668
FXUS62 KCHS 180338
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1038 PM EST FRI JAN 17 2025
SYNOPSIS
HIGH PRESSURE WILL PREVAIL THROUGH THE REST OF THE WEEK. AN
AREA OF LOW PRESSURE AND ASSOCIATED COLD FRONT WILL IMPACT THE
REGION THIS WEEKEND. ANOTHER LOW PRESSURE SYSTEM COULD IMPACT
THE REGION EARLY TO MID NEXT WEEK.
NEAR TERM /UNTIL 6 AM SATURDAY MORNING/
JUST LIKE THE PAST FEW NIGHTS, TEMPERATURES ARE THE BIGGEST
CHALLENGE OVERNIGHT. LATE FRIDAY TEMPERATURES RANGED FROM 33F
NEAR HUGER TO 51F ON TYBEE ISLAND. TEMPERATURES WILL COOL A BIT
MORE EARLY TONIGHT, BEFORE CLOUD COVER THICKENS FROM THE WEST IN
ADVANCE OF A 175+ KT UPPER JET MOVING THROUGH THE DEEP SOUTH,
AND SOME MID LEVEL ENERGY OUT AHEAD OF IT. ACTUAL LOWS WILL
OCCUR EARLY TONIGHT IN THE UPPER 30S AND LOWER 40S MOST PLACES,
EXCEPT FOR SOME LOWER AND MIDDLE 30S IN BERKELEY COUNTY AN
PARTS OF NORTHERN CHARLESTON AND NORTHERN DORCHESTER. A FEW
PLACES CLOSER TO THE OCEAN WILL ONLY DROP TO THE MID 40S.
IT'LL TAKE SOME TIME FOR THE LOWER LEVELS TO MOISTEN UP, SO WE
FEEL THAT ANY RAINFALL WILL STAY OFFSHORE NEAR A COASTAL TROUGH
AND UPSTREAM TO THE WEST IN ADVANCE OF BETTER DYNAMICS.
VISIBILITY EARLY FRIDAY EVENING WAS REPORTED DOWN TO 1 1/4
MILES AT KMHP, AND KSAV HAS SHOWN SMOKE IN ITS OBSERVATION FOR
SEVERAL HOURS (BUT WITH NO REDUCTION IN VISIBILITY). THE HRRR
AND RAP DO HAVE SMOKE PERSISTING TO SOME DEGREE OVERNIGHT, BUT
DOES NOT SHOW ANY REDUCTIONS IN VISIBILITY. FOR NOW WE PREFER
NOT TO INCLUDE SMOKE IN THE FORECAST, BUT BE ADVISED THAT A FEW
PLACES STILL MIGHT HAVE MINOR REDUCTIONS IN VISIBILITY DUE TO
SMOKE FROM THE FIRES.
SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/
SATURDAY AND SUNDAY: SATURDAY WILL BE A WET DAY ACROSS
SOUTHEAST SOUTH CAROLINA AND SOUTHEAST GEORGIA AHEAD OF COLD
FRONT. MODEL VERTICAL CROSS SECTIONS SHOW STRONG FORCING INDUCED
BY A SERIES OF EMBEDDED SOUTHERN STREAM SHORTWAVES PASSING
THROUGH JUXTAPOSED WITH DEEP MOISTURE WITH MEAN RH VALUES >90%
THROUGHOUT THE COLUMN. THIS SHOULD RESULT IN A LARGE AREA OF
LIGHT TO MODERATE RAIN MOVING STEADILY EAST ACROSS THE DEEP
SOUTH, WHICH IS ON TARGET TO PUSH WEST- EAST ACROSS THE LOCAL
AREA DURING THE DAY SATURDAY. HREF POPS FOR QPF >0.01" REMAIN
NEAR 100% AND THE FORECAST WILL CONTINUE TO REFLECT CATEGORICAL
POPS WITH THE HIGHEST POPS FOCUSED ON THE MORNING HOURS.
ELEVATED RAIN CHANCES WILL PERSIST INTO SATURDAY NIGHT INTO
SUNDAY AS ANTHER SURGE OF SHORTWAVE ENERGY PASSES THROUGH AHEAD
OF THE ARCTIC COLD FRONT. A DRIER TREND SHOULD OCCUR SUNDAY
AFTERNOON AS THE FRONT PUSHES OFFSHORE AND COLDER, DRIER AIR
BEGINS TO ADVECT INTO THE REGION. HIGH WILL WARM INTO THE 58-65
DEGREE RANGE SATURDAY (WARMEST SOUTH OF I-16) WITH LOWER-MID 60S
SUNDAY BEFORE FROPA. LOWS SUNDAY MORNING WILL DROP INTO THE
UPPER 40S/LOWER 50S. IT WILL BEGIN TO GET A BIT BREEZY MID-LATE
AFTERNOON SUNDAY WITH THE ONSET OF POST-FRONTAL COLD AIR
ADVECTION.
