Long Duration Nor 'easter - Heavy Mixed Precip./Snow Storm
December 9-11, 2014

This was a monumentally complex and challenging storm to forecast due to near freezing temperature profiles from the surface up through the mid levels of the atmosphere which made the call on precipitation types and duration of any one type of precipitation difficult to forecast in what was known would be a long duration storm as jet stream blocking to the region's northeast was not going to allow any area of low pressure to rapidly move away. Typically in cases when the temperature profiles are marginal for favoring any one precipitation type over another, small scale factors such as terrain elevation, time of day (day vs. night) and precipitation intensity, can swing the precipitation type from rain to freezing rain and sleet to snow and back again. And this very scenario is exactly what played out across eastern New York and western New England with the Nor 'easter as it developed and tucked itself in close to the New Jersey coast and only slowly meandered across southeast New England through December 10th.

Photograph Posted to Facebook by: Linda Armour: Thousand Acre Rd. Delanson December 10, 2014
(There were power outages in this area due to the combined ice and heavy snow weighting branches down on power lines)


Heavy snow weighted trees in Delanson, December 10, 2014


Time Line
Tuesday December 9: Phase I
Precipitation broke out primarily as sleet and freezing rain through the early to mid morning with little if any snow observed at the onset. With temperatures in the 20s to around 30° untreated surfaces quickly glazed over resulting in numerous early morning accidents on areas roads. Icy conditions continued into the afternoon with a change to rain in the major valleys, such as the Mohawk and Hudson, during the late morning and early afternoon as well as across most of Berkshire County as surfaces temperatures climbed to just a few degrees above 32°. Glazing of 0.1" was common with a few locations, such as Peru, MA coming in with 0.20" of ice (more the exception than the rule.)

As precipitation intensity increased through the afternoon rain changed to snow in higher elevation locations throughout the Catskills, Vermont, and northern Berkshire County as well as across the Adirondacks (where it was lighter), due to a process called dynamic cooling which causes a reduction in air pressure due to strong lift occurring in the atmosphere. The lift and subsequent reduction in air pressure causes the air aloft to cool. In addition to dynamic cooling, the process of melting snow, which is a process that absorbs latent heat from the atmosphere, caused further cooling. The net result of the combined effects of elevation, the existing borderline temperatures near freezing through the mid levels, dynamic cooling, and the cooling caused by melting snow as it fell through the column, allowed the air to cool sufficiently to support a change to heavy wet snow through the day in higher elevation locations, with the heaviest snowfall in the Catskills, Helderbergs and high elevation locations (1800' and higher) in southern Vermont and northern Berkshire County.

Bright banding on the radar (as shown in the Instant Doppler 6 image below) was observed during the period of dynamic cooling and indicated that snow was in fact melting at lower and lower elevations through the afternoon. (Bright banding is a radar signature which indicates melting snow or sleet as it's falling from the clouds to the ground. Melting ice is highly reflective to a radar and shows up as a bright yellow, orange, or red, which could otherwise suggest heavy precipitation to an untrained observer.)

Instant Doppler 6 Image Between 2pm and 2:30pm Tue. Dec. 9, 2014: The bright colors are indicating melting snow and sleet as it was falling through the atmosphere. Ground truth during this period indicated light to moderate rain in the valleys and snow in higher elevation location was falling.


Instant Doppler 6 Radar Image between 2pm and 2:30pm Tuesday December 9, 2014, indicating bright banding

Tuesday Late Afternoon - Evening: Heavy Capital Region Snow Burst with Lightning and Thunder (5pm-9pm):
The Nor 'easter strengthened just south of western Long Island through the late afternoon and evening and through doing so dramatically increased the lift in the atmosphere northwest of the low center which happened to line up directly over the Capital Region-Hudson valley. The result of the increased lift, nightfall, strong dynamic cooling, and cooling due to melting snow as it fell through the column allowed rain to switch to exceptionally heavy snow (snowflakes at times as large as silver dollars) from the late afternoon through the evening. Snowfall rates of 1" to 2" per hour and surface temperatures right at 32° or 33° allowed for rapid accumulations of the heaviest and wettest snow possible of 3"-5" between 5pm and 9pm and particularly hazardous travel conditions across mainly Rensselaer, Albany, southern Washington, Saratoga and Schenectady counties. Several cloud to ground lightning strikes also occurred between 6:15pm and 6:30pm on the Rensselaer-Saratoga County border during the local scale event. It's interesting to note that in nearby Fulton and Montgomery counties (the Mohawk valley) where precipitation rates were much lighter, generally light to moderate rain was falling during the period of blinding snow over the Capital Region. Even from Saratoga Springs on north to Glens Falls, rain, mixed at times with the heavy wet snow during this period illustrating the effect of precipitation rate and the rate of cooling across one portion of the region vs. another. The snow burst event ended as the precipitation became lighter after 9pm with a change back to light rain or drizzle in the Capital Region-Hudson valley through the balance of the night with snow of generally lighter and variable intensity persisting in the higher elevations of the Helderbergs, Schoharie County and the Catskills, as well as the southern Adirondacks. Snowfall amounts prior to midnight ranged as high as 15" in the Helderbergs and higher terrain in Schoharie and Greene counties with Delanson checking in with 15.5", Summit with 15", Mariaville and Prattsville with 14" as examples vs no snow accumulation in the Mohawk valley due to ongoing rain or drizzle.

