textproduct: Columbia

WHAT HAS CHANGED

Forecast remains on track for widespread storms on Friday with flash flooding and damaging winds being the main threats.

KEY MESSAGES

- 1. Severe weather and flash flooding possible Friday.

DISCUSSION

KEY MESSAGE 1: Severe weather and flash flooding possible Friday.

Upper troughing amplifies over the eastern US Friday promoting SW flow into the forecast area. PWAT values rise to near or above 2 inches by the afternoon as surface low pressure develops near the area. Convergence along a surface boundary over the Carolinas will serve as the focus for thunderstorms in the afternoon as the air mass destabilizes. mlCAPE values should range from 1000 to 2000 J/kg over the area with highest values in the eastern Midlands and Pee Dee. Steep low level lapse rates and height falls will support strong updrafts and the potential for damaging winds. Models have trended lower on shear values indicating less potential for organized storms but higher potential for flash flooding given overall slower storm movement. The threat of localized flooding should be highest in the northern Midlands and Pee Dee, closest to the surface boundary. The REFS indicates the most likely timing for severe weather will be between 3 PM and 7 PM but the threat could extend into the evening depending on the timing of shortwaves passing through the broader trough. As the upper trough axis slowly moves through the area Saturday, the bulk of the convective activity should shift to the east with drier air moving into the area from the west.

Otherwise, today atmospheric moisture remains relatively limited with just isolated to widely scattered storms expected in the eastern Midlands and Pee Dee. Although we cannot rule out an isolated damaging downburst chances are low. Cooler weather is likely next week with temperatures closer to normal along with seasonal, diurnal thunderstorm chances.

AVIATION /12Z THURSDAY THROUGH MONDAY/

VFR conditions expected to persist through Thursday outside of possible convection.

Clear skies and quiet conditions this morning. Low level moisture is quite robust across the area, with mid 70s dewpoints present. This could lead to some patchy ground fog at OGB, AGS and AIK which are prone to shallow fog. After 15Z, VFR cumulus will likely develop as light southerly winds push moisture into the area. Convection is possible this afternoon and evening but coverage and timing are quite uncertain across the area. CAE/CUB/OGB have the best chances for showers/storms and have added a PROB30 group for convection to account for this possibility.

EXTENDED AVIATION OUTLOOK...Thunderstorm chances increase Friday and Saturday with scattered to widespread convection expected.

CAE WATCHES/WARNINGS/ADVISORIES

SC...None. GA...None.