249
FXUS62 KCHS 210057
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
757 PM EST MON JAN 20 2025
SYNOPSIS
HIGH PRESSURE WILL PREVAIL THROUGH TONIGHT. A STORM SYSTEM WILL
IMPACT THE AREA TUESDAY AFTERNOON THROUGH WEDNESDAY MORNING.
ANOTHER WEAK STORM SYSTEM COULD IMPACT THE AREA THURSDAY AND
THURSDAY NIGHT.
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
NO SIGNIFICANT CHANGES MADE TO THE GOING FORECAST THROUGH
THE OVERNIGHT PERIOD. LOTS OF CLEAR SKIES OUT THERE THIS EVENING
AND TEMPERATURES HAVE ALREADY DROPPED INTO THE UPPER 20S TO
LOWER 30S AWAY FROM THE BEACHES. MID AND HIGH-LEVEL CLOUDS WILL
BEGIN TO INCREASE AND THICKEN AHEAD OF THE APPROACHING WINTER
STORM DURING THE OVERNIGHT. THIS WILL LIKELY STOP THE TEMP
FREE-FALL...POSSIBLY REVERSING THE TEMP TREND. BUT NOT BEFORE
TEMPERATURES FALL INTO THE LOWER-MID 20S INLAND TO THE UPPER
20S/LOWER 30S CLOSER TO THE COAST AND SOUTH OF I-16. ONGOING
NORTHERLY WINDS WILL PUSH WIND CHILLS INTO THE 10-15 DEGREE
RANGE NORTH OF I-16 WITH 15-20 DEGREES SOUTH OF I-16. A COLD
WEATHER ADVISORY REMAINS IN EFFECT FOR ALL AREAS TONIGHT.
SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/
A WINTER STORM WARNING IS NOW IN EFFECT FROM 5 PM TUESDAY TO
NOON ON WEDNESDAY.
TUESDAY AND WEDNESDAY: THE FORECAST AREA WILL ENTER A VERY
ACTIVE WEATHER PATTERN TUESDAY INTO WEDNESDAY. THE FORECAST SET
UP IS VERY CHALLENGING, WITH SEVERAL DIFFERENT PRECIPITATION
TYPES IN THE FORECAST ACROSS THE REGION. A LARGE SCALE TROUGH
WILL BE PRESENT ALOFT OVER MOST OF THE EASTERN CONUS.
ADDITIONALLY AN UPPER LEVEL JET WILL BE LOCATED JUST TO THE
NORTHEAST OF THE FORECAST AREA, PUTTING THE REGION IN THE RIGHT
ENTRANCE REGION. AT THE SURFACE HIGH PRESSURE WILL ATTEMPT TO
BUILD INTO THE FORECAST AREA FROM THE WEST, USHERING IN A CHILLY
AIRMASS. A STALLED BOUNDARY OFF THE SOUTHEASTERN COASTLINE WILL
BE THE CENTER POINT OF THE SYNOPTIC PATTERN AS LOW PRESSURE
DEVELOPS ALONG THE BOUNDARY AND IN THE PRESENCE OF UPPER LEVEL
DIVERGENCE ON TUESDAY. THE FORECAST AREA WILL BE PLACED BETWEEN
THE HIGH PRESSURE INLAND AND THE DEVELOPING LOW PRESSURE
OFFSHORE, COMBINING THE PRECIPITATION FROM THE LOW PRESSURE WITH
THE ARCTIC AIRMASS ASSOCIATED WITH THE HIGH PRESSURE. WINTER
WEATHER WILL OVERSPREAD THE FORECAST AREA BEGINNING TUESDAY
EVENING AND TAPERING OFF WEDNESDAY MORNING.