Albany (ENX) Doppler Radar reflectivity image (6:24pm December 9, 2014) showing intense heavy wet snow throughout the Capital Region during the snow burst period. Three cloud to ground lightning strikes are also shown in western Rensselaer County. (The lightning was the result of strong lifting in the atmosphere within the intense snow band coupled with a layer of unstable air aloft and the mixing of both liquid drops and ice which is a mechanism that separates charges resulting in lightning. Although not frequent, lightning is not uncommon in strong winter storms.) Additionally, giant snow flakes were occurring with an extremely high water content to the snow due to a deep isothermal layer in the lower levels of the atmosphere right at 32°. Also at this time, rain was falling throughout much of Fulton and Montgomery counties with a rain snow mix from Saratoga Springs on north to Glens Falls. Moderate snow was falling throughout most of Schoharie County and the higher elevations of Otsego and Delaware counties with mixed rain and snow in Vermont and the northern Berkshires.


Albany NWS Doppler Radar Image at 6:24pm Tuesday December 14, 2014

Albany (ENX) Doppler Radar reflectivity image (7:58pm) showing the area of intense snowfall in the process of diminishing in areal coverage.


Albany NWS Doppler Radar Image at 7:58pm Tuesday December 14, 2014


Albany (ENX) Doppler Radar reflectivity image (9:16pm December 9, 2014) showing the main axis of elevation snow and valley rain weakening and shifting north and west of the Capital Region with a significant dry slot working up through western New England and the mid Hudson valley. Precipitation from the Capital region on east generally became a stiff drizzle through the remainder of the night with temperatures just a little above freezing through Wednesday morning December 10.

Albany NWS Doppler Radar Image at 9:16pm Tuesday December 14, 2014 

Wednesday December 10, 2014: Phase II
Patchy areas of moderate snow were ongoing through the morning of the 10th in the Helderbergs and Catskills with a stiff drizzle, borderline light rain, in the Capital Region Hudson valley. The storm center at this time had migrated to southeastern New England and had weakened from the night before with the zone of heavy precipitation which had impacted eastern New York and western New England into Tuesday night pushed back into central and western New York where heavy accumulating snow was falling.

The upper atmosphere was a degree or two colder on the 10th so as a second zone of heavy precipitation began developing during the early afternoon, a quick switch from drizzle and light rain to snow occurred with a rapid expansion of snow across the region through the afternoon. Moderate to heavy snow fell into Wednesday night with snowfall rates of 1" per hour common and surface temperatures at 32° or a little below. That slight bit of cooling allowed for rapid accumulations on untreated and less traveled roads causing widespread hazardous travel conditions due to the slick surface conditions and low visibility in heavy wet snow. The following sequence of two radar images below illustrate the development of the zone of heavy snow between 1:30pm and 3:15pm. Ultimately this snow zone expanded west and dumped between 5"-10" on the Capital Region, Lake George Saratoga Region, the Adirondacks, Mohawk valley and much of Schoharie County as well as several inches of snow in the mid Hudson valley and Berkshire county, areas that had little to no snow during the first phase of the storm on the 9th. In the Mohawk valley, all of the storm's 7"-11" of snow came from this phase of the event and additional light snow which persisted through the early afternoon on the 11th.

Albany Doppler Radar (ENX) Reflectivity Image at 1:44pm Wednesday December 10, 2014 showing a narrow developing deformation band of moderate to heavy snow extending from the Mohawk valley, through the Capital Region to Berkshire County. The snow zone was slowly moving to the west and expanding in areal coverage.


Albany NWS Doppler Radar Image at 1:44pm Wednesday, December 10, 2014

Albany Doppler Radar (ENX) Reflectivity Image at 3:12pm Wednesday December 10, 2014 showing the expansion of the heavy snow area over the region. Heavy snow ultimately moved into the western Catskills, Adirondacks, and Mohawk valley between 5pm and midnight dumping anywhere from 5"-10" of snow in areas of Fulton and Montgomery counties which had no snow on the 9th. Similarly, in the mid Hudson valley across eastern Greene and Columbia counties where no snow fell on the 9th, accumulations of 2"-7" occurred with the storm from this phase.

