Monday June 21, 2021
Severe T'Storm Event

A fairly classic late spring/early summer severe weather set-up evolved over the Northeast and Appalachians on this day which resulted in over 500 severe wind reports across the outbreak region (45 locally) in what amounted to a series of short lines an clusters of severe thunderstorms which ultimately culminated with a squall line moving through eastern New York and western New England during the evening. In addition to the wind reports there was a confirmed tornado in western Pennsylvania, one in Dryden, NY, and at least four in the St. Lawrence valley in Quebec province Canada with one of those an EF2 in a Montreal suburb responsible for considerable damage and one fatality.

SET-UP
The atmosphere was characterized by sunny, hot and humid conditions across the local area with daytime maximum temperatures reaching the upper 80s to around 90° and dewpoints ranging from the upper 60s to the lower 70s. Aloft, a strong mid level jet stream trough approached from the west putting the region in moderate to strong west to southwest flow in the mid levels which was coupled with a strong south to southeast surface flow that was maximized in north-south valleys through the day with frequent gusts from 25-35 mph. A strong surface low going up through Quebec Canada aided in increasing the low level gradient which enhanced the wind fields. Wind shear as a result in both speed and direction was moderate to high across the region. The strong shear coupled with some cooling aloft due to the approach of the mid level trough allowed for both strong updraft development and for the updrafts to be sustained over long time periods.

CAPE values (convective available potential energy) increased to between 2500 and 3000 j/kg, indicating high amounts of instability favoring robust tall convective updrafts capable of bringing down strong winds from aloft. The turning of the wind and increase in speeds with height also favored transient circulations within storms, especially those that tracked across the Adirondacks, Lake George Region into Rutland County in VT. These small scale circulations, or mesovortices, are an ingredient that aides in small hail production as well as increasing the likelihood of damaging wind gusts at the surface.

Tropical storm Claudette was a bit player in the set-up with that storm emerging off the mid Atlantic coast early in the day then moving quickly to the northeast well south of New England through the evening. A ring of subsiding (sinking) air around the western and northern periphery of the circulation extended into the local area through the day and effectively capped thunderstorm development, despite convective temperatures being achieved early in the afternoon. This resulted in a quiet day for much of the region and allowed for instability to build uninhibited, which would play a role during the evening in sustaining updrafts and allowing for strong storms to continue well after sunset.

THE EVENT
The main focus for thunderstorms during the early to mid afternoon was across western and central NY and points south as well as across the Adirondacks, along the periphery of the subsidence zone around Claudette and in advance of a pre-frontal low pressure trough running in advance of a cold front approaching western New York. With the high shear and instability in place severe weather erupted after 2:30pm in Herkimer and Hamilton counties with several clusters of damaging storms moving across the southern Adirondacks to the Lake George region as well as northern Washington and Rutland counties through 6pm. Numerous reports of wind damage resulted from these storms as well as locally torrential rain which lead to brief localized poor drainage type flooding.

As Claudette's influence waned through the evening, thunderstorms that had been over central New York moved east ultimately evolving into a squall line which moved from west to east across the region between 7 and 11pm, impacting the Capital Region between 8:30 and 10pm. Transient mesovortices were evident in a cluster of storms through the early to mid evening in Herkimer, northern Fulton, Hamilton, Warren and northern Washington counties where additional wind damage occurred in numerous locations, including locations like Lake George through northern Washington County where wind damage had occurred with the first round of storms earlier in the day.

Farther south, however, only pockets of wind damage were observed mainly in the western Catskills, Schoharie, Greene, Columbia, and northern Berkshire counties, despite storm updrafts remaining quite intense. I suspect that subtle boundary layer cooling after sunset allowed enough low level stabilization to occur to limit the amount of damaging wind making to the ground with gusts generally observed to be in the 45-50 mph range with the storms as they came into the Capital Region and Hudson valley after 8:30-9:00pm. (Severe gusts are 58 mph or greater) Intense cloud to ground lightning, coming in barrages, however, was common with the storms in especially Saratoga, northeast Albany, Washington and Rensselaer counties due to the strong updrafts being driven by what was still considerable instability with CAPE values running between 1500 and 2000 j/kg. Rainfall rates were also quite high with 1/2" to 1.00" amounts falling in under an hour in the stronger storms. 0.91" of rain fell at Saratoga Springs in 30-45 mph with the passage of storm during the evening.

The thunderstorms ultimately weakened with a stabilizing atmosphere due to diurnal cooling and outflow dominate storms as they went through Bennington and Berkshire counties between 10 and 11pm with the event thus concluding.

