199
FXUS62 KCHS 242340
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
640 PM EST SAT JAN 24 2026
WHAT HAS CHANGED
24/23Z TEMPERATURES WERE RUNNING A BIT COOLER THAN EXPECTED AS
THE CAD WEDGE BECOMES MORE FIRMLY ESTABLISHED AND DIABATIC
PROCESSES INITIATE WITH THE ONSET OF ISENTROPICALLY INDUCED
SHOWERS. HOURLY TEMPERATURES WERE NUDGED DOWN A BIT BASED ON THE
CURRENT TRENDS AND MATCH PRETTY CLOSE WITH A BLEND OF THE NAM12,
RAP AND NBM25. THIS BRINGS FREEZING TEMPERATURES IN A BIT
QUICKER BY A FEW HOURS ACROSS PARTS OF NORTHERN/EASTERN
BERKELEY COUNTY WITH FREEZING TEMPERATURES EXPANDING WEST INTO
FAR INTERIOR AREAS AS DAYBREAK APPROACHES. THE INITIAL BATCH OF
ISENTROPIC SHOWERS ACROSS COASTAL GEORGIA WILL MOVE NORTH INTO
THE LOWCOUNTRY OVER THE NEXT FEW HOURS WITH ADDITIONAL ACTIVITY
DEVELOPING OVER THE ATLANTIC AND STREAMING INTO THE CHARLESTON
TRI-COUNTY OVERNIGHT. THE MAIN PRECIP AREA OVER THE DEEP SOUTH
WILL LIKELY ONLY BRUSH FAR INTERIOR AREAS PRIOR TO DAYBREAK.
GIVEN THE ABOVE TRENDS, THE RISK MINOR IMPACTS FROM FREEZING
RAIN OR FREEZING DRIZZLE STILL LOOK CENTERED IN THE CURRENT
WINTER WEATHER ADVISORY AREA, BUT ICE ACCUMS WERE NUDGED UP
SLIGHTLY IN NORTHERN AND EASTERN PARTS OF BERKELEY COUNTY WHERE
THE LONGEST JUXTAPOSITION OF PRECIP WITH FREEZING RAIN WILL
OCCUR THROUGH DAYBREAK.
KEY MESSAGES
- 1) WIDESPREAD PRECIPITATION IS EXPECTED TONIGHT THROUGH SUNDAY
NIGHT, WITH FREEZING RAIN POSSIBLE TONIGHT INTO SUNDAY MORNING
ACROSS INLAND PORTIONS OF THE SC LOWCOUNTRY AND SE GA.
- 2) ARCTIC AIR WILL YIELD VERY COLD TEMPERATURES MONDAY NIGHT
INTO NEXT WEEKEND, WITH COLD WEATHER ADVISORIES POSSIBLE.
DISCUSSION
KEY MESSAGE 1: WIDESPREAD PRECIPITATION IS EXPECTED TONIGHT
THROUGH SUNDAY NIGHT, WITH FREEZING RAIN POSSIBLE TONIGHT INTO
SUNDAY MORNING ACROSS INLAND PORTIONS OF THE SC LOWCOUNTRY AND
SE GA.
INFRARED SATELLITE TODAY IS VERY INTERESTING, SHOWING THE ARCTIC
SURGING SOUTHWARD FROM CENTRAL CANADA OVER THE U.S., SPANNING THE
AREA FROM THE GREAT PLAINS TO NEW ENGLAND. BY THIS AFTERNOON, THE
CENTER OF THE 1040 MB HIGH WILL SLIDE OVER NEW ENGLAND, RIDGING
SOUTH ALONG THE EAST FACING SLOPES OF THE APPALACHIANS. COLD AIR
DAMMING (CAD) WILL CONTINUE TO BUILD THROUGH TONIGHT, RAPIDLY
COOLING TEMPERATURES AND DEEPENING THE CAD ACROSS THE FORECAST AREA
THIS EVENING. NEAR-TERM GUIDANCE INDICATES THAT A SFC LOW WILL
ORGANIZE AND DEVELOP OVER THE GULF STREAM THIS EVENING AS H5
LONGWAVE TROUGH APPROACHES FROM THE WEST. ONCE THE LOW DEVELOPS, IT
IS EXPECTED TO TRACK NORTHEAST OFF THE SC COAST TONIGHT.
