The best chance to see severe thunderstorms, which are defined as storms with gusts of at least 58 mph or hail of at least one inch in diameter, is approximately from 3 to 8 p.m. Weather Forecast Center put parts of the area are under a level 2 out of 5 risk of severe weather. In the DC area, risk level 2 is concentrated south of I-95, with risk level 1 covering the rest of the region.
Clouds were mostly present in the morning, but some sunny spells in the afternoon could help support any increasing thunderstorms.
Weather forecast, coverage and first risks
Timing: Storms could develop as early as 2 or 3 p.m. in Frederick, Loudoun and Fauquier counties. It is likely to be a thunderstorm in the period from about 3 to 8 pm, potentially coinciding with the heart of the exchange. Showers or weaker storms may persist past 8 pm
Coverage: The weather is mainly scattered when it is from west to east, but a few larger grapes could be grown. We are expecting most storms near and east of 95.
Risks: The most serious primary hazard is the potential for scattered, damaging isolated winds, up to 60 to 70 mph, which could bring down trees and power lines, with the greatest chance east and south of I-95. Hello, a brief shower and frequent lightning possible. Pollucius’ power is lower but not zero.
Rain: A little bit as much as rain fingers. Seriously. Because storms can be dispersed in nature, some spots would be unable to see anything, perhaps only the wet ground, while others would be able to pick up a quick finger or two. Totals of up to 2 to 3 inches are not impossible if the storms pass through the same area repeatedly.
Today features a cold front moving slowly across the area from the west, with heat and humidity from the south preceding and following the front.
Meanwhile, in the air, a stream of jets dipped down from the Ohio Valley. A combination of cold and windy air aloft, plus a front, will force an unstable air mass to build up late Thursday afternoon and evening.
It is also possible that a weak area of low pressure will later escape through the front in Virginia, which will increase the potential for increased winds and storms.
Wind shear, or the increased strength of the winds at altitude, is another joke. Fairly strong wind shear was detected by the storm balloons released this morning, and is expected to increase throughout the day as the jet stream approaches. That supports more organized long-lived cell storms, including multi-cell clusters, and potentially some spin in the middle atmosphere that could lead to supercells.
One factor that could have stopped the storm’s development was the tight instability found by the weather balloon. To destabilize the atmosphere, a sufficient area of surface heating by the sun would be needed. Those regions that get more sunshine during the morning to afternoon have a better chance of seeing strong to severe storms.
It is possible, perhaps even likely, that the Weather Service will issue a severe thunderstorm watch through the ninth hour for at least some parts of the DC area. Severe weather is possible with severe weather but it is not yet certain that a watch has been issued.
We will be monitoring the situation and will issue updates as needed.