Nor'easter - Significant Snow Storm
Monday-Tuesday February 1-2, 2021

8pm Surface Analysis Monday February 1, 2021
(Strong 994mb Low Pressure System (Nor'easter) south of Long Island)

Nor'easter: A strong extra-tropical cyclone along the upper Atlantic, New England or southeast Canada coasts. The term is derived from the direction with which the wind in advance of the storm blows, from the northeast.

Surface map around 8pm Monday February 1, 2021 showing the position of the Nor'easter well south of Long Island 

From two inches to two feet, that was the spread in snowfall accumulations between Glens Falls and the Catskills with this snow storm where local terrain played a key role in how and where snow both piled up the most as well as where it also piled up the least.

This storm developed and tracked far enough south to put the local area, especially from the Capital Region and Vermont on north, in the far northwest quadrant of the snow shield and somewhat removed from the best upper level lifting mechanisms associated with the system. As such, much of the storm's ability to generate snow locally came from a deep layered strong easterly flow of moisture laden air (a cold conveyor belt) in excess of 50 knots in the lowest few thousand feet of the atmosphere. In these types of cases, the local terrain becomes an even more important player than typical in both enhancing and decreasing precipitation coverage and intensity through the wind's interaction with the mountains in a process called orographic lift.

The conceptual physical process of orographic lift is pretty basic. When a flow of moisture rich air encounters a mountain, that air is forced to rise (upslope flow) causing it to cool which forces the water vapor in the air mass to condense into either water droplets or snow crystals, depending on temperature, which subsequently leads to an enhanced area of precipitation along the windward slope of the mountain. Both magnitude and duration of the flow ultimately governs how much precipitation falls. Conversely, as the air continues along its path and flows down the leeward slope of the mountain (downslope flow,) it's compressed causing it to warm and dry which leads to a precipitation minimum or a shadow effect.

NOAA/NWS Orographic Lift Explainer Graphic

The effects of upslope and downslope flow play out locally all of the time here due to the unique configuration of the east-west Mohawk valley intersecting with the north-south Hudson valley bounded by the Adirondacks to the north, Catskills to the southwest, Taconics, Greens, and Berkshires to the east, which allow for both precipitation and temperature impacts in many wind direction scenarios. In the case of this storm, the impacts of both enhancing and diminishing snowfall over the various parts of our region was maximized due to the deep layered strong easterly flow intersecting the southern Green mountains, Berkshires and eastern Catskills perpendicularly. The orographic impacts, however, in other storms can be significantly muted when there are other players in the atmosphere contributing to precipitation generation or in cases when the wind does not line up as well with the mountains or is not particularly strong. In other words, every storm has its own unique character with the end results specific to each individual event.

Storm Evolution and Impacts
An initial round of light snow, generated from a weakening primary low pressure system moving through the Ohio valley, put down 1"-3" in the Catskills, mid Hudson valley to southern Berkshire and Litchfield counties between midnight and 8am prior to the snow from the coastal storm getting underway. Cold dry air over the region, courtesy of a strong high pressure system over southern Canada, coupled with the developing strong easterly flow over the top of the nor'easter resulted in considerable downslope flow through the day which subsequently dried the air from especially the Mohawk valley, Capital Region and Vermont on north. The process acted to slow the northward progress of the snow shield across the region. While snow increased in coverage and intensity across the Catskills, mid Hudson valley, Berkshire and Litchfield counties from the late morning through the mid afternoon, it did not begin in the Capital Region until the late afternoon and not in the Mohawk valley, Saratoga region and Vermont until the evening with the Adirondacks dry until after 10 to 11pm.

Orographic lift was important in greatly enhancing snowfall across the eastern Catskills, the Litchfield hills and the east facing slopes of the southern Green mountains and the Berkshires, it was not the only process at play. This region, being closer to the slow moving nor'easter, was also impacted by strong mesoscale banding caused by strong lift over an elevated warm front, or frontogenesis region, that first set up across eastern Pennsylvania, northern New Jersey, through New York City and Long Island during the morning, where pockets of snow accumulations ranged from an extreme 30"-35" in especially northern New Jersey. This intense snow band gradually pushed north into Dutchess and Litchfield counties and into the eastern Catskills by mid afternoon in response to the coastal storm center moving north. Ultimately the banding lifted north through the Berkshires with the heaviest snow stopping just short of the Capital Region through midnight. Snowfall rates in the zone shade in purple on the map below ranged from 1"-3" per hour at times from the mid afternoon through midnight with smaller more transient bands of snowfall with rates from 1/2" to 1"/hour lifting to the west and north through the Mohawk valley and Capital Region into early Tuesday February 2.

Storm Prediction Center Mesoscale Heavy Snow Outline

Albany Doppler Radar Image around 3:30pm Monday February 1, 2021 showing the narrow intense snow band across Dutchess and Litchfield County, CT. The yellow shading on the radar image indicated blinding snowfall rates as high as 3"/hour.

