textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the impending 12Z TAFs.

KEY MESSAGES

1. Widely scattered showers and storms expected Thursday, mainly across the Upstate, as a cold front crosses the area. 2. Periods of rain continue through the weekend. A much drier air mass may arrive next week.

DISCUSSION

Key message 1: Widely scattered showers and storms expected Thursday, mainly across the Upstate, as a cold front crosses the area.

Quiet conditions continue across the area this morning, with scattered mid- and high-level clouds and patchy dense fog now settled into the NC mountain valleys. Isolated areas of dense fog have developed in parts of the Upstate and Piedmont as well. Lows are on track to land in the mid to upper 60s in most spots this morning.

Forecast thinking remains much the same for Thursday, with a backdoor cold front expected to settle across the area through the afternoon hours. The latest 00z round of CAMs depicts the front making it far enough south that by the time afternoon destabilization occurs, it may be near the state line. Afternoon convection seems likely to be focused along the boundary, so rain chances have trended lower for the Piedmont, and remain generally chance to likely across the Upstate. As a consequence of this, the bulk of convection is now forecast to take place in an environment with a solid 2000-2500 J/kg sbCAPE but barely able to eek out 20kts of bulk shear. So, in general, expect a very limited severe threat, though a couple of strong storms, perhaps even a severe one, remain possible. Based on coverage alone, flooding rain threat appears low. PWs in the 1.5-1.7 range further reinforce this thinking.

Thursday night, a period of drying is expected behind the front, with dewpoints falling as a dry air mass settles across the area and the front itself stalls to our south.

Key message 2: Periods of rain continue through the weekend. A much drier air mass may arrive next week.

Not much change to the forecast over the weekend and early next week. Ensembles broadly depict a series of upper vort lobes reactivating a stalled frontal boundary to our south, resulting in a resurgence in low-level upglide beginning Friday night and continuing into Saturday. There's quite a bit of spread in QPF during this period, but totals appear fairly unimpressive at this point. Though ensembles continue to struggle with the setup, they're tending more toward the development of hybrid cold-air damming than toward the front actually lifting north and opening us up to a warm sector air mass. This should generally keep more widespread convective downpours at bay.

Thereafter, there's an increasingly consistent signal for a secondary backdoor cold front crossing the area sometime in the Sunday/Monday timeframe, ushering in a drier air mass for the beginning of next week. Rain chances appear considerably lower past Monday than we've seen the last week plus...as once the postfrontal air mass settles into the region, any showers would be mainly diurnal and limited in coverage.

AVIATION /09Z THURSDAY THROUGH MONDAY/

At KCLT and elsewhere: VFR expected throughout the 12Z TAF period, with the exception of AVL and other mountain terminals, which continue to see patchy, sometimes dense, valley fog and low stratus. SHRA and TS possible again on Thursday afternoon, mainly for the Upstate sites...but included VCSH at CLT. AVL and HKY appear unlikely to see any precipitation through the period. Light and variable winds this morning will become N/NE through late morning across the NC terminals, and N during the afternoon at the Upstate terminals, as a cold front settles across the area. Mountain valley fog may again develop on Friday morning. Generally quiet, unperturbed conditions continue into Friday, while winds toggle around to the SE.

Outlook: The pattern remains unsettled through the weekend, with rain likely returning by Saturday and persisting into Sunday. A drier pattern may be in store for next week.

GSP WATCHES/WARNINGS/ADVISORIES

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