A wave of low pressure moved eastward along a stalled frontal boundary across the area as a strong upper level disturbance passed over region, aiding in the development of showers and thunderstorms across east central New York during the day Friday July 31st. The airmass in place was very humid, allowing storms to produce torrential downpours.  In addition, the storms were slow movers.
Generally, 1 to 3 inches of rain was reported across the area, with the highest totals across portions of Albany, Columbia, Rensselaer and Ulster counties. The ground was waterlogged and rivers and streams were already running high from the torrential rains which fell in the couple of days prior. Northern Columbia and southern Rensselaer counties were hard hit by flash flooding on Wednesday, so the heavy rain on Friday resulted in additional flash flooding and damage.
States of Emergency which were declared across portions of northern Columbia and southern Rensselaer counties remained in effect into Friday night.

Flash Flood in ALBANY, NEW YORK
From 31-JUL-09 09:15:00 to 31-JUL-09 14:15:00 (EST-5)
Location: VOORHEESVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Mountainview Street and Helderberg Parkway, also known as Route 85A, in Voorheesville were closed due to flash flooding from very heavy rainfall.

Flash Flood in WASHINGTON, NEW YORK
From 31-JUL-09 09:17:00 to 31-JUL-09 14:15:00 (EST-5)
Location: EAST WHITEHALL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Upper Turnpike Road in Whitehall was closed due to flash flooding from very heavy rainfall.

Flood in COLUMBIA, NEW YORK
From 31-JUL-09 16:40:00 to 31-JUL-09 20:55:00 (EST-5)
Location: CLAVERACK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A state of emergency was declared in the Town of Claverack due to widespread flooding from intense rainfall. Numerous roadways remained closed.

Flash Flood in GREENE, NEW YORK
From 31-JUL-09 13:30:00 to 31-JUL-09 15:15:00 (EST-5)
Location: NEW BALTIMORE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

County Route 61, also known as Main Street in New Baltimore, was closed due to flash flooding from very heavy rainfall.

Flood in COLUMBIA, NEW YORK
From 31-JUL-09 16:20:00 to 31-JUL-09 20:55:00 (EST-5)
Location: LORENZ PARK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A state of emergency was declared in the Town of Greenport, including Greenport Center, due to widespread flooding from intense rainfall. Numerous roadways remained closed.

Flood in COLUMBIA, NEW YORK
From 31-JUL-09 11:52:00 to 31-JUL-09 15:45:00 (EST-5)
Location: CHATHAM
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A roadway was flooded at Elm Street and Payne Avenue in Chatham due to heavy rainfall.

Flash Flood in RENSSELAER, NEW YORK
From 31-JUL-09 12:08:00 to 31-JUL-09 14:15:00 (EST-5)
Location: STEPHENTOWN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

The intersection of Routes 22 and 43 in Stephentown was closed due to high water from very heavy rainfall. A service station at the intersection had 4 to 6 inches of standing water inside.

Flash Flood in SARATOGA, NEW YORK
From 31-JUL-09 09:07:00 to 31-JUL-09 14:15:00 (EST-5)
Location: BEMIS HGTS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Route 4 and Route 32 were closed in Stillwater due to flash flooding from very heavy rainfall.

Flash Flood in GREENE, NEW YORK
From 31-JUL-09 11:50:00 to 31-JUL-09 15:45:00 (EST-5)
Location: CATSKILL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

West Main Street in the Village of Catskill along the Catskill Creek was closed due to flash flooding.

Flash Flood in COLUMBIA, NEW YORK
From 31-JUL-09 11:52:00 to 31-JUL-09 15:15:00 (EST-5)
Location: CHATHAM
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Heavy rain resulted in flash flooding in Chatham at the intersection of Elm Street and Payne Avenue.

Flash Flood in COLUMBIA, NEW YORK
From 31-JUL-09 12:21:00 to 31-JUL-09 15:15:00 (EST-5)
Location: GHENT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Flash flooding from intense rainfall resulted in a road closure along Wood Avenue in Ghent.

Flood in GREENE, NEW YORK
From 31-JUL-09 14:00:00 to 31-JUL-09 15:15:00 (EST-5)
Location: CATSKILL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Route 23, Hamburg Road, Allen Street, and West Main Street in Catskill were reported partially closed due to flooding from to heavy rainfall.