Sunrise 6:22 AM   Sunset 8:31 PM Moonrise 5:00 PM   Moonset 3:34 AM

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FXUS62 KGSP 200608 AFDGSP

Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 208 AM EDT Mon May 20 2024

SYNOPSIS
Warming high pressure will build atop the region through the first half of the week. Along and ahead of a stalling cold front, showers and storms return on Thursday with chances continuing all weekend.

NEAR TERM /THROUGH TODAY/
As of 150 AM: Weak sfc high now centered over Virginia, beneath positively tilted upper ridge. Sfc winds are almost all calm following apparent decoupling Patchy stratocu are seen along the Appalachians from WV to NE GA where weak low level flow bears an easterly component. Observed cloud heights suggest some of these are being generated by shallow convection beneath subsidence inversion; they generally look to persist in the NW half of the CWA thru daybreak, although likely variable in coverage. Dewpoint depressions are small across the board, but especially so in the SE area where skies have been clearest. NAMNest and HRRR depict some fog/stratus forming via radiation but so far have appeared overdone in their extent. Shallow nature of the moist layer suggests any fog will be similarly transient to the aforementioned cloud decks.

Today, flow will veer to SE as sfc high builds slightly further south and east. Still looks like the resulting upslope flow will trigger some isolated convection over the mountains owing to a few hundred joules of SBCAPE, but still with tame PWATs of around an inch by peak heating, weak shear, and plenty of dry air to entrain. Not particularly concerned for severe wx or for flash flood threat although any cells will be slow-moving.

SHORT TERM /TONIGHT THROUGH WEDNESDAY/
As of 1205 PM EDT Sunday: The warming trend will continue through the forecast period as lower elevation max temperatures climb into the middle 80s by Wednesday. Building upper ridge atop the SE CONUS will keep the atmosphere suppressed, save for diurnal isolated ridgetop deep conection in the NC mtns Tuesday.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
As of 100 PM EDT Sunday: With developing lee trough and some downslope warming, Thursday has the potential to be the hottest day of the week with piedmont upper 80s possible, as long as convective and/or debris clouds limit insolation too early in the day. It looks like an active frontal zone is progged to approach and stall in or near the cwfa on Thursday as it becomes parallel to the upper flow.
This baroclinic zone should be able to aid in showers and tstms becoming numerous, especially across the mountains Thursday afternoon. Within the wavy quasi zonal flow atop the region Friday and into next weekend, daily, diurnally enhanced tstms are probable each day with temperatures averaging above the late May climo.

AVIATION /06Z MONDAY THROUGH FRIDAY/
At KCLT and elsewhere: NE PBL flow continues via weak sfc high centered over Virginia. Mountain valley fog and stratus expected to persist through daybreak, with generally LIFR to VLIFR at KAVL. Otherwise, stratocu are being generated apparently via weak convergence and/or upslope east of the Blue Ridge Escarpment, with distinct layers at 030-040 and 060-080. Think these clouds are likely to be seen over all the terminals at some point before 12z, with periodic cigs possible, but cigs not likely to last long enough to allow valley fog to dissipate. Some sources depict radiation fog in the Piedmont in the predawn hours but presently not expected to extend to TAF sites. The NE winds will continue until early afternoon, with diurnal cu forming at MVFR to low VFR level but probably not causing cigs. Winds go SE with aftn mixing and southward migration of sfc high. Ridgetop SHRA or even TSRA are possible but chance still not mentionable at KAVL. SE flow tonight will produce low stratus near the Escarpment, and MVFR is possible at KAVL after 06z, along with valley fog. Otherwise VFR tonight.

Outlook: High pressure remains dominant over our area thru Wed, but isolated mountaintop convection still expected each afternoon. Precip and restrictions possible with next front arriving late Thu or Fri.

GSP WATCHES/WARNINGS/ADVISORIES
GA...None.
NC...None.
SC...None.

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