Saturday February 25, 2017
Widespread Severe Weather Outbreak

Shelf cloud coming into the hamlet of Sprakers, NY, Montgomery County, Saturday afternoon February 25, 2017

Shelf cloudy approaching Sprakers, NY Saturday afternoon February 25, 2017


From 3pm through 7pm on Saturday February 25, the atmosphere unleashed a rare, but not unprecedented, widespread outbreak of strong and locally severe thunderstorms, rooted in a historically warm and humid air mass, and driven by a strong surface cold front and powerful jet stream winds aloft.

Initially, short line segments of intense thunderstorms with frequent cloud to ground lightning developed along an advancing cold front stretching from the Adirondacks to Otsego County early in the afternoon with the convective system consolidating into a wavy squall line with individual bowing segments as it approached the Hudson valley and Capital Region late in the day. Strong 40-45 mph cold outflow outran the line as it came into the immediate Capital region which caused some brief weakening of the cells over Saratoga, Schenectady, and Albany counties.  The squall line, however, quickly reformed between 6 and 6:30pm along the outflow boundary stretching from Washington County on south along the Hudson river where it merged with a bowing severe thunderstorm line segment coming up from eastern Ulster and Dutchess counties.  The resultant line raced across Rensselaer, Columbia and Berkshire counties producing wind gusts up to 70 mph with a significant concentration of wind damage reports in eastern Ulster, Dutchess, and central and southern Berkshire counties.

As the thunderstorm cluster moved northeast out of the Berkshires it went on to produce a brief EF1 (110 mph) tornado with the initial touchdown in Goshen, MA in Hampshire County and a track into Conway, MA in Franklin County where it produced some significant damage just east of the Berkshire County line.

Albany Doppler Radar Base Reflectivity 6:54pm February 25, 2017

Conway Tornado Report
Time: 7:18 - 7:25pm
Path Length: 5 miles
Path Width: 200 yards
Rating: EF1: 110 mph winds
Note: This is the first (to date) February tornado on record in Massachusetts


A significant tornado also occurred earlier in the day around Scranton, PA

Wilkes-Bare Scranton Tornado Report
Time: 2:35 - 2:50pm
Path Length: 12 miles
Path Width: 500 yards
Rating: EF2: 120 mph winds

And a major microburst was confirmed near the town of Lumberland, NY in Sullivan County

Lumberland Microburst Report
Time: 5:05pm
Path Length: 25 miles
Path Width: 200 yards
Estimated Max Wind Speed: 100 mph
100 to 200 trees either snapped or uprooted, some homes damaged due to falling trees


On the cold side of the front, and while the squall line was going through the Hudson valley and Berkshire County, rain had changed to a heavy wet snow, accompanied by occasional lightning and thunder, over the Adirondacks, Mohawk valley and the higher elevations in the western Catskills and Schoharie County, as shown on the winter composite radar image below. Localized snow accumulations of 1”-3” occurred before the precipitation ended from west to east between 8 and 10pm.  

Albany Doppler winter composite radar image, 6:48pm February 25, 2017 

The following series of Albany Doppler radar images illustrates the progress of the squall line from west to east across the region between 3 and 7pm.

Albany Doppler Radar Image at 3pm showing the squall line extending from Hamilton County south through southern Herkimer, and Otsego counties. Frequent cloud to ground lightning was occurring at this time, especially across the southern portion of the line around Oneonta.


Albany Doppler Radar Base Reflectivity 3pm February 25, 2017

Albany Doppler Radar Image at 4pm showing the eastward progress of the squall line into NW Warren, Fulton, Montgomery, eastern Otsego and Delaware counties. The small thunderstorm segment north of the "S" in Gloversville on this image showed a brief period of mid level rotation and produced significant wind damage from near Fort Plain in Montgomery County to just west of Perth in Fulton County between 3:25pm and 4pm.

Albany Doppler Radar Base Reflectivity 4pm February 25, 2017 

Albany Doppler Radar Image at 5pm - weakening of the squall line over Warren, Saratoga and Schenectady counties was evident here as cold 40-45 mph thunderstorm outflow had raced ahead of the line cutting off the warmer and more unstable inflow. Strong storms with frequent lightning and wind, however, continued across Schoharie and Delaware counties.

Albany Doppler Radar Base Reflectivity 5pm February 25, 2017 

Albany Doppler Radar Image at 6pm - Redevelopment of downpours and thunderstorms was underway at 6pm in Washington, Rensselaer, and Albany counties along the outflow boundary. An arching line of severe thunderstorms near Kingston over Ulster County merged with the redeveloping northern line segments going on to produce significant wind damage into Berkshire County through 7:00pm.

