Friday May 4, 2018
Severe Weather Outbreak - Damaging Squall Line
(Widespread High End Convective Wind Event)

Photograph contributed by Andrew Kovalovich- Large tree blown down onto a car in Johnstown, NY, Fulton County Friday evening May 4, 2018. This was just one of many examples of downed trees throughout the region, some falling on vehicles with some falling on homes.

Tree damage in Johnstown, Fulton County Friday May 4, 2018


The blast of wind was brief, lasting only only a few minutes, but it was intense as a fast moving severe squall line, a well organized QLCS (quasi-linear-convective-complex,) raced from west to east across the local area between 7 and 10pm. Wind gusts ranged from 50 to 60 mph on average with some gusts recorded and estimated to have reached or exceeded 70 mph locally as high momentum air was effectively mixed down to the ground. The result was extensive damage to trees and power lines in wide swaths, as well as structures and vehicles that were in the path of falling limbs and trees. National Grid reported 210,000 upstate New York customers lost power, a massive number, Friday evening due to the passage of the squall line with some communities still without power three days later through Monday May 7.

Wind damage was reported throughout the region with every county in the CBS6 coverage area, except Litchfield, CT, going under a severe thunderstorm warning. The most concentrated zone of wind damage, however, occurred within a swath that included the Adirondacks, Mohawk valley, Lake George-Saratoga Region, Capital region as well as Washington County and Rutland and Bennington counties in Vermont. The majority of the power outages occurred in this zone with widespread reports of significant tree and power line damage.


Significant wind damage corridor, Friday evening May 4, 2018

SET UP
THERMODYNAMICS

Morning cloudiness and widely scattered showers, largely prior to daybreak, gave way to a period of partial sunshine from the late morning through the afternoon allowing an already unseasonably warm atmosphere to further heat up with daytime highs ranging from the low to mid 80s (Albany's high = 84°.) Dewpoints climbed to a range of 60°-65° as a gusty southerly wind, ranging from 15-20 mph with gusts to 30 mph, transported moisture into the area through the afternoon as a warm front lifted through the Capital Region to a position across northern New York and northern Vermont by the late afternoon and early evening. The air aloft, however, was not particularly cold with unimpressive mid level lapse rates which resulted in fairly weak instability and CAPE (convective available potential energy) values generally ranging from 500 to 1000 j/kg just prior to the event.

DYNAMICS:
Wind speed and shear in the atmosphere, however, were off the charts impressive for the Northeast creating what's considered a high shear-low CAPE storm environment. Bulk shear values increased to 50-70k knots with a powerful mid level westerly jet of 80-100 knots blasting across the region through the evening. Objective analysis late in the afternoon indicated a very strong unidirectional westerly flow of 90 knots at roughly 10,000 feet and 100 knots at 18,000. Meanwhile at the surface, strong pressure falls were occurring in response to a deepening low pressure system passing through northern Michigan as well as from the developing convection over western New York late in the afternoon which caused surface winds locally to back into the south to southeast and increase to 20 knots or greater enhancing the low level turning of the wind and creating, when coupled with the powerful westerly winds aloft, strong storm relative helicity values of around 250 m2/s2, with values as high as 400m2/s2 across northern New York and northern Vermont. Strong shear like this is a prime ingredient in tornado development and was the reason the Storm Prediction Center issued a tornado watch at 4:15pm for the northern part of the region. Because of the relatively small amount of instability present, however, the potential for large long track tornadoes was quite low with a brief spin up type tornado the main concern with the event in addition to the greater potential for widespread straight line damaging wind swaths. In the end, no tornadoes were reported to have occurred with all of the damage caused by intense outflow winds which were likely locally enhanced by transient meso-vortices embedded within the squall line.


Tornado Watch area, Friday evening May 4, 2018

A severe thunderstorm watch was issued for the remainder of the region at 6:20pm to cover the wind damage threat from the inbound squall line.

