textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Minor adjustments to evening PoP based on radar and latest CAMs. Updated the aviation discussion for the 00Z TAFs.

KEY MESSAGES

1. Mainly isolated to scattered diurnal convection will continue each day through the week, with some potential for isolated pulse severe storms and localized excessive rainfall. 2. Humid and hotter conditions are forecast through at least the end of the week. Some Piedmont/Upstate locations could see daily heat index between 98-103 each afternoon.

DISCUSSION

Key message 1: Mainly isolated to scattered diurnal convection will continue each day through the week, with some potential for isolated pulse severe storms and localized excessive rainfall.

Scattered convection lingers across the area early this evening then should begin a diminishing trend. An isolated strong storm or some brief, heavy rainfall remains possible until the convection ends.

Weak/low-amplitude upper trough is forecast to develop east of the forecast area by Monday afternoon, allowing for some degree of drying in the mid/upper levels. This combined with westerly low level flow may bring some small relief to afternoon humidity Monday and Tuesday, but at least moderate destabilization is expected each day. The relatively drier overall profiles are likely to reduce the amount of diurnal convective coverage compared with the last couple of days, with mainly 30-40 PoPs forecast across the mountains, and 10-30% elsewhere both afternoons. Nevertheless, instability will be sufficient to support continued potential for a few strong-to-severe microbursts.

During the latter half of the work week, the mid-level flow across the region is forecast to accelerate a bit from the NW as a southwest Conus ridge begins to flatten and move east, while an area of significant height falls progresses across the Northeast. This could result in remnant organized convection originating from the very unstable environs over the Midwest to make overnight/morning runs toward the southern Appalachians, although this is all in the hypothetical realm at this point. Nevertheless, PoPs increase a bit to solid chance across the mountains and lower chances east, mainly from Friday through next weekend.

Key message 2: Humid and hotter conditions are forecast through at least the end of the week. Some Piedmont/Upstate locations could see daily heat index between 98-103 each afternoon.

Upper heights will rise very gradually through the first half of this week, as a flattening upper ridge builds into the Southeast from the southwest quadrant of the country. Max temps are forecast to mainly from 3-5 degrees above normal through much of the week. The increasing heat will also be accompanied by slightly drier vertical profiles along with westerly low level (downslope) flow. This could promote better afternoon mixing in comparison with recent days, but conditions will nevertheless be plenty humid, and heat index values as high as 103 will be likely each day of the week across at least a portion of the Piedmont. The synoptic pattern will not be especially conducive to a persistent excessive heat event, but we can't rule out at least brief periods of 105+ heat index across the lowest elevations. This will be especially true next weekend, when the global models are beginning to depict a strengthening anticyclone over the Southeast.

AVIATION /00Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: Convection lingers across the area this evening. A 2 hour PROB30 needed at KCLT where cells are nearby. Elsewhere, will make a game time decision for convection mention based on radar returns. Convection should diminish by 02Z or so. Mountain valley fog/low stratus is expected to become widespread again late tonight into early Monday, with LIFR conditions forecast to develop at KAVL by daybreak. There are lower chances for mainly low stratus at the other TAF sites, but the probability is high enough to include a few hours of SCT005 centered around 12Z Monday. Scattered diurnal convection expected again on Monday with guidance favoring all but KCLT and KHKY. Have only introduced PROB30s at the other sites where chances are higher. Winds become light and variable this evening and overnight, then pick up from the WSW, NNW at KAVL, during the day Monday.

Outlook: Isolated-to-scattered diurnal showers and thunderstorms with associated flight restrictions are expected through the week. Patchy fog and low stratus is possible each morning, especially in the mtn valleys and anywhere that received significant rainfall the previous afternoon/evening.

GSP WATCHES/WARNINGS/ADVISORIES

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