Area Forecast Discussion
Issued by NWS Charleston, SC

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864 FXUS62 KCHS 250502 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 102 AM EDT Tue Jun 25 2024 .SYNOPSIS... High pressure will remain over the western Atlantic while a weak cold front approaches the area. This front will likely linger near the area through mid-week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Tonight: Convection to the west of the local area has diminished this evening with the loss of daytime heating and the low-lvl inversion in place. To the north, a cluster of showers/thunderstorms are ongoing, aided by stronger low-lvl convergence, shear and deeper moisture supply along the northeast periphery of sfc low pressure that resides by a trough axis/front. These showers and thunderstorms will make a run to the coast during the next few hours as the front nudges into the local area, and should brush northern locations of Berkeley and Charleston Counties through midnight/1 AM, before shifting offshore across coastal waters. Although instability continues to weaken through the night, high levels of DCAPE (1000- 1200 J/kg) and 0-3 km lapse rates around 7 C/km could support a stronger thunderstorm with gusty winds, especially at locations near the Santee River during the next 2-4 hours. Once convection moves offshore, a warm/humid night will remain in place with lows ranging in the low-mid 70s well inland to lower 80s at the beaches and Downtown Charleston. && .SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY/... Broad troughing will persist across the East Coast on Tuesday, gradually shifting to zonal flow on Wednesday and a return to broad troughing Thursday. At the surface a weak cold front will likely linger in the vicinity of the forecast area through midweek. 850 hPa temperature anomalies will remain rather warm through the period, which combined with little mixing each day, will yield hot and humid conditions. Heat index values are forecast to reach 102-107F inland. A few spots may make a run at 108F along the coastal counties, however coverage of these values is not enough to warrant Heat Advisories at this juncture. Each afternoon isolated to scattered showers and thunderstorms will be possible, as PWATs remain elevated with the front in the vicinity. PWAT values are forecast to remain near 1.6-1.8", which is slightly above normal for this time of year. CAPE values are forecast to reach around 1500 J/kg, with model soundings indicating >1000 J/kg of DCAPE. A strong to marginally severe thunderstorm cannot be ruled out any afternoon, with strong wind gusts as the main hazard. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... An anticyclone aloft will be positioned over the southern U.S. and will slowly shift eastward over the southeastern states through the weekend. At the surface high pressure will extend into the forecast area from the east with the center of high pressure centered over Bermuda. Hot and humid conditions will likely persist into the weekend. Heat index values are forecast to reach from around 103-105F inland with values approaching 108F along the coastline. Head Advisories may be required. A summertime pattern is expected through the period, with the highest precipitation chances in the afternoon hours. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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KCHS/KJZI: A few clusters of showers and thunderstorms will move through the terminals through around 06Z or so and heavy rainfall could drop visibilities into the MVFR range. Thereafter, cannot rule out a touch of fog develop across the tri-county region overnight including the terminals. On Tuesday, VFR conditions prevail through the day into Tuesday night. Hit and miss shower and thunderstorms are possible during the afternoon hours although confidence in coverage/timing and duration is too low to include in the forecasts at this juncture. KSAV: VFR conditions prevail through the TAF period. Hit and miss showers and thunderstorms are possible across southeast Georgia during the afternoon hours. But again, confidence in coverage/timing and duration is too low to include in the forecasts at this juncture. Extended Aviation Outlook: Brief flight restrictions will be possible at all terminals with afternoon showers and thunderstorms.
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&& .MARINE... Tonight: The pressure gradient will remain enhanced this evening between high pressure centered well offshore and a trough/front advancing toward the coast late. As a result, south to southwest winds between 15-20 kt will be common across most local waters. The gradient remains even more pinched across nearshore SC waters along the Charleston County coast late this evening, supporting gusts around 25 kt ahead of a cluster of showers/thunderstorms approaching the area after midnight. A Small Craft Advisory has been issued until 4 AM for the Charleston Harbor and nearby coastal waters along Charleston County given the gradient is expected to remain quite strong until showers/thunderstorms arrive and dampen wind fields. However, a few stronger thunderstorms with gusty winds are possible across northern most waters along the Charleston County Coast until the trough/front arrives and/or stalls nearby. Heading closer to daybreak, southwest winds should trend below Small Craft Advisory levels for all waters, with gusts returning to around 15 kt across nearshore waters and perhaps upwards to 20 kt across offshore Georgia waters. Seas will average between 3-5 ft, largest beyond 10 nm from the coastline. Tuesday through Friday: Generally tranquil marine conditions are expected through the period. Winds will gradually back each day and veer overnight, strongest along the coastline as the afternoon sea breeze/overnight land breeze develops. Seas should average 2 to 3 ft. && .CLIMATE... The low temperature at KCHS so far today is 80. If this holds, this will break the previous record high minimum of 79 set back 2016. && .CHS WATCHES/WARNINGS/ADVISORIES...
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GA...None. SC...None. MARINE...Small Craft Advisory until 4 AM EDT early this morning for AMZ330-350.
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&& $$ NEAR TERM...DPB AVIATION...Adam MARINE...DPB