Severe T'Storm Watch area, Friday evening May 4, 2018

THE EVENT
The severe event in the Capital Region - Hudson valley and western New England was preceded by a line of quick hitting downpours and isolated thunderstorms which formed along a surface trough during the late afternoon. One cell between 4:30 and 5:30pm, which tracked from western Ulster County, through Columbia and central Berkshire counties, produced some small hail and occasional cloud to ground lightning but otherwise was not severe. During this time, however, discrete mini-supercell storms had developed and were in progress across northern New York and northern Vermont along and south of the warm front producing pockets of damaging wind. A few of these storms skirted through northern Herkimer and northern Hamilton counties and had developed in advance of the squall line which was simultaneously coming together over western New York. The squall line subsequently organized and raced across the the local area between 7 and 10pm, traveling east at up to 55 mph. Lightning was limited due to the shallow nature of the QLCS with storm tops generally ranging from only 15,000 to 20,000 feet. Ordinarily storm tops of at least 20,000 feet are necessary to get enough water droplet and ice crystal mixing to cause charge separation in the cloud creating an environment favorable for lightning. Rainfall was also limited to generally under 1/2" due to the fast forward speed of the system which limited the duration of heavy rain along with the lack of any significant stratiform rain following the squall line.

The following series of Instant Doppler 6 radar images documents the passage of the QLCS across the local area.

Instant Doppler 6 image at 7:36pm showing the squall line moving through the Adirondacks, the Mohawk valley and the western Catskills. A wind gust to 69 mph was recorded by our Hessville WeatherNet 6 spotter Jeff Baldwin at 7:28pm causing damage to his porch roof.

Instant Doppler 6 reflectivity image at 7:36pm, Friday May 4, 2018 as the squall line was moving through the Adirondacks, Mohawk valley and western Catskills

Instant Doppler 6 image of the squall line at 7:51pm. Widespread significant straight line damaging wind was in progress at this time from Warren County through Saratoga, eastern Fulton, eastern Montgomery and Schoharie counties. Our Freihofer's weather station at Amsterdam recorded a gust to 57 mph at 7:45pm.

Instant Doppler 6 image of the squall line at 7:51pm, Friday May 4, 2018 

Instant Doppler 6 image at 8:09pm - Widespread damaging wind was in progress across Saratoga, Schenectady and Schoharie counties at this time. Our Freihofer's weather station on top of the MVP building in Schenectady (100' above ground level) recorded a 67 mph gust 8:11pm with a gust to 51 mph recorded by a Davis instrument on the roof at CBS6 at 8:14pm. And at 8:13pm a gust to 61 mph was also recorded by the ASOS at the Floyd Bennett Memorial Airport (Glens Falls.)


Instant Doppler 6 image at 8:09pm, Friday, May 4, 2018

Instant Doppler 6 image at 8:31pm - The northern portion of the line was the most intense at this time with damaging wind occurring through Washington County.

Instant Doppler 6 image at 8:31pm, Friday May 4, 2018 

Albany (ENX) base reflectivity lowest tilt at 8:39pm - A large bowing line segment was producing significant and widespread damaging wind in Bennington County, VT at this time.

Albany Doppler radar base reflectivity image at 8:39pm Friday May 4, 2018 

Storm Relative Velocity image from the Albany Doppler radar (ENX) lowest tilt - The radar caught one of what were likely many transient meso vortices here near Manchester, VT. These quick rotations along small bowing segments in the QLCS were responsible for pockets of enhanced wind velocities and the pockets of more significant damage which occurred along the track of the squall line.

Storm relative velocity image from the Albany Doppler radar, lowest tilt, 8:46pm May 4, 2018 

Instant Doppler 6 image at 8:48pm showing the position of the squall line from Rutland and Bennington counties in VT through Rensselaer, eastern Albany, eastern Greene and western Ulster counties.

Instant Doppler 6 image at 8:48pm Friday May 4, 2018

Instant Doppler 6 image at 9:14pm - Damaging wind was coming into Berkshire County at this time with a peak wind gust at Pittsfield, MA of 58 mph recorded ten minutes after this radar image at 9:24pm.

 Instant Doppler 6 image 9:14pm Friday May 4, 2018

Storm Prediction Center Storm Reports Graphic for Friday May 4, 2018 showing the locations of reported severe wind and storm damage.

