12:20 p.m. — Early blooming rains and storms are already coming Some showers and thunderstorms have developed ahead of schedule and are moving quickly along the Route 15 corridor (Leesburg to Warrenton). These are generally not severe, so expect mostly brief showers and perhaps some lightning with this activity as it sweeps eastward over the next 60 to 90 minutes. However, activity could pick up a bit — especially after crossing Interstate 95 around 1 p.m. This activity can use up some of the atmosphere’s available energy, reducing the chances of additional storms later. We will reassess the storm threat in the late afternoon once they are completed.

Original article from late morning Breezy air is spreading across the Washington area, displacing the low moisture we enjoyed on the 4th of July. The arrival of this warm, moist air sets the stage for potentially severe thunderstorms Tuesday afternoon through early evening. The National Weather Service’s Storm Prediction Center has placed our area in a level 2 out of 5 severe storm danger zone, noting the potential for “damaging gusts” and “isolated large hail.” Any storms affecting the area should pass quickly, reducing the risk of flooding. However, some of the areas flooded Saturday night (ie, saturated ground in the northern District and southern Montgomery and northern Prince George’s counties) may again experience high water levels if heavy storms move through. How torrential rain lashed the province and northern suburbs on Saturday night Short-range computer models suggest the best chance for storms is between about 3 and 6 p.m., with showers sweeping in from the west to the east. By late morning, showers and thunderstorms were present from the Ohio Valley into West Virginia and were generally moving east-southeast in the general direction of the Washington area. Storm Time: While subject to change, storms should arrive and exit the following areas during the following windows:

Interstate 81 (Hagerstown to Front Royal): 2 to 4 p.m Route 15 (Frederick to Leesburg to Warrenton): 2:45 to 4:45 p.m. Interstate 95 (Baltimore to DC to Fredericksburg): 3:30 to 5:30 p.m. Route 301 (Bowie to La Plata): 4:15 to 6:15 p.m.

Storms should be fast moving, lasting anywhere from 30 to 45 minutes. Note that some scattered showers and thunderstorms are possible after the initial round, but should decrease in coverage and intensity after dark. Storm coverage: Scattered — each individual area has about a 60 percent chance of measurable rain.

Possible: Torrential rain, lightning, gusty winds (up to 30-40 mph) Possible: Damaging winds (up to 60-70 mph), small hail Very low chance of: Large hail, flooding, tornado

Chance of rain: In areas affected by storms, 0.25 to 0.5 inches is likely, with isolated totals of up to 1 to 2 inches. Today’s potential severe weather pattern features a warm front moving through the area (as shown on the map below), introducing a moister air mass into the southerly winds. Additionally, an upper-level disturbance in the jet stream will move into the Mid-Atlantic from the Ohio Valley. This disturbance has organized scattered showers and thunderstorms across West Virginia, and these may maintain solid to scattered clouds around the DC area throughout the early and afternoon hours. The severity of the storm will depend on how much the atmosphere destabilizes over the next few hours. Any persistent break in the clouds will allow the sun to raise surface temperatures, which is key to destabilization. Perfect weather for a spectacular fireworks show in Washington There is sufficient wind shear (increase in wind speed with altitude) to help the storms become more intense, if they develop, and to organize the cells into clusters and bow lines. The suite of high-resolution models suggests rather early (1 to 2 PM) storm initiation in the Blue Ridge, with those storms then sweeping across the metros as early as mid-to-late afternoon. As the simulated radar fields below show, the line crosses the DC region. The warm frontal border can help organize and strengthen this complex. With these types of fast moving clusters, there is a potential for a streak of damaging wind gusts – and that is likely to be the biggest severe weather risk this afternoon and early evening.