Northeast Weather Blog

Wintry week of weather ahead

By: sullivanweather, 10:27 PM GMT on February 20, 2010

Deep, stacked low pressure over the Canadian Maritimes will slowly give way to a new low advancing towards the Northeast via the Mid-Mississippi Valley. This new low will spread snow across the interior and rain for the coast as far north as southern New England Monday through Wednesday.


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.


-------

Forecast Discussion


Synopsis - Issued - 2/20/10 @ 5:20pm


A stationary area of low pressure over the Canadian Maritimes will continue to spread clouds across the Northeastern US with snow showers for the North Country through the remainder of the weekend. As we begin next week a complex area of low pressure will approach from the south, spreading snow across the northern half of the region, with rain or mixed precip south. As this system reaches the Eastern Seaboard a secondary area of low pressure will form off the Delmarva peninsula then move north along the coast Tuesday and Wednesday spreading precip into New England. Meanwhile, a strong cut-off low will dive into the Ohio Valley, possibly initiating the development of new low pressure along the coast for Thursday and Friday that could spread another round of heavy precip cross the Northeast with snow likely for the interior and rain a good possibility for the coast.




Short-term - Issued - 2/20/10 @ 5:20pm

The deep cut-off low pressure over the Canadian Maritimes has been with us now for quite some time, thanks to blocking high pressure situated over the Davis Strait. Just like the last several days, the Northeast region will remain mostly cloudy over the interior with partly sunny skies along the coastal plain as downsloping wind dry out the cloud field. A few snow showers are scattered about across the higher terrain of northern New York and New England, as well as off the Great Lakes, but these have died down in coverage and intensity since earlier in the week and shouldn't amount to any accumulations. Temperatures this afternoon will rise into the 40's along the coastal plain with 30's common across the interior. Over the higher terrain of the North Country temperatures this afternoon will hold in the 20's. Winds will be out of the west and northwest at 5-15 mph with higher gusts, especially across the north. With the clouds hanging around tonight and winds still kicking up temperatures will only drop 5-8 degrees tonight as the low diurnal variation temperature pattern continues. Lows will generally fall into the 20's across the interior with 30's for the coastal plain.

It will be more of the same Sunday and Sunday night but the pesky stacked low will start to shear out and loosen its grip over the Northeast. Hence there should be a bit more sunshine tomorrow and perhaps a degree or two warmer as well.




Mid-term - Issued - 2/20/10 @ 5:20pm


The first challenge of the forecast comes to open the new work week as low pressure forms over the Mid-Mississippi Valley region and heads northeast towards the lower Great Lakes. This is a low pressure track we got quite used to during the winters of 2007-08 and 2008-09 with the La Nina pattern we were in. However, unlike the previous two winters, blocking over the higher latitudes has acted to keep these systems suppressed and this forecaster sees no reason why this trend of suppression shouldn't continue. As the low advances towards the upper Ohio Valley isentropic lift will increase along and ahead of the warm front trying to push into the region. This will cause precipitation to break out during the day on Monday across western Pennsylvania which will slowly spread north and east as the day progresses. Also, unlike most storms this year, there will be a transition zone across the Northeast to contend with, making for a more complicated forecast. As precipitation begins expect it to do so as snow across a good portion of Pennsylvania, mainly north of I-70. Those areas south of I-70 should see a mixture of snow, sleet and rain eventually changing to rain as temperatures both aloft and at the surface climb above freezing. Precip amount s during the day on Monday will be on the light side, a tenth of an inch or two at most. This should lead to an inch or two of snowfall by day's end. Further north and east across much of New York and New England the region will lie between systems and most should escape with a fine day to begin the week. Partly sunny skies and temperatures running several degrees above the norm with no real arctic air to speak of, just a maritime polar airmass. Here temperatures will rise into the 30's across the interior with 40's along the coast. Back west where precipitation is commencing temperatures will generally remain in the 30's.

A secondary area of low pressure will form at the triple point located over the Delmarva peninsula Monday night and slowly work up the coast as the primary low heads towards the Niagara Frontier. Snow will overspread much of the interior sections of Pennsylvania, New York and western New England while areas closer to the coast will see a mixture of precipitation types trending more toward rain along the immediate coast. A warm nose aloft will be present due to the circulation around the primary low but as the coastal low takes over the northward extent of the warm air aloft will be cut-off and eventually be drawn back south as the coastal becomes the dominant low. which should occur by daybreak. Once again, precipitation amounts will be on the light side as lift becomes diffuse with the transfer of energy from the primary low to the coastal. Expect QPF to average tenth of an inch or two which will lead to only an additional inch or two of snow. In all nothing more than nuisance snow until daybreak Tuesday. High pressure nosing down from northern Quebec will keep much of northern and eastern New England dry with partly cloudy skies. Temperatures are expected to fall into the teens and 20's across northern New England with 20's and 30's across the remainder of the Northeast; warmest along the southern coastal plain.

