Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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035 FXUS62 KGSP 180612 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 212 AM EDT Wed Sep 18 2024 .SYNOPSIS... The remnants of the coastal low will drift east over the region today and dissipate by Thursday. Meanwhile, high pressure begins to build into the region from the north and west giving our region a dry weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 200 AM EDT Wednesday: The remnant low associated with Potential Tropical Cyclone Eight is centered roughly over the central Upstate, and will begin to drift slowly east today. The weakening low should support a little more mixing and some breaks in the clouds later in the day, which will help high temps to rebound from yesterday`s readings. The warmer temps and still cool temps aloft will support at least a few hundred J/kg sbCAPE by midafternoon, especially around the edges of the low (that is, the northern and eastern parts of the forecast area). So isolated to scattered showers may develop before the end of the day (most CAMs show at least some diurnal convection). Instability and forcing will likely be too weak for thunder, but cannot rule out one or two general thunderstorms in the I-40 and/or I-77 corridors. The western and southern parts of the FA will be on the more stable side of the low. Temps are forecast to top out a few degrees below normal under mostly cloudy skies. Tonight, the low will continue to drift east, allowing for most of the mid and upper moisture to exit stage right. However, lingering low-level moisture will likely support an increase in low stratus overnight, with patchy fog possible, especially in the mountain valleys. Lows will a few degrees above normal. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 135 AM EDT Tuesday: The weak closed upper low will open up into a shortwave trough by the beginning portion of the forecast period and lift into the northeast CONUS Thursday night into Friday as the associated trough axis gradually shifts east of the CFWA. Upper anticyclone over northern Mexico and Southern Plains slowly pivots higher heights into the southeastern CONUS in response to a digging upper low that moves into the southwestern CONUS. Lingering mid/low-level moisture should keep isolated to scattered showers across the CFWA on Thursday with a focus on the mountains and drier conditions becoming more evident elsewhere. The upper anticyclone axis will begin to encroach the region from the west as weak high pressure begins to settle in across the area. Dry air entrainment in the upper and mid-levels of the atmosphere will essentially shutoff any shower chance outside of a small chance over the mountains where convergence is maximized. Temperatures Thursday will be a few ticks below normal for afternoon highs as cloud cover will be more extensive and that will carry over into Thursday night as well, with overnight lows a few ticks above normal. More insolation Friday will result in temperatures rising to near normal values for highs and better radiational cooling conditions Friday night leading to near normal temperatures. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 223 PM Tuesday: A tranquil pattern will continue for much of the extended forecast period as upper ridging migrates from the Lower Mississippi Valley into the Southern Appalachians over the weekend. Surface high pressure extending form New England down the spine of the Appalachians will keep dry air in place. This will support healthy diurnal temperature swings of 20-25 degrees each day as deep mixing within the dry airmass promotes highs in the low 80s. Several nights of decent radiational cooling is also expected with overnight lows falling into the upper 50s to low 60s. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... At KCLT and elsewhere: Continued messy TAFs, as a remnant low spins over the forecast area. The center of the low is near the GMU/GSP sites, so LIFR conditions are expected to persist thru mid-morning. Missing obs across the mountains (and especially at KAVL), makes for very low confidence fcst for KAVL. Went with guidance on LIFR conditions and potentially some fog thru mid-morning. The other sites are on the edges of the circulation, and may have more variable conditions. KCLT is starting out VFR, but is expected to see at least some MVFR cigs this morning, which should lift/scatter out to VFR by midday. Guidance agrees on scattered showers developing across the mountains and the NC Piedmont in the aftn, so will carry PROB30 for those sites. Deep convection/thunder still looks low, given lack of instability. The low will begin to drift to the east/north and some clearing of moisture aloft may allow for areas of fog and low stratus forming again tonight. Winds will be light thru the period, favoring a NE direction overall. Outlook: A weak upper low will lift northeast tonight into Thursday. Restrictions return again tonight thru Thursday morning. On Friday, sfc high pressure builds into the area from the north allowing drier weather and VFR conditions to return into this weekend. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...ARK/DEO NEAR TERM...ARK SHORT TERM...CAC LONG TERM...TW AVIATION...ARK