585
FXUS62 KCHS 171144
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
644 AM EST WED DEC 17 2025
SYNOPSIS
HIGH PRESSURE WILL PREVAIL THROUGH THURSDAY BEFORE A COLD FRONT
PUSHES OFFSHORE FRIDAY MORNING. HIGH PRESSURE RETURNS DURING
THE WEEKEND, FOLLOWED BY ANOTHER COLD FRONT ARRIVING EARLY NEXT
WEEK.
NEAR TERM /THROUGH TONIGHT/
TODAY: ALOFT, THE AXIS OF A WEAK/BROAD RIDGE OVER THE SOUTHEAST
WILL SHIFT OFFSHORE EARLY, FAVORING A SOUTHWEST FLOW ACROSS THE
REGION AHEAD OF H5 VORT ENERGY TRAVERSING THE DEEP SOUTH. AT
THE SFC, HIGH PRESSURE EXTENDING ACROSS THE AREA FROM THE
ATLANTIC WILL REMAIN THE DOMINANT WEATHER FEATURE, RESULTING IN
DRY/WARMER CONDITIONS WITH A LIGHT SOUTHWESTERLY WIND FOR THE
DAY. ALTHOUGH HIGH CLOUDS ARE EXPECTED TO SPREAD ACROSS THE
REGION AND THICKEN, TEMPS SHOULD STILL REACH THE MID 60S FOR
MOST AREAS, AND POTENTIALLY THE UPPER 60S SOUTH OF I-16 ACROSS
SOUTHEAST GEORGIA.
TONIGHT: ALOFT, LITTLE CHANGE IN THE OVERALL PATTERN OCCURS, BUT THE
FIRST SIGNS OF H5 VORT ENERGY SHOULD ENTER THE REGION AFTER
MIDNIGHT. THE MOST NOTABLE CHANGE OCCURS AT THE SFC, WITH GUIDANCE
SUPPORTING THE DEVELOPMENT OF A COASTAL TROUGH ALONG THE
SOUTHWESTERN EDGE OF THE ATLANTIC HIGH OFFSHORE. INCREASING LOW
CLOUDS WILL LIKELY ACCOMPANY THIS FEATURE, SPREADING ACROSS
SOUTHEAST GEORGIA, THEN SOUTHEAST SOUTH CAROLINA STARTING DURING THE
EVENING. BY MIDNIGHT, SUFFICIENT LOW-LVL MOISTURE AND FORCING
SUPPORTS FEW TO SCATTERED SHOWERS DEVELOPING ACROSS NEARBY COASTAL
WATERS AND SHIFTING ONSHORE, IMPACTING MOST BEACHES SOUTH OF THE
CHARLESTON VICINITY ACROSS SOUTHERN SOUTHEAST SOUTH CAROLINA AND
SOUTHEAST GEORGIA. ACTIVITY SHOULD EVENTUALLY MAKE A PUSH INLAND,
RESULTING IN RAINFALL AMOUNTS AROUND 1/10 OF AN INCH IN SPOTS PRIOR
TO SUNRISE. OVERNIGHT LOWS WILL BE CONSIDERABLY WARMER THAN THE
PREVIOUS NIGHT, GENERALLY RANGING IN THE MID-UPPER 40S INLAND TO LOW-
MID 50S NEAR THE COAST.
SHORT TERM /THURSDAY THROUGH SATURDAY/
THURSDAY: PRECIPITATION CHANCES WILL GRADUALLY INCREASE AS A
POWERFUL MID-LVL SHORTWAVE AND ASSOCIATED COLD FRONT PROPAGATES
TOWARDS THE SOUTHEAST. AHEAD OF THIS FEATURE, LOW-LVL SOUTH-
SOUTHWESTERLY FLOW WILL ADVECT WARM AND HUMID AIR INTO THE REGION,
YIELDING PWAT VALUES ~1.5 INCHES BY THE AFTERNOON. MODEL CROSS
SECTIONS SUGGEST FORCING AHEAD OF THE SHORTWAVE WILL BE MODEST AS
DPVA INCREASES + THE PASSING OF THE SUBTROPICAL JET STREAK ALOFT.
IT'S IMPORTANT TO NOTE THAT SBCAPE VALUES REMAIN QUITE LOW (~200-300
J/KG), BUT THIS MIGHT NOT MATTER WITH ENOUGH LIFT ALONG THE COLD
FRONT. THIS SHOULD AT LEAST RESULT IN SOME LOW-TOPPED CONVECTION
RIGHT ALONG THE BOUNDARY. EXPECT PRECIPITATION TO DEVELOP IN THE
EARLY MORNING HOURS, AND THEN SLOWLY EXPAND ACROSS THE REGION
THROUGHOUT THE DAYTIME. HIGHEST CHANCE OF HEARING A FEW RUMBLES OF
THUNDER WILL BE IN THE AFTERNOON INTO THE LATE EVENING AS THE
FRONTAL ZONE INTERACTS WITH THE WARM, MOIST PRE-FRONTAL AIRMASS. A
SLIGHT CHANCE OF THUNDERSTORMS HAS BEEN INTRODUCED ACROSS THE REGION
TO ADDRESS THIS POTENTIAL. RAINFALL AMOUNTS REMAIN LIGHT WITH ~0.5
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
ACROSS THE REGION. IT'S POSSIBLE TO A CONTINUATION OF 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 THE EARLY MORNING HOURS (BEFORE 10AM) LOOK THE
MOST REASONABLE. THEREAFTER, HIGH PRESSURE IS EXPECTED TO BUILD INTO
THE REGION FROM THE WEST AND SKIES SHOULD GRADUALLY CLEAR THROUGHOUT
THE DAY. THIS WILL YIELD TEMPERATURES IN THE LOW TO MID 60S ACROSS
THE LOWCOUNTRY. 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.
