119 FXUS62 KCHS 161313 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 913 AM EDT Sun Oct 16 2022 .SYNOPSIS... High pressure over the area will move offshore tonight. A strong cold front will move through the region Monday night, followed by cool high pressure into next weekend. && .NEAR TERM /THROUGH TONIGHT/... Today: It will be another spectacular day for Southeast South Carolina and Southeast Georgia. High pressure will maintain its influence today while slowly shifting farther offshore. Some cirrus will being to move in from the northwest by late afternoon; otherwise, plentiful sun and rain-free conditions will prevail. Highs look to top out in the lower-mid 80s after a another chilly start with values similar to full-sun thickness values. Other than lowering dewpoints a bit more mainly west of I-95, no major changes were made for the mid-morning update. Tonight: The cold front is forecast to push across the Southern Appalachians, emerging over the Foothills by daybreak Monday. The pressure gradient between the cold front and western Atlantic high should remain high enough to support light and steady SW winds through tonight. HREF indicates that BKN-OVC high and mid clouds will build across the region tonight. The combination of steady SW winds and increasing sky cover should limit cooling to the low to mid 60s. && .SHORT TERM /MONDAY THROUGH WEDNESDAY/... A powerful closed upper low over the Great Lakes region will shift southeast on Monday. At the surface, cold Canadian high pressure will drop southeast across the Central United States, pushing a strong cold front through the area Monday night. Some moisture advection will occur ahead of the front, with surface dewpoints rising into the low/mid 60s near the coast Monday afternoon. With high temps in the lower 80s, surface-based CAPE of 500-1000 J/kg could develop, mainly across the eastern fringe. At least isolated showers and thunderstorms should develop late Monday afternoon or early evening as the front sweeps through, though the best coverage is expected over the marine area once the front moves offshore. Given the modest destabilization and 40-45 kt bulk shear values, SPC continues to highlight the eastern half of our area in a Marginal Risk for severe thunderstorms. Any precipitation that occurs with the front should be off the coast by mid to late Monday evening. Much colder, drier air will overspread the region late Monday night through Wednesday. Strong cold air advection will result in a chilly Tuesday night, with lows dipping into the low/mid 30s far inland, with lower 40s coastal. Some frost is possible far inland but a few knots of wind could preclude more widespread frost development. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... Wednesday night will be the coldest so far this season due to ideal radiational cooling. Clear skies, light winds, and a cold airmass will yield lows in the low to mid 30s across the western half of the area, likely resulting in at least patchy frost. Dry weather and gradually moderating temperatures anticipated Thursday through Saturday. && .AVIATION /13Z SUNDAY THROUGH THURSDAY/... VFR conditions are expected at KCHS/KJZI/KSAV terminals through 12Z Monday. Extended Aviation Outlook: Isolated showers and thunderstorms possible late Monday afternoon and early evening ahead of a cold front. && .MARINE... The forecast area will remain between sfc high pressure centered over the western Atlantic and a cold front over the Southern Appalachian region today and tonight. Winds across coastal waters will becoming southerly 5-10 kt later this afternoon. Winds are expected to shift from the southwest and increase to 10-15 kts tonight. Seas 1-2 ft today will build to 2-3 ft tonight. On Monday, southwest winds will increase out ahead of the cold front. Gusts over the SC nearshore waters as well as Charleston Harbor could approach 25 kt during the afternoon hours. Winds will turn to the northwest late Monday night behind the front, then more northerly by Tuesday evening. The strongest wind surge is expected Tuesday night where some 25 kt gusts will be possible. Small Craft Advisories may eventually be needed. Northerly winds will continue through late week but speeds will diminish as the surface high expands over the waters. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$