Sunrise 6:46 AM   Sunset 8:02 PM Moonrise 2:18 PM   Moonset 3:28 AM

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FXUS62 KGSP 181846 AFDGSP

Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 246 PM EDT Thu Apr 18 2024

SYNOPSIS
Showers and thunderstorms are possible Friday as a cold front crosses the area, but unseasonably warm weather continues through Saturday. Below-normal temperatures and widespread light rain is expected Sunday with cool but drier weather on Monday. Drier and warmer weather will return to the area Tuesday through Thursday of next week.

NEAR TERM /THROUGH FRIDAY/
As of 235 PM Thursday: Ridgetop cumulus developing across the mountains with some cirrus passing by. A few showers will be possible, especially from the Balsams drifting to the SE this afternoon. Otherwise, hot and dry conditions continue.

A series of short waves pushes a cold front toward the area tonight.
The guidance agrees on increasing mid and upper clouds, with lower clouds increasing toward daybreak. The guidance, synoptic and CAM, disagree on the coverage of any pre-frontal convection moving in, mainly after midnight. They do generally agree that convection should weaken as it moves across the mountains, although some stronger cells are possible, and could continue until daybreak. Have gone with the guidance blend showing best PoP across the mountains with isolated coverage over the western Upstate and NE GA. QPF doesn't look especially heavy either, although some moderate amounts are possible. Lows around 10 degrees above normal.

The convection continues to diminish as it moves east during the morning, but reignites for the afternoon as the cold front itself moves in from the west. Best coverage will be over NC and the central and eastern Upstate, with isolated coverage over the Upper Savannah River valley. An isolated severe storm or two will be possible with moderate CAPE and shear developing. Right now, it doesn't look to be especially organized even with the front moving in. Again, some moderate QPF is possible but significant coverage of heavy rainfall is unlikely. Highs will be a little tricky given the clouds and potentially two rounds of convection. For now, have highs around 10 degrees above normal.

SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/
As of 200 PM EDT Thursday: A cold front will be draped across the center of the forecast area early Friday evening before gradually pushing south and east Friday night into daybreak morning. CAMs show the potential for lingering isolated convection through late Friday evening, so have chance PoPs in place through late Friday night across the western and eastern zones. The SPC Day 2 Severe Wx Outlook has the western Carolinas in Marginal Risk for isolated strong to severe storms, thus a few strong to severe storms will be possible through the evening hours. The main potential impacts with any storm that manages to become severe will be large hail and damaging wind gusts. Lows Friday night will end up around 12-15 degrees above climo thanks to increasing cloud cover and convection.

The cold front will be located just south of the forecast area on Saturday, which may allow additional isolated convection to develop during the afternoon and evening hours. Have chance PoPs in place again on Saturday to account for this potential, but the NAMnest shows mostly dry conditions. Thus, confidence on PoPs for Saturday is low. The severe weather threat looks to be lower on Saturday, but we cannot not rule out an isolated strong storm or two if convection manages to develop. Despite cloud cover lingering on Saturday, highs will be around 4-8 degrees above climo across most locations.
However, the NC/TN border will likely see highs a few to several degrees below climo behind the cold front.

The front will stall across the Gulf Coast Saturday night into Sunday while sfc high pressure gradually builds into the central CONUS leading to much cooler temperatures. Meanwhile, upper shortwaves will track across the Southeast Saturday night into Sunday leading to gradually increasing rain chances. Could not rule out some isolated thunderstorms Saturday evening thanks to lingering instability. However, thunder is not expected on Sunday thanks to in- situ CAD leading to a more stable airmass. Have chance PoPs Saturday night with likely to categorical PoPs on Sunday. Lows Saturday night will end up around 4-7 degrees above climo, with highs on Sunday ending up around 10-13 degrees below climo.

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/
As of 230 PM EDT Thursday: Rain chances will linger through Sunday evening before gradually tapering off overnight as the upper shortwaves push east of the western Carolinas. Thus, have chance PoPs in place through late Sunday night across the forecast area.
Lows Sunday night will end up near climo to a few degrees below climo despite lingering cloud cover. The aforementioned sfc high in the short term will gradually push into the eastern CONUS Monday into Tuesday leading to drier conditions. CAD looks to linger through Monday before gradually dissipating Monday night into early Tuesday. This will lead to another round of below climo temps, ~7-11 degrees, Monday afternoon. Highs on Tuesday will be noticeably warmer thanks to the sfc high being directly overhead the Carolinas and leading to S/SSW'ly flow. Lows Monday night will end up a few degrees below climo thanks to mostly clear skies. Lows Tuesday night will end up a few degrees above climo ahead of an approaching cold front. A cold front looks to track across the western Carolinas overnight Tuesday into Wednesday, mainly leading to increased cloud cover, especially along the western North Carolina mountains. Rain chances also look to return with this front, but should remain confined to the western North Carolina mountains. Thus, capped PoPs to slight chance for now across these zones. Both highs and lows on Wednesday will end up a few degrees above climo. Dry high pressure will build back into the region behind the departing front Wednesday night into Thursday leading to drier conditions and slightly cooler temps.

AVIATION /19Z THURSDAY THROUGH TUESDAY/
At KCLT and elsewhere: Ridgetop cumulus and patchy cirrus will continue through the afternoon. Winds are a little squirrelly, varying between SW to NW. Winds are "supposed" to be NW this afternoon but aren't cooperating. Went with current conditions at each site, but they could switch from time to time. Expect mid and high clouds to increase overnight as a frontal system approaches from the west. Guidance is all over the place on potential for any convection to move in overnight as well. Have gone with a blend for the timing which brings a chance of showers to KAVL toward daybreak, then KGMU/KGSP/KHKY a little after daybreak, and KCLT TSRA for the afternoon. KAVL also gets prevailing SHRA for late morning. KAND may miss out on the convection, but that's far from certain. Expect generally low VFR, but MVFR is possible in any heavier showers or storms.

Outlook: Unsettled conditions are expected to continue into the weekend, and possibly Monday, with periodic precip/possible TS and restrictions. Drier conditions return for Tuesday.

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

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