textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Temperatures continue to trend slightly cooler late this week and into next weekend.

KEY MESSAGES

1. Elevated heat index values continue thru Wednesday. Cooler temperatures later in the week should provide some relief from the heat. 2. A few strong thunderstorms remain possible this evening across our South Carolina and Georgia counties, along with areas of heavy rain. Scattered convection returns on Monday with a few severe storms again possible. Less convective coverage is anticipated on Tuesday, before a weak cold front brings increased coverage and the potential for more severe weather on Wednesday.

DISCUSSION

Key message 1: Elevated heat index values continue thru Wednesday. Cooler temperatures later in the week should provide some relief from the heat.

Highs cool a bit more on Monday but increase slightly again on Tuesday. Max heat index values will mostly be 103 degrees or less Monday in the warmest areas of the Piedmont (SE of I-85), but with temps trending back slightly warmer Tues and Wed and dewpoints remaining near 70 each afternoon, more widespread instances of heat index in the 102-105 range near/SE of I-85 can be expected. The heat and humidity finally diminish by Thursday as a cold front arrives from the NW and induces airmass change. Until then, stay hydrated, take frequent breaks in air-conditioned or shaded areas, and never leave children or pets unattended in vehicles.

Key message 2: A few strong thunderstorms remain possible this evening across our South Carolina and Georgia counties, along with areas of heavy rain. Scattered convection returns on Monday with a few severe storms again possible. Less convective coverage is anticipated on Tuesday, before a weak cold front brings increased coverage and the potential for more severe weather on Wednesday.

A weak frontal boundary now near the northern border of TN/NC will slowly drift southward through Monday morning, at the base of a broad trough over the NE/Midwest CONUS. The front stalls over the Carolinas on Monday; slightly better than typical July shear is seen, 0-6km approaching 20 kt and 0-3km 15-20 kt also. This is similar to what was seen for Sunday; there are some indications a weak shortwave or MCV could come into play. The atmosphere will remain very unstable with high PW values and steep low-level lapse rates. SPC has a Marginal Risk for severe storms across a good chunk of our forecast area, namely the NC Piedmont and adjacent counties. A few clusters of storms producing damaging wind remain possible. Diurnal convective chances linger on Tuesday, but the overall coverage should be lower, especially outside the mtns. Coverage will likely increase again on Wednesday as another upper trof amplifies over the eastern CONUS and moves yet another cold front into our area. Severe storm potential may also increase again on Wednesday. More typical diurnal convection returns by the end of the week.

AVIATION /00Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: Outflow boundaries along an axis south of KCLT/KGSP/KGMU, drifting slowly southward toward KAND could spawn isolated TSRA in the vicinity of all those sites in the first couple hours of the period. Activity should gradually wane nocturnally so VCSH is allowed to drop off by 03-06z. A weak frontal boundary will shift slowly southward into the terminal area through Monday morning; cannot completely rule out some redevelopment of SHRA/TSRA near daybreak ahead of that feature though impacts are unlikely enough to omit. KAVL got a heavy downpour during the day and winds should remain light overnight. A TEMPO for IFR was included in the middle of the night followed by a prevailing mention for ground fog toward daybreak. KHKY also saw RA Sun aftn and included tempo IFR there also. The aforementioned boundary does not look to induce a wind shift during the day, but will maintain elevated moisture and forcing such that convective coverage is expected to be similar to Sunday across the terminal area. Thus PROB30 TSRA is already included for all sites diurnally Mon aftn.

Outlook: SHRA/TSRA may return again Tue though more likely to remain near the NC mountains that afternoon as compared to Monday. Coverage is expected to increase again on Wednesday then decrease Thursday. Low stratus and/or fog will be possible each morning, mainly in the mtn valleys.

GSP WATCHES/WARNINGS/ADVISORIES

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