Albany Doppler Radar Base Reflectivity 6pm February 25, 2017 

Albany Doppler Radar Image at 7pm - A damaging line segment of thunderstorms was located over central and southern Berkshire County at this time. A brief EF1 tornado developed out of the Berkshire County cluster of thunderstorms producing spotty damage in Goshen, MA in Hampshire County and significant damage in Conway, MA in Franklin County. This was the first tornado on record in the Bay State in the month of February. Moderate to heavy rain at this time was widespread throughout the Hudson valley and Capital Region. Thunder snow was widespread at this time across the Adirondacks, Mohawk valley, western Catskills, and Schoharie County.

Albany Doppler Radar Base Reflectivity 7pm February 25, 2017 

Perspective
Severe weather is rare here in the cold season, but does happened occasionally with noteworthy events including February 24, 2016 when a strong convective line moved across the region producing heavy rain and localized flooding as well as isolated severe weather.  A significant storm brought isolated severe weather on March 8, 2008 with a historically damaging convective and synoptic wind event on February 17, 2006 along with a major outbreak of severe thunderstorms on December 1, 2006. In comparison, this event was significant with wind damage was more localized in nature as compared to major events on both February 17, 2006 and December 1, 2006 when damage was more widespread.

Set Up
The pre-convective environment was a classic cool season high shear (strong increase and turning of the wind with height) but low instability,) set-up.  The lack of high heat and high surface moisture limited the amount of potential instability that might otherwise be observed during the warm season. However, strongly wind sheared environments can often overcome low instability to support severe weather, which was the case in this event.

Convective lines in events like this one are described as strongly forced, as the brute force of the wind energy overcomes the poor thermodynamic environment to produce damaging convection. In this case, the 0-6km bulk shear values ranged from 50-75 knots, with 0-1 km values of 30-40 knots, very high values.  CAPE, or convective available potential energy, a measurement of instability, however, was low, ranging from 100-500 j/kg. Typically the air on its own will not rise rapidly in low instability environments.  Aiding the process, however, in this case, along with the low level strength of the wind and the shear, was a favorable placement of two upper level jet streaks at the 250mb level, one riding through the northern branch of the jet across southern Canada, and the other riding through a subtropical jet through the mid Atlantic.  The positioning of the jet streaks put New York and Pennsylvania in a favorable region for strong upper level venting and upward lift of the air through transverse vertical circulations which form in the both the right entrance and left exit regions of upper level jet streaks.  It just so happened that the right entrance region of the northern jet streak was co-located with the left exit region of the mid Atlantic jet streak, which greatly increased the lift over the cold front enhancing the evolution of the squall line.  Favorable mid level lapse rates (the rate of temperature drop with height) also existed which enhanced the development of convective updrafts.

(Thermodynamics) Temperatures and Surface Moisture
February 25 was the third consecutive day of record shattering warmth. Temperatures surged well into the 60s to right around 70° (Record high of 70° was established at Albany for this date – average high = 37°) with upper 60s to low 70s as far north as Burlington, VT.  A lingering warm front draped over the Adirondacks through Warren and Rutland counties during the morning, where temperatures ranged through the low and mid 30s, vs the upper 50s to lower 60s from the Mohawk valley-Capital Region and Bennington counties on south, surged north allowing for a 25-30 degree temperature jump in one to two hours as a strong southerly wind scoured out the pockets of shallow chilly air across the north country. The strong southerly gradient flow, frequently gusting from 30-40 mph through the day, not only pushed the temperatures up, but dewpoints also climbed to anomalous levels ranging from 50°-55°. Simultaneously, across western New York, on the cold side of a cold front, temperatures ranged through the upper 30s to lower 40s.  The resultant thirty degree temperature gradient on either side of the front over a very short horizontal distance created a sharp cold frontal lifting surface, favorable for convective development. Temperatures dropped some 15-20 degrees in as little as fifteen to thirty minutes with the passage of the squall line and front illustrating the very tight nature to the gradient.

3pm Northeast Temperature Observations, Saturday February 25, 2017

3pm Northeast Temperature Observations, Saturday February 25, 2017

The combination of the sharp cold frontal surface, the significant temperature gradient on either side of the front and the strong wind energy available, were more than sufficient to overcome the low instability to force the squall line. The mild air in advance of the line also made it easier for strong wind gusts to be mixed down to the ground. Typically in the cold season, low surface temperatures create a strong inversion (warmer air over colder air) which does not readily mix. In these cases, strong wind is not easily mixed down to the ground, which is a reason why severe wind gusts at the surface from convection is fairly rare in the winter, making this case unique.

Storm Prediction Center Storm Reports Graphic for Saturday February 25, 2017 showing the locations of reported storm damage.

