textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

No major changes.

KEY MESSAGES

1. Showers and thunderstorms continue through the evening, with an isolated flash flood threat, especially across the NC foothills. 2. Daily chances for showers and thunderstorms continue into the weekend. Drier conditions may return briefly on Friday but confidence is low. We will have a better shot at dry weather early next week as high pressure builds in from the north.

DISCUSSION

Key message 1: Showers and thunderstorms continue through the evening, with an isolated flash flood threat, especially across the NC foothills.

There will be a higher threat for isolated, localized flash flooding thanks to wet antecedent conditions through the evening. Rainfall amounts through 12Z Tuesday look to mostly range from an 0.25-1" east of the mountains and ~0.50-1.5" across the mountains. Locally higher rainfall amounts up to 1.5-2" are possible east of the mountains but will be dependent on where the heaviest downpours track/train. Across the mountains, locally higher amounts of 2-3+" appear to be confined to the northern escarpment per the 12Z HRRR/NAMNest. The 12Z REFS shows a 20% to 40% chance of rainfall greater than 2.5" along the northern escarpment. Although these probabilities are fairly low, there is still a low-end concern for highly localized flash flooding across this area in particular if these higher rainfall amounts were to materialize due to training/slow storm movement. Went with WPC for QPF through tonight as this matched up better with high-res guidance trends compared to the NBM. With this threat expected to remain highly localized, opted not to issue a Flash Flood Watch as this product is reserved for more widespread heavy rain/flash flood events.

Patchy fog and low stratus should return again overnight with a moist airmass lingering in place. Highs this afternoon will end up near to just below normal with lows tonight ending up 7-10 degrees above normal thanks to cloud cover and rain.

Key message 2: Daily chances for showers and thunderstorms continue into the weekend. Drier conditions may return briefly on Friday but confidence is low. We will have a better shot at dry weather early next week as high pressure builds in from the north.

Daily chances for showers and thunderstorms (mainly during the afternoon/evening hours) will continue through Wednesday as an upper ridge centered offshore the southeast coast in the western Atlantic works with an upper low over the West Coast to pull in moisture from the Gulf. Convective chances will linger through Thursday as a backdoor cold front tracks across the forecast area. Brief drying may develop behind the front on Friday as dry high pressure attempts to briefly build in from the north but confidence is low with the high expected to gradually weaken. The front will stall across the southeast through the weekend keeping shower and thunderstorm chances around. Global model guidance is now showing the potential for drier conditions to return as early as Sunday, lingering into early next week. However, confidence is low with this being towards the end of the forecast period. Highs should end up near normal to just below normal Tuesday afternoon, becoming near normal to just above normal Wednesday afternoon. Highs on Thursday ahead of the front will end up a few degrees above normal before dropping to a few degrees below normal Friday behind the front. Cold air damming looks to develop this weekend into early next week so highs should end up ~5-10 degrees below normal. Depending on the strength of the wedge, as well as how widespread rain ends up being, highs may trend even cooler.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

At KCLT and elsewhere: Multiple areas of showers with embedded thunderstorms are ongoing across the Terminal Forecast Area this evening. TS coverage is such that tempos for SHRA are mostly favored this evening, with TSRA carried at KHKY and KAND, which are under the most immediate threat of storms. Periods of restricted (mostly MVFR) visby are expected with the SHRA, with as low as 1-2SM possible in TS and heavier SHRA. Convection is forecast to begin tapering off from late evening into the overnight, but isolated/widely scattered showers are possible at any location/time.

Otherwise, low clouds are expected to begin filling in in conjunction with the diminishing convection late this evening into the overnight. Reduced visby in BR is also anticipated, and could reduce to IFR in locations that receive heavy rain this evening. Conditions should improve to MVFR by late Tue morning, then to VFR at most sites during the afternoon. Diurnal convection will again fire during the afternoon, with Prob30s for TSRA warranted at all TAF sites.

Outlook: The pattern remains unsettled through the workweek with at least scattered diurnal convection expected each day (possibly persisting into the overnight hours) and lowered visibility and ceilings forecast each night.

GSP WATCHES/WARNINGS/ADVISORIES

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