Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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751 FXUS62 KGSP 070732 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 332 AM EDT Sun Jul 7 2024 .SYNOPSIS... A weak surface front will increase the chance for thunderstorm activity outside the mountains today. An active pattern of afternoon and evening showers and storms is expected to continue into the coming week. && .NEAR TERM /THROUGH TONIGHT/... As of 330 AM Sunday: A weak frontal boundary will remain draped across the forecast area today, as it`s roughly parallel to deep-layer SWLY flow aloft. Copious moisture along the frontal zone (PWATs > 2 inches) will result in plenty of cloud cover today and another round of convection this aftn into this evening. Moisture has worked back NW into the mountains and convective initiation will likely start along the ridges early in the aftn. The Piedmont may get off to a later start, thanks to stratus taking its time scattering out. But the latest guidance is in good agreement on outflows kicking off convection east into the Piedmont (aided by convergence near the front) by late aftn or early evening, with most of the forecast area getting worked over before convection wanes. So likely to categorical PoPs looks on track with locally heavy rainfall and isolated flash flooding a concern again today. Instability will be modest (generally 2000 J/kg or less), so severe threat will be low. Cannot rule out a few strong wind gusts with the tallest updrafts and any cell mergers. Highs will be near normal. Tonight, plenty of lingering cloud cover and continued elevated dewpts should make for another warm, muggy night. Lows a few degrees above normal. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 145 AM Sunday...A moist and weakly forced atmos remains in place thru the short range. Upper heights vary little Mon as Atl moisture flux increases due to an eastward shift i Bermuda High ridging. Very hard to determine a main focusing zone as llvl bndrys remain ill defined. There is a decent signal for upslope precip/convec across the BR escarpment and further west into the NC mtns, however, and have the best PoPs there, pushing into the likely range, yet lower than the more deterministic NBM output. A solid chance precip will be maintained east of the mtns as PWATS remain quite high and subtle terrain lift could help instigate multicell outflow driven cells. Due to little changes in the overall synoptic pattern, will go with a persistence type fcst featuring high precip storms moving slowly northeast or east within the mean steering flow aloft. Thus, expect a chance of hydro issues, esp considering the increase in antecedent conds across localized areas. A few severe level storms will be possible as well with damaging outflow winds the main threat. More uncertainty on coverage and storm mode exists Tue as sfc troffing may develop from the west while the remnants of TC Beryl push up the MS Valley with differing timing solns seen on the op models. So, PoPs have been adj/d down a little yet still remain abv climo values. Max temps will hover near or arnd normal levels each day with no widespread HI issues expected. Mins will be held abv normal by a few degrees each morning. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 225 AM Sunday...A highly moist atmos remains in place to begin the period, but this could change Wed into Fri as the guidance looks to be trending drier. The latest op model runs all have remnant TC Beryl more closed off and cyclonic then previous runs. This could lead to higher moisture levels remaining tightly wound arnd the former TC while dry continental air swings arnd the base into our area from the west. Cross sections show a sigfnt lowering of theta/e air in the mid/low levels and PWATS levels dropping arnd an inch. This pattern change would curtail convection chances west of the dry/density front and shift the focus of afternoon tstms across the ern most zones of the FA into the latter ext period. Thus, have cut back on PoPs giving some weight to this possibility. Still have abv climo PoPs, but these may continue to lower on subsequent fcsts if the latest pattern idea holds. Temperatures are still on track to reach arnd normal thru the period. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... At KCLT and elsewhere: Despite plenty of high-based cigs, MVFR to LIFR clouds are beginning to form across the lower Piedmont, and should generally expand in coverage thru the pre-dawn hours, resulting likely IFR cigs at all the Piedmont sites by daybreak. The clouds will then be slow to lift to MVFR and finally scatter out to VFR by around midday. This may delay the diurnal convection, but with such moist air mass, expect scattered to numerous SHRA and TSRA starting in the mountains, then generally working east late aftn into the evening. Will go with a TEMPO at KAVL, where confidence and coverage warrants, while the other sites can still be handled with PROB30 groups. Convection should wane by late evening, leaving plenty of mid clouds around thru 06z. Areas of MVFR to LIFR cigs and patchy fog will likely form in the 06z-12z time frame again Monday morning. Winds will be light thru the period (except possible gusts and variable around convection). Outlook: An active summertime pattern continues for most of the upcoming week, leading to scattered to numerous showers/thunderstorms and possible restrictions each afternoon/evening. Fog or low stratus may develop each morning, especially over areas that received rain the previous day. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...SBK NEAR TERM...ARK SHORT TERM...SBK LONG TERM...SBK AVIATION...ARK