SUNDAY NIGHT AND MONDAY: BOTH PERIODS LOOK TO REMAIN DRY AS
ARCTIC HIGH PRESSURE BUILDS INTO THE REGION. HIGHS WILL ONLY
REACH THE LOWER 40S FOR MANY AREAS MONDAY AFTERNOON WITH LOWS
SUNDAY NIGHT DROPPING INTO THE MID 20S INLAND TO UPPER 20S
CLOSER TO COAST. ENHANCED NORTHWEST WINDS WILL HELP PUSH WIND
CHILLS INTO THE 15-20 DEGREE RANGE, WHICH IS SOLIDLY IN COLD
WEATHER ADVISORY CRITERIA.
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 /MONDAY NIGHT THROUGH FRIDAY/
THE FORECAST IS STARTING TO NARROW IN ON A WETTER AND COLDER
SOLUTION FOR THE UPCOMING MID-WEEK WINTER EVENT AS ARCTIC HIGH
PRESSURE SETTLES IN. ALL OF THE OPERATIONAL RUNS OF THE GFS, EC
AND CMC ARE STARTING TO ALIGN WITH SUPPORT FROM MANY OF THEIR
ACCOMPANYING ENSEMBLE MEMBERS. THIS COUPLED WITH TRENDS NOTED IN
THE NBM IS FINALLY ALLOWING FOR SOME INCREASED CONFIDENCE IN
HOW THE EVENT WILL UNFOLD AS LOW PRESSURE PASSES BY TO THE SOUTH
AND OFFSHORE. THERE REMAINS SOME UNCERTAINTY ON HOW THE P-TYPES
WILL EVOLVE AS THE EVENT PROGRESSES, BUT IT IS BECOMING
INCREASINGLY FAVORABLE FOR A SNOW/FREEZING RAIN EVENT WHICH
COULD BRING IMPACTS, POSSIBLY SIGNIFICANT, TO SOUTHEAST SOUTH
CAROLINA AND SOUTHEAST GEORGIA. COMPLICATING MATTERS IS THERE
ARE SIGNALS THAT ENHANCED FORCING INDUCED BY BANDS OF MID-LEVEL
FRONTOGENESIS COULD YIELD CORRIDORS OF ENHANCED PRECIPITATION
RATES, WHICH COULD RESULT IN POCKETS OF MODERATE TO LOCALLY
HEAVY PRECIPITATION. HOW MUCH OF THIS ENHANCEMENT WILL OCCUR IS
YET TO BE DETERMINED AND CAN NOT BE READILY IDENTIFIED THIS FAR
OUT. THIS IS CERTAINLY SOMETHING TO WATCH AS THESE BANDS COULD
AUGMENT BOTH P-TYPES, PRECIPITATION RATES AND ACCUMULATIONS. IT
IS STILL TOO FAR OUT TO IDENTITY ANY SPECIFIC SNOW/ICE
ACCUMULATIONS AND IMPACTS THIS FAR OUT, BUT THE PROBABILITIES
FOR BOTH ACCUMULATING SNOW AND ICE ARE INCREASING AND THE
FORECAST WILL REFLECT THIS TREND. TIMING FOR THE PERIOD OF
GREATEST IMPACTS LOOKS TO CENTER ON THE TUESDAY AFTERNOON TO
EARLY WEDNESDAY PERIOD WHEN THE COLDEST AIR WILL ALIGN WITH THE
STRONGEST FORCING AND HEAVIEST PRECIPITATION. SOME LIGHT
PRECIPITATION COULD REACH PARTS OF THE GEORGIA COAST BEFORE
DAYBREAK MONDAY WITH PRECIPITATION ENDING WEDNESDAY MORNING.
IN ADDITION TO WINTER WEATHER, BITTERLY COLD TEMPERATURES WILL
OCCUR. TEMPERATURES ARE TRENDING COLDER WITH HIGHS MID-WEEK
POISED TO STAY IN THE 30S BOTH TUESDAY AND WEDNESDAY AFTERNOONS.
