Dangerous DC Area Severe Weather Outbreak Possible Thursday

Jefferson Memorial Sunrise, photo credit Patrick Gillespie

A dangerous severe weather outbreak is going to impact the Deep South and portions of the Mid-Atlantic Wednesday night through Thursday afternoon.  Here in the Washington Area, storms will threaten

during the pre-dawn hours continuing into the early afternoon hours on Thursday.  Hail, damaging wind gusts, torrential rain, & cloud to ground lightning is likely with some of the thunderstorms. 

Wind Shear values will be running high but CAPE (Convective Available Potential Energy) will be running low posing a challenging forecast for where isolated tornadoes could pose the greatest threat. 

As of this evening, the greatest risk of super-cells containing possible tornadoes is from central Virginia, through the Fredericksburg Area and across southern Maryland.  The Storm Prediction Center has placed parts of the Washington Area under a slight to enhanced risk for severe thunderstorms.  Those of you in Fredericksburg, Stafford, Spotsylvania, King George, Charles, St. Mary’s and across the northern neck counties of Virginia… you need to be prepared for severe weather.  Nocturnal tornadoes are the most dangerous weather event and while a widespread tornado outbreak is not looking likely, any storms that do form on Thursday during the pre-dawn hours could pose an increased threat as most of us will be sleeping.

After looking at the latest SREF (Short Range Ensemble Forecast) models and the NAM (North American Model) here are my preliminary thoughts on where the greatest threat (of damaging wind gusts, hail and tornadoes) looks to set up across the National Capital Region:

Damaging Wind Gusts: 70% chance

Hail: 60% chance (with cold air aloft on Thursday afternoon)

Tornadoes: 30% chance

Latest NAM Model (Timing):

The images below are from the latest run (18z) of the North American Model (NAM)

First line of strong to severe thunderstorms may impact the Washington Region between 4AM and 11AM.

Second line of strong to severe thunderstorms may impact the Washington Region between 12PM and 2PM as the cold front crosses the interstate 95 corridor.  Scattered thunder-showers are possible through Thursday’s evening rush hour.  With rapidly falling heights at 500mb, any lingering thunder showers could contain hail. 

I’ll provide an update tomorrow as timing becomes more clear (any slow down in this frontal boundary would only increase the threat for widespread severe thunderstorms Thursday afternoon).  Bottom line, if you have a weather radio, Wednesday night is a good time to have it on “alert mode” as strong to severe thunderstorms may impact our region during the pre-dawn hours while most of us are sleeping.

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