The remnants of Laura will merge with a cold front and move across the Mid-Atlantic region on Saturday. Ahead of Laura, there’s a chance for scattered strong to severe thunderstorms this evening that may produce damaging winds and frequent lightning.
Tropical moisture means rainfall rates of 1 to 2 inches per hour in any storm. Flash Flood Watches have been issued for Northern Virginia and the Roanoke and New River Valleys through late tonight due to heavy rainfall possibly occurring over saturated ground, resulting in areas of flooding or flash flooding.
The Storm Prediction Center has highlighted locations east of the Blue Ridge under a SLIGHT RISK (Level 2 out of 5) for severe weather on Saturday. Timing for severe storms will be from 11:00 a.m. across the western counties through 6:00 p.m. along the coast. Some storms may produce damaging wind gusts up to 70 mph, frequent lightning, and the potential for a few isolated tornadoes. With a tropical air mass in place and Laura and a cold front combining, you can expect thunderstorms to once again produce very heavy rainfall that may lead to flash flooding.
Late Tonight: Additional showers and thunderstorms are expected to develop across the Shenandoah Valley and the Blue Ridge Mountains. The main threat tonight will be locally heavy rain, frequent lightning, and gusty winds. While the tornado potential is very low, it’s not zero. Since we are dealing with moisture from a tropical system, an isolated tornado can’t be ruled out.
Early Saturday Morning: Additional showers and thunderstorms are expected across the mountains and the Roanoke and New River Valleys. If showers and thunderstorms linger through the morning hours, this could help to limit severe thunderstorms later in the day.
Saturday Early Afternoon: Showers and thunderstorms will move east to the Interstate 95 corridor. Once again, timing and sky conditions are very important to the EAST of these storms. If Eastern Virginia experiences any breaks in the clouds, the better the chance that some of these storms may turn severe, with the threat for a few tornadoes.
Our “Severe Threat Index” goes up to a “5” along and east of Interstate 95, but just southeast of the D.C. area. This area has the greatest potential of seeing storms that could produce damaging winds and a few tornadoes. We will reassess and post an update early Saturday morning and make note of any changes (if needed) to the forecast.