473
FXUS62 KCHS 201045
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
545 AM EST SAT DEC 20 2025
SYNOPSIS
HIGH PRESSURE WILL PREVAIL OVER THE WEEKEND, WITH ANOTHER COLD
FRONT FORECAST TO IMPACT THE AREA MONDAY.
NEAR TERM /THROUGH TONIGHT/
TODAY: LATEST SURFACE ANALYSIS REVEALED HIGH PRESSURE ANCHORED OVER
THE OHIO RIVER VALLEY AND ALABAMA. IN THE MID-LEVELS OF THE
ATMOSPHERE THE SHORTWAVE WHICH PUSHED THE COLD FRONT THROUGH
YESTERDAY, WILL BE QUICKLY EXITING EAST ACROSS THE CANADIAN
MARITIMES. AS THIS OCCURS, THE CORE OF THE AGEOSTROPHIC CONVERGENCE
WILL QUICKLY MOVE EAST ALONG WITH THE SURFACE HIGH. FOR EARLY THIS
MORNING, TEMPERATURES ARE ALREADY IN THE 40S FOR MOST LOCATIONS WITH
A FEW RURAL SPOTS ALREADY IN THE MID 30S. EXPECT TEMPERATURES TO
START SATURDAY MORNING MOSTLY IN THE MID 30S WITH SOME LOWER 30S
POSSIBLE IN RURAL AREAS. TEMPERATURES WILL THEN QUICKLY WARM INTO
THE 50S BY MID-MORNING AS THE LOW LEVEL INVERSION LIFTS. HIGH
TEMPERATURES WERE ALSO TRICKY AS 1000/850 MB THICKNESSES START NEAR
1350M SATURDAY MORNING AND RISE TO 1360M BY THE LATE AFTERNOON. AS
SUCH, LATEST BLENDED GUIDANCE HAS HIGHS IN THE LOWER 60S, BUT
THINKING IS THAT HIGHS WILL BE MORE IN THE MID 60S WITH SOME UPPER
60S POSSIBLE ACROSS SOUTHERN GEORGIA. LATER THIS AFTERNOON, SURFACE
HIGH PRESSURE WILL BE RAPIDLY LOSING COHESION AS THE AGEOSTROPHIC
CONVERGENCE PULLS AWAY AND THEN STARTS TO COLLAPSE. AS SUCH, A WEAK
COASTAL TROUGH WILL DEVELOP AND MOVE INLAND BUT NO PRECIPITATION IS
EXPECTED. THE MAIN SENSIBLE WEATHER CHANGE WILL BE A NOTICEABLE
UPTICK IN RELATIVE HUMIDITY VALUES FROM RISING DEWPOINTS.
TONIGHT: THE LEFTOVER SURFACE HIGH PRESSURE WILL BE NEARLY
DISSIPATED AND WELL OFFSHORE WITH WEAK SOUTHERLY WINDS ACROSS THE
REGION. SIMULTANEOUSLY, ANOTHER COLD FRONT WILL BE MOVING EAST
ACROSS THE MIDWESTERN UNITED STATES WITH WINDS OVER COASTAL SOUTH
CAROLINA AND GEORGIA VEERING FROM THE WEST. EXPECT LOW TEMPERATURES
IN THE UPPER 30S, OR SLIGHTLY WARMER FROM THIS MORNING DUE TO THE
SLIGHTLY LESS IDEAL RADIATIONAL COOLING.
