textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 12z TAF issuance.

KEY MESSAGES

1. Drier and slightly below-normal temperatures Monday trough Wednesday, with moisture and rain chances increasing in the second half of the week.

DISCUSSION

Key message 1: Drier and slightly below-normal temperatures Monday trough Wednesday, with moisture and rain chances increasing in the second half of the week.

A series of shortwaves will ride thru the base of a broad longwave trough, helping deepen it and allow dry, cooler air to push in from the north today thru Tuesday. A sfc cold front is still crossing the CWFA attm, but should be clear to our south far enough to result in a dry day today. Highs will be a few deg below normal in the mountains, and near normal across the Piedmont, with noticeably lower humidity as dewpts mix out into the 50s to lower 60s. Even cooler thicknesses will push in from the north on Tuesday, and combined with thickening high clouds, highs are expected to be around 5 deg below normal.

The deterministic models are in good agreement on a vigorous shortwave diving into the Upper Midwest just as a weak tropical disturbance drifts northward near the NW Gulf Coast. Height falls associated with the upper wave may activate a stalled frontal boundary draped across the Deep South. Moist upglide over the frontal zone may bring rain chances back into the southern part of the CWFA Tuesday night. Temps warm back to near or just above normal Wednesday, as SWLY flow increases ahead of the wave. Models show generally weak instability and low PoPs, as dewpts remain in the 50s to mid 60s. From there, fcst uncertainty increases, as models disagree on what will happen with the tropical wave as it rides along the frontal zone across the Southeast. The 00z ECMWF continues to show a stronger low than other guidance, and is later on ejecting it, while the GFS is on the faster side and has the wave crossing the area Thursday. Even if the wave ends up very weak or staying to our south, increased PoPs looks like a good bet for Thursday thru Friday, as a cold front pushes in from the NW and SWLY low-level flow increases across the region. The wave may bring increased gusty winds Thursday and/or Friday, depending on the exact timing. A heavy rain and severe threat may also accompany the wave, but confidence remains low. The front should push thru the area and bring drier air and cooler air from the north on Saturday, as the upper trough axis shifts east from the Midwest to the East Coast.

AVIATION /12Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: Patchy IFR clouds in the Upstate and MVFR clouds in the mountain valleys should dissipate fairly quickly after sunrise this morning, so VFR conditions are expected at all TAF sites thru the 12z TAF period. Otherwise, it should be dry today with few to sct high clouds and a few Cu in the aftn. High clouds and potentially some lower VFR clouds may increase after 06z tonight. Gusty NNW winds at KAVL thru midday and possibly into the aftn. Winds expected to be light elsewhere, mainly NW or WNW, except W to WSW at KAND.

Outlook: Mostly quiet conditions expected thru midweek. MVFR to IFR stratus may form across GA and expand NE into the Upstate and western NC mountains Tuesday night thru Wednesday morning, then should scatter out. A similar setup may occur again Wednesday into Thursday morning. Diurnal convection and associated restrictions will likely return Thursday and Friday.

GSP WATCHES/WARNINGS/ADVISORIES

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