Albany NWS Doppler Radar Image at 3:12pm Wednesday December 10, 2014 

Thursday December 11: Phase III
A much weaker surface storm meandered across northern New England through the 11th with the parent upper level low stalled about directly over the Capital Region through the day. Occasional light snow with bursts of moderate snow at times fell between midnight and noon with scattered nuisance type snow showers and flurries through the remainder of the day. Additional accumulations were light, generally a coating to 3"

Synopsis of the Event:
The entire system came together over the Northeast largely as a result of strong jet stream blocking over maritime Canada which forced the merger of a strong upper level storm tracking southeast through the Midwest and Ohio valley with an offshore low pressure well east of the Carolina coast which was forced to move west-northwest back in towards the coast Monday evening and night December 8. The merger of these systems over the a moderately strong temperature gradient between the U.S. mainland and the ocean, allowed the moisture rich low pressure to develop and strengthen very close to the New Jersey coast through the day Tuesday December 9 and only move very slowly across Long Island to near Boston through the 10th.

Meanwhile, strong surface high pressure, responsible for sending in a layer of shallow cold air into the Northeast, retreated away from the region but allowed enough shallow cold air to remain in place to support a mixture of sleet and freezing rain to break out during the early morning of the 9th with temperatures aloft warming so rapidly to prohibit much of any snow to form through the first portion of the storm. The nor 'easter ultimately became moderately strong and due to it's slow motion and ultimately gradual cooling in the atmosphere lead to a sizeable snow event for the region, which was very much terrain enhanced. Snowfall amounts were highly variable due to even the most subtle variations in terrain and thus subtle variations in temperatures over short horizontal distances. Many cases of a few inches of snow occurred within a mild or two of snow accumulations of 10" or more. In general snowfall in the Helderbergs and Catskills, especially from elevations of 1400' and higher) where the event was primarily a snow event, ranged from 12"-24". Localized accumulations of almost 30" occurred at elevations above 2200' in southern Vermont, but were much more the exception than the rule. A general 7"-11" of snow accumulated over the three day period in the Mohawk valley, much of the Capital Region into Washington County with much lighter amounts in the mid Hudson valley and central and southern Berkshire County. Snowfall in the Adirondacks generally ranged from 11"-15". Liquid equivalent precipitation with the storm was quite high with amounts ranging from 1.5" to 3.0" on average. In fact a whopping storm total of 2.58" of rain/liquid equivalent precipitation fell on Albany, which had it been all snow would have measured at well over two feet given a standard 10:1 ratio. Minor flooding occurred in parts of the mid Hudson valley as a result of heavy rain which primarily fell on the 9th.

Photograph Posted to Facebook by: Steve Schleimer: Flooding on Route 43 in Stephentown, Rensselaer County Dec 9, 2014

Street flooding in Stephentown, Rensselaer County on Route 43 near the MA border, December 9, 2014

Power Outages:
Because of the exceptionally heavy and wet nature to the snow coming down on in many cases ice coated trees, significant power outages were reported in Schoharie, Greene, and Warren counties with sporadic outages throughout the rest of the region. National Grid reported 10,000 customers out in Schoharie and Greene counties at the height of the second round of snow on the 10th. Scattered power outages lingered into the region on the 11th in areas that had the heaviest snowfall.


WeatherNet 6 Observed Snowfall Distribution for the December 9-11, 2014 Storm
(Note: Because of the very tight horizontal gradients in snowfall across many parts of the region which cannot be adequately resolved with a graphic of this scale, this is meant to serve as more of a general idea of the snowfall distribution across the region. (For Example, in Schoharie County, in the zone of 15"-22", there are lower elevation communities there which had under 10" of snow. )

December 9-11, 2014 Snowfall Distribution 


Experimental Snowfall Distribution Graphic Generated by the Albany National Weather Service Forecast Office using snowfall observations from the storm. Computer analysis allowing for a higher resolution to the distribution, illustrating the incredible variation in snowfall amounts over short horizontal distances.

