Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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655 FXUS62 KGSP 190622 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 222 AM EDT Thu Sep 19 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 TONIGHT/... As of 200 AM Thursday...An upper low is finally opening up as it drifts east across the Carolinas today. This places the forecast area in deep-layer NLY flow. At the sfc, a weak sfc high over the eastern Great Lakes will keep a light NELY flow across the area. The morning will start out mostly cloudy with areas of fog and low stratus, but should see a decent amount of breaks in the clouds by early to mid afternoon. Temps will continue a warming trend, with highs getting into upper 70s to lower 80s in the lower mountain valleys and the Piedmont. This combined with dewpts in the mid 60s should result in a little more instability. So expect another round of mainly scattered diurnal convection developing, with isolated tstms possible. Not expecting any severe storms, as CAPE will still be modest at best. But locally heavy rainfall and gusty winds cannot be ruled out. Tonight...Convection may linger into the evening, as activity drifts south out of VA and extreme NW NC. But this activity should be on a weakening trend and not expected to be organized. With less mid and high clouds expected than last couple nights, may see a better radiation fog night with possibly some low stratus developing as well. Lows will be a category or so above normal. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 145 AM EDT Thursday: The CFWA will be situated between the departing shortwave trough lifting into the northeastern CONUS and an upper anticyclone over northern Mexico and the Southern Plains at the beginning portion of the forecast period. As a result, expect for increasing subsidence over the area as higher heights filter into the CFWA through much of the period as upper ridging slowly propagates eastward and essentially shuts down rain chances for most locations. Surface high will sliver down the Appalachians from the Atlantic Canada/Hudson Bay area and keep dry conditions in place, outside of a slight chance PoP over the Blue Ridge Escarpment on Friday. Drier airmass will be in place, but model guidance have a hard time sending a backdoor front this far south in response to the area of high pressure nosing into the region. In this case, dewpoints will remain in the 60s, with increasing temperatures and thus, a drier but still humid airmass will remain in place. Not much change in the sensible weather for Saturday, but the upper ridge axis will continue to make a run at the southeastern CONUS from the west, so afternoon highs for Friday will be a few ticks above normal, while Saturday`s afternoon highs uptick to a category or two above normal. Overnight lows will run a few ticks above normal for both Friday and Saturday night thanks to elevated dewpoints despite better radiational cooling conditions. && .LONG TERM /SUNDAY 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 /07Z THURSDAY THROUGH MONDAY/... At KCLT and elsewhere: A mid-level low continues to spin over the terminal forecast area, producing a lot of 5000-10000 ft clouds. But plenty of breaks in those clouds are allowing radiation fog and LIFR stratus to form in spots. For the rest of the night thru daybreak, it is challenging to forecast how much of the fog and low cigs will form at the TAF sites, but will continue to show some development in the 06z TAFs. Note that in the mtn valleys, the fog could drop the vis down into the LIFR category and VLIFR is not out of the question. From there, fog and stratus should gradually improve to VFR late morning thru early aftn. Diurnal convection is expected to form across the NC mountains mid to late aftn, but little of that activity will be able to drift south-southeast into the Piedmont. Will add PROB30 for SHRA at KAVL and KHKY where chances are highest. Wind will be light N/NE or calm. Some redevelopment of patchy fog and low stratus will be possible across the area tonight, so will show some vsby reduction at KCLT beyond 06z tonight. Outlook: On Friday, sfc high pressure builds into the area from the north allowing drier weather and VFR conditions to return thru this weekend. No appreciable return of moisture or precip chances expected until early to middle of next week. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...ARK SHORT TERM...CAC LONG TERM...TW AVIATION...ARK