FXUS62 KCHS 131822 AFDCHS
Area Forecast Discussion National Weather Service Charleston SC 122 PM EST Sat Dec 13 2025
.SYNOPSIS...
High pressure will prevail today, then an arctic cold front will sweep through Sunday. Dry high pressure will then build overhead for much of the coming week.
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.NEAR TERM /THROUGH TONIGHT/...
Comfortable temps and sunny skies continue this afternoon as high pressure to the south and east remains in control.
Tonight: Aloft, a zonal flow prevails for much of the night in advance of the digging trough across the Midwest. At the sfc, the Atlantic high will extend across the Southeast, while some troughing develops north and inland overnight. Although the pressure gradient remains modest between these features, conditions will remain noticeably more mild than the previous night while a light southwesterly wind advects warmer air into the region well in advance of a cold front. Only potential hazard to highlight overnight is the low (10% or less) risk for some patchy fog away from the immediate coast. Failure to decouple for an extended period, and increasing clouds late, should preclude any dense fog threat.
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.SHORT TERM /SUNDAY THROUGH TUESDAY/...
...Bitter Cold Temperatures later Sunday into Tuesday...
Sunday: Timing of arctic cold front Sunday coming into better agreement, crossing the area late morning. High temperatures of 60-65 will likely be reached midday, with strong CAA ensuing by early afternoon. A few showers are expected immediately ahead of the front, but rainfall rates will be modest and total rainfall will remain .25 in or less across the area. West- southwest winds in the morning will veer sharply to northwest and increase behind the front by midday. Wind gusts of 20-30 mph are possible early-to-mid-afternoon, with a Lake Wind Advisory now in effect for Lake Moultrie Sunday afternoon through Sunday night.
By Sunday night, a strong arctic surface ridge will build from the northwest, keeping northwest to north winds through the night. Temperatures expected to drop into the upper teens well inland, and lower to mid 20s else where, warmest near the coast. Ensemble suites are in good agreement, making windchill values of 5-15 early Monday morning (away from the water) a high predictability, high confidence forecast. Currently, highest probs (30-50%) for wind chill values less than 10F exist across the SC Lowcountry and interior SE GA, which probs are lower (20% or less) along the GA coast. The current configuration of Extreme Cold Watches and Cold Weather Advisories reflect these probabilities.
Monday: Deep ridging is shown by all models to settle over the region, with lighter winds and mostly sunny/sunny skies. Despite full sun, guidance continues to hold high temperatures in the upper 30s to mid-40s, 15 to 20 degrees below normal! Monday night, high pressure will start centered over the region, then slowly shift offshore by late night. Light winds, clear skies and dry low levels should allow for strong radiational cooling. Very cold temperatures again expected, with lows around 20 well inland, to the mid 20s to near 30 closer to the coast.
Tuesday: This period begins the moderation in temperatures, with the surface ridge shifting further offshore, allowing for low level winds to veer to southwest by afternoon. Under mostly sunny skies, highs rebounding into the 50s all areas, which is still a tad below normal.
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.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
All global and blended model solutions show that the large scale/synoptic pattern shifts to zonal, with moderating temperatures through the period. Tuesday night will be the coldest period, with freezing temperatures again expected inland, and mid to upper 30s closer to the coast. Then Wednesday through Saturday, temperatures continue to warm, with temperatures near normal on Wednesday, to above normal Thursday through Saturday. The biggest forecast issue for this period will be how to handle the model differences with chances for precip. late in the period. Some models indicate the potential for another cold front to approach the area later Thursday and early Friday, but timing and amount of deep layer moisture vary between models. For now, the most likely scenario is for a weakening cold front to bring limited precipitation to the area Fri/Sat, with dry high pressure returning thereafter.
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.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
VFR conditions prevail at CHS/JZI/SAV terminals through 18Z Sunday. There is a low probability (<10%) of patchy/shallow fog at CHS and SAV, but occasional mixing and increasing clouds late limit the potential for fog to impact airport operations. Additionally, a few showers are possible Sunday morning, ahead of an approaching cold front, but limit coverage justified little more than VCSH for the Charleston area TAFs at this time. More noteworthy is the abrupt wind shift, and development of gusty NW winds behind the cold front, which will likely cross the terminals late Sunday morning.
Extended Aviation Outlook: Generally VFR conditions are expected Sunday nigh through mid week.
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.MARINE...
Today and Tonight: High pressure continues to dominate tonight, though increasing gradient late ahead of an approaching cold front will bring slowly increasing winds. A few wind gusts up to 20 kt are possible across northern South Carolina waters and outer Georgia waters by the pre-dawn hours. Seas become 2-3 ft overnight in mostly local windswell.
...Hazardous Marine Conditions later Sunday into Monday...
A strong arctic cold front will move through the waters later Sunday morning, likely passing through the entire region by midday. Southwest winds will veer sharply to northwest as the front crosses, with gusts to 35 kt possible across the coastal waters where a Gale Watch is now in effect Sunday afternoon through early Monday morning. Inshore waters, including the Charleston Harbor, will also see gusty conditions as winds readily mix over the relatively warmer waters Sunday evening and overnight, with an SCA in effect accordingly. Hazardous conditions, especially for seas, are expected to remain through later Monday, especially beyond 20 nm offshore. Winds and seas are expected to fall below any highlight levels Tuesday through Wednesday.
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.CLIMATE...
Record Low Temperatures:
December 15: KCHS: 15/1962 KCXM: 23/1943 KSAV: 19/1962
Record Low Maximum Temperatures:
December 15: KCHS: 39/1943 KCXM: 38/1904 KSAV: 38/1904
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.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Extreme Cold Watch from Sunday evening through Monday morning
for GAZ087-088. Cold Weather Advisory from 10 PM Sunday to 10 AM EST Monday for GAZ099>101-114>119-137>141.
SC...Extreme Cold Watch from Sunday evening through Monday morning
for SCZ040-042>045-050-052. Cold Weather Advisory from 10 PM Sunday to 10 AM EST Monday for SCZ047>049-051. Lake Wind Advisory from 4 PM Sunday to 4 AM EST Monday for SCZ045.
MARINE...Small Craft Advisory from 1 PM Sunday to 9 AM EST Monday for
AMZ330. Gale Watch from Sunday afternoon through Monday morning for AMZ350-352-354-374.
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NEAR TERM... SHORT TERM... LONG TERM... AVIATION... MARINE...