Friday March 2, 2018
Major Nor'easter


Cobleskill, NY, Schoharie County - Part of a Snow Bomb Epicenter
Snow accumulation in excess of 30" - Photograph contributed by Trista Bradt via Facebook


CLICK HERE FOR THE RADAR PAGE - A SERIES OF RADAR IMAGES DETAILING THE STORM'S PROGRESS FROM 10AM - 7PM

Deep snow in Cobleskill, NY, Schoharie County, Friday March 2, 2018

The storm was a snow bomb with an epicenter over Schoharie County. Twenty five to as much as forty inches of concrete consistency snow buried the County in an onslaught of silver dollar to ping bong ball sized snow-flakes falling at rates of three to five inches per hour at times through the day.  Twenty to thirty inches of snow encased the surrounding higher elevations into the Helderbergs in Albany County and the hills in western Schenectady County on south through western Greene and western Ulster counties on west through eastern Otsego and Delaware counties.  And while the entire Catskill Region was ground zero for exceptional snow amounts, heavy accumulations also occurred in the Mohawk valley and Capital Region-Hudson valley with a range of roughly 10”-18” on average with much of that accumulation occurring between midnight and 9am during the first half of the storm.  Amounts across the Adirondacks were lighter ranging from 5”-10” with totals of 3”-6” on average across Vermont and the Berkshires with the exception of elevations of 2000’ and higher in northern Berkshire County and Vermont where 10”-14” fell.

The brunt of the storm occurred from midnight to 6pm with scattered areas of snow persisting through about midnight before it ended everywhere.  At its peak, the system ’s central pressure south of New England dropped into the mid 970 mb range with the storm undergoing a period of rapid intensification where the pressure dropped 24 mb in 24 hours officially classifying it as a bomb.

WeatherNet 6 Snowfall Amount and Distribution Analysis of the March 2, 2018 Major Nor'easter

WeatherNet 6 Observed Snowfall Distribution for the March 2, 2018 Storm

Albany National Weather Service March 2, 2018 Snowfall Analysis

Albany NWS Snowfall Analysis of the March 2, 2018 Event 

THE CHALLENGE OF THE STORM
Often with Nor’easters one of the more significant forecast challenges in the days leading up to the event is storm track, as slight deviations east or west can mean an outcome ranging from no snow, a little snow, or a whole lot of snow.  In this case, however, the most significant uncertainty revolved around a marginal temperature profile from the ground up in the atmosphere which was not easily resolved even within a few hours prior to the onset of the storm.  The temperature margin of error was very small, with a degree or two of warming or cooling in the low and mid-levels meaning the difference between either mainly a rain event or a snow event in the Hudson valley. The colder outcome obviously prevailed which resulted in big snows down to the valley floor despite surface temperatures in and around Albany ranging from 33° to 34° through the duration of the event. (This is why most of the accumulation in the Capital Region-Hudson valley occurred by 10am as significant melting of the snow occurred while it fell during the day with that melted aided by a higher March sun angle.) The snow in the Hudson valley in this case was as close to rain as it could possibly be, without it actually being rain.

HOW THE ATMOSPHERE CAN COOL
The heavy snow scenario that materialized in the Capital Region-Hudson valley likely did so as a result of the diabatic processes of evaporative cooling along with cooling through the process of melting snow as snow falls through the atmospheric column as well as through the adiabatic process of cooling during heavy precipitation through strong vertical ascent.

EVAPORATIVE COOLING
When precipitation falls into and through dry layers in the atmosphere, some of it evaporates as it falls through the column.  For the evaporation to take place, latent heat must be extracted from the atmosphere which subsequently cools it.  In this case, dry air had been filtering into the Northeast on an increasing northerly wind which was observed at the surface with dewpoints falling into the mid and upper 20s during the evening of March 1. 

COOLING THROUGH MELTING

After the onset of precipitation, which begins high in the atmosphere as snow, that snow will melt if it falls through layers in the atmosphere that are above freezing.  In this case, there was a deep layer of just slightly above freezing air in the atmosphere which was observed during the evening of March 1.  The melting process, like the evaporative process, extracts latent heat from the atmosphere which causes it to cool with an equilibrium right at the freezing point, which then supports snow as the predominant precipitation type down to the valley floor, absent of any other mechanism or air movement which might cause the temperature to rise again.

Both of these diabatic processes are generally enhanced during periods of very heavy precipitation where a third adiabatic process, called dynamic cooling, often will also come into play.  In the dynamic cooling process, strong vertical ascent lifts parcels of air which causes those parcels to cool due to less air pressure being exerted on them. 

