Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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882 FXUS62 KGSP 010136 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 936 PM EDT Sun Jun 30 2024 .SYNOPSIS... Hot and humid conditions today, as well as showers and thunderstorms ahead of a robust cold front. Drier and cooler conditions settle in behind the front Monday and Tuesday, before the summer heat returns Wednesday and beyond. && .NEAR TERM /THROUGH MONDAY/... Evening Update...Ongoing convec continues to wane as a sfc front pushes in across the NC mtns. A few stronger cells are diving across the Upstate and these will weaken due to loss of deep sbCAPE and increasing llvl CIN. Will be close for dense fog formation overnight, but the guidance continues to bring in moderate llvl winds before daybreak, which will help dry the sfc layer. With the decent amt of precip earlier, still think fog will form, but will keep it above 1/2 mile for now due to the late night mixing potential. As of 200 PM Sunday...Seeing a few obs with heat indices at or above 105, but convection should start to bring those down. Scattered convection has developed along a pre-frontal trough roughly parallel to the NC/SC border and drifting southeast. Meanwhile, the actual sfc front is still back over the Cumberland Plateau and eastern KY. There is about 3000 J/kg of sbCAPE south of the pre-frontal trough, while debris cloudiness is limiting CAPE somewhat to the north across eastern TN and much of western NC. So decent convection with a few strong storms should continue to affect the Upstate and NE GA, while we may need to wait until late aftn or early evening for activity to really ramp up across the NC mountains. The latest CAMs are not too excited about the activity coming in from the NW this evening, and generally dissipate it before reaching the eastern Escarpment. This is not exactly how the PoP/Thunder grids are currently, so an update may be needed if these trends hold. Still may see a few damaging wind gusts with whatever storms do develop and maximize the CAPE. But shear looks too weak to really get updrafts organized. A fair amount of clouds will linger overnight, and the front should usher in some drier air that will limit fog potential. Lows will remain a few degrees above normal. Monday looks much quieter, with a return to seasonable temps and humidity. The cold front will push well south of the area, while a fairly dry and mild 1028 mb high will nose down from the Great Lakes. There will probably be enough lingering moisture in the Upper Savannah Valley and Lakelands for isolated convection, mainly showers in the aftn. But otherwise, just some fair wx cu. Highs mainly in the mid 80s to around 90 in the mountain valleys and Piedmont. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... As of 150 PM Sunday: Not too much change in the short term. Synoptically, high pressure builds in from the west with an amplifying high over the southern CONUS. To the north, a dissipating trough turns flow aloft NW, on Tuesday, but turns more westerly as the upper high moves over the area. High pressure at the sfc will slide toward the NE of the CWA by Wednesday, maintaining a stream of drier and somewhat cooler air for the short term. Modeled upper air guidance shows a stout subsidence aloft with a mid-level inversion at the top of the BL, reducing rain chances Tuesday and Wednesday afternoon. Despite a few slight chance PoPs (15%-30%) mainly concentrated over the NC mtns, there is almost no QPF response. Another concern is the wide dewpoint depression at the surface and at the top of the BL. With very dry air aloft, this could mix down toward the surface, dropping RH values lower than model guidance suggests. This would present more issues in terms of fire concerns. Fuel moisture is dry, especially east of the mountains meaning vegetation is more prone to ignition. Will continue to monitor. Otherwise, temperatures look to be closer to climo and begin an upward trend into the next period. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... As of 200 PM Sunday: The summertime pattern continues into the extended. Wednesday night and into the extended period. The strong area of high pressure continues to grow over the southeast and Mid- Atlantic regions. Persistent height rises over the region will create temperatures well above normal through the weekend. Guidance from the GFS and EURO depicts moisture returning toward the end of the week as the sfc high to the north slides off shore and winds become more southerly. The advection of moisture does look to keep dewpoints in the low to mid 70s by end of week. This will have a direct impact on heat indices, especially those locations east of the mountains. 100 plus values are possible by Thursday and into the weekend for areas south of I-85 and eastern NC Piedmont. Will continue to monitor, but confidence is increasing given the persistent high pressure settling over the area. Once the high pressure moves offshore, a return to more diurnally driven convection is possible across the mountains, though confidence is low. QPF response still remains low as well. As for fire concerns, guidance does keep a stout amount of dry air aloft with a a well mixed boundary layer. Once again, RH values have the potential to be lower than guidance is depicting should the drier air mix down. Will continue to monitor. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... At KCLT and elsewhere: Convective activity is waning and dont expect thunder impacts at most airfields this evening, except possibly at KGSP and KGMU as isol cells continue to move off the escarpment over the next couple hrs. The main frontal line should bring only -shra to KAVL, KHKY, and KCLT this evening and push southeast of the area by 03z. No great chance of fog overnight and flight conds shud remain VFR thru the remainder of the period at all sites. Winds will weaken overnight and become aligned ne/ly across the non/mtns Mon morning as a dry sfc wedge builds in. Low-end gust will be possible as well aft daybreak into the afternoon and the late period at KCLT. Winds at KAVL will be more tricky, but most likely align nw/ly into the early afternoon and possibly shift more nne/ly or se/ly into the evening. Outlook: A cold front will stall just south of the area, resulting in quiet weather thru mid-week. A return of more typical mid-summer diurnal convection is expected by Thursday into the weekend. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...CP NEAR TERM...ARK/SBK SHORT TERM...CP LONG TERM...CP AVIATION...SBK