A warm front stalled along the northern Massachusetts border.  Low pressure moved from the Mid Atlantic states up across Southeast Massachusetts during the night of the 18th and early morning of the 19th.  High moisture values in place south of the warm front and a low level jet to generate lift over Southeast Massachusetts led to a period of torrential downpours from New Bedford to Outer Cape Cod.

Flash Flood in BARNSTABLE, MASSACHUSETTS
From 18-AUG-17 23:38:00 to 19-AUG-17 09:00:00 (EST-5)
Location: NORTH EASTHAM
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Amateur Radio

At 1138 PM EST, Cable Road near Nauset Regional High School in Eastham was flooded and impassable.  At 1154 PM EST, there were multiple reports of flooded basements on Jennie Clark Road. There were also reports of flooded basements on Kingswood Drive and Cestaro Way. At 1204 AM EST a car on Gail's Way was trapped in flood waters in a road washout. At 1252 AM EST there was three feet of water on Old Orchard Road near Kettle Hole Road.  At 111 AM EST, two cars were trapped in flood waters on Brackett Road.  At 6 AM EST, a Cocorahs observer in Eastham reported a storm total rainfall of 8.25 inches.

Flash Flood in BARNSTABLE, MASSACHUSETTS
From 18-AUG-17 23:39:00 to 19-AUG-17 03:00:00 (EST-5)
Location: SOUTH BREWSTER
Flood cause: Heavy Rain
Property damage: 12.00K
Crop damage: 0.00K
Reported by: Amateur Radio

At 1139 PM EST, a basement was flooded on Robbins Hill Road in Brewster.  At 1215 AM EST, the Ocean Edge Mansion on Main Street had flooding in the parking lot and the west wing of the building. At 1220 AM EST, a basement was reported flooded on Endicott Lane. At 1 AM EST, a basement was flooded on Lunds Farm Way.

Flash Flood in BARNSTABLE, MASSACHUSETTS
From 19-AUG-17 00:18:00 to 19-AUG-17 07:00:00 (EST-5)
Location: DENNIS
Flood cause: Heavy Rain
Property damage: 7.00K
Crop damage: 0.00K
Reported by: Amateur Radio

At 1218 PM EST, a car was trapped in flood waters on Upper County Road near the Hart Farm. At 1220 AM EST, the parking lot at Ring Brothers Marketplace was flooded. At 1224 AM EST, Bob Crowell Road was flooded near the intersection with State Route 134 and the DPW was requested for assistance. At 1230 AM EST, the Sea Shell Motel on Chase Avenue had flooding on the first floor.  At 321 AM EST, an amateur radio operator measured 6.95 inches of rain.

Flash Flood in BARNSTABLE, MASSACHUSETTS
From 19-AUG-17 00:42:00 to 19-AUG-17 05:30:00 (EST-5)
Location: CAHOON HOLLOW
Flood cause: Heavy Rain
Property damage: 4.00K
Crop damage: 0.00K
Reported by: Amateur Radio

At 1242 AM EST, a car was reported trapped in a sinkhole near the Beachcomber on Cahoon Hollow Road in Wellfleet. At 1248 AM EST, US Route 6 was reported impassable due to flooding in the area near the Wellfleet Post Office.  At 107 AM EST, Cottontail Road was reported flooded and impassable.  At 530 AM EST, a Cocorahs observer in Wellfleet reported storm total rainfall of 5.30 inches.

Flash Flood in BARNSTABLE, MASSACHUSETTS
From 19-AUG-17 01:12:00 to 19-AUG-17 03:00:00 (EST-5)
Location: CHATHAM
Flood cause: Heavy Rain
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Amateur Radio

At 112 AM EST, the Chatham Town Hall basement and parking lot were reported to be flooded. At 300 AM EST, the Automated Surface Observation platform at Chatham Airport reported storm total rainfall of 5.27 inches.

Flash Flood in BARNSTABLE, MASSACHUSETTS
From 19-AUG-17 01:23:00 to 19-AUG-17 04:00:00 (EST-5)
Location: DENNIS
Flood cause: Heavy Rain
Property damage: 0.20K
Crop damage: 0.00K
Reported by: Amateur Radio

At 112 AM EST, State Route 6A in Yarmouth was reported flooded and impassable. At 600 AM EST, a Cocorahs observer in Yarmouth reported a storm total rainfall of 5.15 inches.

Flood in BRISTOL, MASSACHUSETTS
From 18-AUG-17 23:00:00 to 19-AUG-17 02:00:00 (EST-5)
Location: NORTH BRISTOL
Flood cause: Heavy Rain
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Amateur Radio

At 11 PM EST, State Route 18 at Cove Street was closed due to flooding.  At 1114 PM EST, a car was trapped in flood waters on southbound Route 18 at the Purchase Street ramp. At 1125 PM EST, Route 18 was closed in both directions due to flooding between Cove Street and Potomska Street.