AS THE LOW PASSES OFF THE COAST, ISENTROPIC LIFT WILL INCREASE
ACROSS THE FORECAST AREA, ESPECIALLY ALONG AND WEST OF THE I-95
CORRIDOR. NAM12 SHOWS ISENTROPIC LIFT INCREASING BETWEEN 285-295K
THIS AFTERNOON, GENERALLY REMAINING INTO THE DAYLIGHT HOURS SUNDAY
MORNING. FORECAST SOUNDINGS INDICATED SATURATED CONDITIONS BELOW H7,
ESPECIALLY BELOW A STRONG WARM NOSE CENTERED AT H9. THE COMBINATION
OF THE PW IN EXCESS OF AN INCH WITH ROUNDS OF ISENTROPIC LIFT SHOULD
YIELD ROUNDS OF DRIZZLE OR LIGHT PRECIP WITHIN THE WEDGED AIR MASS.
THE FALLING PRECIP SHOULD LEAD TO SOME DEGREE OF DIABATIC COOLING AS
TEMPERATURE APPROACH THE WET BULB. IN ADDITION, STEADY NNE WINDS WILL
ADVECT COOLER TEMPERATURES ACROSS THE SC LOWCOUNTRY AND SE GA
TONIGHT. HIGH RESOLUTION GUIDANCE INDICATES THAT THE FREEZING LINE
WILL PUSH OVER THE INTERIOR COUNTIES, JENKINS COUNTY NORTH TO
BERKELEY COUNTY, BY DAYBREAK SUNDAY. THIS CORRIDOR OF COUNTIES IS
EXPECTED TO SEE AN OVERLAP OF LIGHT PRECIP WITH SUB-FREEZING
TEMPERATURES, RESULTING IN ROUNDS OF FREEZING RAIN OR FREEZING
DRIZZLE. GUIDANCE AS TRENDED A BIT DRIER, BUT AT LEAST A LIGHT GLAZE
TO A FEW HUNDREDTHS OF AN INCH OF ICE IS POSSIBLE BY EARLY SUNDAY
MORNING. A WINTER WEATHER ADVISORY WILL REMAIN FOR A TIER OF
COUNTIES FROM JENKINS COUNTY EAST TO BERKELEY COUNTY FROM 7 PM THIS
EVENING UNTIL 1 PM SUNDAY.
GUIDANCE CONTINUES TO INDICATE A STRONG COLD FRONT APPROACHING THE
CWA FROM THE WEST ON SUNDAY, TIMED TO REACH THE INLAND COUNTIES
DURING THE EARLY EVENING AND THE COAST BY MIDNIGHT. HIGH RESOLUTION
GUIDANCE SHOWS A SOLID BAND OF SHOWERS WITH EMBEDDED THUNDERSTORMS
REMAIN ALONG AND AHEAD OF THE COLD FRONT. FORECAST SOUNDINGS
INDICATE THAT WEAK INSTABILITY MAY DEVELOP AHEAD OF THE LINE,
RESULTING IN 100-200 J/KG OF CAPE ACROSS PORTIONS OF SE GA. HOWEVER,
WIND SHEAR REMAINS VERY STRONG, FEATURING 0-1 KM SRH IN EXCESS 250
M2/S2 AND BULK SHEAR AROUND 50 KTS. 12Z HREF INDICATES STP VALUES
APPROACHING ONE UNIT ACROSS EXTREME SE GA. IT IS POSSIBLE THAT A
SEVERE THUNDERSTORM OR TWO COULD REACH SE GA SUNDAY EVENING, SOME
POSSIBLY FEATURE QLCS STRUCTURE WITH ROTATING UPDRAFTS. ELSEWHERE,
STRONG THUNDERSTORMS REMAIN POSSIBLE, WITH WIND GUSTS AS THE PRIMARY
THREAT. COLD AIR WILL FOLLOW THE COLD FRONT, HOWEVER ALL MOISTURE IS
EXPECTED TO BE OFFSHORE BY THE TIME THE COLD AIR ARRIVES.
