Tuesday Night-Wednesday January 11-12, 2011
Major Nor'easter: Significant Snow Storm

A monster "Bomb" Nor'easter exploded south of Long Island during the pre-dawn hours on Wednesday January 12 unleashing bands of tremendous snowfall across much of southern and central New England while "Clipping" eastern New York with a moderately heavy snowfall, through Wednesday afternoon.

At midnight, the storm's central pressure was approximately 1003mb while it was located off the mid Atlantic coast. By noon Wednesday the system had transformed into a tightly wound compact powerful storm located near Cape Cod with a central pressure of 984mb. Three to four inch per hour snowfall rates quickly developed in the storm's exploding snow shield during the pre-dawn hours on Wednesday as the storm rapidly strengthened with the western most intense snow band pushing into eastern Bennington, Berkshire, and Litchfield counties. Several hours of blinding snowfall in western, southern, and central New England yielded snowfall totals by midday of 20"-25" on average. It's not often that the right ingredients come together to build a storm strong enough and track it close enough to the coast to produce so much snow in such a short period of time, a period of approximately ten to fifteen hours. Recent similar storms, which tracked further west producing similar amounts of snow, but throughout eastern New York, include the Valentine's day Nor'easter in 2007 and the Christmas Nor'easter in 2002. (Storm write-ups on both of those events are included in this climate and storm summary database.)

Although on the western edge of this Nor'easter, moderate to locally heavy snow accumulated across much of eastern New York, aided by a high snow to water ratio due to the cold air in place with surface temperatures in the teens to lower 20s. The ratio of snow to water was approximately 17:1 (17" of snow to 1" of liquid equivalent) which created a very light and fluffy powdery snow. The combination of snowfall directly linked to the passing storm and a period of more localized terrain enhanced snow which flared up along a surface low pressure trough late Wednesday afternoon and Wednesday evening in especially the Mohawk and Schoharie Valleys-Capital Region, lead to significant snowfall accumulations of 10"-15" in the Hudson valley. A total of 12.8" of snow fell at the Albany National Weather Service office in the CESTM building on Fuller Road in Albany on the 12th setting a 24 hour snowfall record for the day. Lighter accumulations of snow, but still considerable, of 6"-10" on average occurred in most areas west of the Hudson river valley with the event. This was a fast moving storm with the bulk of the snow accumulation occurring within a twelve hour period from midnight to noon on the 12th.

Considerable terrain enhancement during the main storm occurred in the higher elevations of Berkshire and Bennington counties to push snow totals at our two high elevation WxNet 6 spotters sites on top of Woodford, MT, VT in Bennington County to 35.0" and to 40.5" on top of the mountain in Savoy, MA, Berkshire County, both 2000' + elevation locations. In Woodford, approximately 25" of snow fell from the main storm, with approximately 35" of snow @ Savoy, MA. The additional accumulations at these locations came from upslope induced snowfall which continued well into Wednesday night and early Thursday morning the 13th, after the main storm had moved east.

WeatherNet 6 Snowfall Distribution Observation for the January 11-12, 2011 Major Nor'easter

January 11-12, 2011 Snowfall Distribution 

Set Up:
This storm formed out of a classic dual northern-southern branch large scale jet stream structure. The northern jet delivered an energetic storm which moved from the west coast across the central part of the country into the Ohio valley and western Pennsylvania by Tuesday evening producing generally light to moderate snowfall along its track. The southern branch storm produced widespread heavy snow and ice on its trek across the deep south with major wintry impacts from north Texas through Alabama, Georgia, and up through the Carolinas and Virginia through Tuesday evening.

