FXUS62 KCHS 161144 AFDCHS
Area Forecast Discussion National Weather Service Charleston SC 644 AM EST Tue Dec 16 2025
.SYNOPSIS...
High pressure will prevail today through Thursday before a cold front pushes offshore Friday.
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.NEAR TERM /THROUGH TONIGHT/...
Early Morning: Dry high pressure will prevail across the area, which has already led to light/calm winds and strong radiational cooling under clear skies. Recent sfc observations indicate temps in the upper teens/low 20s away from the coastal corridor, which will continue to support a Cold Weather Advisory until 9 AM this morning. Lows in the upper 20s to lower 30s remain closer to the coast.
Today: Aloft, a northwest flow will prevail between a broad trough exiting off the Northeast Coast and a ridge expanding from the Deep South across the Southeast. At the sfc, high pressure will prevail for the day, but will gradually become more centered offshore by the afternoon, supporting a light west-southwesterly wind under a full day of sunshine. The day will start off chilly, but the combination of a dry downslope wind aloft and a light west-southwesterly wind under clear skies will help modify the airmass and lead to noticeably warmer afternoon temps compared to the previous day. In general, high temps should range in the mid-upper 50s (warmest across Southeast Georgia). A few locations could see temps reach 60 degrees along the Altamaha River in Southeast Georgia. These temps along with a dry downslope pattern also suggest another day where relative humidity values dip into the 20-25% range across areas well inland during peak heating. However, winds will remain very light throughout the day, limiting fire weather concerns locally.
Tonight: Aloft, a weak ridge will be placed directly overhead while sfc high pressure centered across the western Atlantic extends west across the Southeast. Any light wind that has developed during the daytime will quickly go calm around sunset, setting up the stage for radiational cooling early. However, airmass modification along with clouds arriving during the second half of the night will likely support temps about 10-15 degrees warmer than the previous night. In general, lows should range in the low-mid 30s inland to low-mid 40s closer to the coast.
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.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
Wednesday: A gradually moderating pattern will be in place as high pressure shifts offshore and weak upper-lvl ridging builds over the Southeast. Low-lvl flow will veer from northerly in the morning to west-southwesterly by the afternoon, allowing modest WAA to develop. This pattern will yield warming conditions and the forecast should remain rain-free with temperatures into the low to mid 60s with some spots reaching in the upper 60s across extreme southeast Georgia. While winds should be generally light and variable, it's possible a weak resultant sea breeze could develop near the beaches in the afternoon. The combination of mostly cloudy skies and slightly higher dewpoints should allow temperatures to stay mild with lows in the mid to upper 40s. The atmosphere looks to remain stable through the night with no meaningful forcing.
Thursday: Low-lvl south-southwesterly flow will advect warm and humid air into the region, yielding PWAT values ~1.5 inches by the afternoon. Mostly cloudy skies will limit insolation, however thickness values will allow highs to climb into the upper 60s to low 70s with slightly cooler temps. along the immediate coastline. Precipitation chances will gradually increase throughout the day as an upper-lvl trough advances eastward towards the region with an associated cold front. Expect scattered showers to develop and expand from west to east overnight with the highest chance after midnight. It's important to note that even though overall instability remains limited, there is a slight chance for thunderstorms to develop over southeast Georgia late Thursday night. Rainfall amounts remain light with less than 0.50 inches expected in the span of 24 hrs. Overnight temperatures will remain mild due to the overcast skies with lows ranging from low to mid 50s.
Friday: Broad mid-lvl troughing will extend into from the Bluegrass region into the Deep South as the associated cold front progresses eastward towards the region. It's possible to see some light showers in the morning before the cold front passes through. There has been a bit of uncertainty in the timing of the front amongst guidance, however sometime in the morning hours looks reasonable. Expect high pressure to build into the region from the west afterwards. Skies should gradually clear throughout the day and allow temperatures to reach into the low to mid 60s across southeast South Carolina and mid to upper 60s across southeast Georgia. Overnight lows will be a bit cooler than the previous couple nights with temps. dipping into the low 30s across the interior counties and upper 30s to low 40s closer to the coastline.
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.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
Expect a return of cool and dry conditions as high pressure continues to build into the region. This pattern will yield mostly sunny skies, light winds, and a cool start to the mornings. Temperatures will moderate back to above normal through early next week. There is potential for another cold front to approach the region on Sunday, however confidence remains low with the timing and impacts of this at the moment.
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.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
VFR conditions will prevail at CHS/JZI/SAV terminals through 12Z Wednesday.
Extended Aviation Outlook: Periods of MVFR possible on Thursday night as increasing cloud cover and showers might result in lower ceilings and vsbys. Conditions should improve on Friday behind the passage of the cold front.
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.MARINE...
Today and Tonight: High pressure will dominate the pattern, becoming more centered across the western Atlantic during the afternoon, then persisting through the night. Wind/seas are expected to remain well below Small Craft Advisory levels through the period, with a 10 kt northerly wind today turning more northeast and weakening overnight. Seas will also subside during the period, from 2-5 ft early today to 1-3 ft across nearshore waters and 3-4 ft across outer Georgia waters tonight.
Wednesday through Saturday: Situated between a weakening high offshore and a developing low across the central CONUS, expect the pressure gradient to gradually tighten across the local waters on Wednesday and Thursday. The period of largest concern remains to be on Thursday night into Friday ahead of the approaching cold front. Southwesterly winds will become elevated with speeds of 15 to 20 kts with gusts of 25 kts possible. Also, east-southeasterly swell will build into the waters with seas ranging from 3 to 5 ft with some 6 footers reaching into nearshore Charleston and outer Georgia waters. Small Craft Advisories will likely be needed on Thursday night into Friday.
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.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Cold Weather Advisory until 9 AM EST this morning for GAZ087-
088-099>101-115-116.
SC...Cold Weather Advisory until 9 AM EST this morning for SCZ040-
042>045-047.
MARINE...None.
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NEAR TERM...DPB SHORT TERM...Dennis LONG TERM...Dennis AVIATION...Dennis/DPB MARINE...Dennis/DPB