Storm Reports for Saturday February 25, 2017 


NWS Storm Reports for Saturday February 25, 2017. Note, these reports are used to verify the NWS warnings which were issued for this event and therefore do not necessarily represent an accounting for all of the wind damage which may have occurred during the event.

Town County Storm/Wind Report Time
Roessleville Albany Gradient Wind Damage (Non T'Storm) Downed Tree 12:21pm
2 Miles SSW of New Scotland Albany Gradient Wind Damage (Non T'storm) Downed Tree 12:52pm
1 Mile E. of Cohoes Albany Gradient Wind Damage (Non T'storm) Tree Down 1:47pm
1 Mile NNE of Dormansville Albany Gradient Wind Damage (Non T'storm) Tree Down 1:47pm
1 Mile N. or Goodell Corners Herkimer T'Storm Wind Damage: Power Outage 2:00pm
1 Mile W. of Fort Plain Montgomery T'Storm Wind Damage: Downed Power Lines 3:25pm
Eppie Corners Fulton T'Storm Wind Damage: Trees and Wires Blown Down 3:47pm
1 Mile S. of Cork Fulton T'Storm Wind Damage: 15 Trees Uprooted 3:47pm
1 Mile NE Smiths Corners Fulton T'Storm Wind Damage: Trees and Wires Blown Down 3:48pm
2 Miles W. of Perth Fulton T'Storm Wind Damage: Trees and Wires Blown Down 3:56pm
Newtonville Albany T'Storm Wind Damage: Downed Tree 5:15pm
Fort Hunter Albany T'Storm Wind Damage: Downed Tree 5:21pm
1 Mile WSW of West Albany Albany T'Storm Wind Damage: Downed tree at the intersection of Western Avenue and Manning Blvd. 5:40pm
1 Mile W. of Westmere Albany T'Storm Wind Damage: Downed Tree 5:40pm
1 Mile N. of Lyonsville Ulster T'Storm Wind Damage: Tree down on Buck Rd. between Cherryhill Rd. and Mill Rd. 5:45pm
Lyonsville Ulster T'Storm Wind Damage: Tree blown down on Bone Hollow Rd. between Whitefield Rd. and Smith Lane 5:45pm
2 Mile SSE of Galeville Ulster Measured 76 mph wind gust 5:48pm
Flint Ulster T'Storm Wind Damage: Tree down on Plains Road at New Hurley Road 5:51pm
Mckownville Albany Gradient Wind (Non T'Storm) Tree blown down in front of Crossgates Mall 5:52pm
Bruceville Ulster T'Storm Wind Damage: Tree down at 26 Fairview Ave between Lucas Ave. and the dead end 5:57pm
Stone Ridge Ulster T'Storm Wind Damage: Tree down on Legget Rd., 500 feet from the intersection with State Route 209 5:57pm
1 Mile E. of Kripplebush Ulster T'Storm Wind Damage: Tree down on Pine Bush Rd. between Buck Rd. and County Route 2 5:57pm
1 Mile SW of Rosendale Ulster T'Storm Wind Damage: 8 Hour road closure due to downed trees and wires 5:58pm
1 Mile SW of Esopus Ulster T'Storm Wind Damage: Tree blown down on Old Post Road at Swarterkill Rd. 6:02pm
New Scotland Albany T'Storm Wind Damage: Downed Tree 6:04pm
Port Ewen Ulster T'Storm Wind Damage: Connelly Rd. closed between Route 9W and Millbrook Drive due to a downed tree 6:04pm
1 Mile SSW of Wilbur Ulster T'Storm Wind Damage: Downed tree on New Salem Road between Callahans and Tooley Drive 6:04pm
1 Miles ENE Union Center Ulster T'Storm Wind Damage: Tree down on the southern portion of River Road 6:04pm
1 Mile W. of Wappingers Falls Dutchess T'Storm Wind Damage: Trees and wires blown down 6:05pm
1 Mile SE of Fort Hunter Albany T'Storm Wind Damage: Power lines down 6:05pm
Hickorybush Ulster T'Storm Wind Damage: Trees, wires, and poles blown down 6:05pm
1 Mile ESE of Jefferson Heights Greene T'Storm Wind Damage: Tree blown down onto a house 6:10pm
1 Mile ENE of Weys Corners Dutchess T'Storm Wind Damage: 50 trees blown down 6:11pm
1 Mile ESE of Kinderhook Columbia T'Storm Wind Damage: Trees blown down blocking a road 6:15pm
Red Hook Dutchess T'Storm Wind Damage: Downed trees, lines, and poles, 6 hour road closure 6:15pm
Hancock, MA Berkshire 69 mph Wind Gust 6:28pm
Coltsville, MA Berkshire Tree down on Cheshire Rd 6:39pm
Latham Albany Gradient Wind Damage (Non T'Storm) Wire blown down 6:40pm
Egremont Plain, MA Berkshire T'Storm Wind Damage: Trees and wires down on Rt. 41 6:41pm
Sheffield, MA Berkshire T'Storm Wind Damage: Wires down on Route 41 6:43pm
Lanesborough, MA Berkshire T'Storm Wind Damage: Tree down on south State Rd 6:43pm
1 Mile N. of Berkshire, MA Berkshire T'Storm Wind Damage: Tree blown onto a car on Green Acres Rt. 8 6:49pm
New Marlborough, MA Berkshire T'Storm Wind Damage: Multiple trees and wires blown down 6:50pm
Adam, MA Berkshire T'Storm Wind Damage: Wires down 6:51pm
Zylonite, MA Berkshire T'Storm Wind Damage: Roof of the bounty Fair Restaurant Damaged 6:51pm
Otis, MA Berkshire T'Storm Wind Damage: Trees and wires down on Route 23 7:01pm
Gloversville Fulton FLOOD: Cayadutta 3 feet above river banks in the village 8:42pm

