Strong thunderstorms possible in the DC area this afternoon

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12:20 p.m. — Early showers and thunderstorms are already coming

Some showers and thunderstorms have developed earlier than expected and are moving quickly through the Hwy 15 corridor (Leesburg to Warrenton). These aren’t usually severe, so expect mostly brief showers and maybe some lightning with this activity as it sweeps eastward over the next 60-90 minutes. However, activity may pick up a bit, especially after crossing Interstate 95 around 1 p.m.

This activity can use some of the energy available in the atmosphere, reducing the chance of additional storms later.

We will reassess the storm threat in the late afternoon after they pass.

Late Morning Original Article

The heavy air is spreading through the Washington area, displacing the low humidity we enjoyed on July 4th. The arrival of this warm, humid air sets the stage for potentially intense thunderstorms from Tuesday afternoon through early evening.

The National Weather Service Storm Prediction Center placed our area in a Level 2 out of 5 hazard zone for severe storms, noting the potential for “damaging gusts” and “isolated large hail.”

Any storms that affect the area are expected to move quickly, reducing the risk of flooding. However, some of the areas that were inundated on Saturday evening (i.e. saturated ground in the northern part of the district and southern parts of Montgomery and northern Prince George counties) could again face flooding. in the event of heavy storms.

How torrential rains flooded District and northern suburbs on Saturday evening

Short-range computer models suggest the best chance for storms is between about 3 and 6 p.m., with precipitation sweeping west to east.

By late morning showers and thunderstorms were present from the Ohio Valley to West Virginia and were generally pushing east-southeast in a general direction of the Washington area.

Storm schedule: Subject to change, storms should move in and out of the following areas in the following windows:

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

Storms are expected to move quickly and last around 30-45 minutes in any given area. Note that some widely dispersed showers and storms are possible after the first round, but should lessen in coverage and intensity after dark.

Storm cover: Scattered – any individual area has about a 60% chance of measurable rain.

  • Likely: torrential rain, lightning, gusty winds (up to 30-40 mph)
  • Possible: destructive winds (up to 60-70 mph), small hail
  • Very unlikely: large hail, flood, tornado

Rain potential: In storm-affected areas, 0.25 to 0.5 inches is most likely, with isolated totals of up to 1 to 2 inches.

Today’s potential severe weather pattern includes a warm front moving through the region (as shown in the map below), ushering in a wetter air mass on southerly winds. Additionally, an upper level disturbance in the jet stream flow will move into the mid-Atlantic from the Ohio Valley.

This disturbance has organized scattered showers and thunderstorms across West Virginia, and these can maintain solid to broken cloud cover around the DC area throughout the early to mid-afternoon.

The severity of the storm will depend on the degree of destabilization of the atmosphere over the next few hours. Any persistent breakthrough in the clouds will allow the sun to raise surface temperatures, which is key to destabilization.

Perfect weather for a spectacular fireworks display in Washington

There is enough wind shear (increase in wind speed with altitude) to help thunderstorm cells become more intense, if they bloom, and to organize the cells into clusters and arc lines.

The suite of high-resolution models all suggest a fairly early onset (1 to 2 p.m.) of storms in the Blue Ridge, with those storms then sweeping through the metros by mid to late afternoon.

As shown by the simulated radar fields below, the line crosses the DC region. The warm front border can help organize and intensify this complex.

With these types of fast-moving complexes, there is potential for a band of damaging gusts of wind – and that will likely be the greatest hazard of severe weather this afternoon and early evening.

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