Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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695 FXUS62 KGSP 031828 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 228 PM EDT Wed Jul 3 2024 .SYNOPSIS... Hot and humid conditions will become established once again for the second half of the week. Afternoon showers and thunderstorms will be possible each afternoon starting Thursday, especially over the mountains. A cold front may enhance thunder chances along with the most widespread coverage of showers and storms on Saturday. && .NEAR TERM /THROUGH THURSDAY/... As of 225 PM: Sfc high pressure now centered off the New England coast maintains relatively dry air over most of our CWA, at least compared to points south and west. Deep convection should remain capped off by an inversion centered around 700 mb for the Piedmont and northern mountains; the inversion is a bit weaker and sfc dewpoints higher in the SW NC mountains and Savannah Valley, evidenced by a well developed cu field. Still think a stray shower could develop in the Balsams or vicinity this afternoon with the further addition of ridgetop convergence. Upper ridge over the Appalachian region will become more positively tilted as a shortwave moves south of James Bay; weak frontal zone will lay out near the Ohio River by daybreak Thursday. Sfc high will weaken further, while our low-level flow continues to veer to southwest. This flow appears less likely to foster low early-morning cloud cover than what we saw Wed morning, but should maintain an upward trend in dewpoints thru Thursday, while max temps rise back to around 90 in the mountain valleys and lower to mid 90s for the Piedmont. Winds thru the column will remain pretty weak. Subsidence inversion looks weaker on prog soundings but still persists such that areas near and southeast of I-85 still get below-climo PoPs for Thursday. The inversion will weaken enough that updrafts over the mountains look viable. CAMs however show only spotty QPF response in that area, perhaps reflective of winds being too weak to enhance initiation via upslope. A few vort blobs could eject from convection in KY/TN nearer the front and provide some enhancement, though. We will advertise mainly 20-30% PoPs for isolated or widely scattered coverage for most of our mountains, and higher 30-50% values along the TN border. PWATs are mostly below 1.5 inches; rainfall is not particularly likely to cause flash flooding despite slow storm motion. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... As of 120 PM EDT Wednesday: Mid level ridging will remain in place across the region through the short range period. The expected southwesterly low level flow will bring higher dewpoints back into the area. The main issue is how high the will dewpoints get. Mid 70s dewpoints are not that far away this afternoon, so they could easily advect into our forecast area. However, with the dry ground in our area we have to anticipate those readings could mix a bit lower during peak heating. Confidence is not particularly high, but the possibility of heat indices around 105 degrees exists in the lower Piedmont and around Charlotte on Friday and Saturday afternoons. Later forecast updates will have to fine tune whether this will be an issue. Otherwise, we do expect showers and thunderstorms to develop in the hot and moist air in the mountains with the highest pops being on Friday. Some storm activity will spill out into the Piedmont, but pops will be lower there. Saturday looks like another active convective day as a weak cold front drops into the area from the northwest. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As of 130 PM EDT Wednesday: Mid level ridging will be in place across the region with a seasonably warm and moist air mass persisting. We don`t expect excessive heat indices but do expect an active mainly diurnal shower and thunderstorm setup for Sunday through early next week. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/... At KCLT and elsewhere: Varying degrees of low-VFR cumulus will be seen this afternoon, most common in the Savannah River Valley where influence of dry Atlantic high pressure is weakest. KCLT will see some clouds AOB 045 in the first couple of hours before bases mix higher. Still expecting near-zero chances of diurnal convection near the terminals today, but a stray shower could develop in the mountains west of KAVL. Weak gradient implies variability will continue in sfc winds this aftn and tonight, but direction is most likely to be S to SW thru the period. As such moisture flux in the PBL should not be as effective at producing stratus/stratocu Thu morning as happened today, so no low clouds are mentioned in the current TAFs. Isolated or widely scattered showers are possible Thu aftn mainly over the mountains, but confidence too low to mention at KAVL thru 18z. Outlook: Typical mid-summer humidity and diurnal convection return Friday and persist into early next week, leading to SCT TSRA and possible restrictions each afternoon/early evening. Fog and/or low stratus may develop each morning, especially for areas that received rain the previous day. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...Wimberley SHORT TERM...SCW LONG TERM...SCW AVIATION...Wimberley