High Impact Flooding Event for DC Metropolitan Area

Numerous strong to severe thunderstorms are expected to break out this afternoon and evening across the DC Region, well in advance of the approach of tropical storm Isaias.  Thunderstorms could produce strong, damaging winds with an isolated tornado possible. The image from the latest high resolution NAM model below (courtesy, tropicaltidbits.com) shows a nasty line of storms moving into our region between 4 and 8pm.

The latest ensemble models (spaghetti chart below) shows confidence in a storm track from just east of Richmond, VA to the mouth of the Potomac before crossing over the Bay into Delaware and New Jersey.

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Flash Flooding Potential Increasing as Isaias Tracks through Mid-Atlantic

Forecast models have narrowed on a solution which tracks Tropical Storm Isaias from the Tidewater of Virginia northeastward to near the mouth of the Potomac River on Tuesday.  If this track verifies, much of the Washington Region will receive rainfall amounts of  two to four inches with some locations, especially along and east of interstate 95 potentially picking upwards of 4 to 6“.

Numerous thunderstorms are expected Monday afternoon through the overnight hours ahead of tropical storm Isaias. Rainfall totals from theses storms will easily drop an inch or two before the core of the tropical storm passes to our southeast on Tuesday.  On Tuesday rainfall rates in excess of 1” per hour are likely leading to the threat of widespread flash flooding of area creeks and streams and low-lying urban areas.  This amount of rain in under 12 hours will likely create flash flood emergencies and water rescues!

The Latest Spaghetti Models

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