As the secondary low takes over on Tuesday and easterly flow increases off the Atlantic precipitation will increase in coverage and intensity. The trough axis extending between the coastal and the primary areas of low pressure will serve as a conduit for the moisture streaming in from the ocean. Intense low-level convergence will drive moderate to heavy snowfall from northeast Pennsylvania into central and eastern New York and western New England. Model QPF's Tuesday and Tuesday night have been in the three quarters of an inch to an inch and a half range. These amounts will lead to well over 6" of snow across the interior. Along the coast /I-95 corridor/SE Pennsylvania up to southern New England most, if not all, of this precipitation will be in liquid form. In locations still struggling with massive piles of snow leftover from the blizzards earlier this month flooding will start to become a concern. As the low continues north on Wednesday it will start to shear out as it runs into confluence over the Canadian Maritimes. Snow will overspread much of northern New England with rain continuing along the southern New England coast. The deformation axis of snowfall will extend back into northern New York as well with wrap around moisture bringing snow showers across the lakes region and down into western Pennsylvania.





Long-term - Issued - 2/20/10 @ 5:20pm


Second challenge in the forecast comes by Wednesday afternoon as a significant shortwave rotates around the deep cut-off low pressure over the Ohio Valley and reaches the Mid-Atlantic Coast. Several medium range models are indicating cyclogenesis to occur as this disturbance reaches the coast with another area of precipitation blossoming to the north of this development Wednesday night into Thursday. This secondary development should affect areas a bit further east and the first system with New England looking to be the target. Colder air will also be in place following the passage of the first low and snow should be the predominate precipitation type. Eventually the whole mess will merge under the upper level cut-off and become stationary over the Northeast through the end of the forecast period. This will keep snow showers in the forecast for all areas with the higher terrain and lake effect snow belts expected to receive the most in the way of accumulations. Temperatures will be seasonable with little diurnal variation due to the persistent clouds and precipitation.


___________________________________________________________


Radar: Northeast Region Loop

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


___________________________________________________________

Local SST's

Northeast SST's
Fig.4 - Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


___________________________________________________________



All hits.
hit-counter-download.com .

Unique hits.
hit-counter-download.com .


Adopt one today!
My weather dragon!

Permalink

More snow coming for I-95 corridor

By: sullivanweather, 9:13 PM GMT on February 13, 2010

Yet another nor'easter is taking aim at the I-95 corridor of the Northeast to start next week. Six to twelve inches of snowfall is possible with lighter amounts further inland. Cold with lake-effect snow follows.


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.


-------

Forecast Discussion


Synopsis - Issued - 2/13/10 @ 4:05pm


Fairly tranquil weather will continue this weekend for the Northeast region of the country, with the exception being the area in and around the Great Lakes and the higher terrain of the North Country where occasional snow showers will dot the landscape. The next chance for significant precipitation comes on Monday and Tuesday as an upper level disturbance drops south out of central Canada and takes a path similar to the last major snowstorm. Although extreme amounts of snow aren't expected this go'round amounts up to 10-12 inches are possible. This low becomes incorporated into the large vortex stationary over the Canadian Maritimes mid to late next week keeping clouds and snow showers around with the likely candidates receiving accumulating snowfall being the snow belts off the lakes and the upslope regions across the Northeast Kingdom.




Near-term - Issued - 2/13/10 @ 4:05pm


This afternoon's satellite imagery shows a good deal of clouds spread across most of the Northeast. This cloud cover is thinnest over New England with very little cloud cover over Maine. Under these clouds across New York and Pennsylvania one will find widely scattered snow showers due, in part, to the passage of a weak mid-level trough and northwest flow off the lakes. Accumulations should be fairly light during the day, with an inch or so in persistent snow showers. Along the Allegheny Front and upslope regions of the Laurel's perhaps as much as 2-3" of snow may fall in heavier bursts. Otherwise, most of the remainder of the region will remain precipitation-free through dusk. Temperatures will hover a few degrees below normal for mid-February this afternoon with 20's spread fairly uniformly across the interior with low to mid 30's down along the coastal plain. Winds will continue out of the west to northwest at 10-15mph with some higher gusts.



Short-term - Issued - 2/13/10 @ 4:05pm


Clouds and moisture will continue to circulate around the broad stacked low in place over the Gulf of St.Lawrence on down into the Northeast tonight into Sunday. In fact, with weak cold air advection occurring behind the passage of today's shortwave, the lake effect snow will become more prevalent as 850mb temps drop into the -12 to -14°C range. Favored areas downwind of the lakes should receive a fairly broad 2-4". There is a bit of shear below the inversion which should keep bands from organizing, preventing a larger event. Snow showers will also become quite numerous across the upslope regions of northern New York and New England where an inch or two of snow may coat the ground as well. Not much of this precip will make it over the mountains, however, leaving most locales along the coastal plain high and dry. Skies will be partly cloudy and winds will become a bit blustery during the daylight hours. There may be some problems with black ice overnight and in the morning across those locations that saw afternoon temperatures today have climb to freezing and above today. Overnight lows tonight will dip into the teens across the interior with single digits across the higher terrain of the Adirondacks and Greens. These temperatures will warm into the upper teens to upper 20's on Sunday. Along the coastal plain lows tonight will fall into the low to mid 20's with temperatures recovering tomorrow back into the low to mid 30's.

