Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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442 FXUS62 KCHS 170544 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 144 AM EDT Tue Sep 17 2024 .SYNOPSIS... Low pressure will shift inland across the Carolinas and weaken tonight into mid week. High pressure should develop inland late week into the weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Low pressure center has advanced to near the central South Carolina/North Carolina border with all associated precip well north of the local area. Respectable wedge of drier air is wrapping in along the southern flank of the system into our area with some upper 50s dewpoints noted over the far western/southwestern part of the forecast area. But, a fair amount of lower cloud cover continues to rotate through a good portion of the forecast area, but getting eroded along the southern/western edges. Rest of tonight: Lower cloud cover should steadily erode SW-NE through the overnight hours as drier air continues to wedge into the region. With diminishing clouds and weakening winds, temperatures will end up in the lower to middle 60s around sunrise, with some upper 50s possible well inland. && .SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY/... The remnant low of PTC8 should be somewhere over the Carolinas at the start of the period. The surface low will continue to weaken with time. An associated trough axis/weak boundary should transition back towards the coast and possibly offshore on Thursday. Tuesday should actually be rain-free over the local area, then isolated to perhaps scattered showers will return for Wednesday and Thursday with deeper moisture and upper trough moving back overhead. High temperatures a touch below normal on Tuesday will warm to the mid to even upper 80s for mid week. Lows will range from the upper 60s inland to low/mid 70s at the immediate coast. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Mid level trough axis initially stretched down the east coast should push a bit east over the weekend as a ridge centered over southern Texas nudges into the region. Still some spread between models during the latter half of the weekend with regards to if a mid level low forms off the coast and how far offshore that would be. At the surface, high pressure is expected to build south into the Carolinas and Georgia. This pattern generally favors lower rain chances, so PoPs are no higher than 20% and only located closer to the coast. Temperatures will lean on the cooler side of normal through the period. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... MVFR cigs will persist at CHS/JZI through around 10Z this morning before scattering out and trending VFR around the morning push. VFR conditions will then prevail at both terminals through 06Z Wednesday. At SAV, MVFR ceilings persist but should scatter out by 08Z. Expect VFR conditions to then persist through 06Z Wednesday. Extended Aviation Outlook: Low chance for brief flight restrictions in showers and thunderstorms Wednesday and Thursday. && .MARINE... Tonight: Conditions will gradually improve as low pressure centered north of the area moves slowly northwest and further away from the region overnight. The pressure gradient is expected to relax substantially as the low weakens inland and guidance indicates 1000 mb geostrophic winds decreasing to 20 kt. Given recent marine obs and expected trends, Small Craft Advisories have been ended for nearshore waters south of Edisto, SC to the Altamaha Sound in Georgia. Small Craft Advisories will continue across offshore Georgia waters where 5-7 ft seas persist during the night and across nearshore waters off the Charleston County coast where west-northwest winds gust up to 20-25 kt at times and seas range between 4-6 ft. However, conditions will continue to improve during the night, likely ending the Small Craft Advisory across nearshore waters within a few hours after midnight. Tuesday through Saturday: Fairly benign marine conditions are expected through at least Friday with wind speeds generally less than 15 knots. Seas will subside on Tuesday, settling in 2-4 foot range thereafter. High pressure should build south into the Carolinas and Georgia late week into the weekend. Winds will turn out of the northeast and could see some increase in speeds with the pressure gradient tightening. Rip Currents: Lingering swell of around 3 ft every 10 seconds and astronomical influences from the full moon and perigee will maintain a High Risk of rip currents for all beaches through Tuesday. It is worth noting that local calculations for Georgia beaches were borderline moderate-high but opted to maintain the High for now. && .TIDES/COASTAL FLOODING... As we continue into mid to late week, the risk for at least minor flooding will continue for Charleston and Coastal Colleton Counties due to high astronomical tides with the full moon on September 17th. Beaufort County, SC, south to McIntosh County, GA: Waters levels could be close to minor flood levels later this week as onshore winds return. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...High Risk for Rip Currents through this evening for GAZ117-119-139- 141. SC...High Risk for Rip Currents through this evening for SCZ048>051. MARINE...Small Craft Advisory until 2 AM EDT early this morning for AMZ350. Small Craft Advisory until 1 PM EDT this afternoon for AMZ374. && $$ NEAR TERM...Adam SHORT TERM...ETM LONG TERM...ETM AVIATION...Adam/ETM MARINE...DPB/ETM