In cases where the temperatures in the column is either very warm or very cold, the changes that occur in the temperature of the column during storms due to cooling or warming processes are not sufficient to cause any changes in the anticipated precipitation type at the ground.  It’s when the temperatures in the column are very close to freezing, either a couple of degrees above or below, that these diabatic and adiabatic processes become critical with their effect often very difficult to forecast well in advance. In this case, the temperature of the column was close enough to freezing that the adiabatic and diabatic cooling processes that occurred were more than enough to cool the atmosphere over the Capital Region-Hudson valley sufficiently for snow to be the primary precipitation type. In the Catskills, Mohawk valley and the Adirondacks, the temperature of the column was observed to be colder, a little below freezing at the onset of the storm with the diabatic and adiabatic processes cooling if further, which was expected and why the snowfall forecast was of much higher confidence in those regions and generally verified nicely.

WHY THE SNOW ACCUMULATION WAS SO HEAVY
Several factors contributed to the excessive amounts of snow which occurred in this event.  These factors included a strong slow-moving surface cyclone and its associated deep feed of sub-tropical moisture into the region.  This was evident by storm total quantitative precipitation amounts of greater than 3” in the Catskills with 1”-2” across much of the remainder of the region.  Further, the effect of terrain played a critical role as the deep moisture was slammed up against the east facing slopes of the Catskills which further increased the ascent enhancing snowfall rates, in a process of upslope flow.  The slow motion of the storm also supported a prolonged period of very heavy snow through the day which was further enhanced by a significantly diffluent flow aloft north of the mid-level storm center.  Additionally, a quasi-stationary mesoscale excessive snow band set-up west of the Hudson valley extending from northwest Saratoga County through eastern Fulton, eastern Montgomery, western Schenectady, western Albany, Schoharie, eastern Otsego and eastern Delaware counties, where the heaviest snow accumulations were observed, due to slantwise instabilities in the mid-levels of the atmosphere as the strong flow around the cyclone was forced to ascend over a stationary mid-level frontal zone. (This was the same heavy snow zone which produced the heavy snowfall between midnight and 10am in the Capital Region-Hudson valley as it moved west of the valley and then stalled.) And Lastly, temperatures in the mid-levels of the atmosphere in the vicinity of this frontal zone were optimal for snow crystal growth, around -15° degrees Celsius, which created large dense snowflakes which effectively and rapidly accumulated.

OTHER FACTORS THAT AFFECTED THE AREA SNOWFALL
Western New England
This issue here was a question of how far west the intense storm circulation would be able to rotate a layer of mid-level warm air, which would have the next effect of reducing snowfall totals due to either a finer snow developing or more in the way of mixing.  As it turned out, some mid-level warming did occur in this region which accounted for the lower snowfall totals that were observed.

Western Vermont, eastern Washington and northeast Rensselaer counties
Strong mid-level easterly winds occurred around the storm center which became more northeast to north at the surface through the day.  The northeast flow effectively downsloped along the west slopes of the Vermont Green mountains to create a shadow across western Rutland and western Bennington counties as well as across eastern Washington and northeast Rensselaer counties.  A downslope flow warms and dries through compression and has the net effect of reducing precipitation amounts. This process accounted for the zone of lower snow totals observed in this region. The downslope effect was muted in the Capital Region-Hudson valley as the wind shifted from ENE to north rapidly which limited any impact.

Saugerties-Kingston Area
Rain was largely observed in these areas with a period of rain reported in Catskill right as well along the river.  It’s likely that the Hudson river played a role in a heat transfer from the water to the atmosphere right in the vicinity of the water supporting an atmosphere warm enough for rain. Temperatures in this area were observed to range from 35°-38° during the storm.

IMPACTS
The heavy wet snow coupled with a gusty NNE wind, which ranged from 25-35 mph in gusts on average to locally 40-45 mph across higher elevations, especially over the southern half of the region, brought down trees and power lines resulting in power outages throughout the region.  National Grid reported approximately 50,000 outages by the early afternoon as a result of the storm.

Travel, however, in the Capital Region and Hudson valley was not significantly impacted after sunrise up as the much higher March sun angle coupled with temperatures a little above freezing through the storm allowed for well traveled main roads to remain largely wet. The travel situation, however, was much more difficult west of the Hudson valley where the very heavy snowfall rates were sufficient to overcome the marginal surface temperatures to produce snow covered roads and hazardous travel.  A blizzard warning was even hoisted by the Binghamton NWS around 3pm for Otsego and Delaware counties to account for the dangerous conditions due to heavy snow, wind, and low visibility.

