1:25 p.m. update: Tornado watch has been issued for southern Maryland (including Calvert, Charles, and St. Mary’s county in Maryland), east central and southeast Virginia (including Fredericksburg, Charlottesville, Richmond and Norfolk), and the eastern Carolinas. The sprawling watch is in effect through 8 p.m. and indicates the potential for 1” diameter hail, thunderstorm wind gusts to 75 mph, and dangerous lightning in addition to tornadoes.
From 12:50 p.m.: A powerful cold front will blast through the mid-Atlantic this afternoon and evening, potentially igniting a line of strong to severe thunderstorms.
For the D.C. region, the best chance of storms is east, south, and southeast of I-95, especially towards southern Maryland and the northern neck of Virginia. These areas coincide with the area designated by NOAA’s Storm Prediction Center (SPC) as having a slight risk of severe thunderstorms (see above, yellow area on left panel).
Of greater significance, from extreme southern Maryland through southeast Va. into the eastern Carolinas, SPC indicates there is a moderate risk of severe thunderstorms (see above, red area on left panel), including substantial damaging wind potential and the possibility of tornadoes.
Already, a tornado watch is in effect for portions central and southwest Virginia (interestingly, the same region that saw significant accumulating snow just this past Sunday). A broken line of thunderstorms has developed in that region and is likely to expand and progress eastward this afternoon.
The storms will have their best chance to intensify as they encounter very warm, humid air over southeast Va. and the eastern Carolinas, where temperatures are well into the 70s and even low 80s. These storms may be able to mix down very strong winds aloft “supporting the potential for widespread...and possibly very damaging...surface gusts...along with the risk for a few tornadoes” according to SPC.
SPC says a new tornado watch is likely to be issued over a large area extending from northeast South Carolina all the way into Washington, D.C.’s southern suburbs.
The National Weather Service forecast office in Wakefield, Va. - which forecasts for the southeastern third of Va., calls the wind damage “the primary risk” but notes tornadoes “could occur ahead of the lines of convection and in any discrete supercells which develop ahead of the line.” The most likely timeframe is from 2 to 5 p.m. for severe weather in that area.
The risk of storms quickly diminishes around the District and especially to the north due to cool, stable air over the region. A stubborn cold wedge has held temperatures in this area to 45-55 degrees, whereas just 75-100 miles to the south, temperatures range from 65-75 degrees.
But showers and strong gusty winds are still possible as the front approaches the District and areas to the north. The front is most likely to arrive in the eastern panhandle of West Virginia around 3 p.m. and the Chesapeake Bay around 6 p.m.