Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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211 FXUS62 KGSP 221727 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 127 PM EDT Sun Sep 22 2024 .SYNOPSIS... High pressure will linger across the region through the weekend helping keep temperatures above normal. A more moist airmass will spread over the area on Monday and linger through at least mid-week. && .NEAR TERM /THROUGH TONIGHT/... As of 125 PM EDT: An upper ridge axis to our west will become centered over the Appalachians by the end of the period. Cumulus is developing across the area but mostly sunny skies will remain for the bulk of the day. Another hot and relatively muggy day, with max temps expected to average almost 10 degrees above climo. Moderate destabilization, with forecast soundings indicating an uncapped environment will create some potential for spotty diurnal convection late in the day...especially across the western half of the area, where 20-30 PoPs are advertised. Any convection should diminish by late evening, although some activity originating from a frontal zone across the Ohio Valley could wander toward the southern Appalachians toward daybreak Monday. Min temps will be 5-10 degrees above normal. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 3:05 AM EDT Sunday: The short-term fcst picks up at 12z on Monday with broad upper ridging still in place over the Southeast. The upper ridge is expected to linger over our area thru the period, though it does get suppressed by an embedded upper trof that rides up and over the ridge from the SW on Tuesday. At the sfc, a complex low will develop over the Ohio River Valley and move a broad area of deeper moisture SE and down the spine of the Appalachians and into our fcst area as the period begins early Monday. This moisture is expected to linger for the rest of the period and spread further SE early Tuesday. By the end of the period early Wednesday, another low will spin up over the Ohio River Valley and bring another cold front to our doorstep from the west. As for the sensible fcst, I bumped up precip chances across our northern zones for both Monday and Tuesday afternoon/evening. In addition to showers, we could also see some thunderstorms as some amount of instability will be present over the fcst area during the afternoon/evening. High temperatures will moderate on Monday and Tuesday under increased cloud cover, yet still remain above climatology across most of the CWA. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 3:15 AM EDT Sunday: The extended fcst picks up at 12z on Wednesday with upper ridging still lingering over the far SE CONUS as broad upper trofing amplifies over the central CONUS. The operational models appear to be coming into better agreement wrt the evolution of the upper trof during the first part of the period. The majority of the long-range guidance has a fair- ly large upper low spinning off the backside of the trof over the central CONUS on Wednesday, while the trof itself continues to translate eastward with the trof axis passing to our north early Thursday. On Friday, another large upper low is expected to quickly dive southward and over the New England area as the above-mentioned upper low lingers just to our west. Beyond this point, it is difficult to predict how these lows will interact with each other, but most of the guidance has the central CONUS upper low remaining to our west thru the weekend. At the sfc, a low pressure system will lift north over the eastern Great Lakes and move another cold front into our fcst area later on Wednesday. It`s looking increasingly likely that the front will stall out over our area while broad high pressure remains well to our NW for Thursday and Friday. At the same time, a robust tropical low from the Gulf of Mexico will track north and over our area as early as Friday. We will need to see how consistent the long-range guidance is over the next few days with this sys- tem before we can have much confidence wrt how it will impact our area. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... At KCLT and elsewhere: VFR cumulus this afternoon with isolated convection generally along and west of I-26. Chance still too low for TAF mention. MVFR then IFR stratocu moves SW across the area late this evening and overnight. Have it for the NC sites, where fog may also develop at KAVL and KHKY. There is a chance the cloud deck makes it to KGSP/KGMU, but that is more uncertain so put FEW MVFR for now. Vsby should improve quickly after daybreak, but cigs will take longer to go VFR. Scattered convection expected during the afternoon, so have PROB30 at KAVL where it starts sooner and KCLT wit the longer TAF period. Light N to NE wind becomes through the overnight becomes light S on Monday. Outlook: A weak cold front will slowly approach from the west this week before tracking over the area on Thursday. Chances for diurnal showers and thunderstorms will increase Monday and remain elevated through at least Thursday. A tropical cyclone may move into the SE late in the week. Mountain valley fog/low stratus may develop each morning around daybreak. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...JPT NEAR TERM...JDL/RWH SHORT TERM...JPT LONG TERM...JPT AVIATION...RWH