Monday May 1, 2017
Squall Line - Severe Weather

Photographer: Sean Organ - Cloud to ground lightning strike Monday evening May 1, 2017 - Boght Corners, Albany County

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

An intense squall line developed in advance of a cold front and strong low pressure system across eastern Ohio early in the afternoon on Monday May 1, subsequently racing east across Pennsylvania and New York producing widespread significant wind damage, especially across Pennsylvania, western and central New York where the most favorable combination of strong winds aloft, strong wind shear, and instability (CAPE of 500 to 1000 j/kg on average) existed.

Conditions across eastern New York and western New England, however, were much less favorable for severe weather due to a general lack of instability (hardly any CAPE with surface temperatures reaching the upper 60s to lower 70s and dewpoints peaking out mainly in the upper 50s.) The late arrival time of the squall line, during the evening when the atmosphere naturally becomes increasingly stable due to diurnal cooling, also was a large negative factor. Nevertheless, thirty eight reports of wind damage came in across the CBS6 coverage area as the squall line moved from west to east across the region between 8 and 10:30pm.

The maintenance of the line was due largely to brute wind force as strong wind fields, which were quite low in the atmosphere, along with a sharp turning of the wind with height (strong directional shear) as well as the shear momentum of the well organized line, allowed the system to continue to produce pockets of wind damage in very localized bursts as it moved through, ultimately weakening across western New England, the eastern Catskills and the mid Hudson valley.

At the surface, a warm front was in the process of lifting north across the region at the time of the squall line's arrival which enhanced the low level wind shear and likely aided in storm maintenance as the system tracked across the region. Low level cooling in advance of the line, however, did produce enough of an inversion to aide in preventing widespread damaging wind gusts from reaching the ground, with instead smaller microbursts in areas where the the strong rear inflow jet feeding the line was able to burst through with gusts in excess of 80 mph in a few locations such as Middleburgh in Schoharie County where wind damage was reported. Other pockets of fairly widespread wind damage occurred across central and southern Washington County in a line segment which briefly intensified after 10pm.

A tornado watch was issued for much of central and western New York, Pennsylvania and eastern Ohio, with a severe thunderstorm watch for all of eastern New York and western New England with the exception of Berkshire and Litchfield counties. The tornado watch was hoisted due to the strong wind shear that was in play which is a key ingredient in producing storm rotation and tornadoes. As it turned out, the low instability made the formation of classic supercell thunderstorms unfavorable with a QLCS (quasi-linear-convective-system) being most favored, which is what formed. Brief meso vortices formed at times along some of the bowing segments along the QLCS, or squall line, which went on to produce the swaths of more substantial wind damage which occurred along the leading edge of the system. Only one brief tornado was confirmed by NWS damage surveys across north central PA with the rest of the damage caused by straight line winds, up to 100 mph in some cases.

Rainfall with the line was locally but only briefly torrential with most areas coming in with between 1/2" and 1", but in a very short period of time. Brief urban and poor drainage flooding occurred on some roadways, but otherwise no significant flooding resulted from the line's passage.

Lightning was limited with the line as well due to it's shallow nature which limited mixing of ice and water which largely creates the electrical charge centers within the clouds and the ground which creates the lightning. There were periods of enhanced lightning activity at times as the line moved through and within the stronger line segments which developed as well as some random positively charged strikes in the stratiform rain which occurred as the line moved east.

Instant Doppler 6 around 8:30pm, Monday, May 1, 2017 showing the squall line entering the local area

Instant Doppler 6 reflectivity image around 8:30pm as the squall line was moving through the Adirondacks, Mohawk valley and western Catskills

Shortly before this radar image an intense micorburst occurred 2 miles NE of Norwich in Chenango County which downed an estimated 100 healthy trees along a 1 mile path. The microburst occurred at roughly 8:18pm with winds estimated to have ranged from 90-100 mph. A tornado warning was issued on that storm up into Otsego County for a brief time as a mesovortex was indicated on radar. Additional microburst damage from that same storm occurred at 8:20pm in Oxford, also in Chenango County where winds were downburst winds were estimated to have ranged from 80-90 mph along a 3.5 long by 1 mile wide path.

Instant Doppler 6 image of the squall line at around 9pm on May 1, 2017 shortly before significant wind damage occurred in parts of Schoharie County from Jefferson up to Middleburgh, where an 80 mph wind was measured by a HAM radio operator at 9:16pm. Note the rear inflow notches on the western side of the line indicating where strong winds were feeding into the system.