NOW THAT THE PERIOD OF INTEREST IS WITHIN THE TIMEFRAME OF MOST
HIRES GUIDANCE SOME ADDITIONAL TIMING DETAILS AND PRECIPITATION
TYPE WERE ABLE TO BE INCLUDED IN THE FORECAST. FORECAST
SOUNDINGS SHOW THAT A MIXTURE OF PRECIPITATION TYPES WILL BE
LIKELY ACROSS THE REGION. AS OF THIS JUNCTURE MOST LOCATIONS
WILL LIKELY BEGIN AS SLEET IN THE LATE AFTERNOON/EARLY EVENING,
WITH MAYBE SOME FREEZING RAIN ALONG THE ALTAMAHA RIVER IN GA. AS
THE EVENING CONTINUES THE SLEET WILL LIKELY TURN OVER TO ALL
SNOW ACROSS MOST INTERIOR LOCATIONS, WITH A MIXTURE OF SNOW AND
SLEET REMAINING ALONG THE COASTAL COUNTIES. COMPLICATING FACTORS
TO THE FORECAST WILL BE A REMNANT COASTAL TROUGH LINGERING IN
THE VICINITY OF SOUTHEASTERN GA AND A BAND OF ENHANCED
FRONTOGENESIS ASSOCIATED WITH THE UPPER LEVEL TROUGH POSITIONED
ACROSS THE FORECAST AREA. THE LINGERING COASTAL TROUGH COULD
ENHANCE THE 850 HPA WARM NOSE, WHICH WOULD INCREASE THE FREEZING
RAIN POTENTIAL OVER SOUTHEAST GA. ADDITIONALLY, THERE WILL
LIKELY BE A REGION THAT COULD SEE SOME ENHANCED PRECIPITATION
RATES IN THE VICINITY OF THE HIGHER FRONTOGENESIS VALUES.
HOWEVER PINNING THAT LOCATION DOWN IS EXTREMELY DIFFICULT. AS OF
THIS JUNCTURE IT IS BELIEVED THAT AN AREA ROUGHLY FROM
STATESBORO, GA NORTHEASTWARD TOWARDS SUMMERVILLE AND MONCKS
CORNER, SC COULD BE IN THE FAVORABLE POSITION FOR SOME
ADDITIONAL SNOWFALL VALUES. GENERALLY SNOW TOTALS ARE AROUND 1
TO 2 INCHES ACROSS THE FORECAST AREA. IT IS WORTH NOTING THAT
SLEET WILL LIKELY IMPACT THE OVERALL TOTALS ACROSS COASTAL SC.
ICE ACCUMULATIONS ACROSS COASTAL SE GA UP TO 0.25 INCHES ARE
POSSIBLE.
AS OF WEDNESDAY MORNING PRECIPITATION WILL BE TAPERING OFF,
WITH A FEW LINGERING SNOW SHOWERS POSSIBLE ALONG THE COASTAL
COUNTIES. THE MAIN FORECAST HIGHLIGHT OF WEDNESDAY WILL BE THE
COLD TEMPERATURES. AS THE ARCTIC AIRMASS CONTINUES TO INFILTRATE
THE FORECAST AREA HIGH TEMPERATURES ARE ONLY FORECAST TO REACH
INTO THE UPPER 30S. COMBINED WITH SNOW ON THE GROUND AND
NORTHERLY WINDS, WIND CHILL VALUES ARE FORECAST TO DIP INTO THE
UPPER TEENS TO LOW 20S AT TIMES. A COLD WEATHER ADVISORY IN
EFFECT TUESDAY THROUGH WEDNESDAY EVENING.
