FXUS62 KCHS 121831 AFDCHS
Area Forecast Discussion National Weather Service Charleston SC 131 PM EST Fri Dec 12 2025
.SYNOPSIS...
High pressure will prevail through Saturday, then an arctic cold front will sweep through late Sunday. Dry high pressure will then rebuild into the region.
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.NEAR TERM /THROUGH TONIGHT/...
The forecast area will remain under a broad H5 trough through tonight. A weak cold front should remained positioned upstream of the region tonight. This pattern will support light southwest winds across the forecast area tonight. Conditions should remain dry with mostly clear skies. Low temperatures tonight are forecast to range from the upper 30s inland to the low to mid 40s along the coast.
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.SHORT TERM /SATURDAY THROUGH MONDAY/...
...Bitter Cold Temperatures expected Sunday night...
The most impactful part of this period will be the bitter cold temperatures expected behind an arctic cold front Sunday.
Saturday: As high pressure continues to situate itself across the region, zonal upper-lvl flow and low-lvl southwest winds will dominate the forecast. Expect highs on Saturday to warm to above normal in the mid 60s to low 70s. There would be the warmest temperatures we've had so far this month in December! A mild night is in-store for Saturday as a deep upper trough takes shape over the Great Lakes and into the mid-Atlantic. With southwest low-lvl flow, lows will stay in the upper 40s inland to the low to mid 50s closer to the coastline.
Sunday: As the upper-lvl trough gradually sharpens eastward, an associated arctic front will approach the region on Sunday morning. Marginal moisture will be available with PWAT values below 0.5 inches, thus other than some isolated showers, not expected much in terms of precipitation ahead of the front. Temperatures will likely reach their highest through early afternoon, then begin to fall through the 50s behind the strong cold front through the remainder of the afternoon. Through the overnight, expect temperatures to drop into the upper teens to low 20s as north-northwesterly winds drive arctic temperatures southward through the region. Therefore, an Extreme Cold Watch has been issued for South Carolina Lowcountry and inland southeast Georgia for Sunday evening through Monday morning. Also, a Cold Weather Advisory has been issued for most of southeast Georgia and the lower South Carolina Lowcountry for Sunday evening through Monday morning as well. These type of cold temperatures will be very hazardous, and could cause issues with exposed pipes/plumbing.
Monday: After the passage of the front, a surface ridge shifts across the region with lighter north-northeasterly winds. Even with sunny skies, post-FROPA conditions will keep temperatures below normal with highs only reaching in the upper 30s to low 40s!
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.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As the surface ridge continues to sit over the region, expect light winds with mostly clear skies on Monday night. It'll be a tad warmer overnight on Monday with temperatures in the low 20s across the inland counties and mid 20s to upper 20s along the coastline. It's important to note that patchy to scattered frost could be possible on Monday night as well. Thereafter, temperatures will warm back up to near normal throughout the week as zonal flow takes over the forecast. There are model differences with precip. chances late in the week as coastal trough tries to form nearby.
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.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
VFR conditions will prevail at KCHS, KJZI, and KSAV through 18z Saturday.
Extended Aviation Outlook: Behind a strong arctic cold front, expect breezy winds on Sunday into Monday morning. Otherwise, should be VFR conditions.
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.MARINE...
Tonight: West winds should remain around 10 kts overnight. Wave heights between 1 to 2 ft.
Saturday into Saturday night: Fair conditions expected across the marine zones. Winds should remain between 10 to 15 kts. Seas between 1 to 2 ft on Saturday, increasing to 1 to 3 ft by late Saturday night.
A passing arctic cold front will result in strengthening winds and building seas late Sunday through Monday. Winds are forecast to peak Sunday evening and night, with gusts in the mid 20s to low 30s across the CHS Harbor and nearshore waters of GA and lower SC. In addition, wind gusts across the Charleston County nearshore and outer GA waters may see periods of gale force. As a result, wave heights will increase to 5-6 ft across the nearshore waters with 7-9 ft across the outer GA waters. The marine conditions may be highlighted with a Gale Watch or Small Craft Advisory.
Tuesday, winds and seas are expected to fall back below criteria levels as high pressure builds over the waters. Winds generally 15 knots or less and seas 2 to 4 feet, highest well offshore.
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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...NED SHORT TERM...Dennis LONG TERM...Dennis AVIATION...Dennis/NED MARINE...NED