Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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202 FXUS62 KCHS 211500 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1100 AM EDT Sat Sep 21 2024 .SYNOPSIS... High pressure across the region will prevail through early next week. A weak cold front may approach from the west around the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... No major changes were needed with this update as the foundation of the forecast remains solid. Today: Aloft, a trough will continue to nudge east across the western Atlantic while a ridge centered across Texas extends further east across the Deep South and into the Southeast United States by late day. At the sfc, high pressure will remain across the Southeast United States, but will show signs of drifting off the Mid-Atlantic coast with the approach of additional mid-lvl vort energy traversing the Northeast. The pattern will result in notable subsidence across the region, bringing mostly dry weather locally under few clouds. Given mid-lvl ridging expanding across far inland areas, sfc temps could warm a degree or two higher than the previous day. Afternoon highs should range in the low-mid 80s closer to the coast to upper 80s inland. A few areas could top out near 90 degrees across far inland zones of Southeast Georgia. Tonight: Dry conditions will prevail with sfc high pressure settled across the local area and mid-lvl ridging extending from the west aloft. Although a bit of cirrus could move across the region, conditions should favor another decent radiational cooling night with light/calm winds for much of the night for areas away from the coast. Low-lvl moisture is a bit lacking, so fog is generally not anticipated. Overnight lows should range in the mid 60s inland to upper 60s/lower 70s near the beaches. && .SHORT TERM /SUNDAY THROUGH TUESDAY/... The synoptic pattern will remain largely unchanged through the period with a large upper ridge across the Deep South, slowly progressing eastward with time. Broad surface high pressure will remain over the eastern CONUS and extreme western Atlantic providing subsidence and generally quiet weather conditions through the period. Mostly sunny skies are expected each day through Tuesday. Any potential for convection will be largely suppressed due to relatively dry air aloft and the lack of significant forcing mechanisms. No mentionable rainfall chances have been included during this period. Temperatures will be mild/slightly above normal through the period due to the ridge aloft with highs in the upper 80s/low 90s each day. Sunday and Monday night will feature lows in the upper 60s inland and lower 70s near the coast. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... The long-term forecast features increasing chances for showers and perhaps a few thunderstorms. The region will see a slight uptick in moisture as the upper ridge axis shifts offshore Wednesday. Slight chance POPs return Wednesday evening with peak rain chances anticipated to occur later in the week as an upper trough and cold front approach. Temperatures will start mild with highs in the upper 80s initially and trending cooler into the lower 80s by next weekend. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... VFR conditions are expected at CHS/JZI/SAV terminals through 12Z Sunday. Extended Aviation Outlook: VFR conditions expected to prevail. && .MARINE... Today and Tonight: A modest pressure gradient will prevail between high pressure inland and a weak trough well south of the local area. The setup will yield 10-15 kt northeast winds for much of the day with a few gusts up to 20 kt across nearshore South Carolina waters off the Charleston County Coast and across offshore Georgia waters as well. Expect winds to gradually veer and weaken overnight as the pressure gradient relaxes. Seas will generally range between 2-4 ft across nearshore waters and 4-5 ft across offshore Georgia waters during the day, but should gradually subside a foot during the night. Sunday through Wednesday: As high pressure begins to migrate offshore, winds will shift out of the east/southeast around 10 kt or less. Seas will average 2-3 ft within 20 nm and 3-4 ft for the GA waters from 20-60 nm. Rip Currents: Onshore winds approaching 10-15 kt, 2 ft swell near 10 seconds along with local RCMOS model data favor a Moderate Risk for rip currents along Georgia beaches today. && .TIDES/COASTAL FLOODING... A Coastal Flood Advisory is in effect for the entire coast for this late morning`s high tide. For Charleston Harbor, the current 7.9 ft MLLW forecast appears to be on track, which will result in moderate salt-water flooding. There remains some concern that levels could touch major flood (8.0 ft MLLW), but this scenario has about 10% probability of occurrence. Fort Pulaski will be in the minor flood category, peaking near 9.9 ft MLLW. Levels could touch moderate flood (10.0 ft MLLW), but this scenario also has about a 10% probability of occurrence. Positive tidal anomalies and high astronomical tides from the recent full moon will lead to elevated tides through the weekend. Although the astronomical high tides are lowering, coastal flooding is expected with each daytime high tide cycle along the Charleston and Colleton County coasts. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Coastal Flood Advisory until 2 PM EDT this afternoon for GAZ117-119-139-141. SC...Coastal Flood Advisory until 2 PM EDT this afternoon for SCZ048>051. MARINE...None. && $$ NEAR TERM... SHORT TERM...BRM LONG TERM...BRM AVIATION...BRM MARINE...BRM