WEDNESDAY NIGHT THROUGH THURSDAY: BETWEEN THE ARCTIC AIRMASS
AND RECENT SNOWFALL TEMPERATURES ON WEDNESDAY NIGHT WILL PLUMMET
INTO THE UPPER TEENS INLAND AND MID 20S ALONG THE COASTAL
COUNTIES. CLOUDS WILL BEGIN TO MOVE INTO THE REGION AROUND
MIDNIGHT, LIKELY KEEPING TEMPERATURES STEADY THROUGH THE NIGHT
INSTEAD OF CONTINUING TO PLUMMET. ANOTHER COLD WEATHER ADVISORY
WILL BE REQUIRED WEDNESDAY NIGHT. ADDITIONAL PRECIPITATION IS
POSSIBLE THURSDAY MORNING ASSOCIATED WITH A STALLED BOUNDARY
OFFSHORE. HOWEVER, GUIDANCE CONTINUES TO COME IN DRIER SO THE
FORECAST HAS CONTINUED THE DOWNWARD TREND OF POPS. 15 TO 25%
POPS HAVE BEEN MAINTAINED IN THE FORECAST, MOSTLY ALONG THE
DIRECT COASTLINE. WITH THE ARCTIC AIRMASS STILL IN PLACE, ANY
PRECIPITATION THAT FALLS WILL LIKELY BE OF THE FROZEN VARIETY.
THE CURRENT FORECAST FEATURES A SLIGHT CHANCE OF FREEZING RAIN
THURSDAY MORNING. TEMPERATURES WILL AGAIN BE QUITE COLD ON
THURSDAY, REACHING ONLY TO AROUND 40.
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
ANOTHER TROUGH ALOFT WILL SWING THROUGH THE EASTERN US FRIDAY
AND SATURDAY, BUT WITH VERY DRY MID-LEVEL AIR EXPECTED A DRY
FORECAST REMAINS IN PLACE. AT THE SURFACE, INLAND RIDGING FRIDAY
MAINTAINS SURFACE CAA AS AN 850 MB FRONT SLIDES FURTHER OFF THE
COAST WITH FRIDAY NIGHT BRINGING A REINFORCEMENT OF COLD DRY
AIR. FINALLY, ON SATURDAY, THE SURFACE HIGH WILL SHIFT OFF THE
COAST, WITH A A WARM FRONT LIFTING THROUGH THE AREA BRINGING THE
END OF THE PROLONGED COLD SPELL AND SIGNALING A RETURN BACK
TOWARD NORMAL TO CLOSE OUT THE WEEKEND. THE NEXT CHANCE FOR
RAINFALL ARRIVES SUNDAY NIGHT INTO MONDAY AS A COLD FRONT COULD
APPROACH FROM THE NORTH AND WEST.
AVIATION /01Z TUESDAY THROUGH SATURDAY/
21/00Z TAF DISCUSSION:
KCHS/KJZI/KSAV: VFR THROUGH MID TO LATE AFTERNOON TUESDAY
ALTHOUGH WITH INCREASING AND LOWERING CLOUD COVER. CONDITIONS
DETERIORATE QUICKLY TO MVFR LATE TUESDAY AFTERNOON WITH A WINTRY
MIX OF PRECIPITATION SPREADING INTO THE TERMINALS AFTER 21Z.
EXTENDED AVIATION OUTLOOK: FLIGHT RESTRICTIONS ARE EXPECTED
TUESDAY EVENING THROUGH WEDNESDAY MORNING DUE TO WINTER WEATHER.
ADDITIONAL FLIGHT RESTRICTIONS ARE POSSIBLE THURSDAY MORNING,
WITH LOW PROBABILITIES OF FREEZING RAIN ALONG THE COAST.
MARINE
TONIGHT: NORTH WIND WILL VEER TO THE NORTHEAST OVERNIGHT AS HIGH
PRESSURE BUILDS SOUTH INTO THE AREA. SPEEDS OF 10-15 KT WILL
INCREASE TO 15-20 KT OVERNIGHT IN RESPONSE TO A TIGHTENING OF
THE PRESSURE GRADIENT. SEAS 1-3 FT THIS EVENING WILL BUILD TO
2-4 FT OVERNIGHT.
