268
FXUS62 KCHS 181423
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
923 AM EST SAT JAN 18 2025
SYNOPSIS
AN AREA OF LOW PRESSURE AND ASSOCIATED COLD FRONT WILL IMPACT
THE REGION TODAY THROUGH SUNDAY MORNING. ANOTHER LOW PRESSURE
SYSTEM COULD IMPACT THE REGION EARLY TO MID NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
TODAY: THE FORECAST IS PRETTY MUCH ON TRACK, BUT POPS WERE
BUMPED BACK UP TO 100% GIVEN CURRENT RADAR AND HREF TRENDS.
HOURLY TEMPERATURES WILL BE A BIT UNUSUAL TODAY AS DIURNAL
HEATING WILL BE FIGHTING SOME DIABATIC COOLING WITH THE
APPROACHING RAIN SHIELD. HIGHS WERE NUDGED A TAD LOWER IN SOME
SPOTS, BUT THE GENERAL FLAVOR FOR HIGHS IN THE UPPER 50S/LOWER
60S.
TONIGHT: LATEST GUIDANCE SUGGESTS A SECOND ROUND OF PRECIP OCCURRING
DURING THE OVERNIGHT PERIOD, PRIMARILY LATE EVENING AND INTO LATE
NIGHT AS LOW PRESSURE DEVELOPS ALONG THE SOUTHERN FLANK OF A COLD
FRONT APPROACHING THE LOCAL AREA WITHIN A FEW HOURS PRIOR TO
DAYBREAK. FOR THIS REASON, THE LATEST FORECAST REFLECTS PRECIP
CHANCES INCREASING ONCE AGAIN LATE EVENING, THEN SLOWLY SHIFTING
EAST-SOUTHEAST WITH TIME AS THE FRONT NEARS. TEMPS WILL REMAIN MILD
THROUGH THE NIGHT AHEAD OF THE FRONT, GENERALLY RANGING IN THE LOW-
MID 50S FOR MOST AREAS. A FEW LOCATIONS COULD DIP INTO THE UPPER 40S
POST FROPA, PRIMARILY WELL INLAND AND/OR NORTH LATE.
SHORT TERM /SUNDAY THROUGH TUESDAY/
SUNDAY AND SUNDAY NIGHT: AHEAD OF THE APPROACHING COLD FRONT,
TEMPERATURES WILL BE ABLE TO REACH INTO THE LOW TO MID 60S MAKING IT
PROBABLY THE WARMEST DAY THIS WEEK. ANY PRECIPITATION SHOULD CLEAR
OUT IN THE MORNING AND ALLOW FOR A RAIN-FREE AFTERNOON. THE COLD
FRONT WILL PASS THROUGH THE REGION BY THE AFTERNOON AND TEMPERATURES
WILL BEGIN TO DROP THROUGHOUT THE AFTERNOON AS COLD, DRY AIR ADVECTS
INTO THE REGION BEHIND THE FRONT. ALONG WITH THIS, NORTHWESTERLY
WINDS COULD BECOME QUITE BREEZY BEHIND THE FRONT WITH WIND SPEEDS
CLIMBING TO 10 TO 15 MPH WITH GUSTS OF 20 MPH. OVERNIGHT, LOWS WILL
DROP INTO THE LOW 20S INLAND AND MID TO UPPER 20S CLOSER TO
COASTLINE. HOWEVER, WINDS WILL MAKE TEMPERATURES FEEL CLOSER TO THE
15-20 DEGREE RANGE, WHICH IS SOLIDLY IN THE COLD WEATHER ADVISORY
CRITERIA.
