textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

No major changes.

KEY MESSAGES

1. Dry and more humid today. Daily shower and thunderstorm chances return Friday into early next week, peaking on Saturday. Although the heat and humidity will peak on Friday, the humidity and above normal temperatures will linger through early next week.

DISCUSSION

Key message 1: Dry and more humid today. Daily shower and thunderstorm chances return Friday into early next week, peaking on Saturday. Although the heat and humidity will peak on Friday, the humidity and above normal temperatures will linger through early next week.

The flattening upper anticylcone that has been over the Southern United States the last few days gets pinched off into two separate areas of high pressure today. One drifts westward and set ups over the Desert Southwest while the other drifts eastward and sets up just off the Southeast coast. The western periphery of the upper high will remain extended over the Southeast through Friday, allowing the heat and humidity to tick up each day. Although the heat and humidity will peak on Friday, both humidity and above normal temperatures will stick around through early next week as yet another upper anticylcone builds back over the southern United States. Although we are still not expecting to reach Heat Advisory criteria (which starts at 105 degrees) any day through the forecast period, locations in the Upper Savannah River should see heat index values climb into the triple digits each afternoon through Monday. Some locations in the Charlotte Metro should also see heat index values climb into the triple digits, mainly on Friday. Confidence on reaching triple digit heat index values on Saturday is low at this time as more widespread shower and thunderstorm chances should limit heat indices.

It still appears that a cold front will approach from the north through Friday but confidence on whether the front actually makes it into GSP forecast area remains low as it should reactivate as a warm front and lift back north Friday night into early Saturday. Thus, mostly dry conditions are expected again today with shower and thunderstorm chances returning tomorrow, peaking on Saturday. 00Z CAMs are not terribly excited about coverage tomorrow, showing isolated to scattered (at best) activity, which lines up well with the NBM which only has chance PoPs for Friday afternoon. Much better coverage is expected on Saturday per the 00Z global model guidance which matches up well with the NBM which has 70-90% PoPs by Saturday afternoon. Should see activity become more suppressed, especially east of the mountains, Sunday into early next week as the aforementioned anticylcone builds back over the region. Could not entirely rule out a low-end hydro threat, mainly on Saturday, with above 90th percentile PWATs in place per the GFS and EURO. However, confidence is low at this time as NBM rainfall totals continue to look fairly muted through the weekend, ranging mostly from 0.30"- 0.60" east of the mountains and 0.50" to 1.5" in the mountains. It still appears that this will be mostly beneficial rainfall. However, we will closely monitor trends regarding rainfall amounts in the coming days. Once the CAMs are able to go out through the entire weekend we should have a better picture of whether the hydro threat will be of much concern. The severe weather threat will remain very low due to global models only showing 15-20 kts or less of deep layer shear in place through early next week.

AVIATION /06Z THURSDAY THROUGH MONDAY/

At KCLT and elsewhere: Dry and VFR again through the 06Z TAF period outside of the potential for another round of fog and low stratus across the mountain valleys and at KHKY. Thus, maintained the TEMPO at KAVL for LIFR vsbys and cigs (09Z-13Z) and introduced a TEMPO for IFR vsbys at KHKY (11Z-13Z). Confidence is higher that restrictions will reach KAVL compared to KHKY. Fog and stratus will lift shortly after daybreak. Winds will be mainly S/SW through much of the TAF period. KAND and KAVL should see calm winds through daybreak. Calm winds should return overnight at KAVL. Cirrus will continue streaming over the terminals through the period, with cumulus developing during the afternoon/early evening hours.

Outlook: A cold front just to our north will bring back daily shower and thunderstorm chances (and possibly restrictions) Friday into the weekend. The probability of morning fog/low stratus will also increase, especially in the mountain valleys.

GSP WATCHES/WARNINGS/ADVISORIES

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