TUESDAY AND WEDNESDAY: A LOW PRESSURE SYSTEM WILL DEVELOP OFF
THE SOUTHEASTERN COAST ON TUESDAY AS HIGH PRESSURE BUILDS INTO
THE REGION FROM THE WEST. THE LOCAL FORECAST AREA WILL BE
PINCHED BETWEEN THESE TWO FEATURES, YIELDING AN ENHANCED
PRESSURE GRADIENT. NORTHERLY WINDS WILL SURGE TO 20 TO 25 KNOTS
WITH GUSTS APPROACHING 30 KNOTS ACROSS THE MARINE ZONES. THE
CHARLESTON HARBOR WILL SEE WINDS 15 TO 20 WITH SOME GUSTS
APPROACHING 25 KNOTS. SMALL CRAFT ADVISORIES ARE IN EFFECT FOR
ALL MARINE ZONES OUTSIDE OF THE CHARLESTON HARBOR, ALL BEGINNING
AT VARYING TIMES ON TUESDAY. ADDITIONALLY, SEAS WILL BUILD AS A
RESULT OF THE DEVELOPING LOW PRESSURE. BY WEDNESDAY SEAS OVER
THE 20 TO 60 NM OFFSHORE GA WATERS WILL APPROACH 7 TO 9 FT, WITH
4 TO 6 FT ACROSS THE NEARSHORE WATERS.
THURSDAY AND FRIDAY: A COASTAL TROUGH WILL DEVELOP ON THURSDAY
BEFORE HIGH PRESSURE BUILDS INTO THE REGION ON FRIDAY. WINDS
WILL LIKELY WANE TO BELOW SMALL CRAFT ADVISORY CRITERIA, HOWEVER
WILL REMAIN SLIGHTLY ELEVATED. SEAS WILL ALSO SLOWLY DECREASE,
WITH 3 TO 5 FT FORECAST BY FRIDAY.
CLIMATE
RECORD LOW MAXIMUM TEMPERATURES:
WEDNESDAY, JANUARY 22:
KCHS: 31/1970
KCXM: 31/1970
KSAV: 34/1970
THURSDAY, JANUARY 23:
KCHS: 34/1970
KCXM: 38/2016
KSAV: 40/2016
RECORD LOW TEMPERATURES:
THURSDAY, JANUARY 23:
KCHS: 19/1985
KCXM: 24/2003
KSAV: 19/1960
RECORD SNOWFALL:
TUESDAY, JANUARY 21:
KCHS: T/1984*
KSAV: 0.2/1910
WEDNESDAY, JANUARY 22:
KCHS: T/2022*
KSAV: T/2011*
* A TRACE IS NOT CONSIDERED A RECORD IN TERMS OF THE DAILY
CLIMATE. TRACE AMOUNTS SHOWN ABOVE ARE MORE FOR INFORMATION OF
WHEN THE LAST INSTANCE OF SNOW OCCURRED ON THE LISTED DATE.
CHS WATCHES/WARNINGS/ADVISORIES
GA...COLD WEATHER ADVISORY UNTIL 6 PM EST WEDNESDAY FOR GAZ087-088-
099>101-114>119-137>141.
WINTER STORM WARNING FROM 5 PM TUESDAY TO NOON EST WEDNESDAY
FOR GAZ087-088-099>101-114>119-137>141.
SC...COLD WEATHER ADVISORY UNTIL 6 PM EST WEDNESDAY FOR SCZ040-
042>045-047>052.
WINTER STORM WARNING FROM 5 PM TUESDAY TO NOON EST WEDNESDAY
FOR SCZ040-042>045-047>052.
MARINE...SMALL CRAFT ADVISORY FROM 1 PM TUESDAY TO 1 AM EST THURSDAY
FOR AMZ350.
SMALL CRAFT ADVISORY FROM 3 PM TUESDAY TO 1 AM EST THURSDAY
FOR AMZ352.
SMALL CRAFT ADVISORY FROM 9 AM TUESDAY TO 7 AM EST THURSDAY
FOR AMZ354.
SMALL CRAFT ADVISORY FROM 5 AM TUESDAY TO 1 AM EST SATURDAY
FOR AMZ374.
ST/CPM/BAH/CEB/TBA
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