KEY MESSAGE 2: ARCTIC AIR WILL YIELD VERY COLD TEMPERATURES MONDAY NIGHT
INTO NEXT WEEKEND, WITH COLD WEATHER ADVISORIES POSSIBLE.
AS A STRONG ARCTIC HIGH PRESSURE USHERS COLD, DRY AIR INTO THE
REGION BEHIND A COLD FRONT ON MONDAY NIGHT/TUESDAY MORNING, TEMPS.
ARE FORECAST TO DROP INTO THE TEENS AND LOW 20S WEST OF I-95 AND
ACROSS MUCH OF THE FRANCIS MARION FORECAST. IT'LL BE A TAD WARMER
NEAR THE COASTLINE WITH TEMPS. RANGING IN THE LOW TO MID 20S. MIXED
THE NAM12/NBM10 INTO THE OVERNIGHT TEMPERATURES AS THE NBM APPEARED
TO BE STRUGGLING TO REALIZE THE PRESENCE OF THE COLD-AIR DAMMING
(CAD) ACROSS THE REGION. THESE CONDITIONS COMBINED WITH LIGHT WEST-
NORTHWESTERLY WINDS COULD RESULT IN WIDESPREAD WIND CHILL VALUES IN
THE MID TO UPPER TEENS FROM INTERIOR COUNTIES ALL THE WAY DOWN TO
THE COASTLINE. SOME GUIDANCE HAS BEEN INDICATING THAT MINIMUM WIND
CHILL VALUES COULD DROP RANGE AROUND 10 DEGREES ACROSS PORTIONS OF
INLAND SE GA. A COLD WEATHER ADVISORY SHOULD EVENTUALLY BE NEEDED
FOR THE ENTIRE AREA ACROSS SOUTHEAST SOUTH CAROLINA AND SOUTHEAST
GEORGIA. FORECAST REMAINS A BIT WARMER ON TUESDAY NIGHT/WEDNESDAY
MORNING AS TEMPS. RANGE IN THE LOW TO MID 20S ACROSS THE INTERIOR
COUNTIES WITH LOW 30S ALONG THE COASTLINE. THUS, CONFIDENCE WITH
NEEDING A COLD WEATHER ADVISORY SEEM LESS LIKELY FOR THIS TIME
PERIOD WITH PROBABILITIES FOR TEMPS. LESS THAN 20 DEGREES RANGE FROM
20-40%. IT'S IMPORTANT TO NOTE THAT MODEL CONFIDENCE CONTINUES TO BE
FAIRLY HIGH AS THE IQR SHOWS A 1 TO 2 DEGREE SPREAD FOR LOWS TUESDAY
AND WEDNESDAY MORNING.
THIS COLD AIRMASS WILL LIKELY STICK AROUND THROUGH LATE THIS WEEK AS
A REINFORCING COLD FRONT MOVES THROUGH ON THURSDAY AND PUSHES
ANOTHER SHOT OF COLD AIR INTO THE REGION FROM THE NORTHWEST. IT'S
REASONABLE TO SAY THAT WE COULD HAVE A FEW HOURS OF WIND CHILL
VALUES BELOW 20 EVERY MORNING INTO THE WEEKEND AND ADDITIONAL COLD
WEATHER ADVISORIES MIGHT BE NEEDED.