The two system essentially merged into one as the energy from the Ohio valley trough made its way to the coast. Strong divergent flow aloft with the left front quadrant of a powerful 140 knot upper level jet stream traveling under and east of the main upper air trough, as well as a strong temperature gradient between the land, where abundant cold air was in place, and the warmer ocean, produced the classic set of ingredients for a new coastal storm to develop and rapidly intensify. Favorable mid level temperatures in the region of maximum atmospheric lift supported optimal dendritic snow crystal growth as well as a track hugging Long Island to Cape Cod during the period of maximum intensification, lead to a storm that would produce exceptionally heavy snow from Connecticut through Massachusetts, Rhode Island eastern Vermont and New Hampshire with near hurricane force wind gusts in mostly rain on Cape Cod and the Islands. (Note: A light NNE wind occurred over eastern New York and western New England through the duration of the storm.)

Snow began over eastern New York and western New England between 10pm Tuesday January 11 and 1am Wednesday January 12. This first wave originated from the weakening storm over northwest Pennsylvania and packed a punch with briefly heavy snowfall rates of about 1"/hour. Snowfall rates backed off a bit until after 3am when snow from the now rapidly developing coastal storm backed into the region. Snowfall rates again picked up, especially in the Hudson valley to 1"-2" per hour, with 3"-4" per hour snowfall rates in western New England. By noon Wednesday, much of the snow accumulation throughout the region had occurred, with snow generally ending in most areas in New York between noon and 2pm. Light to occasionally moderate snow, partially enhanced by the local terrain, lingered in Washington County, as well as in Vermont and Berkshire County well into the afternoon.

Late Afternoon/Evening Bonus Snow
The post storm environment over the local area Wednesday afternoon and night was one of plentiful and deep moisture in the atmosphere with several smaller scale weather features both aloft and at the surface present. These features came together to produce some additional snowfall for parts of the Mohawk and Schoharie valleys, Capital Region, southern Vermont and Berkshire county. The key feature appeared to be a surface low pressure trough which extended west through the Capital Region and Mohawk valley from the departing Nor'easter which aided in enhancing local convergence that helped to produce additional bursts of moderate snow. There was also some evidence of moisture channeling along the trough from Lake Ontario, which may have aided in supporting the batch of snow in the Mohawk and Schoharie Valleys which yielded on average an additional 1"-3" of snow between 4pm and 9pm. In the immediate Capital Region, and especially across southern Saratoga and Rensselaer counties, a batch of moderate to at times heavy snow produced locally 3"-6" of additional snowfall between 3pm and 10pm as a north to slightly northwest wind produced a favorable upslope condition, especially in Rensselaer County, and also enhanced the convergence along the surface trough to support the snow. There was some evidence of moisture channeling from Lake Champlain with may have aided in supporting this small region of enhanced snowfall. This "Bonus Snow Zone", however, was quite localized as indicated by a tight horizontal accumulated snowfall gradient of six to seven inches from the part of Colonie close to the Niskayuna border where 9" of storm total snowfall was reported to have fallen by our WeatherNet 6 spotter in Colonie, vs 14" to 16" in nearby Latham. The surface trough and subsequent convergence broke down around midnight as the wind shifted more to the west-northwest and increased in response to the deepening storm in the Gulf of Maine, along with some drying in the atmosphere, to bring an end to the accumulating snow in the capital Region. Upslope snow, however, did persist in the west to northwest flow in the higher elevations of Bennington and Berkshire counties through early Thursday morning January 13, boosting snow totals in the mountains to between an incredible 30" to 40" for the event.

WeatherNet Storm Total Snowfall Reports for January 11-12, 2011
(Note: The reports for Woodford, VT and Savoy, MA include snow that fell between midnight and daybreak on January 13)

