FXUS62 KCHS 130635 AFDCHS
Area Forecast Discussion National Weather Service Charleston SC 135 AM 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 rebuild into the region.
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.NEAR TERM /THROUGH TONIGHT/...
Today: Aloft, a zonal west-southwest flow will prevail across the Southeast United States in advance of a large trough digging across the North-Central United States and Midwest. At the sfc, dry high pressure will dominate the pattern, resulting in a light southwest wind and warmer conditions under sunny/mostly sunny skies. In general, high temps should range in the mid-upper 60s across Southeast South Carolina and around 70 degrees across Southeast Georgia. Should these temps occur, it will be the warmest day experienced in the month of December thus far.
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 arriving the next day. In general, lows should only dip into the upper 40s/lower 50s, remaining warmest along the coast. Some guidance even hints at the potential for some patchy fog late as sfc dewpts increase. However, the arrival of some clouds should limit the coverage of fog late night.
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.SHORT TERM /SUNDAY THROUGH TUESDAY/...
...Bitter Cold Temperatures expected much of this period...
Sunday: A strong/arctic cold front is still shown by all models to push through the region between late Sunday morning and early/mid Sunday afternoon. High temperatures of 60-65 will likely be reached just ahead of the front through early afternoon, then begin falling through the 50s during the afternoon behind the front. Latest blended guidance has increased PoPs to low end chance levels over much of our SC zones, and 15-24% for much of our GA zones. Any precip. along and ahead of the front will be in the form of showers, since it will be too warm at that time for any frozen precip.. QPF values are expected to be generally less than 0.10 inch. West- southwest winds in the morning, will veer sharply to northwest and increase behind the front by afternoon. Wind gusts of 20-25 mph will be possible. 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. Wind chill values all areas expected to reach Cold Weather Advisory levels /20 degrees to 11 degrees/ all areas, and could dip to 10 degrees or colder over portions of the northern area, where we currently have a Extreme Cold Watch in place.
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 to 40 to 45, 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 FRIDAY/...
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 blended model solution brings back slight chance PoPs for Thursday and Thursday night. This will likely need adjusting with later forecasts.
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.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions are expected at CHS/JZI/SAV terminals through 06Z Sunday.
Extended Aviation Outlook: Generally VFR conditions are expected Sunday through mid week. However, a strong arctic cold front will move through on Sunday, with gusty winds Sunday afternoon into Sunday evening.
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.MARINE...
Today and Tonight: High pressure will dominate the weather pattern for the day and night, leading to quiet marine conditions across local waters today, but a noticeable uptick in wind speeds as a modest pressure gradient develops late night. In general, south- southwest winds should top out around 10 kt today, then increase to 10-15 kt this evening. A few wind gusts up to 20 kt are possible across northern South Carolina waters and outer Georgia waters late night. Seas will range between 1-2 ft today, then build about a foot overnight.
...Hazardous Marine Conditions later Sunday into Monday...
A strong arctic cold front will move through the waters on Sunday, likely passing through the entire region by late afternoon. Southwest winds will veer sharply to northwest during Sunday afternoon, increasing to high end SCA levels, to possibly low end Gale conditions, especially for AMZ350 and AMZ374. 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.
MARINE...None.
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NEAR TERM...DPB SHORT TERM...RFM LONG TERM...RFM AVIATION...DPB/RFM MARINE...DPB/RFM