318 FXUS62 KCHS 070523 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1223 AM EST Wed Dec 7 2022 .SYNOPSIS... High pressure will briefly build in tonight and persist through Thursday before a cold front sweeps through late Friday. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Early this morning: Surface observations continue to show fog is expanding across the Midlands and beginning to move into and develop across the Lowcountry and southeast Georgia. Fog will continue to be the primary forecast issue overnight. && .SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/... High pressure will prevail both aloft and at the surface on Wednesday and Thursday. Subsidence from the building high pressure will create rain-free conditions as well as well above normal temperatures. Highs on Wednesday and Thursday will be 10 or so degrees above normal, with mid to upper 70s forecast. Some locations may even make a run at 80 degrees. Overnight lows will also be many degrees above normal, with mid to upper 50s featured in the forecast. Surface low pressure will pass well to the north on Friday, while a cold front approaches and sweeps through the region. Aloft, a trough will ripple through the Mid-Atlantic states. With the main source of upper level forcing and moisture displaced to the north only isolated showers are possible with FROPA on Friday. Temperatures will again be well above normal, in the mid to upper 70s. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... The aforementioned cold front will likely clear the region Friday night/Saturday. Temperatures Saturday will be slightly cooler, however still above normal. High pressure will build into the region at the surface while zonal flow prevails aloft. Several shortwave troughs will ripple through the region Sunday and into early next week. PWATs will be elevated across the southeastern states as a surface low pressure system progresses eastward, advecting moisture into the region. Isolated to possibly scattered showers are possible, mainly Monday and Tuesday. Temperatures will drop to near normal. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... Fog is the primary forecast concern for the 06z TAF period at KCHS, KJZI, and KSAV through the overnight. Fog is starting to develop across the area and expand in coverage, especially from the Midlands. We have delayed the onset time of fog at the terminals a few hours, favoring more like 08-09z for IFR conditions. Visibilities could dip to a quarter of a mile or less and then linger that way after sunrise. Visibilities should improve by mid morning, though IFR conditions could linger to midday. Conditions should be then be VFR through the afternoon and evening. Extended Aviation Outlook: Fog is possible Wednesday night into Thursday morning, otherwise prevailing VFR. && .MARINE... Generally light and variable conditions are expected across the marine zones tonight. Seas should remain steady between 3-4 ft. The primary issue tonight will be determining how much fog that develops over land drifts over the CHS Harbor or adjacent nearshore waters. It is possible that a Dense Fog Advisory could be issued for a portions of the waters tonight. Wednesday through Sunday: High pressure will prevail across the marine waters with tranquil conditions expected. Winds generally westerly 5 to 10 knots. Seas should average 2 to 3 feet. A cold front will push through the region Friday and into Saturday, causing a slight surge in winds and seas. Northerly to northeasterly winds 10 to 15 knots are forecast with seas building to 3 to 4 feet from the coastline out to 20 nm, and 5 to 6 ft in the 20 to 60 nm offshore GA waters. A Small Craft Advisory may be needed this weekend. && .EQUIPMENT... Temperature data at the KSAV ASOS are suspect. Parts are on order and will arrive this week. Use data with caution. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...BSH SHORT TERM...CPM LONG TERM...CPM AVIATION...BSH/CPM MARINE...CPM/NED EQUIPMENT...