accumulate with this feature should it develop. Temperatures will average well below normal as 850mb temps plunge to –12°C to –20°C. High pressure crests south of the region on Thursday with a surface ridge axis extending into the Northeast, cutting off the lake effect snow and providing partly cloudy to mostly sunny skies for the first half of the day. By afternoon clouds move back into the region as another clipper drops southeastward from Canada. This system arrives Thursday night providing snow showers, mainly across the North Country, through Friday. By the weekend the trough finally begins to lift out of the region with moderating temperatures. A southern stream system may approach by Sunday with wintry precip types north and rain showers south.

___________________________________________________________


Radar: Northeast Region Loop

NE radar

___________________________________________________________

Current snowcover

Northeast Snowcover


___________________________________________________________

Local SST's

Northeast SST's


___________________________________________________________

2008-09 Winter Forecast


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About sullivanweather

Thomas is an avid weather enthusiast, landscaper and organic gardener. This blog is dedicated to Northeast and tropical weather forecasting. Enjoy!

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