SHORT TERM /SUNDAY THROUGH MONDAY/
UPPER LEVEL FLOW REMAINS QUASI-ZONAL HEADING INTO SUNDAY AS A
SHORTWAVE STRENGTHENS SOUTH OF THE JAMES BAY AREA. MEANWHILE, AT THE
SFC, MODELS SHOW AN ADVANCING COLD FRONT PROGGED TO PUSH EASTWARD
ACROSS THE APPALACHIAN MOUNTAINS, AND INTO OUR AREA BY MONDAY. THAT
BEING SAID, OVERALL MOISTURE REMAINS QUITE MEAGER, KEEPING THE
FORECAST DRY. IN REGARD TO TEMPERATURES, HAVE AFTERNOON HIGHS
WARMING INTO THE MID TO UPPER 60S SUNDAY PRIOR TO FROPA, WITH
TEMPERATURES THEN DIPPING BACK INTO THE 50S TO LOWER 60S MONDAY IN
ITS WAKE. OUTSIDE OF THIS, EXPECT MORNING LOWS MONDAY AND TUESDAY TO
FEEL FAIRLY CRISP, AS CAA DROPS TEMPERATURES INTO THE UPPER 30S TO
LOWER 40S.
OTHERWISE, LOOK FOR SFC HIGH PRESSURE TO BUILD OVERHEAD TUESDAY,
ALLOWING HIGHS TO REBOUND BACK INTO THE UPPER 60S TO LOWER 70S WITH
THE AID OF SOUTHWESTERLY FLOW AND PARTLY SUNNY SKIES.
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
QUIET CONDITIONS CONTINUE HEADING INTO THE HOLIDAYS AS THE
AFOREMENTIONED SFC HIGH STRENGTHENS. UPPER LEVEL RIDGING WILL
ALSO AMPLIFY ACROSS THE CENTRAL CONUS DURING THIS TIME,
RESULTING IN ABOVE NORMAL TEMPERATURES FOR THE REMAINDER OF THE
EXTENDED PERIOD. CURRENTLY HAVE HIGHS LARGELY IN THE LOWER 70S,
WITH OVERNIGHT LOWS GENERALLY IN THE UPPER 40S TO LOWER 50S.
AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
TODAY AND TONIGHT: VFR. SURFACE HIGH PRESSURE OVER THE OHIO
RIVER VALLEY AND ALABAMA WILL RAPIDLY TRANSLATE EAST. CALM WINDS
THIS MORNING WILL BECOME LIGHT AND OUT OF THE NORTHEAST AFTER
SUNRISE. LATER THIS AFTERNOON, WINDS WILL VEER FROM THE EAST AS
A WEAK COASTAL TROUGH MOVES ACROSS THE TERMINALS. NO
PRECIPITATION OR CLOUDS ARE EXPECTED.
EXTENDED AVIATION OUTLOOK: VFR EXPECTED TO PREVAIL THROUGH SUNDAY,
WITH PERIODS OF MVFR POSSIBLE MONDAY MORNING IN THE WAKE OF
FROPA.
MARINE
TODAY AND TONIGHT: HIGH PRESSURE LOCATED OVER THE PIEDMONT OF
NORTH CAROLINA WILL ALLOW FOR NORTHEAST WINDS 5 TO 10 KT WITH
TRANSIENT GUSTS UP TO 15 KT ACROSS ALL WATERS. SEAS 2 TO 4 FT.
SUNDAY: SEAS 2 TO 4 FT WITH WINDS GUSTING UP TO 15 KT AT TIMES. NO
ADVISORIES OR WARNINGS ARE EXPECTED.
EARLY NEXT WEEK: HIGH PRESSURE BUILDING OVER THE MID-ATLANTIC WILL
FORCE A REINFORCING BACKDOOR COLD FRONT DOWN THE COAST LATER SUNDAY
INTO MONDAY. SMALL CRAFT ADVISORIES WILL LIKELY BE NEEDED FOR ALL
ZONES (THE ONE EXCEPTION BEING THE HARBOR), WITH WINDS PEAKING
AROUND DAYBREAK MONDAY. GALE PROBS REMAIN LESS THAN 10% AT THIS
POINT. WINDS WILL GRADUALLY SUBSIDE INTO MIDWEEK AS RIDGING MOVES
MORE DIRECTLY OVERHEAD.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
NEAR TERM...HAINES
SHORT TERM...SST
LONG TERM...SST
AVIATION...HAINES/SST
MARINE...HAINES/SST
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