Town County Snowfall Report Town County Snowfall Report
Canaan, CT Litchfield 27.00" Sharon, CT Litchfield 24.8"
Pittsfield, MA Berkshire 23.0" Lanesborough, MA Berkshire 22.0"
Alford, MA Berkshire 21.0" Savoy, MA Berkshire 40.5"
Clarksburg, MA Berkshire 26.0"      
Latham Albany 14.0" to 16.3" Cohoes Albany 15.5" to 16.0"
Knox Albany 8.7" Colonie Albany 9.0"
Coeymans Hollow Albany 9.3" East Berne Albany 7.2"
Berne Albany 7.0" South Berne Albany 10.0"
Albany (NWS) Albany
Potter Hollow Albany 7.5"
Watervliet Albany 16.0" Medusa Albany 8.0"
Voorheesville Albany 10.0" Feura Bush Albany 8.3"
Taghkanic Columbia 12.9" Ancramdale Columbia 13.8" to 14.3"
Chatham Center Columbia 14.5" Livingston Columbia 10.0" to 14.0"
Ghent Columbia 12.5" North Chatham Columbia 18.5"
Hudson Columbia 8.0" Germantown Columbia 11.3"
Arkville Delaware 7.3" Margaretville Delaware 7.0"
Hopewell Junction Dutchess 12.0" Pine Plains Dutchess 12.0"
Broadalbin Fulton 8.3" to 9.0" Northville Fulton 7.0"
Fish House Fulton 7.0" Gloversville Fulton 10.0"
Caroga Lake Fulton 7.5" Johnstown Fulton 8.0"
Perth Fulton 7.5"      
Ashland Greene 9.0" Freehold Greene 8.3"
Halcott Greene 9.0" Maplecrest Greene 8.0"
Elka Park Greene 10.0" Catskill Greene 8.0"
Greenville Greene 6.5" Durham Greene 6.50"
Jewett Greene 8.0" Round Top Greene 9.0"
Lexington Greene 8.1" Athens Greene 8.0"
Indian Lake Hamilton 5.0" Blue Mountain Lake Hamilton 6.3"
Wells Hamilton 6.1" Long Lake Hamilton 6.0"
Speculator Hamilton 4.5"      
Fonda Montgomery 6.3" Amsterdam Montgomery 8.3"
Glen Montgomery 8.5" Stone Ridge Montgomery 7.5"
Hessville Montgomery 6.5" Hagaman Montgomery 10.0"
Oneonta Otsego 6.0" East Worcester Otsego 9.5"
Cherry Valley Otsego 10.0" Worcester Otsego 9.5"
Schaghticoke Rensselaer 11.0" to 12.0" Center Brunswick Rensselaer 14.8"
Stephentown Rensselaer 15.0" to 21.0" Wynantskill Rensselaer 18.0"
Brunswick Rensselaer 13.0" Taborton Rensselaer 19.0"
Mechanicville Saratoga 10.0" Saratoga Springs Saratoga 8.0" to 10.2"
Charlton Saratoga 9.5" Malta Saratoga 10.0"
Clifton Park (Oaks) Saratoga 11.5" Porter Corners Saratoga 11.0"
Edinburg Saratoga 6.5" Wilton Saratoga 10.5"
Gansevoort Saratoga 11.3"      
Scotia Schenectady 9.3"      
Jefferson Schoharie 9.0" Gilboa Schoharie 8.0"
Richmondville Schoharie 10.0" Charlotteville Schoharie 8.8"
Sloansville Schoharie 10.0" Schoharie Schoharie 8.3"
Huntersland Schoharie 8.3" Fulton Schoharie 10.0"
Seward Schoharie 7.5" Summit Schoharie 8.0"
Middleburgh Schoharie 8.3"      
Esopus Ulster 9.5" Saugerties Ulster 9.5"
West Shokan Ulster 8.7" Phoenicia Ulster 8.0"
Marbletown Ulster 9.5" Whiteport Ulster 7.5"
Kerhonkson Ulster 6.8"      
Queensbury Warren 6.5" to 7.5" Lake Luzerne Warren 7.0"
Warrensburg Warren 7.0" Brant Lake Warren 7.0"
Cossayuna Washington 13.0" Kingsbury Washington 8.0"
Salem Washington 10.5" Granville Washington 12.0"
Fort Edward Washington 9.0" to 10.0" Hebron Washington 10.0"
Hudson Falls Washington 6.1"      
Landgrove, VT Bennington 23.5" Woodford, VT Bennington 35.0"
Bennington, VT Bennington 12.0" to 15.0" Danby, Vt Rutland 14.5"
West Rutland, VT Rutland 12.0"