The following series of Instant Doppler 6 radar images chronicles the progress of the squall line portion of the event from around 7:30 to 10:30pm Monday June 21, 2021

Instant Doppler 6 - 7:35pm June 21, 2021

Instant Doppler 6: 7:35pm June 21, 2021

Instant Doppler 6 - 8:08pm June 21, 2021

Instant Doppler 6: 8:08pm June 21, 2021

 Instant Doppler 6 - 8:38pm June 21, 2021

Instant Doppler 6: 8:38pm June 21, 2021

 Instant Doppler 6 - 8:54pm June 21, 2021

 Instant Doppler 6: 8:54pm June 21, 2021

 Instant Doppler 6 - 9:37pm June 21, 2021

Instant Doppler 6: 9:37pm June 21, 2021

 Instant Doppler 6 - 10:04pm June 21, 2021

Instant Doppler 6: 10:04pm June 21, 2021 

 Instant Doppler 6 - 10:23pm June 21, 2021

Instant Doppler 6: 10:23pm June 21, 2021

NWS Storm Reports for Monday June 21, 2021. 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
Piseco/Arietta Hamilton Major Wind Damage: Numerous trees blown down along Old Piseco Road and boats overturned 3:25pm
6 Miles S. of Speculator Hamilton Wind Damage: Trees blown down at Moffitt Beach near Route 8 3:35pm
Piseco Hamilton Wind Damage: Numerous power poles and trees down along County Route 24 on the backside of Piseco Lake 3:38pm
Piseco Hamilton Wind Damage: Trees and wires down on South Shore Road 3:45pm
4 Miles SW of Eagle Bay Herkimer Wind Damage: Tree blown down on South Shore Road 4:07pm
Hague Warren Wind Damage: Trees and wires down near route 8 and 9N 4:45pm
6 Miles NE of Hague Warren Wind Damage: Trees down across roadway on County Route 1 4:45pm
Bolton Landing Warren Wind Damage: Trees and wires down 4:53pm
Bolton Landing Warren Wind Damage: Tree an wires down on Route 9N 4:56pm
4 Miles ENE of Whitehall Washington Wind Damage: Tree blow down across roadway 5:05pm
Huletts Landing Warren Wind Damage: Tree and wires down on Lands End Way in Dresden 5:10pm
Kingsbury Washington Trees and wires down 5:25pm
Hampton Washington Wind Damage: Trees and wires blown down near Route 22A 5:25pm
1 Mile ENE of the Glens Falls Airport Warren Wind Damage: Tree on power lines on Bardin Rd. in Kingsbury 5:25pm
7 Mile N. of Granville Washington Tree and wires down on south Road in Hampton 5:30pm
Granville Washington Wind Damage: Trees and wires down in Middle Granville 5:40pm
Granville Washington Wind Damage: Trees and wires down on Cross and Butler Road intersection 5:50pm
Granville Washington Wind Damage: Trees and wires down on State Route 22A 6:07pm
Old Forge Herkimer Wind Damage: Trees blown down 6:31pm
Old Forge Herkimer Wind Damage: All lanes on Route 28 in Old Forge blocked between Crosby Blvd. and Adams St. due to wires down 6:35pm
Salisbury Herkimer Wind Damage: Multiple trees blown down 7:04pm
Little Falls Herkimer Wind Damage: Trees blown down 7:07pm
Lake Pleasant Hamilton Wind Damage: Trees blown down near Route 8 7:28pm
Putnam Washington Wind Damage: Wires down on County Route 1 7:55pm
Lake Luzerne Warren Wind Damage: Tree blown down onto wires 8:17pm
Lake George Village Warren Wind Damage: Tree blown down 8:26pm
Bolton Landing Warren Wind Damage: Tree blown down onto wires 8:26pm
Granville Washington Wind Damage: Tree and wires leaning over Stoddard Road 8:30pm
2 Miles NW of Glens Falls Warren Funnel cloud sighted approximately 4 miles north of observer toward Lake George 8:34pm
Summit Schoharie Wind Damage: Wires blown down 8:40pm
Pilot Knob Washington Wind Damage: Tree down on Hogtown and Sly Pond Road intersection 8:40pm
Galway Saratoga Wind Damage: Tree down on wires along Southline Road, lightning strike on a structure resulting in a fire 8:44pm
Fort Ann Washington Wind Damage: Tree and wires down on Buttermilk Falls Road 8:45pm
Corinth Saratoga Wind Damage: Wires down along Antone Mountain Rd. and harris Rd. 8:46pm
Middleburgh Schoharie Wind Damage: Trees and wires blown down 8:50pm
Porter Corners Saratoga Wind Damage: Tree down on wires 8:52pm
Granville Washington Wind Damage: Tree and wires blown down on Middleton Road 9:05pm
Lexington Greene Wind Damage: The northbound lane of Route 42 was closed just south of Spruceton Road due to a downed tree 9:09pm
Lincoln Park Ulster Wind Damage: Trees and wires blown down 9:35pm
New Paltz Ulster Wind Damage: A few trees and wires blown down 9:45pm
2 Miles ENE of Schuylerville Washington Wind Damage: Tree across Hogsback Road 9:55pm
Middle Falls Washington Wind Damage: Tree across Spraguetown Road 9:55pm
Livingston Columbia Wind Damage: Tree and wires blown down 10:10pm
Williamstown, MA Berkshire Wind Damage: Tree down on U.S. Route 7 and Cold Spring Road 10:40pm


Storm Reports: Monday June 21, 2021

Storm Prediction Center Storm Reports For June 21, 2021