Albany Doppler Radar Base Reflectivity Image around 3:30pm Monday February 1, 2021 

Albany Doppler Radar Image around 6:00pm Monday February 1, 2021. The intense snow band stretched from the eastern Catskills through northern Dutchess, southeast Columbia, northwest Litchfield and southern Berkshire counties at this time. The zone of heavy snow only slowly moved to the north northwest through the evening. Snowfall rates of 1"-2" and briefly up to 3"/hour continued with the band at this time.

Albany Doppler Radar Base Reflectivity Image around 6:00pm Monday February 1, 2021 

Albany Doppler Radar Image around 9:30pm Monday February 1, 2021. Intense snowfall with rates from 1"-3"/hour extended from southern Bennington and northern Berkshire counties south and west through northern Columbia, eastern Greene and western Ulster counties at this time. Also noteworthy, the radar echo minimum which stretched from near Manchester, VT southwest through southern Washington, northern Rensselaer, southern Saratoga and northern Albany counties. This radar reflectivity minimum was the result of the significant downslope flow coming over the higher terrain in Vermont effectively drying the air which stopped the northward progress of the eastern end of the snow band by causing it to weaken and break up. Simultaneously, the upslope flow over the eastern Catskills acted to enhance the southwest part of the band allowing it to continue well into the night. This lead to the excessive snowfall accumulations of around two feet in the mountains in Greene County.

Albany Doppler Radar Base Reflectivity Image around 9:30pm Monday February 1, 2021 

Albany Doppler Radar Image around 11:30pm Monday February 1, 2021. This snapshot illustrates the strong downslope flow shadowing that was occurring at this time across northern Saratoga, Warren and Washington counties versus the very heavy snow falling at this time due to the strong upslope flow throughout the Catskills where some 2"+/hour rates in eastern Delaware and Schoharie counties were occurring at this time.

Albany Doppler Radar Base Reflectivity Image around 11:30pm Monday February 1, 2021 

Close-Up Albany Doppler Radar Image around 11:30pm Monday February 1, 2021 showing how the downslope snow shadow appeared on radar with a hole in the returns over especially Washington and Rutland counties at this time.

Albany Doppler Radar Base Reflectivity Image around 11:30pm Monday February 1, 2021 

By 11pm snowfall amounts ranged from 10"-20" throughout the eastern Catskills, mid Hudson valley, Berkshires and Litchfield County, CT with lesser amounts of 2"-4" in the Capital Region and even less than that in the Mohawk valley and points north. Ultimately the storm reached its peak intensity during the pre-dawn hours on Tuesday February 2 then began to gradually weaken while only slowly creeping along well south of the southern New England coast. Strong blocking east of the system allowed it to linger in fact through Wednesday February 3, although the bulk of the snow accumulation locally had occurred by mid morning on the 2nd with lighter more intermittent snow through the remainder of that day. While the brunt of the snow accumulation across the southern half of the region and throughout the Berkshires occurred on the Monday the 1st, most of the snow that accumulated in this storm across the Adirondacks occurred on Tuesday the 2nd in what was a long duration drawn out process.

A general 6" to 10" of snow ultimately fell throughout the western Catskills (somewhat shadowed,) Mohawk valley, Adirondacks and into the Capital Region with a wide shadow zone across northern Saratoga, Warren, Washington and eastern western Rutland counties where 3"-6" fell on average with a region from near Saratoga Springs to Glens Falls to Whitehall with only 2"-4" measured. (This shadow zone was wider and extended farther west than is typically observed, likely because the intensity of the easterly flow was quite strong coupled with this region being displaced farther from the storm center and its lifting mechanisms. Also, dry air from the Canadian high pressure system to the north held on the longest in this area further contributing to the much lighter snowfall.)

In the end the jackpot areas for snow were across the eastern eastern Catskills, Litchfield County, CT and the east facing slopes of the southern Green mountains and Berkshires where 15"-20" fell with locally up to two feet in the hills in southern Schoharie and Greene counties. Widespread 10"-15" snowfalls also occurred in the mid Hudson valley where the mesoscale snow band effectively compensated for the downslope flow in especially Columbia, eastern Ulster, and Dutchess counties.

