Northeast Weather Blog

Nor'easter to deliver unusually early snowfall

By: sullivanweather, 6:09 AM GMT on October 15, 2009

Previous blog - October 2009, coldest on record? may be reposted after this week's wild weather. After this weekend temperatures across the country may moderate for several days which would put breaking the record likely out of reach. Until then I will keep an updated month-to-date anomaly chart here at the top of the blog.





Fig.1 - Month-to-date temperature anomalies for October 2009. (Credit: NOAA Climate Prediction Center)



Current watches, warnings and advisories.


Eastern US current watches/warnings
Fig.2 - Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.

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Forecast Discussion


Synopsis - Issued 10/15/09 @2:10am


A sprawling dome of surface high pressure currently bridges south-central Canada and the northern Great Lakes region with the eastern periphery nosing into the Northeastern United States, responsible for the very chilly air entrenched over the northern third of the US at present. Meanwhile, a series of Pacific disturbances carrying the remnants of once Super Typhoon Melor are riding a fast (120-140kts) zonal jet stream centered near 40°N across the country. As this energy reaches the East Coast a northern stream shortwave will begin to sharpen a trough over the Eastern US causing low pressure to deepen while moving up the coast. This will spread a variety of precipitation types across the Northeastern US, along with wind and coastal flooding. Across the interior elevated terrain, there may be some hefty early-season snowfall accumulations. Then, not to be outdone, the northern stream shortwave which causes the buckling of the jet will form its own coastal low pressure as it crosses the Appalachians. This will continue the unsettled weather along the coast as a second area of low pressure forms and sticks around through the weekend. As this is happening areas to the north along the international border should manage to remain under the influence of the aforementioned high, remaining dry and chilly. The low should finally begin to pull offshore by Monday with moderating temperatures, though readings will continue to run below normal.



Near-term - Issued 10/15/09 @2:10am


Current Northeastern US satellite loop depicts the region in between systems at present, with one strong storm center off the Labrador Coast (Tuesday morning’s trough), one shortwave moving off the southern Mid-Atlantic Coast and another system moving across the Midwest. Despite being triangulated between storms the region still lies under an abundance of clouds which has managed to keep temperatures a little milder than previously anticipated, although they are still quite chilly. There are some clear skies from the Mohawk Valley east to central/southern New England but for the most part, mostly cloudy skies are to be expected this overnight. Aloft, 850mb temps are anomalously cold for Mid-October, with readings ranging from -10°C towards the US-Canadian border, to near 0°C down towards the Mason-Dixon line with surface readings generally in the 20’s north and 30’s south (except 40’s along the southern coastal plain). Temperatures should drop several more degrees before reaching their daily mins as cold air continues to drain south from the dome of high pressure spanning the southern Provinces of Canada.



Short-term - Issued - 10/15/09 @2:10am


As day breaks on Thursday much of the southern half of the region will be socked in with clouds while areas to the north actually begin to clear some as confluent flow over northern New England and southern Canada strengthens. Precipitation should begin to develop around daybreak across southwestern Pennsylvania along and to the south of I-80 as deep-layer ascent increases due to increasing PVA combined with a coupled jet structure and low-level thermal advection. This area of precipitation will rapidly expand eastward and slowly edge north to the New York/Pennsylvania border during the morning and early afternoon hours. Due to the dry airmass over the region, several hours of evaporational cooling will occur during the early morning hours, lowering temperatures as the precipitation starts. This will be crucial for areas where critical thicknesses aloft will be marginal to support snowfall, such as the region from central Pennsylvania, northern New Jersey and southeastern New York along and to the south of the I-80/84 corridors. Current thinking is that evaporational cooing during the first couple hours of the storm will lower temperatures in the boundary layer to support snowfall then as the day progresses and precipitation intensity increases due to increasing lift (omega progged @ -5 to -10 microbars/sec), UVM and dynamic cooling of the column will counterbalance Mid-October insolation and tend to keep precipitation in the form of snow, although this will be highly dependent on precipitation intensity and elevation. Snowfall may even occur in the valleys across this region but accumulations during the daylight hours will be hard to come by and any periods of lower intensity precipitation will tend to change over to rain. Once in the vicinity of the Pennsylvania Turnpike the majority of precipitation will be in the form of rain at elevations below 1,500’, although occasionally a few sleet pellets or wet snowflakes may mix in at times. Thermal profiles aloft are very marginable for snow in this region and boundary layer temperatures may be a couple degrees too warm for all snow during the daylight hours. Once north of I-80 extending to extreme south-central New York State precipitation should primarily be in the form of snow with the exception being the lowest valleys. Temperatures aloft in this region are much cooler but the same dynamics neighbors to the south will see won’t be in place this far north and moisture will be much more limited (precipitable water contents nearly half of those to the south). Hence, precipitation will be lighter and with marginal boundary layer temperatures rain could mix in at times. As far as accumulations go, most areas along and to the north of I-80/84 should get at least a coating on grassy surfaces with upwards of a couple inches as one gains elevation, mainly over 1,500’. Areas to the south of I-80/84 accumulations will be a bit higher as more QPF is expected but one will have to climb higher to see them. Elevations over 2,000’ should get a solid 3-5” of the white stuff while elevated areas between 1,500’ and 2,000’ could walk away with an inch or two. Below 1,500’ there will be little in the way of accumulations as much of the precipitation will be in the form of rain or very wet snow that should melt on contact. For areas along the coastal plain the forecast is a much simpler one, rain and wind.