AVIATION /00Z SUNDAY THROUGH THURSDAY/
25/00Z TAF DISCUSSION:
KCHS/KJZI/KSAV: MVFR CIGS WILL GIVE WAY TO IFR CIGS OVERNIGHT AS
OVER-RRUNNING ATOP THE WEDGE INTENSIFIES. POCKETS OF LIGHT RAIN
WILL LIKELY MEANDER AROUND THE TERMINALS THROUGH THE NIGHT, BUT
NO MEANINGFUL IMPACTS ARE EXPECTED. VCSH WAS HIGHLIGHTED TO
ACCOUNT FOR THIS. ANY RISK FOR FZRA/FZDZ WILL REMAIN WELL TO THE
NORTH AND WEST OF THE TERMINALS. GUSTY WINDS WILL LINGER
THROUGH EARLY MORNING, THEN BEGIN TO DIMINISH A BIT AS THE
COASTAL FRONT OFFSHORE DRAWS CLOSER TO THE COAST. CIGS MAY LIFT
TO MVFR AT KSAV BY EARLY/MID-AFTERNOON SUNDAY, BUT CONFIDENCE ON
TIMING IS POOR GIVEN MODELS ARE NOTORIOUSLY FAST IN ERODING
COLD AIR DAMMING.
EXTENDED AVIATION FORECAST: EXPECT A COLD FRONT TO MOVE ACROSS THE
REGION SUNDAY NIGHT AND YIELD VFR CONDITIONS THROUGH EARLY NEXT WEEK.
MARINE
THROUGH TONIGHT: AS IS TYPICALLY THE CASE IN STRONG CAD EVENTS,
THE MODELS HAVE UNDERPLAYED THE STRENGTH OF THE PINCHED
GRADIENT ALONG THE COAST. WINDS ARE SOLIDLY NEAR GALES WITH
GUSTS APPROACHING STORM FORCE AT TIMES IN THE EASTERN PORTIONS
OF THE SOUTH SANTEE-EDISTO BEACH NEARSHORE LEG. WINDS SHOULD
PEAK OVER THE NEXT FEW HOURS, ONLY TO SLOWLY WEAKEN OVERNIGHT AS
THE COASTAL FRONT OFFSHORE TRIES TO MEANDER CLOSER TO THE
COAST. HOWEVER, MODELS ARE LIKELY BRINGING WINDS DOWN TOO
QUICKLY GIVEN THEIR BIAS TO ERODING THE CAD TOO QUICKLY. A GALE
WARNING CONTINUES FOR ALL WATERS EXCEPT THE CHARLESTON HARBOR
WHERE A SMALL CRAFT ADVISORY CONTINUES.
SUNDAY THROUGH WEDNESDAY: AS A STRONG COLD FRONT APPROACHES THE
REGION FROM A LOW PRESSURE SYSTEM MOVING ACROSS THE SOUTHEAST,
HAZARDOUS MARINE CONDITIONS CONTINUE TO PERSIST THROUGH EARLY NEXT
WEEK. NORTHEASTERLY FLOW WILL VEER OUT OF THE SOUTH SUNDAY AFTERNOON
WITH WIND SPEEDS OF 20 TO 25 KT WITH GUSTS UP TO 30 KT POSSIBLE.
SEAS REMAIN A BIT CHAOTIC WITH WAVE HEIGHTS 6+ FT ON SUNDAY AND
MONDAY, AND THEN EXPECT THE SWELL TO RETREAT ON MONDAY NIGHT AND
SEAS TO SLOWLY DIMINISH. SMALL CRAFT ADVISORIES REMAIN IN EFFECT
UNTIL TUESDAY MORNING GIVEN THE ELEVATED WINDS AND SEAS.
EQUIPMENT
THE KCLX RADAR WILL REMAIN OUT OF SERVICE. CRITICAL PARTS ARE ON
ORDER AND SHOULD ARRIVE ON MONDAY. USERS SHOULD USE ADJACENT WSR-88D
SITES, INCLUDING KCAE, KLTX, KJAX, KVAX AND KJGX.
CHS WATCHES/WARNINGS/ADVISORIES
GA...WINTER WEATHER ADVISORY UNTIL 1 PM EST SUNDAY FOR GAZ087-088.
SC...WINTER WEATHER ADVISORY UNTIL 1 PM EST SUNDAY FOR SCZ040-
042>045.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EST SUNDAY FOR AMZ330.
GALE WARNING UNTIL 1 AM EST SUNDAY FOR AMZ350-352-354-374.
ST
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