Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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698 FXUS62 KGSP 181818 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 218 PM EDT Wed Sep 18 2024 .SYNOPSIS... The remnants of the coastal low will gradually dissipate or move off the Mid Atlantic coast by Friday. Meanwhile, high pressure begins to build into the region from the north and west giving our region a dry weekend. Temperatures will be near normal. && .NEAR TERM /THROUGH THURSDAY/... A cutoff upper low continues to provide enuf lift to produce periods -ra/dz over most areas. The srn and ern zones have seen increasing insol and therefore deeper showers have formed there. Not a great threat for thunder this afternoon as soundings still indicate only arnd 200 J/kg of skinny sbCAPE. There could be a few isol strikes later this afternoon, yet not enuf confidence is had to mention in the HWO. The upper low will lose any connection with the sfc pattern overnight and slowly shift east of the FA thru the day on Thu. Still expect a good amt llvl wrap around moisture in the wake, which will be able to develop isol/sct pulse showers and possibly a few general thunderstorms with increasing instability during the afternoon. Overall, an improving pattern as far as lessening cloud cover and temps will respond to arnd 80 F outside the mtns, a few degrees warmer toward NE GA, and u70s mtn valleys. A dense fog threat is possible arnd daybreak across the NC mtn valleys as better rad cooling conds interact with a rather moist sfc layer. Lows will generally be held a couple degrees abv normal. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... As of 157 PM Tuesday: As we head into Friday and Saturday, upper ridging will slowly drift east from the Southern Plains into the Lower Mississippi Valley. Heights will rise through the period across the Southern Appalachians with increasing subsidence. At the surface, high pressure will extend down the spine of the Appalachians form a parent high centered near the Hudson Bay. Guidance still indicates the presence of a backdoor cold front oozing into portions of the Carolinas from Virginia. A noticeable change, however, is that guidance is less aggressive with clearing the boundary through the area, thus keeping dewpoints in the low to mid 60s. The airmass will be drier, relatively speaking compared to the tropical origins of the current airmass, but PWATs may not fall as appreciably. While a stray shower or two cannot be ruled out, increasing subsidence from the building upper ridge will generally preclude mentionable PoPs outside of the Blue Ridge escarpment on Friday. Temperatures will continue to warm through the period with highs back into the low to mid 80s. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As of 206 PM EDT Wednesday: A warming trend will continue Sunday into early next week as the axis of the upper ridge becomes centered over the Appalachians. Warming H85 temperatures and deep/efficient mixing of the boundary layer will promote high temperatures in the mid to upper 80s on Sunday, which will likely be the hottest day of the period. A few locations may even reach the 90 degree mark across the Upper Savannah Valley. The forecast will remain dry, however, as a stout subsidence inversion present on forecast soundings deters any convection. By Monday into Tuesday, a shortwave trough swinging across the Midwest will drag a cold front towards the area. Timing of the trough and attendant front remains elusive at this time range, but a gradual uptick in PoPs will be warranted across the mountains as the boundary nears. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... At KCLT and elsewhere: A tricky TAF set in store as an upper low continues to produce low clouds and VSBY issues. Expect some improvement to VFR this afternoon, esp at KCLT. The wrn sites could remain socked in (MVFR/IFR CIGs) for a while with deeper moisture continuing to train and lift over the area. All sites will likely drop to IFR, mainly due to CIGs, overnight with MVFR VSBY probable as well. At KAVL, a good signal for a drying column as the low shifts east thereby setting up a possible dense fog threat arnd daybreak. Expect improving conds late period all sites to either MVFR or VFR. Winds remain light thru the period favoring a ne/ly direction. Outlook: On Friday, sfc high pressure builds into the area from the north allowing drier weather and VFR conditions to return into this weekend. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...SCW SHORT TERM...TW LONG TERM...TW AVIATION...SBK