The second shortwave disturbance will reach the coast during the afternoon hours, providing a shot in the arm for the developing coastal low pressure east of Delmarva with the central pressure of this low dropping from ~1006mb Thursday afternoon to ~1000mb by the wee hours of Friday morning. Nothing too impressive but this will tighten the pressure gradient between the low offshore and the high over southern Canada resulting in a stronger northeasterly fetch. This will also help to transport Atlantic moisture back across the Northeast in the cold conveyor flow to the north of the developing cyclone. Additionally, ageostrophic flow should promote cold air drainage into the storm during the evening hours, helping to push the rain/snow line south and to lower elevations, possibly 500’ by midnight. QPF during the overnight is a solid two to four tenths of an inch across the southern half of the Northeast, mainly south of the NY/PA border region. With the lack of insolation snow will begin to accumulate in areas that failed to see accumulations during the daylight hours while the elevated terrain will continue to add to their totals. Accumulations should range from 1-4” depending on elevation during the overnight. This additional snowfall combined with snowfall from earlier on Thursday would result in 4-7” at elevations over 2,000’ by daybreak on Friday with 2-5’ of snowfall for elevations from 1,000-2,000’. There should even be a coating to an inch down in the valleys, possibly more if mesoscale features line up. Meanwhile, strong high pressure to the north will keep precipitation at bay across the northern half of the region, although there will be an increase in high cloudiness. Temperatures will be extraordinarily chilly across the region with highs on Thursdays likely remaining in the 30’s across the interior with only 40’s down along the coastal plain. Southern New Jersey may break into the low 50’s towards late in the afternoon as marine air comes ashore but even these readings are well below normal. In some cases areas of central Pennsylvania will see highs more than 20 degrees below the average for Mid-October. Temperatures during the overnight period will drop only a couple degrees across the southern half of the region where clouds and precipitation should limit the diurnal range. Areas to the north where high pressure will be in control should see a more marked fall in temperatures. Especially if the high cloud deck thins at all. Here readings should fall into the low to mid 20’s with teens across the higher elevations.

By Friday morning the situation begins to get more complicated as the first storm heads out to sea as a second area of low pressure begins to take shape over the central Appalachians. This second area of low pressure will begin to tap into the cold conveyor of moisture in the long east-northeasterly fetch coming off the North Atlantic directly into the Northeastern US. As dynamics increase once again within the vicinity of this secondary low precipitation will once again increase in intensity across central Pennsylvania to the northwest of the 700mb low track in the area of strongest mid-level frontogenesis. As was the situation on Thursday, the transition zone will lie in pretty much the same region and precipitation type will once again be determined by elevation and precipitation intensity. This low will reach the coast Friday night and begin to turn up the coast on Saturday with precipitation remaining confined to within 100-150 miles of the low track. Several more inches of heavy wet snowfall may coat the elevated terrain of central Pennsylvania through southeastern New York. With most of the trees still carrying much of their foliage the possibility exists for major tree damage along with the potential for power outages. Along the coastal plain precipitation should remain in the form of rain throughout much of the time during the second system, although some wet snow may mix in at times late Friday night in the tier of counties away from the coast. All the while northern New York and New England continue to be shielded from the adverse weather by the strong surface high. Once again, temperatures Friday through Saturday will run 10-25 degrees below normal for highs and 5-10 degrees below normal for lows.



Fig.3 - Total snowfall through Saturday AM.
More snow is expected after this period but will not be included in this map.


Mid/long-term - Coming soon

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Radar: Northeast Region Loop

NE radar
Fig.4 - Radar loop of the Northeast region. Courtesy of Weather Underground.


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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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Updated: 3:36 AM GMT on October 16, 2009

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First widespread snow for the mountains tonight

By: sullivanweather, 2:35 PM GMT on October 12, 2009

Previous blog - October 2009, coldest on record? may be reposted after this week's wild weather. After this weekend temperatures across the country may moderate for several days which would put breaking the record likely out of reach. Until then I will keep an updated month-to-date anomaly chart here at the top of the blog.



Fig.1 - Month-to-date temperature anomalies for October 2009. (Credit: NOAA Climate Prediction Center)



Current watches, warnings and advisories.