SATURDAY: EXPECT A RETURN OF QUASI-ZONAL FLOW ALOFT AS THE
AFOREMENTIONED SHORTWAVE CONTINUES TO PROGRESS OFFSHORE. AT THE
SURFACE, HIGH PRESSURE WILL SITUATE ITSELF ACROSS THE REGION AND
YIELD COOL AND DRY CONDITIONS. EXPECT SUNNY SKIES + LIGHT WINDS AS
TEMPERATURES MODERATE BACK TO NEAR NORMAL. IT LOOKS LIKE ANOTHER
COLD NIGHT IS IN-STORE WITH LOWS DROPPING INTO THE UPPER 30S TO LOW
40S.
LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/
EXPECT HIGH PRESSURE TO PREVAIL FOR THE WEEKEND WITH SIGNALS THAT
ANOTHER COLD FRONT TO APPROACH THE REGION LATE ON SUNDAY, HOWEVER
CONFIDENCE REMAINS LOW WITH THE TIMING AND IMPACTS OF THIS AT THE
MOMENT. TEMPERATURES WILL MODERATE BACK TO ABOVE NORMAL ON
SUNDAY INTO EARLY NEXT WEEK.
AVIATION /12Z WEDNESDAY THROUGH SUNDAY/
VFR CONDITIONS WILL PREVAIL AT CHS/JZI/SAV TERMINALS THROUGH 06Z
THURSDAY. HOWEVER, CLOUDS WILL INCREASE ACROSS THE AREA DURING
THE NIGHT AS A COASTAL TROUGH DEVELOPS OFFSHORE. A FEW SHOWERS
AND/OR MVFR CIGS ARE POSSIBLE AT THE TERMINALS LATE IN THE TAF
PERIOD (06Z TO 12Z THURSDAY), ESPECIALLY AT SAV. CONFIDENCE
REMAINS TOO LOW TO START PREVAILING GROUPS, BUT FLIGHT
RESTRICTIONS COULD NEED TO BE ADDED IN LATER TAF ISSUANCES.
EXTENDED AVIATION OUTLOOK: PERIODS OF MVFR POSSIBLE ON THURSDAY AND
THURSDAY NIGHT AS INCREASING CLOUD COVER AND SHOWERS MIGHT RESULT IN
LOWER CEILINGS AND VSBYS. A RISK FOR LOW-LVL WIND SHEAR COULD
DEVELOP THURSDAY NIGHT AS A STRONG, PRE-FRONTAL LOW-LEVEL JET (45-50
KT) PUSHES EAST THROUGH THE REGION. CONDITIONS SHOULD IMPROVE ON
FRIDAY BEHIND THE PASSAGE OF THE COLD FRONT.
MARINE
TODAY AND TONIGHT: HIGH PRESSURE WILL PREVAIL ACROSS THE
WESTERN ATLANTIC, LEADING TO QUIET MARINE CONDITIONS THROUGH THE
DAY. IN GENERAL, NORTH WINDS WILL TURN MORE EASTERLY THIS
AFTERNOON, REMAINING AROUND 10 KT OR LESS. SEAS WILL RANGE
BETWEEN 1-3 FT. OVERNIGHT, A COASTAL TROUGH IS ANTICIPATED TO
DEVELOP ALONG THE SOUTHWESTERN EDGE OF THE ATLANTIC HIGH, WHICH
SHOULD LEAD TO SCATTERED SHOWERS AND POSSIBLY A FEW
THUNDERSTORMS ACROSS LOCAL WATERS DURING THE SECOND HALF OF THE
NIGHT. ADDITIONALLY, A SLIGHT UPTICK IN EASTERLY WINDS AND SEAS
ARE POSSIBLE, WITH WIND GUSTS IN THE 10-15 KT RANGE AND SEAS
BETWEEN 2-4 FT (HIGHEST ACROSS OUTER GEORGIA WATERS).
THURSDAY THROUGH SUNDAY: SITUATED BETWEEN A WEAKENING HIGH OFFSHORE
AND AN APPROACHING SHORTWAVE FROM THE WEST, EXPECT THE PRESSURE
GRADIENT TO GRADUALLY TIGHTEN ACROSS THE LOCAL WATERS ON 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 MIX INTO THE WATERS
WITH SEAS RANGING FROM 3 TO 5 FT WITH SOME 6 FOOTERS REACHING INTO
NEARSHORE SOUTH CAROLINA AND OUTER GEORGIA WATERS. SMALL CRAFT
ADVISORIES WILL LIKELY BE NEEDED ON THURSDAY EVENING INTO
FRIDAY.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
NEAR TERM...DPB
SHORT TERM...DENNIS
LONG TERM...DENNIS
AVIATION...DENNIS/DPB
MARINE...DENNIS/DPB
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