Storm Reports for Friday May 4, 2018 


NWS Storm Reports for Friday May 4, 2018. Note, these reports (92 in the CBS6 coverage area) 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
3 Miles NW of Poland Herkimer Several trees blown down 6:56pm
Long Lake Hamilton Trees blown down 6:58pm
1 Mile WNW of Herkimer Herkimer Measured 54 mph wind gust 7:05pm
1 Mile NNE of Dolgeville Herkimer Trees and wires blown down 7:15pm
1 Mile N. of Ilion Herkimer Trees blown down blocking West River Street 7:18pm
St. Johnsville Fulton Wind damage, large trees and wires down 7:21pm
2 Miles WNW of Speculator Hamilton Trees and wires down on Route 30 between Speculator and Indian Lake resulting in the road being closed 7:23pm
7 Miles S. of Speculator Hamilton Trees down along Route 8 7:25pm
5 Miles ENE of Ephratah Fulton Large area with multiple large pine trees blown down 7:26pm
Hessville Montgomery Measured 69 mph gust 7:28pm
1 Mile SSW of St. Johnsville Montgomery Trees blown down 7:30pm
4 Miles SSW of Caroga Lake Fulton Trees down, blocking one lane of Route 10A 7:33pm
Hartwick Otsego Trees and wires down throughout the town 7:32pm
Middlefield Otsego Trees block Route 28 7:34pm
2 Miles E. of Stratford Fulton Trees blown down 7:35pm
Johnstown Fulton Numerous trees blown down in Johnstown from Pleasant Avenue east to Route 30A 7:37pm
Benson Hamilton Trees down in the town of Benson 7:37pm
Johnstown Fulton Tree and wires down on a vehicle 7:40pm
Mayfield Fulton Metal roof torn off a home 7:42pm
Sharon Springs Schoharie Large trees blown down 7:42pm
1 Mile SW of Edinburg Saratoga Trees and wires blown down 7:43pm
2 Miles S. of Sharon Springs Schoharie Tree blown down onto Route 10 7:43pm
Amsterdam Montgomery Measured 57 mph gust 7:45pm
4 Miles SW of Hadley Saratoga Trees, wires, and pole blown down 7:50pm
Fort Johnson Montgomery Tree blown down on Mckay Road 7:50pm
Edmeston Otsego Numerous trees blown down through the town 7:50pm
Glen Montgomery Down tree blocking the road in the town of Glen 7:51pm
Amsterdam Montgomery Power pole snapped 7:51pm
5 Miles NE of Day Center Saratoga Trees blown down 7:54pm
Delhi Delaware Trees and wires down throughout Delhi 7:55pm
Charleston Four Corners Montgomery Tree blown down across NY 30A, just north of Gordon Road 7:58pm
Hancock Delaware Trees and wires down throughout Hancock 8:00pm
2 Miles SE of Rotterdam Junction Schenectady Route 5S closed due to downed trees and wires at Lower Gegg Road 8:04pm
Ballston Spa Saratoga Trees blown down in the village 8:05pm
Lake George Village Warren Multiple trees blown down along Route 9L all the way to route 9 8:06pm
Schoharie Schoharie Two trees reported down 8:06pm
3 Miles NNW of Glens Falls Airport Warren Trees and wires blown down 8:08pm
Middleburgh Schoharie Three trees reported down 8:08pm
1 Mile ENE of Lake George Village Warren Route 9L closed between Bay Road and Beach Road due to downed trees and wires 8:08pm
2 Miles E. of Malta Saratoga Route 9P closed between Plains Road and Lake Road due to downed pole and wires 8:10pm
2 Miles SSW of Ballston Spa Saratoga Trees blown down in a back yard 8:11pm
Schenectady Schenectady Measured 67 mph gust on top of the MVP building (100' above ground level) 8:11pm
1 Mile N. of Scotia Schenectady Trees blown down 8:12pm
Glens Falls Airport Warren Measured 61 mph gust by the ASOS 8:13pm
1 Mile SW of Glenville Schenectady Measured 58 mph gust 8:14pm
Niskayuna Schenectady Measured 51 mph gust at CBS 6 on Balltown Road 8:14pm
Scotia Schenectady Trees down on North Ten Broeck Street 8:14pm
Glens Falls Warren Measured 62 mph wind gust by the NYS Mesonet 8:15pm
East Glenville Schenectady Trees down along Sutherland Drive in East Glenville 8:15pm
1 Mile SW of Berne Albany Tree branches down blocking roads 8:18pm