Eastern US current watches/warnings
Fig.2 - Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.

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Forecast Discussion


Synopsis - Issued 10/12/09 @10:30am


One of the more active October weather patterns in recent memory will continue to wreck havoc with the nation’s weather over the next week. The main feature to watch will be a strong Pacific storm system poised to slam ashore California later tonight and Tuesday. This storm has incorporated the tropical remnants of once Super Typhoon Melor and promises to make a small dent in the prolonged severe drought affecting the West Coast. Rainfall amounts of 2-4” in the low lands and up to 6” in the foothills are possible with this storm in addition to strong winds of 25-45mph along the coast and over hurricane strength as one heads up into the Sierras. Snow levels will be abnormally high due to the warm origins of this storm system but at elevations over 8,000’ two to three feet of Sierra cement is expected.

Meanwhile, from the Front Range of the Rockies to the Central/Northern Plains and Upper Midwest the big story continues to be the cold. Last week a series of strong arctic fronts dove straight south, bringing record shattering cold temperatures. Some of the temperature records are truly astounding. For example, on Saturday the 10th Cheyenne, Wyoming’s high temperature (17°F) was colder than their record low temperature for the date (19°F). The cold postponed Game Three of the NLDS between the host Colorado Rockies and Philadelphia Phillies as temperatures hovered in the mid-20’s all day long after a dusting of snow the night before. South Fork Judith, Montana saw a low temperature on the morning of the 11th of -16°F! The truly amazing cold air for so early in the season broke hundreds of daily low minimum and low maximum temperature over the weekend. Cold wasn’t the only issue to contend with as it also came along with snow. October snowfall isn’t uncommon across the Front Range and High Plains but such impressive amounts are. North Platte, Nebraska received 13.8” of snow at their official reporting station, breaking their October single storm record. Areas outside of town got as much as 17” as a narrow band of heavy snow set up west-east across the state. Even Des Moines, Iowa saw just over an inch, breaking their record for earliest snowfall of an inch or more.



Fig.3 - Daily temperature anomalies for October 10th, 2009. (Credit: NOAA Climate Prediction Center)


Not to be outdone, as the Midwest shivered the Southeast boiled! Temperatures over the weekend rose into the mid 90’s across the interior of Georgia and northern Florida breaking records for heat! The reason for such impressively hot temperatures for October was a strong H5 ridge parked just off the Southeast Coast. Even nighttime lows failed to bring relief as Key West, Florida broke their all-time low maximum for the month of October with a reading of 84°F on the 5th. Key West then went on to tie that record on the 6th, 7th, 9th and 10th!

Between the record cold and the record heat was record rainfall. As the first trough bringing the cold air down into the country progressed eastward last Wednesday, Thursday and Friday a band of heavy rainfall developed across the southern Plains, Mid-Mississippi Valley and Lower Ohio Valley breaking many daily rainfall records and prompting the issuance of widespread flood and flash flood warnings that covered hundreds of counties from Oklahoma to Indiana. Joplin, Mo broke their daily rainfall record on the 8th with 3.59” of rainfall, easily surpassing the 1.65” that fell in 1970.

Focusing a bit closer to home, the Northeast had managed to avoid much of the weather extremes that plagued the country over the last week but did see some weather of note. A minor wind event struck on Wednesday the 7th following the passage of a cold front causing some power outages and downed limbs. Several reports of gusts over 50mph did occur but most areas saw gusts no higher than 45mph. Then last night the coldest night of the season took place with many locales across the interior seeing an end come to their growing season. However, the rain event from the southern Plains to the Ohio Valley petered out before reaching the region, bringing mainly light to moderate showers and the cold, while producing a widespread frost/freeze, hasn’t yet hit with the ferocity seen in the Midwest. But changes are afoot here in the Northeast as we too will get in our fair share of abnormal weather for October as we head through this upcoming week into the weekend. More on that below.



Near-term - Issued 10/12/09 @10:30am



Residents of the Northeast interior woke up to a frosty morning this Columbus Day as cold Canadian high pressure squarely overhead provided ideal conditions for radiational cooling. Temperatures dropped into the 20’s across much of the interior with 30’s down to the coastal plain. Only areas along the immediate coast and urban centers (Southern New England and points south) managed to stay in the 40’s overnight. The aforementioned high will be transient in nature, sliding offshore this afternoon as it gives way to low pressure approaching from the Great Lakes. High clouds have already overspread much of Pennsylvania, New Jersey and western New York in advance of this low but much of New England continues to be under the influence of the high with mostly sunny skies. Whether in sunshine or clouds, temperatures will remain several degrees below normal this afternoon with the chilly airmass in place. Highs will only reach into the 40’s across northern New York and New England and may not do any better across north-central Pennsylvania and south-central New York State where clouds have already overspread the region. This ought to limit the amount of insolation, keeping temperatures held in check. Along the coastal plain temperatures won’t be quite as chilly with highs reaching up into the 50’s. Also, areas of eastern New York and western New England where a fair amount of sun will shine before the cloud deck moves in temperatures will reach into the 50’s as well.


