Thursday July 29, 2021
Widespread Flash Flood Event - Fulton - Saratoga - Washington - Bennington Counties

Seriously eroded stream bed in Manchester, VT - Friday morning July 30, 2021 - WeatherNet 6 spotter Matt Rhode
Four to five inches of rain produced dangerous flash flooding throughout Manchester and Arlington, VT with the level of flooding and resulting damage comparable to the flooding and damage that tropical storm Irene produced in August 2011.

Flooding zone map, Thursday July 29, 2021

Of the numerous heavy rain events that lead to flooding in the local area in July 2021, this event was the most widespread with a large zone of 2-4" rainfall totals occurring in just a couple of hours stretching from southern Herkimer through Fulton, southern Hamilton, northern Saratoga, southern Warren, central Washington, Rutland and northern and central Bennington counties. Although rainfall was not has heavy in the Capital region, the 0.79" of rain that fell at Albany occurred in less than hour as a thunderstorm moved through between 8 and 9pm. This rapid rain burst was an example of how efficiently rain was generated with the storm system that moved through.

Flash flooding during the evening was reported in the following towns and villages

- Gloversville
- Broadalbin
- Northville
- Lake Desolation
- Wilton
- Gansevoort
- Moreau
- Saratoga Springs
- Middle Falls
- Schuylerville
- West Glens Falls
- Fort Edward
- Argyle
- Hartford
- Granville
- Salem
- Arlington, VT
- Manchester, VT
- major flash flooding reported with many roads impacted
- Pittsfield, MA (Minor street flooding)
- Richmond, MA (Minor)

The excessive rain area is outlined in green on the map below with some WeatherNet 6 spotter rainfall totals marked. The heaviest rain fell from the late afternoon (4-5pm) through 8-9pm in this zone. The rain area, which included a few strong thunderstorms with gusty wind and frequent lightning, narrowed and dropped south through the Capital Region, Berkshires and mid Hudson valley between 7:30 and 10pm before dissipating. Rainfall totals generally ranged from 1/2" to 1.00" south of the flood zone in the areas where rainfall did occur. Parts of the Catskills and mid Hudson valley received very little rain, generally 1/4" or less from the event..

Flooding zone map, Thursday July 29, 2021 

Storm Total Rainfall Report Highlights - WeatherNet 6
4.68"
of rain measured in Manchester, VT - Bennington County
3.93" of rain measured in Lake Desolation - Saratoga County
3.62" of rain measured at Salem - Washington County
3.57"
of rain measured at Arlington, VT - Bennington County
3.44"
of rain measured in Corinth - Saratoga County
3.17" of rain measured in Lake Luzerne - Warren County
3.11"
of rain measured in Greenwich - Washington County
2.60" to 2.76" of rain measured at Hartford - Washington County (2 spotter reports)
2.67" of rain measured at Edinburg - Saratoga County
2.48"
of rain measured at Hebron - Washington County
2.20" to 2.34"
of rain measured at Granville - Washington County (2 spotter reports)
2.04" of rain measured at West Arlington, VT - Bennington County
1.87" of rain measured at Glens Falls - Warren County

THE EVENT:
The weather set-up across the Northeast was interesting with this one characterized by a potent mid level disturbance coming in from the west and a series of frontal boundaries that stretched through New York, Pennsylvania and New Jersey. Very warm, humid, and unstable air flooded into eastern PA and New Jersey along and south of a strong warm front which resulted in violent thunderstorms along and south of that boundary and a major outbreak of tornadoes around and to the north of Philadelphia into New Jersey during the late afternoon and early evening. That warm front had stalled out well south of the local area which spared our region from any significant severe weather. It was a secondary and more elevated warm front which had lifted north into the local area through the day that helped to focus the heavy rainfall in the zone just north of the Capital Region during the late afternoon and evening which ultimately lead to the flood event.

The elevated warm front stalled around the Mohawk valley to southern Vermont and served as the main convergence zone for the heavy rain that evolved north of the Capital Region. Strong forcing developed along the front in response to the approach and passage of a potent mid level low pressure wave which had subsequently caused a small surface low (meso-low) to develop and ride down the Mohawk valley. A period of strong southerly inflow winds, with 30+ mph gusts, developed in response to this meso-low during the early evening which transported mid to upper 60 degree dewpoint air into the rain zone fueling the excessive rain event.

