The Storm Prediction Center (SPC) has placed parts of the D.C. Metropolitan Area under a “Slight Risk” for Severe Thunderstorms on Friday afternoon.
The main threat from the thunderstorms will be damaging wind gusts in excess of 60 mph and hail although the risk of an isolated tornado can’t be ruled out as wind shear in the atmosphere will be increasing during the day on Friday.
The image below shows radar estimates of the amount of rain that has fallen across the Washington Region during the past seven days.
An area of low pressure will approach the Mid-Atlantic on Thursday afternoon, passing through the DC Area on Friday increasing the risk of strong to severe thunderstorms and very heavy rainfall.
The image below is of the latest Global Ensemble Forecast System model, showing decent agreement that a surface low pressure system will track out of the Ohio Valley Thursday night and pass very near or right across the DC Region on Friday into Saturday morning.
The upper level ridge of high pressure which is responsible for the ongoing heat wave across much of the nation produces sinking air from the upper levels of our atmosphere all the way to the surface. Ever wonder why it isn’t storming with such ample heat and humidity? The answer is because it is too warm aloft underneath these upper-level ridges of high pressure. However, along the edges of these ridges the jet stream is very active and cooler air aloft allows for large-scale thunderstorm development along the northern periphery of these high pressure systems. This is where the term “Ring of Fire” is coined from in meteorology.
-Watching an MCS (Mesoscale Convective System/large complex of thunderstorms) over Ohio and how it evolves as it makes the trip toward the spine of the West Virginia Appalachians. If this system survives, the southwestern portion of the Washington Region would be in the most favored location for thunderstorms that could produce damaging winds this afternoon. Something to watch (if the MCS survives the trip).
Even if this system begins to weaken, its outflow boundaries may be able to produce some isolated thunderstorms across our region, some of which could become severe with damaging winds being the main threat.