MONDAY AND MONDAY NIGHT: ALONG WITH POST-FRONTAL COLD AIR ADVECTION,
A STRONG ARCTIC AIR MASS WILL BEGIN TO SETTLE INTO THE REGION AND
THE FORECAST LOOKS TO REMAIN COLD AND DRY. HIGHS WILL ONLY REACH
INTO THE LOWER 40S. LOWS WILL DROP INTO THE LOW 20S INLAND AND MID
TO UPPER 20S CLOSER TO THE COASTLINE. THESE TEMPS WILL SUPPORT
ANOTHER NIGHT OF WIND CHILL TEMPS IN THE 15-20 DEGREE RANGE, WHICH
IS AGAIN SOLIDLY IN THE COLD WEATHER ADVISORY CRITERIA.
TUESDAY: LATEST OPERATIONAL RUNS OF THE GFS, ECMWF, AND CMC ARE IN
AGREEMENT THAT A LOW PRESSURE SYSTEM FROM THE GULF OF MEXICO WILL
BEGIN TO TRACK EAST ACROSS FLORIDA TOWARDS THE REGION AND
POTENTIALLY BRING IMPACTS, POSSIBLY SIGNIFICANT, TO SOUTHEAST SOUTH
CAROLINA AND SOUTHEAST GEORGIA. THERE STILL REMAINS SOME UNCERTAINTY
ON THE P-TYPES, BUT SEEMS FAVORABLE FOR A SNOW/FREEZING RAIN EVENT
TO UNFOLD. AS FAR AS TIMING GOES, THE BEST CHANCE FOR FROZEN
PRECIPITATION TO BEGIN LOOKS TO BE TUESDAY AFTERNOON AND POPS WERE
INCREASED ACCORDINGLY. WITH STRONG, COLD AIR IN PLACE, HIGHS WILL
ONLY REACH INTO THE MID 30S INLAND AND UPPER 30S/LOW 40S CLOSER TO
THE COASTLINE.
LAKE WINDS: BREEZY CONDITIONS WILL DEVELOP ON LAKE MOULTRIE LATE
SUNDAY AFTERNOON AS A COLD FRONT PUSHES THROUGH. STRONG POST-FRONTAL
COLD AIR ADVECTION WILL PUSH WINDS INTO THE 15-20 KT RANGE WITH
GUSTS 25-30 KT SUNDAY NIGHT AND A LAKE WIND ADVISORY COULD BE NEEDED
DURING THIS TIME. SPEEDS SHOULD BELOW ADVISORY CRITERIA BY MID-
MORNING MONDAY.
LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/
TRANSITIONING INTO TUESDAY NIGHT AND BEYOND, THE LOW PRESSURE SYSTEM
SEEMS TO TRACK TO THE SOUTH AND OFFSHORE TUESDAY NIGHT AND BRING
WINTRY MIX TO THE REGION. IT IS STILL TOO FAR OUT TO IDENTITY ANY
SPECIFIC SNOW AND ICE ACCUMULATIONS. AS FAR AS TIMING GOES FOR THIS
EVENT, THE GREATEST IMPACTS APPEAR TO BE TUESDAY NIGHT THROUGH
WEDNESDAY MORNING WHEN THE COLDEST AIR WILL ALIGN WITH THE STRONGEST
FORCING AND HEAVIEST PRECIPITATION. MOST OF THE MODELS ARE IN
AGREEMENT THAT MOST OF THE PRECIPITATION SHOULD END BY WEDNESDAY
AFTERNOON.
IN ADDITION TO THIS SYSTEM, IT WILL BE DOWN RIGHT COLD. IF ANY SNOW
AND ICE ACCUMULATE, IT WILL BE STICKING AROUND FOR A COUPLE DAYS.
