FXUS62 KCHS 150854 AFDCHS
Area Forecast Discussion National Weather Service Charleston SC 354 AM EST Mon Dec 15 2025
.SYNOPSIS...
Bitter cold conditions will prevail today through Tuesday. Dry high pressure remains in control through Thursday before the next cold front impacts the area Friday.
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.NEAR TERM /THROUGH TONIGHT/...
Prior to Daybreak: Arctic high pressure will continue to build across the region, resulting in dry and bitter cold conditions prior to sunrise. Temperatures dipping into the low-mid 20s along with northerly winds gusting upwards to 15-25 mph (strongest near the coast) will support wind chill values in the 11-20 degree range and the continuation of a Cold Weather Advisory for all areas until 10 AM this morning. Coldest wind chill values are expected prior to sunrise and before winds start to weaken. A few locations could see wind chill values dip to around 10 degrees across the Tri-County Area and perhaps south along the I-95 corridor, but coverage and duration remain quite short and still representative under a Cold Weather Advisory.
Lake Wind: Strong cold air advection associated with building high pressure post cold front will continue to support wind gusts around 25 kt during the next 1-2 hours. A Lake Wind Advisory remains in effect across Lake Moultrie until 6 AM.
Today: Aloft, a broad trough will prevail across the East CONUS, placing a northwest downslope wind across the local area. At the sfc, cold high pressure will continue to build across the Southeast and prevail through the day. The pattern supports dry conditions for all areas with even some RH values touching 20-25% across inland areas during the afternoon. However, the pressure gradient will weaken considerably during maximum daytime heating, supporting a downward trend in wind speeds, generally to 5-10 mph or less away from the coast, thus limiting fire weather concerns for the day. Strong cold air advection occurring with a northerly sfc wind will also offset warming associated with the downslope pattern and a full day of sunshine, supporting high temps only in the low-mid 40s. A few temps could only peak in the upper 30s across northern Berkeley County.
Tonight: Dry high pressure will settle across the Southeast United States, supporting strong radiational cooling conditions locally under clear skies during the night. The main issue will be cold temperatures. Sfc winds are likely to decouple early, leading to a light/calm wind for most areas away from the beaches. Although temps are likely to cool into the low-mid 20s across inland zones, a calm wind should do little in the way to lower wind chill temperatures below 20 degrees, at least for a majority of the area. A few spots well inland, mainly from a stretch across western Dorchester County, SC to northern Tattnall County, GA, could experience temperatures near 20 degrees briefly, limiting the need for a Cold Weather Advisory late, but trends will continue to be monitored for any slightly colder scenario. Should temperatures trend colder than expected, a Cold Weather Advisory could become necessary for areas well inland.
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.SHORT TERM /TUESDAY THROUGH THURSDAY/...
Overview: Bitter cold temperatures continue through Tuesday morning, then begin to moderate by mid week.
Tuesday and Wednesday: As an upper-lvl trough gradually sharpens over the Atlantic, quasi-zonal flow will dominate the forecast at the surface. Marginal moisture will be available with PWAT values below 0.8 inches, thus not much expected in terms of precipitation. Expect lows to remain chilly on Tuesday night with temperatures in the low to mid 30s (with low 40s near the beaches) as post-FROPA conditions remain in play. Temperatures will likely reach to near to slightly above normal by Wednesday.
Thursday: Expect this quasi-zonal flow pattern to quickly change as an upper-lvl trough tracks eastward into the central CONUS on Thursday. An associated cold front will also track towards the region as moisture slowly advects into the Southeast. This system will allow for precip. chances to return and forecast notes 20-30% PoPs. This front will approach the region rather quickly on Thursday night. Ensemble guidance continues to suggest that rainfall will remain limited with less than 0.50 inches expected. Southeasterly winds will increase in the afternoon ahead of the approaching front and remain elevated throughout the night. There is still some uncertainty regarding the timing of the front, thus there could be small changes with this in the next couple forecast updates.
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.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
The cold front should pass through the region sometime on Fri. morning, and then high pressure should build in from the northeast. It appears there won't be much impact to the area with this system other than a wind shift. Temperatures will hop on a warming trend to above normal through the weekend as upper-lvl flow reverts back to zonal. There is some hinting that another cold front could approach the region late in the period on Sunday, however guidance clustering remains scattered and confidence regarding impacts remains low at this time.
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.AVIATION /08Z MONDAY THROUGH FRIDAY/...
VFR conditions will prevail at CHS/JZI/SAV terminals through 06Z Tuesday. However, gusty north/northeast winds (15-25 kt) are expected at all terminals for much of tonight, before trending weaker post daybreak this morning, then remaining around 10 kt or less for the rest of the day. Light/calm winds are expected at all terminals by around 00Z Tuesday tonight.
Extended Aviation Outlook: VFR conditions prevail for KCHS, KJZI and KSAV through mid-week.
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.MARINE...
Prior to Daybreak: Strong cold air advection associated with building high pressure post front will continue to support north- northeast winds gusting upwards to 25-35 kt (strongest outside the Charleston Harbor). However, the pressure gradient will be on a weakening trend around daybreak. Gale Warnings will continue across all local waters, while a Small Craft Advisory remains in effect for the Charleston Harbor. Seas should build up to 5-8 ft across nearshore waters (largest near 20 nm of the Charleston County Coast) to 7-10 ft across outer Georgia waters.
Today and Tonight: Cold high pressure will continue to spread across the region, leading to gusty wind conditions across all waters during early-mid morning hours. Gale Warnings likely come to an end shortly after daybreak and become replaced with Small Craft Advisories for a few hours as winds gradually trend lower in response to the pressure gradient becoming much weaker by the afternoon. Winds/seas will likely decrease/subside to below Small Craft Advisory levels for nearshore waters by early afternoon (mid- late morning for the Charleston Harbor), but a Small Craft Advisory will likely remain in effect across outer Georgia waters through the evening. After midnight, conditions become quiet with high pressure directly across the Southeast. North/northeast winds should lower to around 10 kt or less while seas subside to 3-5 ft.
Tuesday through Friday: Elevated seas will continue taper back as the swell recedes back out to the Atlantic. Marine conditions will remain benign on Tuesday and Wednesday as high pressure situates itself across the local waters. A coastal trough could develop over the nearshore waters on Thursday as an aforementioned cold front approaches. This might allow for a short-lived swell to take place on Friday, however it looks like it will remain below Small Craft Advisory thresholds. Winds will likely increase ahead of the frontal passage on Thursday, but again, nothing to write home about.
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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...Cold Weather Advisory until 10 AM EST this morning for GAZ087-
088-099>101-114>119-137>141.
SC...Cold Weather Advisory until 10 AM EST this morning for SCZ040-
042>045-047>052. Lake Wind Advisory until 6 AM EST early this morning for SCZ045.
MARINE...Small Craft Advisory until 9 AM EST this morning for AMZ330.
Gale Warning until 7 AM EST this morning for AMZ350-352-354- 374.
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NEAR TERM...DPB SHORT TERM...Dennis LONG TERM...Dennis AVIATION...Dennis/DPB MARINE...Dennis/DPB