LOWS TUESDAY NIGHT WILL DROP INTO THE LOWER-MID 20S WITH UPPER
TEENS/LOWER 20S WEDNESDAY NIGHT. WIND CHILLS WILL DROP 15-20
MONDAY NIGHT, 8-15 TUESDAY NIGHT AND JUST A TAD WARMER FOR
WEDNESDAY NIGHT. A COLD WEATHER ADVISORY WILL LIKELY BE NEEDED
DURING THIS TIME AND THERE IS EVEN A CHANCE FOR SOME AREAS TO
REACH EXTREME COLD WARNING CRITERIA (10 OR COLDER), ESPECIALLY
TUESDAY AND WEDNESDAY NIGHTS.
ANOTHER AREA OF LOW PRESSURE COULD DEVELOP OFF THE SOUTH
CAROLINA COAST THURSDAY INTO FRIDAY. WITH TEMPERATURES STILL
QUITE COLD, A BRIEF PERIOD OF FREEZING RAIN COULD OCCUR, MAINLY
THURSDAY MORNING AND AGAIN EARLY FRIDAY MORNING WITH THE BEST
CHANCES ACROSS THE INTERIOR.
AVIATION /03Z SATURDAY THROUGH WEDNESDAY/
KCHS/KJZI/KSAV: VFR WILL PREVAIL AT ALL SITES TONIGHT, ALTHOUGH
THERE COULD BE A LITTLE SMOKE AT TIME IMPACTING KSAV DUE TO
NEARBY WILDFIRES/BRUSHFIRES. AT THE MOMENT NO VISIBILITY
RESTRICTIONS HAVE BEEN INCLUDED IN THE LATEST FORECAST. LIGHT
TO MODERATE RAINS WILL DEVELOP IN ADVANCE OF ENERGY ALOFT ON
SATURDAY, MOST NUMEROUS DURING THE LATE MORNING THROUGH MID
AFTERNOON (15Z-21Z). THESE WILL BE ACCOMPANIED BY LOWERING
CEILINGS, AND PERHAPS BRIEF MVFR VISIBILITIES. BUT THE BETTER
CHANCES FOR MVFR OR IFR CONDITIONS WILL OCCUR LATE SATURDAY WHEN
THE ATMOSPHERE BECOMES FULLY SATURATED.
EXTENDED AVIATION OUTLOOK: FLIGHT RESTRICTIONS ARE LIKELY
SATURDAY EVENING 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
OVERNIGHT: A WEAK PRESSURE PATTERN WILL EXIST BETWEEN A SUBTLE
INVERTED TROUGH NEARBY, AND A FRONTAL SYSTEM STRETCHING FROM
HUDSON BAY IN CANADA, THROUGH THE GREAT LAKES, CONTINUING TO
TEXAS AND PARTS OF THE GULF COAST STATES. THIS WILL RESULT IN
WINDS THAT ARE VARIABLE IN DIRECTION AT 5 OR 10 KT, WITH LIMITED
SEAS OF JUST 1 OR 2 FEET. SHOWERS ARE EXPECTED TO DEVELOP AS WE
DRAW CLOSER TO DAYBREAK ACROSS THE LOCAL WATERS.
SATURDAY THROUGH WEDNESDAY: GUSTY SOUTHWEST WINDS WILL PREVAIL
SATURDAY INTO SUNDAY AHEAD OF A COLD FRONT. GUSTS WILL BE CLOSE
TO SMALL CRAFT ADVISORY CRITERIA A TIMES. ADVISORY CONDITIONS
ARE MORE LIKELY SUNDAY NIGHT AS STRONG COLD AIR ADVECTION
SPREADS OVER THE WATERS BEHIND A COLD FRONT. STRONGER WINDS ARE
EXPECTED TUESDAY INTO WEDNESDAY AS THE PRESSURE GRADIENT
TIGHTENS BETWEEN INLAND HIGH PRESSURE AND LOW PRESSURE PASSING
WELL OFFSHORE. NORTHERLY WINDS COULD REACH AS HIGH AS 25-30 KT
AT TIMES WITH PERIODS OF GALE FORCE GUSTS. SMALL CRAFT
ADVISORIES ARE LIKELY WITH A POSSIBILITY FOR A GALE
WATCH/WARNING. SEAS LOOK TO PEAK EARLY WEDNESDAY MORNING, 5-8 FT
NEARSHORE WATERS OUT 20 NM AND 9-14 FT OVER THE GEORGIA
OFFSHORE WATERS OUT 20-60 NM. FINALLY, MARINERS SHOULD BE ALERT
THAT SOME WINTER PRECIPITATION COULD FALL OVER THE COASTAL
WATERS MONDAY NIGHT INTO WEDNESDAY MORNING, REDUCING VSBY 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.
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
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