HIGHS WILL ONLY REACH INTO THE 30S BOTH TUESDAY AND WEDNESDAY. LOWS
ON TUESDAY NIGHT WILL DROP INTO THE LOW TO MID 20S WITH WIND CHILL
VALUES IN THE MID-TEENS. THUS, A COLD WEATHER ADVISORY WILL LIKELY
BE NEEDED TUESDAY NIGHT. LOWS ON WEDNESDAY NIGHT GET EVEN COLDER
WITH TEMPERATURES DROPPING INTO THE THE MID-TEENS AND WIND CHILL
VALUES DIPPING BELOW 10 DEGREES IN SOME LOCATIONS. THIS IS REACHING
EXTREME COLD WARNING TERRITORY (10 DEGREES OR COLDER) AND WILL
LIKELY NEED TO BE ISSUED WEDNESDAY NIGHT. WE COULD EVEN BREAK THE
RECORD LOW TEMPERATURES AT KCHS/KCXM/KSAV ON THURSDAY.
ANOTHER AREA OF LOW PRESSURE COULD DEVELOP OFF THE SOUTH CAROLINA
COAST THURSDAY AND APPEARS TO LINGER AROUND FOR A BIT. WITH
TEMPERATURES STILL QUITE COLD, A CHANCE OF FREEZING RAIN WAS
MENTIONED ON THURSDAY, FRIDAY, AND SATURDAY MORNING. DUE TO THIS
BEING FAR OUT IN THE FORECAST, POPS WERE KEPT AT A LOW CHANCE.
AVIATION /14Z SATURDAY THROUGH WEDNESDAY/
VFR CONDITIONS WILL PREVAIL AT CHS/JZI/SAV TERMINALS THROUGH
MID MORNING SATURDAY. RAIN/SHOWERS ARE THEN EXPECTED TO DEVELOP
ACROSS THE REGION WITH THE APPROACH OF A FRONTAL SYSTEM, LIKELY
LEADING TO PERIODS OF MVFR CIGS BY AROUND 19Z AT ALL TERMINALS.
PRECIP COVERAGE EXPANDS THROUGHOUT SATURDAY AFTERNOON WITH CIGS
EXPECTED TO LOWER TO IFR CONDITIONS AT ALL TERMINALS BY AROUND
22Z. IFR CIGS SHOULD THEN PREVAIL THROUGH 12Z SUNDAY AT ALL TERMINALS.
EXTENDED AVIATION OUTLOOK: FLIGHT RESTRICTIONS ARE LIKELY SATURDAY
NIGHT INTO SUNDAY MORNING AS WIDESPREAD RAINS MOVE THROUGH IN
ASSOCIATION WITH A COLD FRONT. THE RISK FOR RESTRICTIONS IN LOW
VSBYS AND CEILINGS WILL RETURN TUESDAY MORNING INTO WEDNESDAY
MORNING AS A POTENTIAL WINTER STORM IMPACTS THE REGION. THERE IS
AN INCREASING CHANCE FOR FREEZING OR FROZEN PRECIPITATION TO
IMPACT ALL TERMINALS DURING THIS TIME PERIOD.
MARINE
TODAY AND TONIGHT: A WEAK PRESSURE GRADIENT WILL BE IN PLACE FOR
MUCH OF THE DAY WHILE A COASTAL TROUGH/LOW SHIFTS NORTH AND AWAY
FROM THE LOCAL AREA THIS MORNING INTO EARLY AFTERNOON. IN GENERAL,
SOUTHEAST WINDS UPWARDS TO 5-10 KT WILL TURN MORE SOUTH-SOUTHWEST
THIS AFTERNOON. SEAS WILL RANGE BETWEEN 1-2 FT. THE PRESSURE
GRADIENT SHOULD SLOWLY STRENGTHEN THIS EVENING AND OVERNIGHT AS LOW
PRESSURE AND ITS ASSOCIATED FRONT NEARS. FOR THIS REASON, SOUTH-
SOUTHWEST WINDS WILL LIKELY INCREASE TO THE 10-15 KT THIS EVENING,
WITH EVEN SOME GUSTS AROUND 20 KT AFTER MIDNIGHT. SEAS WILL ALSO
BUILD TO 3-5 FT TONIGHT, LARGEST ACROSS NORTHERN SOUTH CAROLINA
WATERS OFF THE CHARLESTON COUNTY COAST.
