Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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342 FXUS62 KCHS 021341 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 941 AM 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/... Today: Impressive pockets of heavy rainfall have been observed along the Georgia coast this morning with some spots picking up nearly 5 inches of rain. Showers and tstms will linger in this area this morning before slowly waning through the afternoon. A risk for locally heavy rainfall will persist areas along/south of I-16 through early afternoon with the greatest focus centered along the Georgia coast. Consideration was made to hoist a Flood Watch for the Georgia coast, but considering the heaviest rains should fall along the mostly unpopulated eastern areas of McIntosh, Liberty and Bryan Counties, the decision was made to hold steady. The only exception could be across eastern Chatham County, including parts of Savannah Metro, where more impacts should be realized if heavy rains develop. NWS Staff are coordinating closely with Chatham County Emergency Management (CEMA). Near term pops were adjusted slightly to reflect current trends. Thunder was removed across the far interior where instability will remain limited. Highs were also nudged down in most areas with a rather cool day for July expected, especially over the Charleston Tri-County area. 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 /13Z TUESDAY THROUGH SATURDAY/... KCHS/KJZI: IFR cigs are possible during the next few hours before gradually improving to MVFR mid-late morning and persisting into early afternoon. Should a few showers redevelop across northern areas today, tempo groups of low-end MVFR or even IFR could return. Otherwise, conditions should improve to this afternoon, then prevail through 12Z Wednesday. KSAV: Prevailing IFR cigs will continue for the next few hours before attempting to improve to MVFR later this morning. However, moderate to heavy showers (and potentially thunderstorms) should impact the terminal by mid morning, bringing periods of IFR or even lower conditions through late morning and potentially into early afternoon. Otherwise, conditions should slowly improve mid-late afternoon to VFR and persist into early night. However, there are signs of MVFR cigs returning overnight, thus prevailing MVFR groups have been included from 02Z-12Z Wednesday. 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 2 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... If current tide trends continue, a Coastal Flood Advisory will likely be issued for Charleston and Coastal Colleton with the early afternoon update to address a 7.2 ft MLLW tide in the Charleston Harbor this evening. Favorable onshore winds and the approach of the new moon will lead to elevated tides over the next few days along the Charleston and Colleton county coasts. Tides levels could approach minor coastal flooding criteria of 7 ft MLLW in the Charleston Harbor. Further south, no tide issues are expected. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...Small Craft Advisory until 2 PM EDT this afternoon for AMZ350- 352. && $$