National Weather Service (2024)

Area Forecast Discussion
Issued by NWS Greer, SC

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-- Discussion containing changed information from previous version are highlighted. --563FXUS62 KGSP 121053AFDGSPArea Forecast DiscussionNational Weather Service Greenville-Spartanburg SC653 AM EDT Mon Aug 12 2024.SYNOPSIS...
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A stalled frontal boundary over the Carolinas may lead to isolatedshowers and thunderstorms this afternoon and evening. High pressurebuilds in throughout the workweek while the front stalls over theSoutheast and keeps daily shower and thunderstorm chances around.High temperatures will continue on a cooling trend through theworkweek, with a warming trend expected over the weekend ahead of anapproaching cold front.
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As of 645 AM EDT Monday: No major changes with thisupdate. Convection finally shifted east of the forecast area andthe current PoPs show that trend. Skies have cleared out a fairamount across the mountains, the Upstate and NE GA, but cloudslinger in the NC Foothills and Piedmont. Sky cover was lowered abit for today, but otherwise no changes.Otherwise...a broad upper trough axis will persist roughly alongthe Appalachians, while weak sfc high pressure builds into theOhio Valley. The high may work to try to nudge a stationary frontsouth slightly from where it`s been the last couple days. The00z guidance and the CAMs seem to agree on a relatively quietday convection-wise, with some isolated showers and thunderstormspossible across the southern NC mountains and southern Blue RidgeEscarpment, as well as the southern edge of the forecast area. Themorning may start out with plenty of mid clouds, but should seesome clearing by the aftn. Temps are expected to be similar toyesterday`s highs, near normal in the NE, and a category abovenormal in the Upper Savannah Valley.Tonight, a vigorous shortwave will dive SE across the Ohio Valley,helping dig the longwave trough over the region. The approachingwave will help increase MUCAPE and may trigger some elevatedconvection across the forecast area overnight. The 00z HRRRis most bullish with thunderstorms forming roughly across theI-26 corridor after midnight then spreading east thru daybreakTuesday. The other CAMs hint at some overnight convection, butlook like mainly scattered showers. All of the op models also havesome QPF response by 12z Tuesday in these areas. Will allow forsome slight chc PoPs overnight, which may be bumped up in futureupdates if the model trends hold. Temps will be near normal underincreasing clouds overnight.
-- End Changed Discussion --&&.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Key Messages...1) Isolated Strong to Severe Storms Possible Tuesday2) Severe threat will be Lower Wednesday3) Cooler Temperatures Linger through the PeriodAs of 200 AM EDT Monday...No major changes to short term. Uppertroughing will remain in place through the period while periodicshortwaves track across the forecast area from the northwest. At thesfc, high pressure will expand from the Great Lakes region into theCarolinas while a front stalls over the Southeast. This pattern willallow daily scattered showers and thunderstorms to continue. Thebest instability on Tuesday looks to remain south of the forecastarea although the 00Z global models and CAMs show the potential for1000-1800 J/kg of SBCAPE across the southern half of the forecastarea during peak heating. With deep shear expected to range from 35-45 kts could not rule out the potential for a few isolated strong tosevere storms, especially across the far southeastern zones. The SPCDay 2 Severe Wx Outlook has a Marginal risk place across thesouthern NC Piedmont (south of Charlotte) and the eastern SCUpstate, which looks reasonable. Deep shear will remain around 35-45kts on Wednesday but instability will be considerably lower. Thus,the severe weather threat looks lower on Day 3. Any hydro issuesshould remain limited through the short term due to the higher shearvalues allowing for faster storm motion. Highs look to be a fewdegrees below climo each afternoon everywhere except the UpperSavannah River Valley and the Little TN Valley where highs shouldend up near climo to a few degrees above climo. Lows will remainnear climo to a few degrees above climo through the period.&&.LONG TERM /THURSDAY THROUGH SUNDAY/... Key Messages...1) Severe Threat Remains Low on Thursday with Another Round ofScattered Storms Expected2) Better Coverage of Showers and Thunderstorms Friday into theWeekend Thanks to a Cold Front3) Cooler Temps Continue on Thursday Before a Warming Trend ReturnsFriday into the WeekendAs of 230 AM Monday...Upper troughing with embedded shortwavestracking over the forecast area from the northwest will continueThursday into Thursday night. Friday brief upper ridging builds inacross the Southeast before pushing offshore early Saturday morning.Another upper trough will dig across the Southeast on Saturday,lingering over the region through rest of the weekend. At the sfc,high pressure will gradually track eastward from the Ohio Valleyinto the Northeast Thursday into Friday, with the southern peripheryof the sfc ridge continuing to extend across the Southeast. The sfchigh will push offshore into the western Atlantic Friday intoSaturday as a cold front approaches out of the west. The frontshould track across the Carolinas and northeast Georgia lateSaturday into early Sunday. Scattered shower and thunderstormsreturn again on Thursday, with the severe storm potential remaininglow. Hydro issues will once again be offset by 25-35 kts of deepshear. Better coverage of showers and thunderstorms returns to thearea Friday into the weekend ahead of and along the cold front. 00Zglobal models disagree on if there will be enough instability forstrong to severe storms during this timeframe, so confidence is lowregarding the severe potential. Guidance also shows the potentialfor lower shear despite the front which could lead to slower stormmotion and perhaps increase the excessive rainfall threat. However,with this being towards the end of the forecast period, confidencewill also be low concerning any hydro issues. Highs on Thursday willbe a few degrees below climo area-wide. With a warming trendexpected Friday into the weekend, highs will end up a few degreesabove climo in the Little TN Valley and the Upper Savannah RiverValley with highs elsewhere remaining a few degrees below climo tonear climo. Lows will remain a few degrees above climo through theperiod.&&.AVIATION /12Z MONDAY THROUGH FRIDAY/...
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At KCLT and elsewhere: Patchy mountain valley fog and a fewIFR to MVFR stratocu around to start the morning, but overall,VFR conditions expected today. A mix of cu and cirrus today,with little in the way of deep convection expected across the TAFsites thru this aftn. Isolated TS cannot be ruled out across theUpstate sites late aftn into this evening, but chances are too lowto mention in the TAFs attm. Guidance still hinting at some showersand possibly isolated TS forming late tonight before 12z Tuesday,but chances don`t really increase until Tuesday morning. Will adda PROB30 for SHRA at KCLT, since PoPs warrant it. Winds will belight out of the N to NE thru the period, except possibly togglingto ESE at KAND this evening.Outlook: Expect generally isolated to scattered diurnal convectionacross the region each day through the work week. Patchy fog andlow stratus will be possible each night in the mountain valleysand in locations that receive rainfall.
-- End Changed Discussion --&&.GSP WATCHES/WARNINGS/ADVISORIES...GA...None.NC...None.SC...None.&&$$SYNOPSIS...ARNEAR TERM...ARKSHORT TERM...ARLONG TERM...ARAVIATION...ARK