A small amount of mainly elevated instability developed just to the south of the heaviest rain zone from the Capital Region into the Berkshires and mid Hudson valley in what was a mesoscale warm sector. As the meso-low moved through the region it narrowed the rain zone and pushed it south into the more unstable air through the Capital Region, Berkshires, and mid Hudson valley between 7:30 and 10:00pm. Lightning developed and winds just a few thousand feet off the ground, indicated by Doppler radar, increased to 60-70 mph, suggesting a potential for severe gusts. In fact a few strong gusts did result in a few trees and power lines being blown down from Saratoga Springs to Halfmoon, Hoosick Falls to Canaan and Cheshire, MA. Damaging surface gusts, however, were limited as a shallow stable layer of air near the ground prevented efficient mixing from occurring which fortunately resulted in the strongest winds remaining aloft. In fact observations from the New York State Mesonet sites and the CBS6 weather stations indicated peak winds generally ranged from 35-50 mph in small pockets as the thunderstorms moved through, well below the severe weather threshold of 58 mph.

The event was essentially over between 10:00 and 10:30pm with the passage of the mid level disturbance and surface meso-low with a small zone of heavy thunderstorms pressing south through the Berkshires before dissipating. A few additional scattered showers would occur between 4 and 8am on the 30th as the main cold front moved across the region.

A shot of summer polar air then followed the system from Friday afternoon through Saturday July 31 with dewpoints dropping back into the mid 40s giving the air a decidedly fall-like feel.

The following series of radar images chronicle the rain event from 5 to 10pm.

Albany Doppler Radar Image around 5pm Thursday July 29, 2021 - Heavy rain evolving across the southern Adirondacks through the Lake George-Glens Falls area into Washington County


Albany Doppler radar base reflectivity image, 5pm July 29, 2021 

Albany Doppler Radar Image around 6pm Thursday July 29, 2021 - Areas of torrential rain in progress at this time across central Herkimer, northern Fulton, Washington and Rutland counties. Interesting mesovortices were indicated on radar in Herkimer and Fulton counties at this time.

Albany Doppler radar base reflectivity image, 6pm July 29, 2021 

Albany Doppler Radar Image around 7pm Thursday July 29, 2021 - Intense rainfall, with rates of 1"-2" per hour, was in progress at this time across Fulton and northern Saratoga counties and were expanding into south-central Washington County. Occasional lightning was observed in the rain zone.

Albany Doppler radar base reflectivity image, 7pm July 29, 2021 

Albany Doppler Radar Image around 8pm Thursday July 29, 2021 - A meso-low was located near Saratoga Springs at this time with the rain zone narrowed into a line of thunderstorms which had been pushed south into Montgomery, Schenectady, Saratoga, Washington and northern Bennington counties. Intense rainfall rates of 2"/hour were in progress east of Saratoga Springs to Manchester Vermont. Strong winds of 60-70 mph were indicated a few thousand feet above the ground along and east of the line segment in southern Saratoga and Schenectady counties with surface gusts ranging from 35-45 mph on average.


Albany Doppler radar base reflectivity image, 8pm July 29, 2021

Albany Doppler Radar Image around 8:30pm Thursday July 29, 2021 - Cloud to ground lightning had increased at this time with torrential rain over southern Washington and Bennington counties as well as in a narrow zone across northern Albany and northern Rensselaer counties.


Albany Doppler radar base reflectivity image, 8:30pm July 29, 2021

Albany Doppler Radar Image around 9pm Thursday July 29, 2021 - Torrential rain had ended in the flood zone at this time with a narrow line of strong thunderstorms with frequent lightning in Rensselaer County pressing south into the Berkshires

 Albany Doppler radar base reflectivity image, 9pm July 29, 2021

Albany Doppler Radar Image around 10pm Thursday July 29, 2021 - Heavy rain was reduced to a short line of weakening thunderstorms in Berkshire County at this time. This area of rain continued to contract and ultimately dissipated close to 10:30pm over southern Berkshire County marking an end to the event.

Albany Doppler radar base reflectivity image, 10pm July 29, 2021 

Albany Doppler Radar Rainfall Estimate Map Thursday July 29, 2021 - The zone shaded in purple indicates rainfall amounts ranging from 2"-4" on average and locally up to 5". The most significant flash flooding occurred within this zone. Rainfall amounts of 1"-2" occurred in the blue shaded area both north and south of the axis of heaviest rainfall, with 1/2" to 1" of rain falling in the area shaded in green.

 Albany Doppler radar rainfall estimate map, July 29, 2021

WeatherNet 6 Rainfall Reports - Thursday July 29, 2021

Town County Rainfall Report Town County Rainfall Report
Savoy, MA Berkshire 1.10" Hancock, MA Berkshire 1.03"
Lanesborough, MA Berkshire 0.80" Stockbridge, MA Berkshire 1.11"
Clarksburg, MA Berkshire 0.93"      
           
Albany (ASOS) Albany 0.81" Delmar Albany 0.59"
Glenmont Albany 0.80" Guilderland Albany 0.68"
Loudonville Albany 0.70" Colonie Albany 0.77"
Albany (Downtown) Albany 0.40" Albany (City) Albany 0.40"
           
Taghkanic Columbia 0.12" Livingston Columbia 0.08"
           