Short-term - Issued - 10/12/09 @10:30am


Clouds continue to increase during the evening hours as low pressure approaches from the Great Lakes region. This is a fairly potent disturbance embedded in a fast zonal flow that won’t begin to show signs of it strength until reaching the Northeast. The downstream flow over the North Atlantic will become increasingly blocked, forcing a sharpening of the shortwave trough as it moves into the region. Precipitation will develop within a few hours of midnight across western New York and Pennsylvania then overspread the Northeast during the overnight. The bulk of the precipitation will fall to the north of I-90 where isentropic lift will be highest with mainly scattered lighter precipitation to the south. To the far north, from the Adirondacks to the Green/White mountains of Vermont and New Hampshire, temperatures aloft and critical thicknesses indicate that profiles will be cold enough for snow, especially across the higher terrain. As mentioned above, this is a rather potent disturbance that will be intensifying as it crosses the region. Strong UVM provided by the burst of isentropic lift, +PVA and a narrow band of 850-700mb frontogenesis combined with fairly dry low-levels could also change rain over to snow at elevations down to 500’ as well as dynamic cooling of the column takes place. Overnight QPF from this system ranges from two to four-tenths of an inch on both the GFS and NAM models, hence a couple inches of snow is not out of the question. Accumulations should remain confined to elevations over 1,500’ and could range from 2-4” - highest above 2,500’. Overnight lows will remain in the 40’s across the southern half of the region with 30’s to the north. The higher terrain will see temperatures drop into the upper 20’s with the snowfall.

Low pressure continues to intensify as it crosses New England Tuesday morning and really starts to bomb out upon reaching the coast. To the south of the low track precipitation will remain in the form of rain and be showery in nature with generally a tenth of an inch or less of QPF from eastern New York State across Southern New England. To the north of the low track QPF will be considerably more as the developing gale center begins to tap into Atlantic moisture. Precipitation will become moderate to heavy in the developing comma head/deformation axis from central New Hampshire across Downeast Maine. QPF during the day on Tuesday will range from a third of an inch to three-quarters of an inch or more, with the highest amounts closest to the coast of Maine. Across the higher elevations of the Presidential Range up to 6” of snow or more is possible with snow mixing in with rain at times across the interior of Maine as colder air wraps into the backside of the low. Across the western half of the region it will be chilly and blustery behind the low pressure as cold air advection will be underway behind the front. Skies will be partly to mostly cloudy with a few lake effect showers downwind of Lake Ontario but these will be short-lived as flow quickly goes anti-cyclonic by late in the afternoon. Temperatures will only see the 30’s across the higher terrain of the Northeast Kingdom with 40’s across the lower elevations. Elsewhere across the interior upper 40’s to mid 50’s will do with temperatures climbing to near 60°F along the southern coastal plain. Winds will pick up out of the west-northwest around 15-20mph with higher gusts.



Fig.4 - Snowfall totals Monday night through Tuesday.


High pressure quickly starts to build in from southern Canada on Tuesday night across the western half of the region. Here skies will clear and winds will slacken with decoupling taking place during the overnight hours. This will allow temperatures once again to fall close to or below the freezing mark for much of the interior. Along the coastal plain lows will fall into the upper 30’s to mid 40’s. The eastern half of the region will still feel the western periphery of the developing storm moving into towards Newfoundland. Winds out of the northwest will remain blustery and clouds will be slow to depart but temperatures will be similar to the western half of the region with readings close to or below the freezing mark across the interior with mid to upper 30’s closer to the immediate coast.


Mid/long-term - Coming soon

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Radar: Northeast Region Loop

NE radar
Fig.5 - Radar loop of the Northeast region. Courtesy of Weather Underground.


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Local SST's

Northeast SST's
Fig.6 - Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


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Updated: 2:38 AM GMT on October 14, 2009

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A record cold October 2009?

By: sullivanweather, 3:40 PM GMT on October 06, 2009

For 95% of the contiguous United States the first 5 days of October has started below normal, with about half the country decidedly so, running 5-12 degrees subpar. For much of the Western US and Northern Plains this is a marked change from the month of September when temperatures ran 4-8 degrees above normal for the month. Several locations even recorded their warmest or second warmest September on record. The reason for the record warmth was an anomalously strong ‘Rex block’ over Canada that was bookended by a pair of equally persistent areas of troughiness; one over the Gulf of Alaska and another over Greenland which were both responsible for numerous areas of cyclogenesis during the Month of September (see fig.2). But near the end of the month things began to change. The ‘Rex block’ over Canada began to break down as a series of low pressure areas broke away from the circulation over the Gulf of Alaska and made their way into the Western US. Meanwhile, the +NAO pattern (low pressure near Iceland/high pressure near the Azores) across the North Atlantic pulled a complete one-eighty. Over the last week incredible geo-potential height rises have occurred from Hudson Bay to southern Greenland while a deep closed trough formed near the Azores (see fig.3). In fact, the surface reflection of this deep cyclone over the Northeast Atlantic would undergo a slow process from a cold-core to a warm-core storm, eventually becoming Tropical Storm Grace.