SUNDAY: A COLD FRONT WILL BE LOCATED OVER OR NEAR THE COASTAL WATERS
EARLY IN THE MORNING. IT'LL QUICKLY MOVE OFFSHORE AS THE DAY
PROGRESSES. STRONG, BROAD HIGH PRESSURE WILL THEN GRADUALLY BUILD IN
FROM THE PLAINS STATES. THE COMBINATION OF AN ENHANCED PRESSURE
GRADIENT AND STRONG COLD AIR ADVECTION WILL CAUSE SW WINDS DURING
THE DAY TO TURN TO THE NW DURING THE EVENING AND INCREASE. WIND
GUSTS WILL PROBABLY REACH 25 KT FOR ALL OF THE WATERS, INCLUDING THE
CHARLESTON HARBOR. SMALL CRAFT ADVISORIES WILL BE NEEDED STARTING IN
THE AFTERNOON AND GOING FOR MOST OF THE NIGHT. CONDITIONS START TO
IMPROVE BEFORE DAYBREAK SATURDAY.
MONDAY: STRONG HIGH PRESSURE WILL BE LOCATED OVER THE MIDDLE MS
VALLEY IN THE MORNING. IT'LL SHIFT EASTWARD, BECOMING CENTERED OVER
THE MID-ATLANTIC REGION OVERNIGHT. FOR THE SECOND HALF OF THE NIGHT,
TROUGHING DEVELOPS JUST SOUTH OF OUR COAST AND USHERS MOISTURE TO
THE NORTH. THIS SYNOPTIC PATTERN WILL CAUSE GUSTY NW WINDS EARLY IN
THE MORNING TO QUICKLY EASE, THEN GRADUALLY TURN TO THE NW AND
INCREASE LATE AT NIGHT.
TUESDAY AND WEDNESDAY: A STORM SYSTEM WILL IMPACT THE SOUTHEAST U.S
LATE TUESDAY INTO EARLY WEDNESDAY, WITH THE PRIMARY LOW PASSING WELL
OFFSHORE. AT THE SAME TIME, HIGH PRESSURE WILL BE LOCATED WELL TO
OUR NORTH. THE PRESSURE GRADIENT BETWEEN THESE SYNOPTIC FEATURES
WILL BE VERY ELEVATED. EXPECT STRONG AND GUSTY WINDS RAPIDLY RAMPING
UP TUESDAY MORNING AND PERSISTING INTO WEDNESDAY. THERE COULD BE A
BRIEF PERIOD OF GALE CONDITIONS TUESDAY NIGHT, MAINLY FOR THE
CHARLESTON WATERS AND GA WATERS BEYOND 20 NM. AT LEAST SMALL CRAFT
ADVISORIES WILL BE NEEDED WITH A POSSIBILITY FOR GALE WATCHES/WARNINGS.
BOTH WINDS AND SEAS START TO TREND LOWER WEDNESDAY AFTERNOON,
CONTINUING INTO THE OVERNIGHT HOURS. SEAS LOOK TO PEAK EARLY WEDNESDAY
MORNING, 5-8 FT FOR THE WATERS WITHIN 20 NM AND 8-12 FT FOR THE
GA WATERS BEYOND 20 NM. THOUGH, THEY'LL BE SLOWER TO SUBSIDE INTO
WEDNESDAY NIGHT. FINALLY, MARINERS SHOULD BE ALERT THAT SOME WINTER
PRECIPITATION COULD FALL OVER THE COASTAL WATERS TUESDAY NIGHT
INTO WEDNESDAY MORNING, REDUCING VISIBILITIES TO 1 NM OR LESS AT
TIMES.
CLIMATE
RECORD LOW TEMPERATURES:
THURSDAY, JANUARY 23:
KCHS: 19/1985
KCXM: 24/2003
KSAV: 19/1960
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
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