WeatherNet 6 February 1-2, 2021 Observed Snowfall and Distribution Map

WeatherNet 6 observed snowfall amount and distribution Map - February 1-2, 2021 

WeatherNet Storm Total Snowfall Reports Monday-Tuesday February 1-2, 2021
(Note: Reports with an * notation are NWS relayed and not WxNet 6 spotter observations)

Town County Snowfall Report Town County Snowfall Report
Savoy, MA Berkshire 16.8" Lanesborough, MA Berkshire 12.0"
Becket, MA Berkshire 15.5" Pittsfield, MA Berkshire 10.0"
Stockbridge, MA Berkshire 11.5" Clarksburg, MA Berkshire 8.5"
Canaan, CT Litchfield 13.0"      
Albany (ASOS)* Albany 6.9" Delmar Albany 8.0" to 9.0"
Rensselaerville Albany 18.0" Berne Albany 23.0"
Knox Albany 11.2" Albany (NWS)* Albany 10.0"
Loudonville Albany 8.0" Colonie Albany 6.5"
Cohoes Albany 6.5" Glenmont Albany 14.0"
Livingston Columbia 12.0" to 14.0" Germantown Columbia 12.0"
Spencertown Columbia 11.5" Chatham* Columbia 6.4"
Austerlitz Columbia 11.0" Valatie* Columbia 9.3"
Taghkanic Columbia 12.8" Kinderhook* Columbia 9.0"
Ancramdale Columbia 9.9"      
Margaretville Delaware 18.0" Arkville Delaware 22.0"
Denver Delaware 15.0" Roxbury Delaware 21.7"
Red Hook Dutchess 18.0" LaGrange* Dutchess 21.5"
Beacon* Dutchess 24.0" Pine Plains* Dutchess 17.0"
Millbrook* Dutchess 18.5"      
Perth Fulton 6.5" Gloversville* Fulton 8.4"
Northville* Fulton 7.4" Broadalbin Fulton 5.0"
Catskill Greene 12.5" to 14.4" Greenville Greene 18.0"
Cairo Greene 15.0" to 19.0" Prattsville Greene 20.0"
Haines Falls Greene 22.0" South Cairo Greene 15.0"
East Jewett* Greene 23.0" Lexington* Greene 18.3"
Wells Hamilton 9.8" Piseco Hamilton 8.8"
Indian Lake Hamilton 7.0"      
Florida Montgomery 8.3" Palatine Bridge Montgomery 9.5"
Amsterdam Montgomery 8.5" Glen Montgomery 8.5"
Fonda Montgomery 7.5" Tribes Hill Montgomery 5.8"
Oneonta Otsego 10.5" East Worcester Otsego 11.0"
Cherry Valley Otsego 12.0"      
Center Brunswick Rensselaer 7.3" Petersburg Rensselaer 7.0"
Averill Park* Rensselaer 10.0" Schaghticoke Rensselaer 4.0"
North Greenbush Rensselaer 8.5" Speigletown Rensselaer 6.0"
Troy* Rensselaer 7.5" Hoosick Falls Rensselaer 3.2"
Saratoga Springs Saratoga 3.5" Lake Desolation Saratoga 7.2"
Malta Saratoga 6.0" Ballston Spa Saratoga 7.0"
Clifton Park (Oaks) Saratoga 7.4" Clifton Park Saratoga 6.3"
Charlton Saratoga 7.0" Galway Saratoga 6.0"
Providence* Saratoga 3.8" Wilton* Saratoga 3.2"
Rotterdam Schenectady 7.2" to 10.0" Delanson Schenectady 9.5" to 13.0"
Duanesburg Schenectady 8.0" to 17.0" Glenville Schenectady 9.0"
Schenectady GE Plot* Schenectady 8.1" Niskayuna* Schenectady 7.5"
Conesville Schoharie 22.0" Jefferson Schoharie 11.0" to 17.0"
Richmondville Schoharie 18.0" Charlotteville Schoharie 16.8"
Warnerville Schoharie 12.5" Huntersland Schoharie 21.0"
Middleburgh Schoharie 18.0"      
Olivebridge Ulster 14.0" Phoenicia Ulster 18.1"
Esopus Ulster 14.0" Saugerties* Ulster 25.7"
Kingston Ulster 18.0"      
Warrensburg* Warren 5.5" Johnsburg* Warren 7.3"
North Creek* Warren 5.5" Lake Luzerne* Warren 3.5"
Lake George* Warren 2.0"      
Greenwich Washington 6.0" Granville Washington 3.8"
Granville Washington 4.8" Hartford Washington 4.0"
Whitehall Washington 2.5" Cossayuna Washington 3.0"
Woodford, VT Bennington 17.0" Arlington, VT Bennington 13.0"
Landgrove, VT Bennington 15.2" Manchester, VT* Washington 11.1"
North Bennington, VT Bennington 7.0" Danby, VT Rutland 7.0"
Rutland, VT* Rutland 5.8" Wallingford, VT* Rutland 6.5"

Albany NWS Snowfall Analysis February 1-2, 2021

Albany National Weather Service Snowfall Analysis February 1-2, 2021 

A Deep Snowfall in Kingston, NY - Ulster County - 18 Inches: Tuesday February 2, 2021: Photograph contributed by CBS6 viewer Heather Stock

Deep snow in Kingston, NY - Ulster County Tuesday February 2, 2021