Arkville Delaware 0.22"      
           
Red Hook

Dutchess

0.22"      
           
Halcott Greene 0.17" Cairo Greene 0.20"
           
Indian Lake Hamilton 0.90" Hoffmeister Hamilton 2.32"
           
Amsterdam Montgomery 1.18" to 1.24" Fonda Montgomery 1.03"
Palatine Bridge Montgomery 1.10"      
           
Petersburg Rensselaer 1.05" Troy Rensselaer 0.29"
Center Brunswick Rensselaer 0.46"      
           
Lake Desolation Saratoga 3.93" Saratoga Springs Saratoga 1.37"
Corinth Saratoga 3.44" Galway Saratoga 1.55"
Ballston Spa Saratoga 0.73" to 1.30" Clifton Park Saratoga 0.69'"
Edinburg Saratoga 2.67" Charlton Saratoga 0.50"
           
Rotterdam Schenectady 0.72" Scotia Schenectady 0.75"
Schenectady Schenectady 0.24"      
           
Landgrove, VT Bennington 1.15" West Arlington, VT Bennington 2.04"
Manchester, VT Bennington 4.68" Danby, VT Rutland 0.34"
Woodford, VT Bennington 0.70"      


NWS Flood Reports for Thursday July 29, 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 flood which may have occurred.

Town County Severe Weather Report Time
Wilton Saratoga Flash Flood: Flooded yards and roads throughout the town, small hail reported 6:21pm
Hartford Washington Flash Flood: Roadway washed away on East Starbuck Lake 6:31pm
Fort Edward Washington Flash Flood: Water over Drifting Ridge Road 7:45pm
Argyle Washington Flash Flood: The Dollar General store flooded 7:57pm
Moreau Saratoga Flash Flood: Flooding in several locations with a significant mudslide in Moreau 8:00pm
Manchester, VT Bennington Flash Flood: Street flooding, water flooded roads and yards with gravel and rock flows 8:00pm
Fort Edward Washington Flash Flood: Water over Tori Trace Road 8:07pm
Fort Edward Washington Flash Flood: Route 4 and Backhouse Road impassable due to flooding 8:13pm
Argyle Washington Flash Flood: Water running over numerous roadways, rockslide reported 8:15pm
Argyle Washington Flash Flood: Driveway reported washed out 8:16pm
Middle Falls Washington Flash Flood: Numerous areas of several inches of standing water and water rushing over the road from other roads along Route 29 and 40 from Saratoga to Argyle 8:36pm
Argyle Washington Flash Food: Tree and rock slide on State Route 40 causing the road to become impassable 8:38pm
4 M North of Schuylerville Washington Flash Flood: Blodgett Road impassable due to flooding 8:38pm
Fort Edward Washington Flash Flood: Roadway washed out near O'Brien Road and Anthony Road 8:38pm
Fort Edward Washington Flash Flood: Culvert collapse on Route 4 8:42pm
Schuylerville Saratoga Flash Flood: 3 feet of standing water on Route 32 about 0.2 miles north of Route 4 8:45pm
Argyle Washington Flash Flood: Water over County Rd. 49 8:47pm
Arlington, VT Bennington Flash Flood: Vermont Route 3123 closed due to flooding near Sandgate intersection 9:00pm
2 M NNE of Schuylerville Washington Flash Flood: County Route 113 near Post Office Lane impassable due to flooding 9:00pm
Argyle Washington Flash Flood: Water over the roadway near the intersection of County Route 48 and County Route 49 9:00pm
Manchester, VT Bennington Flash Flood: Many roads reported flooded and closed 9:05pm
Arlington, VT Bennington Flash Flood: Many roads reported flooded and closed 9:05pm
Argyle Washington Flash Flood: Roadway washed out on Hunter Road between Williams Road and Moore Road 9:07pm
Argyle Washington Flash Flood: County Farm Road washed out 9:26pm
Wilton Saratoga Flash Flood: Water rescue (car stuck in flood waters at the intersection of Ballard Road and Route 9, roads closed 9:27pm
Argyle Washington Flash Flood: Culvert plugged, flooded onto East Lake Road 9:34pm
Argyle Washington Flash Flood: Moore Road flooded 9:52pm
Pittsfield, MA Berkshire Flash Flood: Minor street flooding as well as some flooding in yards 10:15pm
Richmond, MA Berkshire Flood: Flooding on Swamp Road 10:57pm
Salem Washington Flash Flood: Water over the roadway on Route 313 between County Route 61 and Hickory Hill Road 12:24am/30th
West Glens Falls Warren Flash Flood: Minor flooding reported in Moreau State Park 6:30am/30th

Albany National Weather Service Rainfall Observation Analysis an Distribution Map - Thursday evening into Friday Morning July 29-30, 2021

Albany National Weather Service Rainfall Analysis July 29-30, 2021