textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 18z TAFs.

KEY MESSAGES

- 1. Thunderstorms today may lead to damaging winds.

- 2. Unsettled weather continuing into the work week.

DISCUSSION

Key Message 1: Thunderstorms today may lead to damaging winds.

Widely scattered thunderstorms across the southern Appalachians and TN river valley are expected ahead of a cold front this afternoon. Wind shear will be marginally favorable for linear convection to develop downshear of the convective cold pools. With very steep low level lapse rates and strong DCAPE in place today but relatively weak or moderate mlCAPE this tends to favor a cold pool driven system developing to our west or northwest and driving into the forecast area in the afternoon or evening. The CAMs have generally been inconsistent with timing but the HRRR which has had decent run-to-run consistency shows the line of storms working into the FA in the late evening, decaying with loss of daytime heating and possibly too cold pool dominant to sustain additional development. There will also be some thunderstorms that develop to our east today closer to the sea breeze which could produce a more isolated threat of damaging downburst winds. This points to at least some concern for damaging winds this afternoon and evening but the threat of widespread severe weather is limited.

Outside of convection, It will be seasonably hot today but heat index values will likely remain below Heat Advisory criteria.

Key Message 2: Unsettled weather continuing into the work week.

The frontal boundary should pass through the area by Monday allowing for drier air to work over the FA. So Monday looks to have lower convective coverage than previously forecast. Beyond that, persistently high IVT (90th percentile per NAEFS) should aid in keeping things unsettled through mid week. By the end of this upcoming week, it appears that another front may make it into the area & another focus for showers and storms.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

VFR conditions expected outside of afternoon/evening thunderstorms.

Scattered high clouds continue over the area. Diurnal cumulus development is expected this afternoon, with scattered thunderstorms developing during the afternoon and evening hours. A few storms could become strong to severe. Hi-res models remain inconsistent regarding the timing and coverage of storms, although some solutions suggest two rounds/lines of convection. One during the afternoon and evening hours (between 18-24Z) and another later tonight. Thunderstorm probabilities remain too uncertain so I continued the PROB30 for this afternoon and evening as well as added another PROB30 group for the 02-08Z time frame. This will need to be monitored once storms start developing.

Surface winds have been somewhat stronger today as the pressure gradient tightens ahead of an approaching upper trough. Southwesterly winds around 10-12 kt with gusts up to 20 kt are expected through the evening. Winds diminish overnight to 5-7 kt, outside of storm coverage areas. The cold front should be right near us by tomorrow morning, shifting winds to WNW at 7-10 kt. Drier conditions and higher clouds will push in for Monday.

EXTENDED AVIATION OUTLOOK...Quieter conditions are expected Monday followed by more unsettled weather through mid week along with possible associated restrictions with a stalled frontal boundary.

CAE WATCHES/WARNINGS/ADVISORIES

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