Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 160717 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 317 AM EDT Thu Aug 16 2018 .SYNOPSIS... An upper level trough of low pressure will develop west of the Appalachians today and persist well into the weekend as a stalled surface front lingers north of the region. Moisture will increase ahead of this system to produce a lengthy period of unsettled weather from Friday onward. A weak cold front will approach slowly from the northwest early next week and likely arrive in the region on Wednesday. && .NEAR TERM /THROUGH TONIGHT/... As of 235 AM: Mountain valley fog and patchy fog outside of the mountains will dissipate this morning leaving copious cirrus and some mid cloud overhead. The ridge axis overhead moves east today as a short wave trough moves toward the area. The best short wave energy crosses the mountains late this afternoon and early evening. Low level flow turns southwesterly but isn`t very strong. Not much in the way of low level forcing develops outside of the mountains, and what does develop is mainly south of the CWFA. The main forcing will be weak terrain triggering across the mountains. Scattered coverage develops there as better moisture returns in the S to SW low level flow. Can`t rule out an isolated cell along the southern tier of the CWFA, but most of the area outside of the mountains will remain dry. Convection will linger into the evening then diminish overnight. However, the moist weakly forced atmosphere may lead to lingering isolated showers across the mountains overnight. Highs should top out a few degrees above normal. Lows will be a few degrees above normal as well. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 145 AM Thursday: An active pattern will continue across the FA thru the short term period. A broad ulvl trof will deepen and slowly cross the ern CONUS with the mean axis remaining west of the mtns. This will leave the area in broad lift with continuous pockets of small-scale dPVA traversing thru the flow. In the low levels...sw/ly moisture adv will continue and the column will remain quite moist. The deep moisture will help keep instability elevated until late afternoon Fri when sbCAPE increases over 1500 J/kg....altho shear parameters will be low. The wrn zone will be under gun for stronger storms aided by mech and dyno will continue the mention of possible svr activity in the HWO inline with the latest SPC Day 2 products. Saturday has similar looking profiles with relatively more deep layered shear so will anticipate isol/sct stg/svr convec within the better large scale lift or wrn half of the FA. Hydro could also be an issue during this time with continued activity over the same localized areas esp across the far wrn zones. Max temps will be arnd or little cooler than climo due to the high cloud cover and precipitating storms. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 200 AM Thursday: Little change was made to the going mid-range fcst as the guidance continues to show a broad and moist ulvl trof dominating the pattern early on. Soundings begin highly saturated Sun and this could be a problem hydro-wise as the overall steering flow weakens during the day and the previous days will likely have generated a broad area of precip coverage. The mid-levels dry out a little Mon into Tue as a h5 ridge traverse the area...but enuf llvl moist flux will keep an active pattern in the works. Surface based CAPE and bulk shear are not will expect a pulse tstm mode with a few stg/svr storms possible. Basically a nominal summertime sensible weather fcst is in store to begin the work week with max temps remaining a little below normal. && .AVIATION /07Z THURSDAY THROUGH MONDAY/... At KCLT and elsewhere: Quite a bit of mid cloud and cirrus across the area this morning. Still expect mountain valley fog to develop after the mid cloud dissipates. Have gone with persistence at KAVL. MVFR fog possible at the normally more foggy sites of KHKY and KAND. Any restrictions should dissipate relatively quickly after daybreak with cirrus remaining and cumulus developing for the afternoon. Best chance of any convection will be across the mountains, so PROB30 has been retained for KAVL. Convection should diminish during the evening but cumulus will linger. Light and variable wind becomes SW for the afternoon then light S to SW during the evening. Outlook: Increasing coverage of diurnal thunderstorms us expected from Friday through the upcoming weekend and into early next week. Restrictions will be limited mainly to areas in heavy showers and low clouds/fog across the mountain valleys each morning. Confidence Table... 07-13Z 13-19Z 19-01Z 01-06Z KCLT High 100% High 100% High 100% High 100% KGSP High 100% High 100% High 100% High 100% KAVL High 86% High 100% High 100% High 100% KHKY High 86% High 96% High 100% High 100% KGMU High 100% High 100% High 100% High 100% KAND High 100% High 100% High 100% High 100% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...HG NEAR TERM...RWH SHORT TERM...SBK LONG TERM...SBK AVIATION...RWH is the U.S. government's official web portal to all federal, state and local government web resources and services.