1 Mile NW of North Easton Washington Several large pine trees uprooted and snapped 8:22pm
4 Miles SSW of Argyle Washington Trees blown down 8:23pm
Argyle Washington Many trees blown down, roof torn off and barn damaged 8:23pm
Rotterdam Schenectady Trees and wires blown down 8:25pm
Schaghticoke Rensselaer Trees blown down 8:25pm
Greenwich Washington Multiple pine trees damaged with the tops sheared off 8:25pm
5 Miles S. of Whitehall Washington Measured 54 mph wind gust 8:25pm
Gilboa Schoharie Trees blown down 8:25pm
3 Miles N. of Guilderland Albany Tree down near Wildwood School 8:27pm
1 Mile NNE of Guilderland Albany Trees blown down 8:27pm
2 Miles SW of Halfmoon Saratoga Trees blown down 8:27pm
Colonie Albany Trees blown down 8:27pm
5 Miles NNW of Salem Washington Many trees blown down around Hebron, West Hebron with the intersection of County Route 30 and 31 closed 8:28pm
Cossayuna Washington Numerous trees and limbs down around the north side of Cossayuna Lake 8:28pm
Cambridge Washington Numerous trees and wires down in and around Cambridge, five large trees on a house with trees down on cars 8:29pm
5 Miles NNW of Salem Washington Numerous trees down near the intersection of Route 30 and Route 31, north of Cossayuna Lake 8:30pm
Westmere Albany Trees and wires blown down 8:31pm
4 Miles SSW of Voorheesville Albany Tree down Stove Pipe Road/Upper Flat Rock Road 8:33pm
Albany Albany Trees and wires blown down 8:39pm
Pittstown Rensselaer Trees down 8:40pm
1 Mile SSW of Arlington, VT Bennington Several trees blown down 8:40pm
3 Miles ESE of Hoosick Falls Rensselaer Trees blown down 8:41pm
1 Mile SE of Dorset, VT Bennington Several trees blown down 8:41pm
Manchester, VT Bennington Several trees blown down 8:45pm
Manchester, VT Bennington Multiple large trees damaged by the wind 8:45pm
Hampton Manor Rensselaer Route 20 closed at Madison Avenue due to downed power pole 8:48pm
Winhall, VT Bennington Trees blown down 8:52pm
1 Mile SE of Phoenicia Ulster Trees and wires blown down 8:54pm
Bennington, VT Bennington Vermont State police report many trees down throughout Bennington County 9:00pm
Valatie Columbia Trees blown down 9:04pm
3 Miles E. of West Shokan Ulster Trees and wires blown down 9:06pm
4 Miles E. of West Shokan Ulster Trees down throughout the Shokan area 9:06pm
Catskill Greene Trees blown down 9:08pm
Olivebridge Ulster Trees down throughout the town 9:08pm
5 Miles S. of Catskill Columbia Tree blown down 9:15pm
2 Miles NNE of Hillsdale Columbia Trees blown down 9:20pm
3 Miles NW of Philmont Columbia Tree and wires blown down 9:20pm
3 Miles NNE of Richmond, MA Berkshire Trees blown down on Route 20 at Hancock Shaker Village 9:22pm
1 Mile SW of Pittsfield, MA Berkshire Tree blown down on West Housatonic Street 9:23pm
3 Miles WSW of Pittsfield, MA Berkshire Tree blown down on Melbourne Road 9:23pm
1 Mile NNW of Pittsfield, MA Berkshire Tree blown down on Mcarthur Street

9:24pm

Pittsfield, MA Berkshire Measured 58 mph wind gust by the ASOS 9:27pm

Photograph contributed via Facebook by Carl Bond: Shelf cloud along the leading edge of the squall line coming into Glenville, Schenectady, County, Friday May 4, 2018. Damaging wind subsequently struck Glenville with power outages in the town lasting well into Saturday May 5.

Shelf cloud over Glenville, Schenectady County Friday May 4, 2018 

Photographs contributed via Facebook by William Swanson Kuban
Widespread significant wind damage throughout Hebron, Washington County

Damage aftermath in Hebron, Washington County Saturday May 5, 2018  Damage aftermath in Hebron, Washington County Saturday May 5, 2018 
Damage aftermath in Hebron, Washington County Saturday May 5, 2018  Damage aftermath in Hebron, Washington County Saturday May 5, 2018