Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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113 FXUS62 KGSP 031852 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 252 PM EDT Fri May 3 2024 .SYNOPSIS... Dry and warm high pressure moves off the Carolina coast as a front approaches from the west then stalls over our region for the weekend. This front will result in periodic thunderstorms and showers starting today and lingering through the weekend. A general summertime pattern sets up early next week, which will likely support scattered thunderstorm development each afternoon. && .NEAR TERM /THROUGH SATURDAY/... As of 220 PM EDT Friday: Upper ridge axis slowly moves east as an upper trough and a series of short waves move into the area. Surface high pressure dissipates as a weak surface low and trough move in. Copious moisture and weak forcing will lead to steadily increasing convective chances. Scattered showers and thunderstorms are developing and will move northeast across the area this afternoon and evening. Atmos is weakly unstable with poor mid level lapse rates. Bulk shear is also weak. That said, there are steep low level lapse rates with DCAPE over 800 J/kg over the the I-77 corridor where heating has taken place. The overall chance of severe is low, but can`t rule out a strong or severe storm. While brief, heavy rainfall is possible with any storm, the flood threat is also low. Lows tonight will be around 10 degrees above normal. Coverage and intensity should drop during the evening. However, CAM guidance shows an uptick in shower activity overnight in the continued moist and weakly forced atmos. Coverage then continues to pick up through the day Saturday as forcing becomes better. Instability and shear will remain on the weak side, while forecast profiles show an even more saturated atmosphere. This suggests and even less chance of strong to severe storms, with a slight uptick in heavy rain potential. That said, the overall flood risk remains low given the relatively dry antecedent conditions. Highs will be near normal due to clouds and precipitation. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... As of 240 PM EDT Friday: The rest of the weekend looks active right into the first part of next week. A baggy upper trof overhead on Saturday night slowly lifts northeast with a short wave passage, and this bit of lingering forcing will be able to keep shower/thunderstorm activity on a slow wane into the early morning hours. Guidance suggests that it will never die off entirely, so the fcst retains some fairly high precip probs. That sets the stage for Sunday. Models show less forcing, but an uptick in the available buoyancy in the afternoon. That should make for a more thermodynamically-driven day, with better than climo coverage of showers and storms. Forecast soundings off the NAM show some pulse-severe wind damage potential with mid-level dry air and a shallow inverted-V, so it would not come as a surprise if it was a busier day than Saturday. A stronger short wave lifting northeast over the TN/OH Valley regions on Monday will continue to support diurnally-enhanced convection, so we continue with above climo precip probs. Temps look to be on the order of five degrees above normal. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 143 PM EDT Friday: The bulk of the medium range looks like a summer preview. After a baggy upper trof moves past Monday night, we should spend the remaining week underneath a low amplitude, relatively fast, WSW flow aloft. Within this flow, the model guidance shows a steady train of short waves moving through, mostly around peak heating each day, that will enhance our convective coverage each afternoon/evening. Overall, the air mass shows little change from one day to the next, as a wavy surface front will be strung out to our north in the WSW flow. Buoyancy will be modest and shear will be light, which suggests that chances for severe storms will be relatively low, but in such a pattern we eventually seem to manage to crank out a few pulse severe storms each day. Precip will be spotty and showery, which keeps the heavy rain threat at bay, but eventually there could be a few spots that start to see an increased risk of flash flooding, especially if a more coherent, stronger short wave comes along, such as what the GFS shows next Friday. Lots of uncertainty, though. Temps will remain in that 5-10 degree above normal range for most days, perhaps on the high side of that either Wednesday or Thursday, which one of those days might get a break in the wave train and thus reduced shower coverage and higher temps. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... At KCLT and elsewhere: Showers and isolated storms are developing across the area and moving NE this afternoon. Have added TEMPOs at the locations most likely to see activity. KCLT with just SHRA for now, while KAVL/KHKY has TSRA. A cell may affect the SC sites but will amend as needed. S to SW wind expected through the afternoon. Activity diminishes somewhat this evening but returns overnight. Have PROB30s in place for that. Cig and vsby restrictions develop overnight as well, so have MVFR to MVFR before 12Z and IFR after 12Z. Light and variable wind expected overnight with S to SE wind for all but KAND, where it will be ENE, Saturday. Outlook: Enhanced moisture will combine with a weak/stalled front through early next week, resulting in a period of active/mainly diurnal convective weather each day. There will also be the potential for restrictions associated with widespread fog and/or low clouds each morning. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...RWH SHORT TERM...PM LONG TERM...PM AVIATION...RWH