Fig.1 - Temperature anomalies for the US through the first six days of October.




Fig.2 - Chart depicting storm tracks over the northern hemisphere for the period 9/5/09-10/4/09. Note the high frequency of storminess in the Gulf of Alaska and in the vicinity of Iceland and the lack of storminess over the Western Us and south-central Canada.



Fig.3 - 500-hPa height anomalies for the northern hemisphere from September 5th to October 4th. Of note is the strong 'Rex Block' over Canada during the month of September transitioning to a pattern of high-latitude blocking, lowering heights across the mid-latitudes, especially in the western hemisphere from the West Coast of North America to the central Atlantic Ocean.


That brings us to where we are today. The pattern changes over the last week are responsible for pushing the jet south into the US, allowing colder air from Canada to become incorporated into the series of Pacific storm systems to march across the country. So cold has this air been, the first major snowstorm across the Intermountain West has already struck, leaving 1-2’ of snow across the Northern Rockies with 3-6” of snow at lower elevations. Snow even raced out into the Northern Plains with up to 4” reported in North Dakota. Unfortunately, those hoping for an Indian Summer following this first major cold blast shouldn’t count on it; this is merely a preview to what’s to come over the next week. One of the coldest air masses on record for this early in the Autumn will be diving straight south from the Arctic, arriving in stages with the first due on Wednesday morning. Low pressure will develop over the Canadian Prairies on Tuesday, helping to drive the first in a series of cold fronts into Montana and the Northern Plains. Vigorous shortwave disturbances diving down the backside of the deep, broad longwave trough carved over North America will not only reinforce the cold air but also but down even colder air from Canada so that by the end of the week a large area of much below normal temperatures will reside over the eastern 2/3rds of the country, save the East Coast where the front may slow before finally pushing through by the beginning of next week. Under the core of the cold airmass (leeside of the Rockies, central/northern Plains/Upper Midwest) expected to invade the US temperatures will average 20-30 degrees below normal and many daily records for both minimum and low-maximum temperature are in jeopardy of falling. This would also leave large portions of the country 10 to 15 degrees below normal or more through the first two weeks of the month. With so much of the country expected so far below normal through the first two week of the month, will the record for the coldest October on record fall?

To answer we need to look back at the coldest October on record – 1925. Does this October bear any resemblance to October of that year? Thus far, yes.



Fig.4 - Contiguous United States temperature record for October (1895-2008)
Credit:NOAA



One of the overriding factors determining the breadth of the cold air across the US in October of 1925 was the succession of three abnormally cold strong surface high pressure areas from northern Canada into the United States. Each one brought progressively colder air with the final arctic high delivering the coldest temperatures on record (to that point) in October with many stations breaking daily and all-time monthly record lows for both minimum and low maximum temperature. During the last cold snap of the month temperatures fell well below zero across a wide area of the Upper Midwest. The coldest reading coming from Montana of -28°F! Temperatures of 15-20 below zero were also common on the coldest night of the cold snap across North Dakota and Iowa, with the zero degree isotherm penetrating into Missouri. Also of note is a very rapid succession of systems across the country with very little time between storms for building heights and a return of warmth. This also contributed to a high amount of snowfall for October 1925, the most on record as well (see fig.5). And not to be outdone, a very rare occurrence for October, not one center of low pressure came ashore the Pacific Northwest during the month of October 1925, as most troughs made their way into the US via Canada after tapping into the cold air that made October 1925 the coldest on record.



October 1925 snowfall
Fig.5 - Total snowfall for the month of October 1925. Click for larger image.


As the next cold front drops south from Canada this week it will also be followed by an abnormally strong, cold surface high pressure cell (~1040mb). Additionally, there will be a very fast west-southwest to east-northeast jet stream racing across the country. Along the East Coast of North America a ~150kt jet stream will be exiting the coast, reminiscent of what one would expect during a winter season but certainly not October. This highly-amplified jet will bring down numerous disturbances from Canada between the 7th and 13th of the month where they will combine with sub-tropical moisture along the Gulf Coast to produce several heavy rain events, also a concurrent pattern during October 1925.



Fig.6 - GFS forecast 850mb temps, 6-hour precipitation, MSLP for 8am on October 9th, 2009. Note the strong areas of surface high pressure building down from Canada into the Northern Rockies/Plains.