National Weather Service Winter Storm Advisories for Friday March 2, 2018

National Weather Service Storm Advisory Board 

WeatherNet Storm Total Snowfall Reports Friday, March 2, 2018

(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 11" Becket, MA Berkshire 4"
Great Barrington, MA* Berkshire 5" Pittsfield, MA* Berkshire 4"
           
Knox Albany 25" Glenmont Albany 15.5"
Albany (Official) Albany 11.9" Delmar Albany 10"
Coeymans Hollow Albany 14.5" Colonie Albany 11.5"
Altamont* Albany 26" Westerlo* Albany 34"
           
Ancramdale Columbia 9.5" Taghkanic Columbia 16.7"
Austerlitz Columbia 11.5" Kinderhook* Columbia 15"
Chatham* Columbia 15" Livingston* Columbia 12"
Valatie* Columbia 13"      
           
Margaretville Delaware 33" Franklin Delaware 21"
Davenport Center Delaware 27" Arkville Delaware 40"
           
Red Hook Dutchess 4" Poughkeepsie Dutchess 5.7"
           
Northville Fulton 15.5" Perth Fulton 13.5"
Broadalbin Fulton 15" Fish House Fulton 15.5"
Gloversville Fulton 12" Oppenheim Fulton 12" to 18"
Mayfield* Fulton 18"      
           
Norton Hill Greene 21" South Cairo Greene 15"
Halcott Greene 35" Catskill Greene 6.3"
Greenville Greene 21" West Kill Greene 26"
Hunter* Greene 28" Windham* Greene 26"
           
Wells Hamilton 6.5" Piseco Hamilton 8"
Indian Lake Hamilton 6.5"      
           
Amsterdam Montgomery 14.8" Fonda Montgomery 16"
Glen Montgomery 28" Florida Montgomery 29.8"
Palatine Bridge Montgomery 19" Tribes Hill Montgomery 13.8"
Hessville Montgomery 15.9"      
           
Oneonta Otsego 16" Worcester Otsego 22"
East Worcester Otsego 31.5" Cherry Valley Otsego 26"
           
Petersburg Rensselaer 7.5" Center Brunswick Rensselaer 15.3"
Speigletown Rensselaer 12" Averill Park* Rensselaer 16.1"
Troy* Rensselaer 15.9" Schodack* Rensselaer 14"
Valley Falls* Rensselaer 11"      
           
Ballston Spa Saratoga 10.5" Lake Desolation Saratoga 15.4"
Edinburg Saratoga 13.3" Charlton Saratoga 10"
Malta Saratoga 10" Saratoga Springs Saratoga 12.1"
Clifton Park* Saratoga 13.6" Halfmoon* Saratoga 8"
           
Delanson Schenectady 24" Rotterdam Schenectady 13"
Glenville Schenectady 9" Duanesburg Schenectady 27"
           
Middleburgh Schoharie 23" Schoharie Schoharie 35.3"
Jefferson Schoharie 37" Charlotteville Schoharie 31"
Richmondville Schoharie 40"      
           
Kingston Ulster 1.69" RAIN Whiteport Ulster 1.69" RAIN
Ulster Park Ulster 1.30" RAIN 6 M NW Phoenicia* Ulster 20"
           
Warrensburg Warren 11" Queensbury Warren 8.5"
Lake Luzerne* Warren 13"      
           
Hartford Washington 9" Hudson Falls Washington 5.9"
Hebron* Washington 7" WhiteHall* Washington 6"
Fort Edward* Washington 6" Salem* Washington 5"
Cambridge* Washington 5"      
           
Woodford, VT Bennington 14" Manchester, VT Bennington 6.8"
West Arlington, VT Bennington 5" Landgrove, VT Bennington 13.5"
Danby, VT Rutland 8.9" West Rutland, VT Rutland 6"
Pownal, VT* Bennington 8" Dorset, VT* Bennington 5"

GOES East Satellite View of the Storm Saturday Morning, March 3, 2018

Satellite view of the storm on Saturday March 3, 2018 - 10am EST

Photograph contributed by Trista Bradt via Facebook - Digging out during the storm in Cobleskill, Schoharie County, Friday March 2, 2018

Digging Out During the storm in Cobleskill, Schoharie County, Friday March 2, 2018

Photograph Contributed by WeatherNet 6 Spotter Jim Meehan - Chatham Columbia County, up to 12" of heavy wet snow weighing down trees, numerous power outages reported - Friday March 2, 2018

Late morning surface analysis, Tuesday March 14, 2017 

Photograph Contributed via Facebook by Ginny Rella Ogno - Summit, Schoharie County (approximately at a 2000' elevation,) at 11:15 am Friday March 2, 2018. The storm ultimately dumped around 40" of snow on the mountain at Summit.

Deep snow at Summit, NY Friday morning March 2, 2018


 Photograph Contributed via facebook by Sue Blodgett Niemiaski - Esperance, Schoharie County
Friday, March 2, 2018


Moderate snow in downtown Schenectady on Thursday February 9, 2017


Photograph Contributed via facebook by Heather Carley Wells
Very deep snow in Stamford, eastern Delaware County - Friday March 2, 2018

Deep snow in Stamford, eastern Delaware County, Friday March 2, 2018