The squall line and subsequent 1-2 hour period of moderate to heavy rain that followed it brought an average of 1/2" to 1" of rain with locally up to 1.5" in that short period of time. Some flash flooding in Otsego and Delaware counties occurred with generally minor flooding of some area streams and creeks due to the runoff from the rain and some contribution from runoff due to snow melt. However, no significant flooding occurred as a result of this event.

WeatherNet 6 Rainfall/Snowfall Reports for Saturday February 25, 2017
Snowfall reports are marked as "Snow", otherwise the reports are "Rain"

Town County Precip. Report Town County Precip. Report
New Marlborough, MA Berkshire 0.59"      
           
Knox Albany 0.8" SNOW Glenmont Albany 1.31"
Coeymans Hollow Albany 0.81"      
           
Livingston Columbia 0.74" Taghkanic Columbia 0.81"
Germantown Columbia 0.68" Ancramdale Columbia 0.64"
           
Arkville Delaware 0.1" SNOW Denver Delaware Trace SNOW
           
Red Hook Dutchess 0.90"      
           
Broadalbin Fulton 1.10" Fish House Fulton 0.50"/0.3" SNOW
           
Athens Greene 0.92" Catskill Greene 0.78"
Halcott Center Greene 0.5" SNOW Greenville Greene Trace SNOW
           
Fonda Montgomery 0.75" Palatine Bridge Montgomery 0.73"
Amsterdam Montgomery 0.65" Hessville Montgomery 1.05"
           
Oneonta Otsego 1.21" East Worcester Otsego 0.91"/1.5" SNOW
Worcester Otsego 1.5" SNOW Cherry Valley Otsego 2" SNOW
           
Lansingburgh Rensselaer 1.00" Speigletown Rensselaer 0.90"
           
Malta Saratoga 0.47" Lake Desolation Saratoga 0.70/2.1" SNOW
Stillwater Saratoga 0.41" Milton Saratoga 0.41"/0.1" SNOW
           
Niskayuna Schenectady 0.25" Duanesburg Schenectady 0.20"
Delanson Schenectady 0.3" SNOW      
           
Richmondville Schoharie 0.21"/1" SNOW Jefferson Schoharie 1.5" SNOW
           
Ulster Park Ulster 0.63" Phoenicia Ulster 0.88"
Kingston Ulster 0.63" Saugerties Ulster 0.43"
West Shokan Ulster 0.38"      
           
Lake Luzerne Warren 0.58" Warrensburg Warren 1.00"/0.3" SNOW
           
Hebron Washington 1.02" Hudson Falls Washington 0.75"
           
Landgrove, VT Bennington 0.60" Woodford, VT Bennington 2" SNOW
Wilmington, VT Windham 0.52" West Arlington, VT Bennington 0.62"
Manchester, VT Bennington Trace SNOW West Rutland, VT Rutland 0.69"
Pawlet, VT Bennington 0.64"      

Additional Radar Images - Instant Doppler 6

Instant Doppler 6 - Squall Line, early afternoon Saturday February 25, 2017

Instant Doppler 6 Squall Line Image - Approximately 3:30pm, Saturday February 25, 2017

Instant Doppler 6 - Squall Line, 4pm Saturday February 25, 2017 - wind damage was being produced at this time by the lead line segment approaching the Sacandaga lake.  

Instant Doppler 6 Squall Line Image - 4pm, Saturday February 25, 2017

Instant Doppler 6 - Squall Line, 5pm Saturday February 25, 2017 - as the line was moving into the Capital Region

Instant Doppler 6 Squall Line Image - 5pm, Saturday February 25, 2017