FXUS62 KCHS 140720 AFDCHS
Area Forecast Discussion National Weather Service Charleston SC 220 AM EST Sun Dec 14 2025
.SYNOPSIS...
An arctic cold front will sweep through Today. Dry high pressure will then build overhead for much of the coming week.
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.NEAR TERM /THROUGH TONIGHT/...
Today: Aloft, a high amplitude trough will dig across the Great Lakes to the Mid-Atlantic states, helping force an arctic cold front through the area mid morning into early afternoon. A southwest wind will help maintain mild conditions locally through morning hours, with high temps likely to occur early prior to fropa, generally in the upper 50s/around 60 inland to low-mid 60s near the coast. However, expect temps to begin a cooling trend by early-mid afternoon as strong cold air advection occurs post front. Latest soundings are not impressive in regards to moisture, but indicate a period of cloudy conditions and light showers during morning hours. QPF will remain low, mainly below a tenth of an inch across Southeast South Carolina. Precip likely ends with fropa (around noon), but gusty northwest winds (20-30 mph) will develop across most areas as strong low-lvl mixing occurs with cold air advection. A Lake Wind Advisory is in effect across Lake Moultrie as a result, starting at 4 PM.
Tonight: Arctic high pressure will build across the region from the north and west, setting up a dry, but cold night. Gusty and dry conditions post fropa will likely have dried out all surfaces during afternoon hours, especially given little rainfall accumulation, thus limiting any concern of slippery roads/black ice during the night. The main issue will be low wind chill values during the second half of the night. Strong cold air advection to the region will help temperatures dip into the upper teens well inland and north to low- mid 20s near the SC/GA beaches and south of I-16 across Southeast Georgia. Temps could approach record low levels (see climate section). These temperatures along with northerly winds gusting upwards to 15-25 mph (strongest near the coast) support wind chill values in the 11-20 degree range. Coldest wind chill temperatures should occur across the Charleston Tri- County Area and perhaps across inland Southeast South Carolina counties. Wind chill temperatures could briefly touch 10 degrees, but the coverage and duration of the event is quite limited prior to daybreak. Thus, the Extreme Cold Watch has been replaced with a Cold Weather Advisory, which is now in effect for all of Southeast South Carolina and Southeast Georgia from 10 PM tonight until 10 AM Monday.
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.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
Overview: Very cold temperatures continue for Monday, then begin to moderate by mid week.
Monday: Deep, cold high pressure will be centered over the region. Even with full sun, highs not expected to make it much past 40, which are near record low max values for the date! Luckily, winds will be light, reducing any wind chill effects. By Monday night, high pressure will start off centered over the area, then it will slide eastward into the Atlantic waters by late night. With light winds, clear skies and a very dry low levels, expect ideal radiational cooling conditions. This will make for another cold night with lows in the 20s most areas, except closer to 30 near the coast. We continue to monitor the potential for another Cold Weather Advisory, but current overnight temperature forecast keeps temps just above the 20 degree threshold. Even with the current forecast, there could be some areas that briefly touch 20 degrees.
Tuesday and Wednesday: The surface ridge continues to move eastward into the Atlantic with zonal mid and upper level flow. This pattern is expected to allow a moderation in temperatures, reaching to near to slightly above normal by Wednesday. No precipitation is expected during this period.
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.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
The general zonal upper level pattern is shown by models to briefly be interrupted by a fast moving upper level trough axis and associated weak cold front Thursday. This upper level trough may have enough deep layer moisture to produce isolated showers Thursday and Thursday night.
Friday through Sunday: the upper flow reverts back to generally zonal, with temperatures above normal, in the 60s to near 70. Models diverge again with the potential for another front and threat for precipitation to approach the area possibly by late in the period on Sunday. Confidence with whether or not this front will have any impact in our area is very low at this time.
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.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
VFR conditions will prevail at CHS/JZI/SAV terminals through 12Z this morning. At CHS/JZI, light showers associated with a cold front could produce MVFR cigs temporarily in the 12-16Z Sunday timeframe, followed by prevailing MVFR cigs through 18Z. At SAV, prevailing MVFR cigs are anticipated between 13-17Z, associated with the passing front. Gusty northwest to north winds (20-25 kt) are also likely at all terminals from 16Z Sunday to 06Z Monday.
Extended Aviation Outlook:
Monday through Wednesday: VFR conditions are expected to prevail for KCHS, KJZI and KSAV.
Thursday: Isolated showers may impact the TAF sites with the potential for brief flight restrictions with any showers. However, confidence is low to moderate for the potential for any showers during this period.
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.MARINE...
Today and Tonight: High pressure extending across the Atlantic will eventually give way to a quickly approaching cold front from the west, leading to deteriorating wind/sea conditions this afternoon. Ahead of the front, a southwest wind in the 10-15 kt range will gradually ramp up to 15-20 kt by late morning, then quickly turn northwest this afternoon as an arctic cold front shifts offshore. Northwest to north winds should gust upwards to 25-35 kt, strongest outside the Charleston Harbor late afternoon and through much of the night. For this reason, the Gale Watch has been upgraded to a Gale Warning for all waters, the exception being the Charleston Harbor where a Small Craft Advisory is in place. Seas will also build with winds surging across local waters late afternoon into the overnight period, reaching 5-7 ft across most nearshore waters, but topping out near 8-9 ft around 20 nm off the Charleston County Coast and across outer Georgia waters.
Monday through Thursday: No highlights are expected through the period. A high pressure ridge at the surface will remain just east of the waters through at least Wednesday. This will keep mainly west-southwest winds of 15 knots or less and seas 2 to 4 feet. A coastal trough may develop over the nearshore waters on Thursday as a cold front approaches from the west. Winds likely to increase from the south on Thursday, but still expected to remain below highlight levels.
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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 from 10 PM this evening to 10 AM EST
Monday for GAZ087-088-099>101-114>119-137>141.
SC...Cold Weather Advisory from 10 PM this evening to 10 AM EST
Monday for SCZ040-042>045-047>052. Lake Wind Advisory from 4 PM this afternoon to 4 AM EST Monday for SCZ045.
MARINE...Small Craft Advisory from 4 PM this afternoon to 9 AM EST
Monday for AMZ330. Gale Warning from 4 PM this afternoon to 7 AM EST Monday for AMZ350-352-354-374.
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NEAR TERM...DPB SHORT TERM...RFM LONG TERM...RFM AVIATION...DPB/RFM MARINE...DPB/RFM