An upper level ridge strengthening over the plains (and extending north into Canada) on Tue/Wed will result in strengthening NW flow aloft downstream over the TN/OH valley and Mid-Atlantic on Wed, and the advection of a modified elevated mixed layer into the region, with H7-H5 lapse rates on the order of 7-8 c/km across NC. A robust shortwave in NW flow aloft is expected to approach the mountains 12-15Z Thursday, crossing NC/VA Thursday afternoon/evening, with an attendant sfc low deepening to 997-999 mb as it tracks east through VA and the DELMARVA. In advance of the shortwave, strengthening southerly low-level flow will advect rich boundary layer moisture northward under the modified EML, resulting in strong instability by peak heating Thu, with MLCAPE values of 2000-3000 J/kg across central NC. Additionally, 0-6 km shear is progged to be on the order of 35-45 knots, which would be sufficient for supercellular organization, especially given steep mid-level lapse rates and strong instability. It appears that the stage is set for an enhanced severe weather event Thu aft/eve, though specifics remain difficult to ascertain given that this is still 72+ hrs out and that there may be ongoing convection that ‘outruns’ the forcing over the TN/OH valley late wed/wed night, potentially crossing the Appalachians Thu morning. Whether or not convection would survive across the mountains is difficult to say, steep mid-level lapse rates will contribute to 1000-2000 J/kg of MUCAPE wed night over central NC, though CIN will rapidly increase within several hours after sunset. At any rate, it seems like the primary severe weather threat in central NC on Thu would be very large hail and damaging winds, perhaps significant wind given DCAPE values progged as high as 1500 J/kg. The tornado threat is a bit more difficult to pin down, though it would appear that the best tornado threat would be in VA and the DELMARVA in closer vicinity to the surface low and warm front where the best low-level shear would be present, with increasingly straight hodographs further south in NC. Additionally, any discrete mode in NC would likely be short lived given strong instability, little or no CIN during peak heating, and high DCAPE that would foster strong cold pools and relatively quick upscale growth into an MCS, though that could result in a significant damaging wind threat, especially in eastern portions of NC/VA.
I see SPC mentioned us in the Day 4-8 outlook, though they didn’t add a 30% prob. Anyone else have thoughts on the upcoming severe potential on Thu?