Fig.7 - GFS forecast 850mb temperatures for 2pm October 11th, 2009. Cold air covers much of the northern tier of the country with the 0°C isotherm extending far to the south, from the central Plains to the Northeast Coast.



Of course, this is only the first two weeks of the month. Looking ahead to the third week of October there are signs that Pacific energy arriving from north of Hawaii could impact the Pacific Northwest, spilling milder maritime air across the western half of the country, at least. However, there are also signs of a re-amplification of the Gulf of Alaska low/near-West Coast ridge after week three and continuing through the remainder of the month which should, in turn, initiate a re-amplification of the longwave pattern over the US. This is still over 10 days out before signs of a pattern change start to take hold and a lot can change by then. Either way, by mid-month temperature anomalies will be deep in the hole.



Fig.8 - GFS ensemble mean 500-hPa height anomalies centered on 8pm October 21st, 2009. Below normal heights in the Gulf of Alaska indicate a stronger than normal Gulf of Alaska low. Above normal heights over the Labrador Coast also indicates blocking around Greenland may persist through the end of the month, helping to keep cold air funneling into the US from Canada.



The year that holds the rank of second coldest October on record was 1976. Once again, this was a month that was dominated by a high-amplitude jet stream across North America with two abnormally cold, strong areas of arctic high pressure crossing the country. The coldest period of October 1976 occurred from the 17-22nd of the month when strong high pressure built down from Canada delivering a record breaking cold airmass across the eastern 2/3rds of the country, ending the growing season for many areas. Also of note was snow falling at locations not accustomed to seeing the white stuff during October, such as central Nebraska and the high plains of Texas, where as much as 6” of snow fell.

A reason for these cold Octobers can be traced to El Nino, the periodic warming of the equatorial waters of the Pacific Ocean. Many Octobers falling on El Nino years tend to be much cooler than average across the US as a higher incidence of high-latitude blocking occurs, forcing a lowering of heights across the mid-latitudes helping to draw in cold air from the north. Climatology of El Nino Octobers would tend to favor at least one more outbreak of cold air during the second half of the month which could keep temperatures low enough to yield one of the coldest Octobers on record considering the very cold start to the month already seen on top of the record cold that’s expected to persist over the next 7-10 days.


References and further reading.


James Wagner, A., 1977: Record Cold over the South and Midwest. Mon. Wea. Rev., 105, 121–127. - http://ams.allenpress.com/archive/1520-0493/105/1/pdf/i1520-0493-105-1-121.pdf

SAMUELS, L.T., 1925: FREE-AIR SUMMARY. Mon. Wea. Rev., 53, 457–459. - http://docs.lib.noaa.gov/rescue/mwr/053/mwr-053-10-0457c.pdf

DAY, P.C., 1925: THE WEATHER ELEMENTS. Mon. Wea. Rev., 53, 459–461. - http://docs.lib.noaa.gov/rescue/mwr/053/mwr-053-10-0459.pdf

, 1925: Chart VII. Total Snowfall, Inches, October, 1925. Mon. Wea. Rev., 53, c7. - http://docs.lib.noaa.gov/rescue/mwr/053/mwr-053-10-c7.pdf



strong>Current watches, warnings and advisories.


Eastern US current watches/warnings
Fig.9 - Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.

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Forecast Discussion


Coming later...
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Radar: Northeast Region Loop

NE radar
Fig.10 - Radar loop of the Northeast region. Courtesy of Weather Underground.


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Local SST's

Northeast SST's
Fig.11 - Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


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Updated: 3:37 PM GMT on October 11, 2009

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Flashback: October 2006 and other early-season lake effect snowfalls

By: sullivanweather, 11:09 PM GMT on October 03, 2009

Over the last several days global forecast models have been insisting on building an anomalously cold airmass over central Canada and dropping it into the eastern US next week following the passage of a significant storm system. Several model runs have shown 850mb temperatures dropping into the negative 10's Celsius along the US-Canadian border with -6°C air @850mb moving across the Great Lakes. An airmass this cold has shown in years past to produce early-season lake-effect snowfall. Other model runs have shown a more modified solution, with air still cold enough for wet snow to mix in with lake-effect rain, but nothing substantial in terms of accumulating snow. Models have centered on the 12-13th as the coldest days of the upcoming 'arctic' blast, which is a popular date for early-season snowfall, it seems.



Three years ago today numerical models were giving meteorologists fits. First to appear on the always questionable-in-the-long-term GFS model near the end of September was an anomalously deep and cold trough diving into central Canada and across the Great Lakes delivering a winter-like blast of arctic air capable of producing a lake effect snow event. Initially shrugged off as a couple of anomalous runs, support slowly gathered. Once within the forecast range of the operational Global GEM (Canadian) model and the operational ECMWF (European) model the same deep and cold trough was there, daring climatology. 850mb temps were progged to be nearly 5-sigma below normal as the core of this cold airmass descended into the US but would this actually happen?

