709 FXUS62 KCHS 062146 AFDCHSArea Forecast Discussion National Weather Service Charleston SC 546 PM EDT Sat Sep 6 2025
.SYNOPSIS... High pressure will extend across the region today. A cold front is expected to move through late Sunday. The front should stall offshore through the middle of next week, while high pressure prevails to the north.
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.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Convection approaching the CSRA and east-central Georgia should largely remain west of the area this evening, although a brief shower or two could impact parts of Allendale, Screven and Jenkins County. 06/13z NBM pops are below mentionable thresholds and were maintained given no active DSS events are ongoing and local messaging is not impacted.
A cold front will continue to approach the forecast area from the west through much of tonight. During the evening, a cluster or two of showers and thunderstorms may track east of the Fall Line of GA and SC ahead of the cold front. This activity is expected to dissipate before reaching the forecast area. Near term guidance times the front push over SE GA/SC during the pre-dawn hours Sunday morning. As the front approaches, mid and high clouds should gradually increase from the west through the overnight hours. Light winds, narrow dewpoint depressions, and late arrival of cloud cover may yield some patchy fog across extreme SE GA before daybreak. Low temperatures are forecast to range from the low 70s inland to the mid 70s along the coast.
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.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/... Sunday: Broad troughing will prevail over the eastern CONUS as a cold front at the surface approaches the region slowly from the west. Ahead of the front moisture will surge, with PWATs reaching 1.7-1.8" by Sunday afternoon. The timing of the front looks to be later in the afternoon, allowing a sea breeze to form. Both the 12Z HRRR and HREF show convection initially initiating along the sea breeze, with an increase in coverage as the cold front approaches. Models are showing DCAPE values around 600-800 J/kg, which in addition to ML CAPE values around 1500 J/kg could result in some strong to severe thunderstorms. Additionally, given high PWAT values, locally heavy rainfall will be possible. High temperatures will reach into the upper 80s to low 90s, with overnight lows in the 60s.
Monday and Tuesday: Troughing will prevail over the southeastern states aloft through mid week. At the surface the aforementioned front will stall just offshore, while high pressure builds into the region from the north. This pattern will yield a tight pressure gradient, with gusty NE winds along the immediate coastline. Additionally, precipitation should be limited to the coastal counties with 20-30% PoPs each afternoon. The inland extent of the precipitation will be determined by the positioning of the stalled front. High temperatures will only reach into the upper 70s to low 80s due to increased cloud cover and steady NE flow.
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.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... Troughing will remain the dominant synoptic feature aloft through the end of the week, while the stalled front remains offshore. There is a chance that a weak coastal low could develop along the stalled boundary mid week. If a low ends up developing precipitation chances would be higher Wednesday, especially along the coastal counties. The current forecast features PoPs around 30-40% each afternoon. Temperatures will remain slightly below normal, given the NE flow and increased cloud cover.
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.AVIATION /21Z SATURDAY THROUGH THURSDAY/... 07/00z TAF Discussion: KCHS/KJZI: VFR for much of the period. Shallow ground fog and possibly some patchy stratus could impact the terminals prior to daybreak. Best chances are at KJZI given its proximity of the Stono River. No major impacts are expected. The risk for showers/tstms will increase mid-late afternoon Sunday as a cold front approaches and the sea breeze meanders inland. Impact probabilities are increasing, so VCTS was indicated after 19-20z for both terminals. The introduction of TEMPO or prevailing groups for TSRA may need to be considered with later TAF cycles.
KSAV: VFR for much of the period. Similar to the past few mornings, there is a low end risk for shallow ground fog impacting the terminal. Guidance has been too aggressive with fog development over the past few nights and tonight looks similar. Model condensation pressure deficits are a tad lower, but still look to remain fairly high. A TEMPO group for 6SM MIFG was introduced 09-12z for now. The risk for showers/tstms will increase mid-late afternoon Sunday as a cold front approaches and the sea breeze meanders inland. Impact probabilities are increasing, so VCTS was indicated after 20z. The introduction of TEMPO or prevailing groups for TSRA may need to be considered with later TAF cycles.
Extended Aviation Outlook: Showers and possibly a thunderstorm could impact the terminals Sunday afternoon. Additional flight restrictions are possible in afternoon showers/tstorms through mid week.
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.MARINE... Tonight: The marine zones will remain east of a front approaching from the west. Conditions across the coastal waters will remain from the ESE between 5 to 10 kt. Seas will remain around 2 ft.
Extended Marine: A cold front will push offshore Sunday night into Monday, stalling across the marine waters through the middle of next week. High pressure will dominate at the surface across the land zones, yielding a pinched pressure gradient between the high pressure and the stalled front. Northeast winds will begin gusting to 20-25 knots Monday morning and persisting through Tuesday night. Seas are forecast to build as well, with 5 to 6 ft by Tuesday afternoon. Small Craft Advisories will likely be required for all marine zones outside of the Charleston Harbor beginning Monday morning. Gusts could come close to 25 knots in the Charleston Harbor, and a Small Craft Advisory cannot be ruled out.
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.TIDES/COASTAL FLOODING... Astronomical tide levels will continue to increase through the weekend, getting as high as 6.4 ft MLLW by the Sunday evening high tide cycle within the Charleston Harbor. However, winds will not be particularly favorable for large tidal departures during this time period but observed peak tides could still top out around 7 ft MLLW at Charleston each evening through Sunday.
Astronomical tide levels will remain high through the middle of next week, given a full moon (9/7) and lunar perigee (9/10). A notable surge of northeast flow along the coast is expected to produce increased tidal departures through at least the middle of next week which will result in an increasing probability of minor to moderate coastal flooding along portions of the SC coast. Minor coastal flooding is possible along the lower SC and GA coast beginning Monday evening.
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.CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None.
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NWS CHS Office Area Forecast Discussion