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.
The European model (image below) courtesy Pivotal Weather, shows Tropical Storm Isaias tracking from near Richmond to the Chesapeake Bay before crossing the Delaware River into New Jersey.
The next two images show Rainfall Forecasts from the NAM and GFS models:
The Risk of Flash Flooding has increased since yesterday, with some locations along and east of interstate 95 potentially picking upwards of 6 to 10″ in the orange colors below (eastern Maryland suburbs of Washington). The images below are courtesy NOAA/WPC.
The latest guidance suggests that the worst conditions from the core of Isaias will begin to impact the immediate Washington Area between 10am and 3pm Tuesday.
For those of you who live in flood prone areas and especially along low-lying areas within the urban interstate 95 corridor and eastward across southern and central Maryland should have a plan of action to seek higher ground if necessary tomorrow.
This type of setup reminds me of the flash flood emergency we had in our area in July of 2019 which flooded interstate 66 and numerous roadways in eastern portions of Fairfax county, Arlington county and roadways in downtown Washington.