National Weather Service United States Department of Commerce

Southwest Monsoon Flooding

Monsoonal conditions in the Southwest will lead to threats of flash flooding through the weekend. Severe thunderstorms will be possible through Friday night in the northern tier of the country and Saturday afternoon in the vicinity of the Southern Great Lakes. Warm conditions have prompted Heat Advisories for portions of the Midwest and ArkLaMiss this weekend. Read More >

Heavy rain and flash flooding in Washington

Thursday afternoon September 10th 2020

 

Early on Thursday afternoon, showers and thunderstorms arose along a weak atmospheric boundary oriented north to south across the Washington area. The storms that formed were fed by tropical moisture to our southeast which allowed for heavy rainfall rates. In addition, weak winds in the atmosphere kept the storms moving slowly. That combination of heavy rain and slow movement allowed for 2-5" of rain to fall in a relatively narrow corridor across parts of the Washington metro area. Most of that rain fell within 2 hours.

The heavy rains produced flash flooding of numerous roads and streams and first responders conducted several water rescues. The hardest hit areas were: the District of Columbia, Arlington and Alexandria Virginia, and the Maryland suburbs in Prince Georges and Montgomery Counties.

 

Listing of rain totals: linked here.

Listing of reports of flooding & flash flooding (received by NWS Baltimore/Washington): linked here.


Map of radar estimated rainfall: (Areas in red are 3"+)

 

Radar Loop showing the storms from 1:25 - 1:49 P.M.

Radar loop

 

Satellite Image at 2:30 P.M.

Satellite image

 

Link to images of flooding: (using internet search "DC flooding September 2020")