Lake effect/upslope snow showers begin to wind down Sunday night as the inversion lowers slightly and the flow over the region becoming more sheared and diffuse. Any additional accumulations will be an inch or less. All eyes now turn to the southwest as our next weather maker approaches. High clouds streaming out ahead of this feature will begin moving into the southern portions of the region after midnight though any precipitation will hold off until Monday. In all, a rather quiet Sunday night with low temperatures dipping back into the single digits and teens across the interior with 20's along the coastal plain.




Mid/long-term - Issued - 2/13/10 @ 4:05pm


Quite similar to last week the northern branch of the jet will produce a tightly wound upper level disturbance tracking southeastward from Alberta that will eventually cross the Appalachians producing a snow event here in the Northeast. However, there will be a few differences that will result in a different outcome this time. For one, there won't be any phasing with a moisture laden southern branch of the jet. Two, the track will be a slightly different which could allow snow to spread further north than what we've seen for much of this winter.

As mentioned, once again we will be dealing with a 'bowling ball' of an upper level disturbance tracking across the eastern half of the nation. Initially this system is rather moisture starved but like its predecessor the tight circulation will harbor a tremendous amount of dynamics which should make for fairly efficient precipitation generation. The low also won't remain moisture-starved for long as it loops rather far south and is able to pick up a slight amount of Gulf of Mexico moisture before turning back northeastward. Isentropic lift increases during the day on Monday with snow breaking out around noon close to the Mason-Dixon line then spreading slowly northward across the remainder of Pennsylvania and New Jersey during the afternoon hours. The snow may mix with rain along the southern New Jersey Shore as the boundary layer should warm several degrees above freezing before precipitation moves in. Where it stays all snow accumulations by dusk will range from a dusting to two inches. Further north a surface ridge axis over northern New England will make for partly to mostly cloudy skies. Highs on Monday will range from the 20's across the interior to the 30's along the coastal plain.

Both the upper and surface low pressure features reach the Eastern Seaboard Monday evening with strong cyclogenesis occurring in the vicinity of the Delmarva Peninsula (how many times have we seen this occur this winter?). Snow will begin to increase in coverage and intensity Monday night as Atlantic moisture is tapped and brought back into the Northeast. This low pressure is fairly well stacked, with the 850, 700, 500mb lows pretty much on top of the surface low. This should act to keep the heaviest snowfall to within a 50-75mi band to the northwest of the low track. In their most recent runs the GFS and ECMWF have been honing in on the I-95 corridor for the low track with the heaviest snow falling jest northwest of the big cities this time. However, the NAM/ SREF has been more offshore with the low track with the heaviest snow falling closer to the coast. The trend over the last 24 hours has definitely been north and I expect that models are starting to reach a consensus on this storm. QPF should be in the half to three quarters of an inch range along the axis of heaviest precipitation which could lead to a solid 6-10" of snow with higher amounts possible, especially given the tightly wound nature of the upper disturbance. It would not be surprising to see some rather high snow:liquid ratios in the vicinity of 18-20:1 in mesoscale banding that develops on the northwest flank of the low track. Snowfall rates in these bands could easily reach 2"/hr. Further inland a steady light to occasionally moderate snow will fall throughout much of the night from central Pennsylvania to central New York, southern Vermont and New Hampshire. Here 2-4" of snow can be expected. Little, if any snow should reach back towards Lake Erie and up towards the St.Lawrence Valley.

Our latest nor'easter continues moving into New England on Tuesday with snow spreading north into the remainder of northern New England and Maine while snow tapers off across Pennsylvania, New Jersey and southern/central New York. Snowfall should range from 3-5 inches north to 4-8 inches south. This low will then replace the old vortex over the Maritimes through the remainder of the week keeping the Northeast locked into a cold moist northwest flow with persistent lake effect/upslope snow showers which will be enhanced by the passage of disturbances rotating around the stacked low.








The next significant precipitation threat occurs next weekend as yet another southern stream disturbance undercuts the western ridge and heads east on the abnormally strong southern branch of the jet. The latest ECMWF model turns this next storm into another blockbuster nor'easter while the GFS has more of a flat wave. Stay tuned!




___________________________________________________________


Radar: Northeast Region Loop

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


___________________________________________________________

Local SST's

Northeast SST's
Fig.4 - Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


___________________________________________________________



All hits.
hit-counter-download.com .

Unique hits.
hit-counter-download.com .


Adopt one today!
My weather dragon!

Updated: 6:33 AM GMT on February 15, 2010

Permalink

About sullivanweather

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

Local Weather

Mostly Cloudy
48 °F
Mostly Cloudy