Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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995 FXUS62 KGSP 071050 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 650 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 645 AM Sunday: Low cigs are not as extensive as the model consensus is depicting, and the mid and high clouds seem to be thinning out somewhat on the nighttime RGB. This may result in a little faster warming and more CAPE as well later this morning. However, forecast soundings have a low CCL, so low clouds may fill in after sunrise. So for now, no significant changes were made with this update. Otherwise...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 /12Z SUNDAY THROUGH THURSDAY/... At KCLT and elsewhere: Lower than average confidence on the low cig potential this morning, as guidance continues to be overdone. But with very moist low-levels and patchy LIFR to MVFR clouds floating around, expect some expansion of these low clouds during the first few hours of the day. The clouds should lift to VFR-level by around midday. Convection is expected to fire across the mountains early in the aftn, then the combination of outflows and a stalled front should trigger storms across the Piedmont late aftn thru the evening hours. So TEMPOs for TS will be carried at all sites (except PROB30 at KAND). Convection should wane by late evening, and similar conditions expected again tonight as we had last night. Plenty of mid and high clouds with patchy lower stratus and fog forming. Once again, guidance seems overdone with prevailing MVFR to LIFR cigs overnight thru Monday morning. Nevertheless, some low cigs will likely form across most of the area tonight. 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