Sunrise 6:16 AM   Sunset 8:23 PM Moonrise 1:06 PM   Moonset 1:53 AM

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FXUS62 KGSP 162339 AFDGSP

Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 739 PM EDT Thu May 16 2024

SYNOPSIS
Brief high pressure moves off the coast tonight as another low pressure approaches from the west. Showers and scattered thunderstorms return Friday and continue into the weekend. Isolated afternoon and evening showers and thunderstorms are expected early next week.

NEAR TERM /THROUGH FRIDAY/
700 PM Update...No sigfnt changes made to the fcst this evening.
Spotty small-scale showers will continue across the NW Piedmont, otherwise all other locales will remain dry.

As of 200 pm EDT Thursday: Heights will fall across the region tonight as a short wave ridge progresses east of the area late tonight and a low-amplitude short wave trough approaches from the southwest late Friday morning. Moisture and lift will increase across the CWA by afternoon, increasing shower chances, with precip chances becoming likely across western areas by 00Z Saturday.
Mid/high level cloud cover overspreading the area during the morning will limit the destabilization potential tomorrow afternoon, while mid-level lapse rates are expected to be very poor. As such, sbCAPE is expected to generally be limited to the 500-1000 J/kg range.
Thus, while shear parameters (esp deep layer shear) will be improving throughout the day, the expected shear/buoyancy combination should preclude a notable severe storm threat. Indeed, SPC has removed our CWA from the Day 2 Marginal Risk. With precipitable waters expected to surge above 1.5", There may be a slightly higher potential for locally excessive rainfall, but again...limited instability and modest forcing should act to tame rainfall rates. Min temps tonight will again above normal, while maxes Friday should be right around climo.

SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/
As of 1245 PM EDT Thursday: Short Term Key Messages

1) Widespread Showers and thunderstorms are expected off and on throughout the weekend.

2) Areas of heavy rainfall may lead to isolated flooding issues this weekend.

3) Isolated strong to severe storms are possible through the weekend but confidence remains low at this time.

Showers and thunderstorms will be ongoing across the western Carolinas and northeast Georgia Friday evening into Friday night as a low pressure system approaches out of the west. There may be a lull in activity the first half of Saturday before another round of showers and thunderstorms returns Saturday afternoon into Saturday night as the low pressure system tracks into the forecast area. Have likely to categorical PoPs (70% to 80%) in place during this timeframe as global models and high-res models agree that there will be multiple rounds of convection. All global models continue to agree that the low will stall over the area on Sunday, thus monotoned likely PoPs (60 to 70%) across the forecast area. With PWATs expected to climb near or above 90th percentile, locally heavy rainfall will be a concern, especially with wet antecedent conditions already in place. The WPC Day 3 Excessive Rainfall Outlook has a Marginal risk across the Carolinas as isolated flash flooding will be possible, especially for areas that saw heavy rainfall the day prior. The flooding threat will steadily increase throughout the weekend as rainfall totals pile up. Currently 0.50- 1.50 inches of rain is expected to fall Friday night through Sunday, with the highest amounts expected to fall across the western and southern zones. Isolated strong to severe storms continue to look possible thoughout the weekend but confidence on this is low as thick cloud cover may limit destabilization. GEFS plumes show less than 1,000 J/kg of SBCAPE through the weekend, with ~35-45 kts of deep shear on Saturday and only ~15-20 kts of deep shear on Sunday.
Thus, Saturday still looks to have the better severe potential, and this matches up with the Day 3 SPC Severe Weather Outlook which has a Marginal risk in place east of the mountains. The main potential hazards with any severe storms that develop are damaging wind gusts and large hail. High temperatures have trended down slightly for the weekend and are now expected to be a few to several degrees below climo. Low temperatures will remain several degrees above climo thanks to both cloud cover and precip.

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/
As of 100 PM EDT Thursday: The low pressure system will linger over the eastern Carolinas through Monday before gradually pushing offshore Monday evening into Monday night. Thus, maintained chance PoPs (15% to 30%) across much of the forecast area Sunday night into Monday. Upper ridging and sfc high pressure will build into the southeast Monday night into Tuesday night, leading to drier conditions, while the low pressure system lingers just off the Southeast Coast. A cold front will approach out of the west on Wednesday before tracking across the forecast area Wednesday night into early Thursday morning. This will allow shower and thunderstorm chances to return towards the end of the forecast period. High temperatures will remain a few to several degrees below climo on Monday, becoming near climo to a few degrees above climo on Tuesday.
Highs are then expected to become a few to several degrees above climo Wednesday into Thursday. Low temperatures will generally remain a few to several degrees above climo through the period, with the exception Monday night as lows east of the mtns will be near or just below climo.

AVIATION /00Z FRIDAY THROUGH TUESDAY/
At KCLT and elsewhere: The overnight period has trended a little drier with the pattern so now have MVFR CIGs at KAVL and KHKY. An uptick in convec activity is in store Fri as an upper disturbance crosses from the southwest. Have PROB30 mention of TSRA at all sites during the afternoon, persisting until 00z. Expect a transition to SHRA for the late period at KCLT. CIGS and VSBY remain generally VFR outside heavier rain showers, but a notable increase in MVFR CIGs seems likely at KAND aft 22z. Winds remain light overnight and become aligned s/ly to sw/ly aft 14z-15z across all sites.

Outlook: Periods of convection, which could be widespread at times, are expected through the weekend. Late night/early morning restrictions in low stratus and/or fog will also be possible. Drier weather is expected to return early in the next work week.

GSP WATCHES/WARNINGS/ADVISORIES
GA...None.
NC...None.
SC...None.

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