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
Latest North American Model Outlines the Potential for Extremely Heavy Rainfall
If the latest NAM model is accurate, the heaviest rain with the core of the tropical storm would impact the immediate Washington Area between 11am and 4pm on Tuesday. Any shift eastward in track would help to lessen the threat of extreme flooding in the DC metro area. Regardless, this storm system poses a significant risk of flooding.
Weather Prediction Center (WPC) Rainfall Potential
The image below, courtesy NOAA/WPC shows the latest forecast for rainfall potential of four to six inches of rain for a majority of the metropolitan region with 6 to 10″ (in orange) in the eastern suburbs of D.C., southern Maryland and Baltimore!
The next image shows currently where the greatest flash flood risk is (courtesy NOAA/WPC) with much of the DC metropolitan area under a moderate risk.
Bottom Line: If you live in a low-lying area, prone to flooding, now is the time to have a plan ready on Tuesday should you need to grab your belongings and evacuate to higher ground.