Widespread Area River Flooding Expected Thursday

The latest Weather Prediction Center (WPC) rainfall forecast indicates 4-6” of rain is likely to fall across the Blue Ridge, portions of Northern Virginia, northern Maryland including Baltimore.

This amount of rain in a short period of time (Tuesday evening through Thursday morning) will likely cause major area rivers to flood on Thursday.

For the immediate Washington Area, the period of heaviest rain appears to arrive Wednesday during the late afternoon continuing through the overnight. Flash Flood Warnings are likely during this time frame.

30 Day Rainfall Totals Nearing 600% of Normal in Spots

Eastern Fairfax county Virginia and the Silver Spring and Wheaton areas of Montgomery county Maryland have received three months worth of rain in the past 30 days with some spots picking up well over 10″ (areas shaded in pink in the image above).

Portions of the Washington Region still Remain Drier than Average:

Outside of the immediate Metro Area it has been “feast or famine” with some locations in the Shenandoah Valley receiving nearly 6-8″ of rain while others have received less than 1.5″ of rain.

The weather pattern next week is looking calmer as we head into the “Dog Days of Summer” with heat/humidity holding strong and scattered showers and thunderstorms during the afternoon.

Damaging Winds and Hail Possible this Afternoon

The Storm Prediction Center (SPC) has placed DC and portions Northern Virginia and Maryland in a “Slight Risk” for Severe Thunderstorms this afternoon, with the main threat being damaging winds in excess of 60mph and hail. 

Ingredients for Severe Thunderstorms

Increasing wind shear, steepening low-level lapse rates, dew points in the 70s (oppressive humidity) and temperatures in the 90s will provide the necessary ingredients for numerous thunderstorms to develop this afternoon and evening.

Timing the Storms

The latest high-resolution NAM model shows a nasty line of storms forming over the Shenandoah Valley around 2pm and then racing eastward across the Washington and Baltimore Metropolitan Areas between 4 and 7pm.

Flash Flooding

Storms may also produce torrential rainfall rates of 1 to 2 inches per hour causing flooding of low lying areas, underpasses and cause creeks and streams to rapidly rise out of their banks. Because of this the National Weather Service has issued a Flood Watch for portions of the DMV.