Instant Doppler 6 image of the squall line at around 9pm, shortly before significant wind damage occurred in parts of Schoharie County from Jefferson to Middleburgh 

Barn silo blown apart and down on Meade Road near Jefferson in Schoharie County, Monday May 1, 2017

Barn silo blown apart and down on Meade Road, near Jefferson, Schoharie County, Monday May 1, 2017

Radar and severe thunderstorm warning composite image showing the squall line and all areas in advance of it under severe thunderstorm warnings at 9:26pm, May 1, 2017. This image was just prior to a 59 mph wind gust which occurred at the Stratton Air National Guard base in Glenville, Schenectady County.

Squall line radar and warning composite image at 9:26pm Monday May 1, 2017 

At 9:55pm the squall line, moving east at over 50 mph, was producing wind damage in Washington County where the strongest line segment was located. The southern extension of the line at this time was weak from Greene County on south to western Ulster County in an area further removed from stronger wind fields and cooling aloft.

Squall line progress at 9:55pm, May 1, 2017  

The squall line at 10:02pm quickly moving east into Vermont. Note the considerable area of stratiform rain behind the squall line which contained a little bit of lightning, but continued well into the night after the severe weather portion moved off to the east.

The squall line at a few mintutes later at 10:02pm 

Instant Doppler 6 image as the strongest t'storm line segment was moving out of Bennington County marking and end to the severe weather risk in the region. The severe thunderstorm watch was cancelled at this point with additional downpours and some thunder continuing well into the night.

Instant Doppler 6 image around 10:30pm May 1, 2017 

Storm Prediction Center Storm Reports Graphic for Monday May 1, 2017 showing the locations of reported storm damage.

Storm Reports for Monday May 1, 2017 

NWS Storm Reports for Monday May 1, 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.

Town County Severe Weather Report Time
Old Forge Herkimer Downed tree due to wind 7:36pm
Russia Herkimer Tree blown down onto wires 7:46pm
Speculator Hamilton Tree blown down in the village 8:25pm
Jefferson Schoharie Barn Silo blown over at Stone Ridge Dr. and Meade Road 8:59pm
1 Mile ESE Carlisle Schoharie Numerous trees and wires down 9:00pm
Jefferson Schoharie Trees and wires blown down 9:02pm
Gloversville Fulton Trees and wires blown down 9:04pm
Fonda Montgomery Trees and wires blown down 9:10pm
Glen Montgomery Tree down across two road lanes 9:10pm
Kilmartin Corners Montgomery Wires down on Kilmartin Road in the Town of Root 9:10pm
Middleburgh Schoharie Measured 80 mph wind gust 9:16pm
2 Miles S. of Amsterdam Montgomery Pole down in the road with wires at Fullers and Bellows Roads in Florida 9:16pm
Middleburgh Schoharie Trees and wires blown down 9:16pm
Honeywell Corners Fulton Tree down on wires on Ridge Road 9:20pm
Charlton Saratoga Multiple trees blown down 9:27pm
1 Mile E. of Berne Albany Power lines down 9:30pm
Berne Albany Tree blown down 9:30pm
1 Mile SE of Berne Albany Large tree branches blown across a road 9:30pm
1 Mile WSW of Malta Saratoga Multiple trees blown down 9:37pm
Malta Saratoga Multiple trees blown down 9:37pm
Stratton Air Base Schenectady Measured 50 mph wind gust 9:39pm
Mckownville Albany 12 inch diameter tree snapped on Church Road 9:40pm
1 Mile N. of Ft. Edward Washington Power lines down on Mcintyre Street 9:49pm
2 Miles NE Durkeetown Washington Tree down on Hinds Road 9:54pm
West Cambridge Washington Multiple trees blown down on Center Cambridge Road 9:54pm
Cambridge Washington Trees and wires blown down 9:55pm
1 Mile SW of Coila Washington Trees and wires blown down 9:55pm
1 Mile ENE of Center Cambridge Washington Tree blown down on County Route 59 9:56pm
1 Mile ENE of Cambridge Washington Tree blown down on a house and car, no injuries 9:57pm
1 Mile S. of Cambridge Washington Tree blown down on a house and car on Whitecreek Shunpike Road - no injuries 9:57pm
1 Mile NNW of Center White Creek Washington Trees and wires blown down 9:58pm
1 Mile N. of Center White Creek Washington Tree split over a house on Owl Kill Road 9:59pm
Cambridge Washington Trees and wires blown down 10:00pm
1 Mile NNE of Valley Falls Rensselaer Tree blown down 10:00pm
1 Mile N. of Ash Grove Washington Tree down and debris on Ashgrove Road 10:01pm
3 Mile E. of Rexleigh Washington Tree down on Camden Valley Road 10:04pm
Hartford Washington Tree blown down on Route 40 10:06pm