As the event grew near and it became apparent that there would be an outbreak of arctic air new questions arose. It had just been the second warmest summer on record, nearly beating out the Dust Bowl year of 1936, and despite a cooler than average September across the Great Lakes region, water temperature anomalies in the Great Lakes ranged 5-8°F above normal, running at all-time highs for early October. Could such anomalously warm lake temperatures yield any lake effect snow or would they moderate the airmass enough to produce lake effect rain?

The front moved through the western lakes on the 11th with the lake effect beginning quickly in its wake. First, rain showers moved off Lake Superior but those slowly changed over to snow showers by the evening. As the night progressed snowfall picked up in intensity off Lake Superior as even colder air flowed over the lake in a lightly sheared surface-700mb environment with several communities in favored areas picking up 6-8 inches of snow by morning. However, lake-effect snow off Lake Superior, the coldest of the five Great Lakes, isn’t all too uncommon in mid-October. For the communities downwind of Lakes Michigan, Erie and Ontario, mid-October lake-effect snow isn’t just uncommon, it’s rare. And climatology was hard to overcome at first. Through the early morning of the 12th most of the lake-effect precipitation moving off Lake Michigan was in the form of rain, save a few localized areas in northern-lower Michigan. But the airmass had other plans. Temperatures aloft continued to cool and by mid-morning, the lake-effect rain had changed over to snow in most areas across the State of Michigan. Even communities close to the lake shore started to see a mixing of precipitation types which eventually changed over to snow.

So the airmass was, in fact, cold enough to deliver the goods in terms of snowfall. Not only was there snow falling but there was snow accumulating. Widespread accumulations of 2-4 inches across southern Michigan were common and in some localized areas, such as Cheboygan, Michigan, near the Straits of Mackinac, up to a foot of snow fell! But would this cold air have enough drive to complete its journey across the Great Lakes to deliver snow to the eastern Great Lakes region, where water temperatures were warmer still? The average temperature of Lake Erie on the morning of the 12th was 65°F, about 5 degrees above normal. And due to the position of the low to the northwest of Lake Erie, the wind flow would have to come down the entire length of the lake, allowing plenty of time for the air to moderate as opposed to the flow over Lake Michigan, which cut widthwise across the lake, leaving less time for a moderation of temperatures.

At first, it seemed the warmer waters of Lake Erie would win out. The front crossed the Niagara Frontier mid-morning of the 12th and several hours after its passage only lake-effect rain fell. But nature always has tricks up her sleeve. The airmass coming over Lake Erie was anomalously cold, but yet not yet cold enough to produce snowfall after moving down the length of warm Lake Erie through early afternoon. Models had projected 850mb temperatures to drop to a marginal -4 to -6°C and upon reaching those temperatures rain continued; some other factors were needed to conjure up a snowstorm. They would soon be realized.

Models are a great tool for guidance but they don’t hold a candle to real-world observation. 1800Z soundings from around the Great Lakes showed an underestimation of how truly cold this airmass was. 850mb temps were a couple degrees Celsius cooler than models had projected them to be. Soon, areas of western New York away from the lake began to mix with graupel and change over to all snow by 2pm. Buffalo airport began to change over to snow around 3pm and snow eventually started falling right to the shores of Lake Erie. A very odd confluence of events started taking shape.

Special upper air soundings from Buffalo showed a dramatically cooling 3,000-6,000’ layer indicating a dynamically cooling atmosphere typical of ‘top down’ snow events. Additionally, inversion heights were off the scale, over 20,000’ and nearly double all previous known events. By 3pm the National Lightning Detection Network (NLDN) noted several cloud to ground lightning strikes within the developing lake band, indicative of frozen precipitation. Due to the unidirectional surface-700mb wind flow, extreme lake-induced instability and incredible inversion heights, as the band developed and intensified the extreme upward vertical motion over the lake required an equally strong inflow of air in the low-levels of the atmosphere. This was the wild card. The air at low-levels was abnormally dry, which aided in evaporative cooling of the column and likely the final factor leading to a complete changeover to snow, despite a lake temperature more than 30°F above freezing!

The snowfall in western New York came in two stages. The first stage resulted in a very heavy wet snow that only accumulated 2-6” during the afternoon and early evening hours. In most locales this initial snowfall melted on contact with the warm ground early on, then later in the afternoon started to coat trees and elevated surfaces. It wasn’t until the sun set that the wet snow began to add up and due to its high moisture content, just two inches was enough to start tree damage. What would follow during the overnight hours was truly one of the more remarkable weather events the Buffalo-metro area would ever see.

