textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 18z TAFs.

Very slight downward trend in high temperatures late in the period, with increasing mountain-area pops Friday into Saturday.

KEY MESSAGES

1. A slow-moving cold front will move through the area this afternoon, bringing a few showers and possibly a couple of thunderstorms to the I-77 Corridor. Behind the front, slightly cooler and drier conditions are expected for Wednesday. 2. Diurnal shower and thunderstorm chances return by the end of the week and into the weekend. High temperatures outside the mountains are expected to climb into the mid to upper 90s this weekend.

DISCUSSION

Key message 1: A slow-moving cold front will move through the area this afternoon, bringing a few showers and possibly a couple of thunderstorms to the I-77 Corridor. Behind the front, slightly cooler and drier conditions are expected for Wednesday.

A cold front has pushed through almost the entire forecast area this morning, with NW breezy winds behind the front. Much drier and somewhat cooler air is filtering in, with the weak CAA competing with downsloping and late June sun. Along the I-77 Corridor, there remains enough moisture and instability underneath the upper trough to trigger some showers and perhaps a couple of thunderstorms this afternoon, but any convection is very limited on the CAMs, and strong to severe storms are certainly not expected. NW flow against the mountains continues to bring clouds with mountain wave activity, and in the gaps clouds are making their way into the foothills and even toward the Piedmont as the primary area of low-level moisture/clouds exits with the front. May see some brief showers with the mechanical uplift in the mountains into this evening, but pops should diminish as we push into overnight.

Temperatures tonight through Wednesday night will run a handful of degrees below seasonal normals for lows and highs, with mainly just some passing clouds in the general weakness aloft.

Key message 2: Diurnal shower and thunderstorm chances return by the end of the week and into the weekend. High temperatures outside the mountains are expected to climb into the mid to upper 90s this weekend.

Weak troughiness will be in place in the upper flow with ridging across the Desert Southwest and the Atlantic late in the work week. Moist southerly flow will return to the Southeast starting Thursday, and as the Atlantic ridge backbuilds into the Southeast, heights and corresponding thicknesses will rise again. Each day Thursday through Sunday will see an incremental increase in afternoon highs, with Piedmont temperatures over the three-day period Saturday through Monday ranging from the mid to in some cases upper 90s. Latest NBM guidance has come in a touch cooler vs previous forecast especially along the I77 corridor on Monday (it's all relative, maybe 96 instead of 98), but still dewpoints high enough to have widespread heat indices around or just above 100 degrees. Cannot rule out Heat Advisory conditions across some of the area depending on how much dewpoints mix out each afternoon and any additional changes to temperature trends. The increased moisture will bring back the diurnal convective trend, with best chances especially Friday and Saturday afternoons along the TN border counties.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

At KCLT and elsewhere: VFR Cu will continue to push east with the cold front, though lingering mountain Cu may occasionally impact KAVL through the afternoon. Otherwise, mainly a wind forecast with N- NNW winds to start the period gusting to near 20k, diminishing this evening into the overnight hours. As high pressure approaches from the west, winds will trend more NNE to lgt/vrb by Wednesday.

Outlook: Mostly dry, VFR conditions expected through Thursday. Diurnal shower and thunderstorm chances increase again on Friday and continue through the weekend, bringing associated restrictions.

GSP WATCHES/WARNINGS/ADVISORIES

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