692
FXUS62 KCHS 180003
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
703 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/
WE DID NEED TO ADJUST SOME TEMPERATURES IN THE FRANCIS MARION TO
COLDER VALUES, BOTH HOURLY AND FOR MINIMUM TEMPERATURES BASED
ON LATEST TRENDS. WITH THESE AREAS TO HAVE THE MOST TIME TO
RADIATE, WE NOW HAVE IT AS COLD AS 37F IN THOSE AREAS, AND WILL
WATCH LATER TRENDS TO SEE IF IT CAN GET EVEN COLDER. OVERALL
THOUGH, WITH INCREASING CLOUDS AND HIGHER DEW POINTS, LOWS
TONIGHT WILL BE MUCH WARMER THAN LAST NIGHT. SATELLITE IMAGERY
CONTINUES TO SHOW SOME FIRES ONGOING IN AND NEAR THE FORECAST
AREA. VISIBILITY HAS BEEN REPORTED DOWN TO 3 1/2 MILES AT KMHP,
AND KSAV HAS SHOWN SMOKE IN ITS OBSERVATION FOR A FEW 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 NO 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.
TONIGHT: MUCH OF THE OVERNIGHT PERIOD WILL BE QUIET AS HIGH
PRESSURE SHIFTS OFFSHORE AND AN AREA OF LOW PRESSURE ORGANIZES
TO THE WEST. FOR THE FIRST PART OF THE OVERNIGHT, CIRRUS WILL
STEADILY INCREASE IN COVERAGE FROM THE WEST. THEN BY SUNRISE
SATURDAY MODEL GUIDANCE IS IN GOOD AGREEMENT THAT THE POTENTIAL
FOR SHOWERS ASSOCIATED WITH THE AFOREMENTIONED SYSTEM WILL
INCREASE FROM THE WEST AS WELL AS FROM OFFSHORE. IN FACT, THE
BEST RAIN CHANCES FOR LATE TONIGHT WILL LIKELY RESIDE ALONG THE
COAST AND WE CONTINUE TO ADVERTISE A 20 PERCENT CHANCE.
TEMPERATURES WILL LIKELY COOL OFF QUICKLY THIS EVENING BEFORE
CLOUD COVER THICKENS ENOUGH TO IMPEDE RADIATIONAL COOLING
CONDITIONS. TEMPERATURES COULD THEN HOLD STEADY OR EVEN RISE
RIGHT AROUND DAYBREAK. REGARDLESS OF THE HOURLY TREND, LOWS ARE
FORECAST TO FALL INTO THE LOW 40S EVERYWHERE, WITH UPPER 30S FOR
INTERIOR SOUTHEAST SC WHERE CLOUDS WILL ARRIVE LAST.
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 /00Z 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. SHOWERS 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
TONIGHT: THE PREVAILING FLOW WILL BE SOUTHEASTERLY TO SOUTHERLY
AND MOSTLY LIGHT, WITH SPEEDS IN THE 5-10 KNOT RANGE. SEAS WILL
ALSO BE MINIMAL, GENERALLY 1-2 FEET ACROSS THE LOCAL WATERS.
SHOWERS ARE EXPECTED TO DEVELOP LATE TONIGHT ACROSS THE WATERS
AND PROGRESS TOWARDS THE COAST CLOSER TO DAYBREAK.
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...
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page