Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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983 FXUS62 KCHS 021609 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1209 PM EDT Tue Jul 2 2024 .SYNOPSIS... A stalled front will linger near the area today before dissipating offshore. A hot and humid air mass will build over the region during the latter half of the week. A weak cold front could approach the region by Monday. && .NEAR TERM /THROUGH TONIGHT/... This Afternoon: The front has now drifted south the Altamaha River, however shower activity has been slow to wane. Showers with a few tstms will linger south of I-16 for a few more hours before most of the activity dissipates. Near term pops were adjusted slightly and the mention of tstms was cut back even more given the mostly stable conditions that are in place. Gusty northeast winds will persist along the South Carolina beaches into Tybee Island, GA, due to pinched gradient conditions behind the front. Highs in the coastal corridor and south of I-16 were also nudged down a bit more. Skies are trying to clear for areas near the CSRA and Southern Midlands, so the warmest conditions will be found well inland. The risk for flooding rainfall along the Georgia coast is steadily diminishing. Tonight: Latest guidance has trended a bit more toward holding onto precip activity south of the front across southeast Georgia. However, diurnal heat loss should result in most convection to wane during evening hours. Additional showers and thunderstorms could redevelop across coastal waters and make a run toward the coast late. At this time, scattered showers and thunderstorms remain in the forecast across coastal areas through much of the night to account for this possibility. Low temps should range between the low- mid 70s inland to upper 70s near the beaches. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... High pressure off the mid-Atlantic coast will extend across the area on Wednesday, while a stalled front lingering nearby eventually dissipates. Aloft, a mid level ridge will build over the Southeast. Best potential for convection will be near the southern South Carolina coast and across southeast Georgia where deepest moisture resides. Further inland and to the north should not see as much activity. Highs will be in the upper 80s to lower 90s. Lows Wednesday night will range from around 70 inland to upper 70s at the beaches. Mid level ridge will dominate the pattern aloft Thursday and Friday. The surface will feature high pressure offshore and a trough of low pressure inland. Mainly just isolated to perhaps scattered diurnally- driven showers and thunderstorms are expected each afternoon and evening. Otherwise, temperatures and humidity will be on the rise. Highs will be in the low to mid 90s on Thursday, with heat indices topping out in the 100-105 range. Friday will be a bit hotter, and heat indices could approach local Heat Advisory criteria of 108 degrees in spots. Lows will be in the 70s. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... Guidance is in good agreement in the extended. Mid level ridge will hold over Southeast coast into the weekend, before weakening. At the surface, a trough of low pressure will persist inland with high pressure offshore. It should get a bit more convectively active than previous days with better instability and possibly weak upper support. Current forecast highlights chance PoPs (generally 40-50%) each day with coverage peaking in the afternoon and evening. We are continuing to monitor the potential for excessive heat. Highs temps mainly in the mid to perhaps upper 90s combined with elevated dew points will make it feel even hotter. Heat indices are forecast to approach or exceed 108 in many locations, with some potential to even hit 113. Excessive heat headlines could eventually be needed. Convection could disrupt temperature trends. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/... 02/18Z TAF Discussion: KCHS/KJZI: VFR through the period. There is a chance near MVFR cigs could develop near KJZI after midnight as shower activity off the lower South Carolina coast tries to develop. VCSH was highlighted at KJZI 08-14z for now. KSAV: MVFR cigs will improve to VFR 20-21z. VFR should then dominate through late evening. After that, the risk for MVFR cigs will increase again as shower activity off the coast draws closer to the coast. Extended Aviation Outlook: Brief flight restrictions are possible in showers and thunderstorms, mainly in the afternoon and evenings through the period. && .MARINE... Winds are howling over the waters north of the Savannah River Entrance this morning where pinched gradient conditions are occurring. Gusts in excess of 30 kt have been observed at times. The Small Craft Advisory was extended south to include the Edisto Beach to Savannah nearshore waters and a Marine Weather Statement was issued to address winds near 30 kt at the Savannah River Entrance where especially rough conditions are likely. The advisory runs through 4 PM. Today and Tonight: A fairly enhanced pressure gradient has developed across northern SC waters off the Charleston County coast outside of convection. Given recent obs across local waters a Small Craft Advisory is now in effect until 2 PM for gusts around 25-30 kt and seas up to 4-6 ft. Thereafter, guidance continues to indicate that the gradient will begin to relax while a ridge of high pressure persists aloft. Otherwise, expect northeast winds between gusting around 20 kt outside shower/thunderstorm activity across southern SC nearshore waters and nearshore GA waters, and more easterly and light south of a stalled front/boundary across offshore Georgia waters. Overnight, the front should begin to drift south of local waters and/or dissipate, but showers and thunderstorms will continue to pose localized higher wind gusts and reduced vsbys at times until that occurs. Outside of this activity, winds should gradually weaken (10-15 kt) and seas should subside to 2-4 ft. Wednesday through Sunday: Northeast/east winds initially will turn southerly by late week. Marine conditions should stay solidly below small craft advisory criteria with speeds 15 knots or less and seas no higher than 4 feet. && .TIDES/COASTAL FLOODING... Charleston Harbor: Minor coastal flooding is likely at Charleston Harbor this evening (606 PM) as departures remain around +1.48 ft above astronomical (as of 1030 AM). Taking a look at the latest P- ETSS and ETSS guidance shows models running behind at initialization with a a 0.5/ 0.7 ft anomaly needed for correction. This is likely due to guidance not handling the tight pressure gradient/ stalled cold front along the coast well. Given the above, the latest forecast for Charleston Harbor is for a 7.2 ft high tide this evening (606 PM) with potential upside to 7.4 - 7.6. A coastal flood advisory will likely be needed. Another round of coastal flooding is then possible Wednesday evening as winds veer around from the southeast. Fort Pulaski: Tidal departures continue to increase this morning and now are up to +1.67 ft above astronomical (as of 1030 AM). Forecast guidance also is running behind this morning, and this is likely due to global guidance (which the ETSS and P-ETTS use as forcing) not capturing the tightening gradient along the coast with multiple offshore reporting sites observing wind gusts just shy of 30 mph. The current forecast high tide at Fort Pulaski this evening (608 PM) is 9.3 ft. There is some upside potential here as the tight pressure gradient from the stalled frontal zone remains in the region. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...Coastal Flood Advisory from 4 PM this afternoon to 8 PM EDT this evening for SCZ049-050. MARINE...Small Craft Advisory until 4 PM EDT this afternoon for AMZ350- 352. && $$