December 9-11, 2014 Snowfall Distribution Generated by the Albany NWS Office 

WeatherNet Storm Total Snowfall Reports for December 9-11, 2014
(Reports are estimates in many cases due to the rapid melting and compression of the snow as it fell, especially during Phase I of the Storm)

Town County Snowfall Report Town County Snowfall Report
Pittsfield, MA Berkshire 6.0" Lanesborough, MA Berkshire 7.0"
Savoy, MA Berkshire 17.9"      
           
Guilderland Albany 4.0" to 8.0" South Berne Albany 15.0"
Latham Albany 11.2" Colonie Albany 11.4"
Newtonville Albany 11.3"      
           
Taghkanic Columbia 6.1" Livingston Columbia 4.0"
Kinderhook Columbia 4.7" Chatham Columbia 5.5"
Austerlitz Columbia 5.5" Ancramdale Columbia 3.3"
Germantown Columbia 2.0" Craryville Columbia 6.0"
Hudson Columbia 2.0" Boston Corner Columbia 5.5"
           
Arkville Delaware 5.5"      
           
Caroga Lake Fulton 11.0" Broadalbin Fulton 12.1"
           
Catskill Greene 2.0" Ashland Greene 17.0"
Greenville Greene 5.5" Halcott Greene 8.8"
Durham Greene 7.0" Jewett Greene 13.0"
West Kill Greene 15.0" Prattsville Greene 14.0"
           
Indian Lake Hamilton 8.0" Wells Hamilton 13.5"
Piseco Hamilton 11.0"      
           
Amsterdam Montgomery 9.3" to 10.3" Fonda Montgomery 10.3"
Florida Montgomery 12.0" Stone Ridge Montgomery 7.8"
Glen Montgomery 7.5" Palatine Bridge Montgomery 8.0"
           
Oneonta Otsego 6.7" Cherry Valley Otsego 8.5"
Worcester Otsego 12.0" East Worcester Otsego 9.5"
Cooperstown Otsego 9.0"      
           
Schaghticoke Rensselaer 10.0" Brunswick Rensselaer 12.0"
Speigletown Rensselaer 12.0" Center Brunswick Rensselaer 9.3"
Grafton Rensselaer 7.5"      
           
Clifton Park (Oaks) Saratoga 10" (estimate) Charlton Saratoga 7.0"
Milton Saratoga 8.3" Saratoga Springs Saratoga 5.5" to 6.6"
Hadley Saratoga 8.0" Wilton Saratoga 6.6"
Corinth Saratoga 5.0"      
           
Scotia Schenectady 9.8" Delanson Schenectady 20.0"
Duanesburg Schenectady 12.0"      
           
Middleburgh (1800') Schoharie 23.0" Charlotteville Schoharie 13.8"
Summit Schoharie 15.5" to 21.5" Jefferson Schoharie 17.0"
Huntersland Schoharie 14.3"      
           
Phoenicia Ulster 2.0" Saugerties Ulster 0.1"
Whiteport Ulster 0.5" Kingston Ulster 0.3"
Highmount Ulster 15.0"      
           
Warrensburg Warren 13.0" Brant Lake Warren 17.0"
Queensbury Warren 8.0" Warrensburg Warren 13.5"
Lake Luzerne Warren 6.5"      
           
Hudson Falls Washington 4.0" Hebron Washington 18.0"
           
Woodford, VT Bennington 28.5" Danby, VT Rutland 18.8"
West Rutland, VT Rutland 9.0"      

Photograph Posted to Facebook by: Robin Sargalis, Amsterdam December 10, 2014: A typical scene across the region

Snow covered trees in Amsterdam, December 10, 2014 

WeatherNet 6 Rainfall Reports (In general these are not storm total reports due to the mixed precipitation nature of the storm and inherit complications in measuring the pure rain vs. liquid equivalent. The time notation next to the report indicates the time and date of the report. The data is included to illustrate the high level of moisture which accompanied the storm. The 1.60" of rain/liquid equivalent measured at Albany on the 9th set a daily record for that day with the total liquid equivalent from the 9th through the 11th coming in at 2.58".

Town County Rainfall Report Town County Rainfall Report
Pittsfield, MA Berkshire 1.20" 8am/10th Lanesborough, MA Berkshire 1.45" 6am/10th
           
Westmere Albany 0.65" 11pm/9th Feura Bush Albany 1.00" 11pm/9th
Latham Albany 0.62" 5pm/9th Glenmont Albany 0.71" 5pm/9th
           
Taghkanic Columbia 0.92" 6pm/9th      
Livingston Columbia 1.44" 8am/10th Ancramdale Columbia 1.14" 5am/10th
           
Perth Fulton 0.68" 5pm/9th      
           
Catskill Greene 1.05" 11pm/9th      
           
Amsterdam Montgomery 0.54" 11pm/9th Fonda Montgomery 0.90" 5am/10th
           
Charlton Saratoga 1.75" 11am/10th Milton Saratoga 0.79" 10pm/9th
Wilton Saratoga 1.40" 11am/10th Saratoga Saratoga 1.10" 6am/10th
           
Saugerties Ulster 1.52" 6am/10th Phoenicia Ulster 1.12" 6am/10th
West Shokan Ulster 1.78" 5am/10th Whiteport Ulster 1.11" 5am/10th
Esopus Ulster 1.20" 4pm/10th      
           
Hudson Falls Washington 0.98" 5am/10th