RARE MODERATE RISK BY SPC FOR DC AREA 8/7/23

The SPC has issued an extremely rare moderate risk for the DC area, mainly for widespread, significant damaging winds. All other hazards(hail, tornado) are on the table too, and this is a rare overlap of good shear and good instability values in the summer. We have a 10% tornado risk, and a 15% hail risk for most of the region as well.

A trough moving through the plains and Ohio Valley will continue to move and eject over the northern Appalachians this afternoon(0z HREF shown), bringing with it strong mid-level winds which will provide large shear values. WAA will create more than enough moisture for the warm sector.

Due to strong WAA and isentropic lift(last night's rain), there will be low-level cloud cover, but it will be eventually burned out by the August sun. There is already clearing in the Blue Ridge and west, and we should start to burn out cloud cover soon too. And for most places, dews are already in the 70s and are rising.

Storms will grow upscale as they progress eastward. The storm mode will be semi-discrete at first in an environment favorable for supercells, but will turn into a QLCS after(intense and potentially embedded with tornadoes). Low level spin will increase through the evening, so if storms fire later there will be a higher tornado threat due to stronger LLJ, but if its earlier, the tor threat is still present but will be a bit less.

This is a great setup for mid-Atlantic standards and is a serious day. It is rare to get this kind of setup.