As night fell and the atmosphere cooled further, the lake-effect band intensified. Snow rates picked up and snow:water ratios rose from 6:1 to 12:1. For about 12 hours the band remained stationary, producing heavy lake-effect thundersnow over the Buffalo-metro area and points towards the northeast extending to the southwest suburbs of Rochester. During the time 12-18 additional inches of snow fall, resulting in a crippling snowstorm. Most trees were still in full leaf and simply couldn’t handle the weight of 1-2 feet of snow. Tens of thousands of trees fell during this storm, knocking out power to over 400,000 residents. The tree damage was exacerbated by abnormally wet weather during the month of September, amounting to 6.95” at the Buffalo airport. Some locations remained without power for up to two weeks due to the widespread damage inflicted by the heavy wet snow. The Buffalo Airport reported a 24-hour snowfall total of 22.6”, which would end up being the city’s 6th largest 24-hour snowfall total, no matter what time of year.

This event will go down in the record books as the earliest lake-effect snowfall of such intensity on record. Looking back through history no other event on record produces as much snow as early as this event. There have been instances of snow falling earlier in the season but those events don’t compare in regard to the amount of snow that actually fell. There is one event where snowfall amounts were similar, but this occurred a week later in the year, on October 19-20th, 1930.

Other notable early-season lake-effect snow events are as follows:

September 29th, 1895 – An unusually strong low pressure moving from Montana to the Great Lakes region tapped into an unseasonably cold airmass over the Canadian Prairies. This cold air was then transported over the lakes resulting in an early season snowfall for much of the region. Buffalo saw up to 6” of snow with snow being reported as far south as Philadelphia! The arrival of this system was anticipated up to 24 hours in advance by telegraph from the Chicago Weather Bureau with a forecast for gales on the Great Lakes, which ended up being a fairly accurate forecast. What took folks by surprise was the snow that accompanied the high winds.

October 10th, 1906 – Once again, a very strong cold front connected to a gale center over Ontario swept over the Great Lakes and Northeast, delivering an unseasonably cold airmass on strong west winds. Snowfall from this storm piled up over a foot in the southern suburbs of Buffalo, causing similar damage to that of the October 12-13, 2006 event. However, the bulk of the snowfall remained south of the city, unlike the 2006 event where the entire metro area was pummeled. Snow was reported as far south as eastern Kentucky, resulting in the earliest snowfall on record for several weather bureaus located in the state. Additionally, killing frosts covered a wide area of the Ohio and Tennessee Valleys.

October 12-13th, 1909 – An early season snowstorm moved from the Northern Plains to the Upper Midwest, depositing 10-22 inches of heavy wet snow to the northwest of the low track across Minnesota, northern Wisconsin and Upper Michigan. As the low pressure pulled into Canada cold west to northwest winds behind the low pressure activated an early-season lake-effect snow event. Generally 2-4” of snow fell downwind of the lakes with several areas picking up as much as a foot of snow. Buffalo, NY recorded 6” of snow by the time it tapered off and killing frosts covered much of the Northeast in the days following.

October 18-19th, 1930 – Similar to the 1906 and 2006 events, one to two feet of snow fell on the Buffalo-metro area downing trees and power lines. Now in the age of the automobile and fast-paced commerce, the snowstorm had devastating effects on the local infrastructure and transport of goods. Many vehicles were stranded by the heavy wet snow, which made roads impassable.

References and further reading.

Bigelow, F.H., 1895: AREAS OF HIGH AND LOW PRESSURE. Mon. Wea. Rev., 23, 325–329. - http://docs.lib.noaa.gov/rescue/mwr/023/mwr-023-09-0325d.pdf

Hamilton, Robert S., Zaff, David and Niziol, Thomas, 2006: “A catastrophic lake-effect snowstorm over Buffalo, NY October 12-13, 2006” – http://ams.confex.com/ams/pdfpapers/124750.pdf

GARRIOTT, E.B., 1906: FORECASTS AND WARNINGS. Mon. Wea. Rev., 34, 478–481. - http://docs.lib.noaa.gov/rescue/mwr/034/mwr-034-10-0478.pdf

COX, H.J., 1909: DISTRICT No. 4, LAKE REGION. Mon. Wea. Rev., 37, 734–741. - http://docs.lib.noaa.gov/rescue/mwr/037/mwr-037-10-0734.pdf

BENNETT, M.C., 1930: THE WEATHER ELEMENTS. Mon. Wea. Rev., 58, 427–428. - http://docs.lib.noaa.gov/rescue/mwr/058/mwr-058-10-0427.pdf







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


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Radar: Northeast Region Loop

NE radar
Fig.2 - Radar loop of the Northeast region. Courtesy of Weather Underground.


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Local SST's

Northeast SST's
Fig.3 Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


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Updated: 5:17 AM GMT on October 06, 2009

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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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