Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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684 FXUS62 KGSP 211048 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 648 AM EDT Sat Sep 21 2024 .SYNOPSIS... High pressure will linger over the region through the weekend with temperatures warming above normal. A more moist airmass will move into our area from the north early next week and linger through mid- week increasing rain chances. && .NEAR TERM /THROUGH TONIGHT/... As of 640 am: Fog and low stratus, including patchy dense fog continues to steadily expand across the forecast area this morning, and may continue to expand for another hour or so before insolation increases. A Dense Fog Advisory remains unnecessary, but a Special Weather Statement for patchy dense fog may be in order. Otherwise, an upper ridge extending from an anticyclone over Texas will continue to nudge into the forecast area through the period, resulting in a continuation of unseasonably hot conditions, with max temps today expected to again be around 5 degrees above normal. Humid conditions will also persist, and the atmosphere is expected to destabilize to the tune of around 1500 J/kg of sbCAPE this afternoon. Spotty diurnal convection is expected to develop within this air mass, especially in areas along/near the Blue Ridge escarpment. 20-30 PoPs are advertised in these areas. An area of height falls will briefly brush the eastern part of the CWA this evening, and most short term and convection-allowing model guidance allows some scattered convection to move into the western NC Piedmont from the northwest between 00-06Z Sunday. This warrants a period of 20-30 PoPs across these areas during that time. Otherwise, min temps will again be at least a category above normal. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 3:05 AM EDT Saturday: The short-term fcst picks up at 12z on Sunday 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. At the sfc, broad high pressure will be in place over the Southeast as the period begins. As we move into Monday, 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. This moisture is expected to linger for the rest of the period and spread further SE by early Tues. As for the sensible fcst, I still expect Sunday to be mostly dry with precip chances increasing on Monday especially over the northern half of our CWA. In addition to showers, we could also see a few weak thunderstorms as some amount of instability will likely be present over the fcst area during the afternoon/evening. Temperatures should peak on Sunday with highs expected to approach and/or exceed 90 degrees across most of our Upstate zones, and mid to upper 80s over our NC Piedmont zones. Temps will moderate on Monday under increased cloud cover. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 2:55 AM EDT Saturday: The extended fcst picks up at 12z on Tuesday with upper ridging still lingering over the SE CONUS as broad upper trofing amplifies over the central CONUS. Over the next few days, the evolution of this trof varies considerably between the operational models. The majority of the long-range guidance has the trof axis passing just to our north by late Wed and then morphing into a large closed h5 low on Thursday. This upper low then lingers somewhere over the Atlantic/New England Coast thru the end of the week and into the weekend. The current GFS solution is quite a bit different and still appears to be an outlier. At the sfc, weakening high pressure will still be lingering to our south as the period begins. A broad area of deeper moisture associated with a complex low pressure system will also be present just to our north. As we move into Wednesday, another cold front is expected to gradually approach our area from the west and move thru our area later in the day. In its wake, broad high pressure will likely spread back over the fcst area from the NW and linger into the weekend. It should be noted that by the end of the period next Saturday, most of the long-range guidance has some sort of tropical system strengthening over the Gulf of Mexico and tracking northward to- wards our area just beyond day 7. Temperatures will moderate thru the period with highs expected to drop just below climatology by the end of the week. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... At KCLT and elsewhere: Low stratus and/or fog has finally become widespread in the mountain valleys this morning, with LIFR being reported at KAVL. This should dissipate by 14Z. VFR generally prevails at the other sites, but the latest guidance is hinting at the potential for low stratus to expand around sunrise before dissipating by late morning...indicating that KGMU/KGSP/KCLT could see some restrictions early in the period. Although this is plausible, we`re not seeing this in observational data at this point, so the potential has been addressed with tempo/s for MVFR fog and FEW/SCT IFR layers. Otherwise, winds will become light southerly by late morning. Isolated diurnal convection is expected this afternoon and evening, but coverage is again expected to be too sparse to warrant a TAF mention at any site. Some fog and low stratus may redevelop toward daybreak Sunday, and this is hinted at in the 12Z TAFs. Outlook: No appreciable return of moisture or precip chances expected until early to middle of next week. Daybreak restrictions could recur each morning especially in mountain valleys. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...JPT NEAR TERM...JDL SHORT TERM...JPT LONG TERM...JPT AVIATION...JDL