A relatively stationary front meandered across southern New England on the 17th and 18th while low pressure slowly moved along the front.  At upper levels, an upper low was moving slowly eastward from the Great Lakes.  With very moisture-laden air in place across the region, the result was heavy rain and flash flooding. In addition, there were rounds of severe thunderstorms and even a weak tornado in northern Connecticut. Rainfall totals ranged from 3.0 to 5.6 inches in northern Connecticut and western and central Massachusetts. Mainly 1.0 to 2.0 inches fell in Rhode Island and eastern Massachusetts.

Tornado in TOLLAND, CONNECTICUT
From 18-JUL-21 17:11:00 to 18-JUL-21 17:18:00 (EST-5)
Location: SOMERS
Tornado F-scale: EF0
Property damage: 45.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

In Somers, a weak tornado touched down in the evening. Amateur radio operators followed up on a tip from a trained Skywarn spotter via social media and then uncovered many reports.  We then spoke with Somers Fire Department officials, an eyewitness who observed the tornado, and viewed several online videos.  The following information summarizes all of these reports.
The tornado touched down on Colonial Drive, then tracked to the north-northeast, impacting Lake Drive just south of Shady Lake, Kibee Drive, a portion of Main Street (Route 190), Battle Street, and ended in the vicinity of Hickory Hill Drive.  This was a path length of 1.9 miles.  The approximate path width was 75 yards.  Damage photos led to estimates of maximum wind speeds of 75 to 80 mph, which put this on the mid to upper range of the EF-0 category of the Enhanced Fujita Scale.  The time, based on radar, fire department logs, and an eyewitness account, was from 611 PM to 618 PM EDT.
Several large pine trees were downed on Colonial Drive and two cars were destroyed by the falling trees.  Approximately 19 trees were snapped, twisted, and uprooted on Lake Drive. A resident of Lake Drive heard a loud whirring noise and observed the tops of trees flying by the house.  Shingles were missing on a house next door.  A playscape was lifted up and landed approximately 50 feet away.  On Main Street, a small corner of a roof was exposed, with additional damage along the length of the gutter.  Farther to the northeast, a few large oak trees were snapped on Hickory Hill Drive.
This storm was low-topped and did not produce any lightning...only heavy rain.  However high humidity and just enough wind shear aloft were sufficient to cause this isolated spin-up.

Thunderstorm Wind in TOLLAND, CONNECTICUT
From 17-JUL-21 15:20:00 to 17-JUL-21 15:20:00 (EST-5)
Location: SOUTH WILLINGTON
Magnitude: 50.00 EG
Property damage: 1.30K
Crop damage: 0.00K
Reported by: Amateur Radio

In Willington, trees and wires were down on Pinney Hill Road.

Thunderstorm Wind in TOLLAND, CONNECTICUT
From 17-JUL-21 16:00:00 to 17-JUL-21 16:00:00 (EST-5)
Location: GURLEYVILLE
Magnitude: 50.00 EG
Property damage: 1.30K
Crop damage: 0.00K
Reported by: Amateur Radio

In Mansfield, trees and wires were down on Codfish Falls Road.

Thunderstorm Wind in WINDHAM, CONNECTICUT
From 17-JUL-21 14:55:00 to 17-JUL-21 14:55:00 (EST-5)
Location: POMFRET CENTER
Magnitude: 50.00 EG
Property damage: 2.60K
Crop damage: 0.00K
Reported by: Amateur Radio

In Pomfret, trees and wires were down on Anderson Road and on Hamlet Hill Road.

Flash Flood in WINDHAM, CONNECTICUT
From 17-JUL-21 17:43:00 to 17-JUL-21 17:43:00 (EST-5)
Location: WEST ASHFORD
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

In Ashford, a bridge on Cushman Road, over Knowlton Brook, which is a tributary of the Mt. Hope River, was washed out due to rapid, heavy rainfall.  Rainfall totals by early evening included 4.95 inches in Pomfret, 4.75 inches in 2.5 hours in Ashford, and 3.42 inches in Woodstock.

Flash Flood in WINDHAM, CONNECTICUT
From 17-JUL-21 16:31:00 to 17-JUL-21 16:50:00 (EST-5)
Location: PHOENIXVILLE
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Amateur Radio

In Eastford, a section of Pilfershire Road was washed out. Rainfall totals by early evening included 4.95 inches in Pomfret, 4.75 inches in 2.5 hours in Ashford, and 3.42 inches in Woodstock.

Flash Flood in WINDHAM, CONNECTICUT
From 17-JUL-21 18:30:00 to 17-JUL-21 18:30:00 (EST-5)
Location: POMFRET
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Amateur Radio

In Pomfret, a portion of Route 244 was partially washed out.  Rainfall totals by early evening included 4.95 inches in Pomfret, 4.75 inches in 2.5 hours in Ashford, and 3.42 inches in Woodstock.

Flash Flood in WINDHAM, CONNECTICUT
From 17-JUL-21 19:20:00 to 17-JUL-21 19:20:00 (EST-5)
Location: WARRENVILLE
Flood cause: Heavy Rain
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

In the Warrenville portion of Ashford, flash flooding closed Route 44 over the Mt. Hope River between Route 74 and Route 89. Rainfall totals by early evening included 4.95 inches in Pomfret, 4.75 inches in 2.5 hours in Ashford, and 3.42 inches in Woodstock.

Flood in TOLLAND, CONNECTICUT
From 17-JUL-21 16:15:00 to 17-JUL-21 16:15:00 (EST-5)
Location: MANSFIELD FOUR CORNE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

In Mansfield, a section of Route 44 was closed due to flooding.

Flood in WINDHAM, CONNECTICUT
From 17-JUL-21 17:07:00 to 17-JUL-21 17:07:00 (EST-5)
Location: EASTFORD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

In Eastford, a section of Old Colony Road was flooded and impassable.