355
FXUS62 KCHS 171504
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1004 AM 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 /THROUGH TONIGHT/
LATE THIS MORNING: A VERY TRANQUIL DAY IS ON TAP AS HIGH
PRESSURE SHIFTS ACROSS THE REGION THIS MORNING. THEN BY THE
AFTERNOON THE HIGH WILL BEGIN TO SLIP OFFSHORE, ALLOWING FOR
SOME SOUTHERLY RETURN FLOW ACROSS THE FORECAST AREA. WE WILL SEE
PLENTY OF SUN TODAY AND ANOTHER AFTERNOON WITH NEAR OR EVEN
POTENTIALLY SLIGHTLY ABOVE NORMAL TEMPERATURES. HIGHS ARE
FORECAST RIGHT AROUND 60 FOR SOUTHEAST SC AND THE LOW 60S FOR
SOUTHEAST GA. THERE COULD EVEN BE A FEW MID 60S ALONG AND SOUTH
OF I-16 FOR SOUTHEAST GA.
TONIGHT: NEAR TERM GUIDANCE INDICATES THAT A H5 SHORTWAVE WILL
RAPIDLY TRACK FROM THE GREAT PLAINS TO THE LOWER MISSISSIPPI
RIVER VALLEY OVERNIGHT. AT THE SFC, BROAD LOW PRESSURE IS
EXPECTED TO GRADUALLY ORGANIZE ACROSS THE DEEP SOUTH. AS THE LOW
TRACKS EAST, PW VALUES ACROSS THE FORECAST WILL STEADILY
INCREASE THROUGH THE NIGHT, REACHING AROUND 1 INCH BY DAYBREAK
SATURDAY. CONDITIONS SHOULD REMAIN DRY DURING THE EVENING. IN
FACT, IT APPEARS THAT THE COOLEST TEMPERATURES WILL OCCUR DURING
THE EVENING, THEN GRADUALLY WARM THROUGH THE REST OF THE NIGHT
AS CLOUD COVER THICKENS. LOW TEMPERATURES WILL GENERALLY RANGE
AROUND 40 DEGREES, WITH MID 40S ALONG THE COAST. ISOLATED TO
SCATTERED SHOWERS ARE FORECAST TO DEVELOP ACROSS THE FORECAST
HOURS DURING THE PRE-DAWN HOURS SATURDAY MORNING.
SHORT TERM /SATURDAY THROUGH MONDAY/
AS A DEEP UPPER-LEVEL TROUGH CENTERED OVER THE MIDDLE PORTION
OF CANADA DIGS IN FROM THE NORTHWEST, AN ASSOCIATED ARCTIC FRONT
WILL BEGIN TO APPROACH THE REGION FROM THE WEST. ALONG WITH
THIS, A RATHER MOIST AIRMASS WILL BE USHERED INTO THE REGION IN
SATURDAY MORNING WITH PWATS >1". THIS WILL ALLOW FOR A RAINY
SATURDAY MORNING AND AFTERNOON WITH MOST AREAS RECEIVING AROUND
0.50 TO 1.25 INCHES. POPS ARE ABOVE 80% FOR MOST OF THE MORNING
AND THEN START TO SLOWLY DIMINISH HEADING INTO SATURDAY NIGHT
AND SUNDAY MORNING AS THE FRONT PUSHES THROUGH SUNDAY AFTERNOON.
HIGHS WILL REACH INTO THE UPPER 50S/LOWER 60S ON SATURDAY AND
SUNDAY. LOWS ON SATURDAY NIGHT DROP INTO THE UPPER 40S TO LOW
50S, HOWEVER SUNDAY NIGHT LOWS DROP INTO THE MID 20S TO LOW 30S
WITH WIND CHILLS 15 TO 20 DEGREES. THIS IS WELL WITHIN COLD
WEATHER ADVISORY CRITERIA (11 TO 20 DEGREES) AND WILL LIKELY BE
ISSUED FOR SUNDAY NIGHT. HEADING INTO MONDAY, STRONG CAA
DOMINATES AND CONDITIONS WILL BECOME BREEZY. HIGHS WILL ONLY
REACH INTO THE MID 40S.
LONG TERM /MONDAY NIGHT THROUGH THURSDAY/
MONDAY NIGHT: WITH STRONG CAA IN PLACE, LOWS WILL DROP INTO THE
LOW TO MID 20S INLAND AND UPPER 20S TO LOW 30S ALONG THE
BEACHES. SOME WIND CHILL VALUES INLAND REACH DOWN TO 15 TO 20
DEGREES AND AGAIN THIS IS WELL WITHIN COLD WEATHER ADVISORY
CRITERIA AND WILL LIKELY BE ISSUED FOR MONDAY NIGHT.
TRANSITIONING TO TUESDAY AND BEYOND, THE FORECAST BECOMES
INCREASINGLY TRICKY AND POTENTIALLY IMPACTFUL. MUCH OF THE
FORECAST DEPENDS ON HOW FAR SOUTH AND OFFSHORE THE LOW PRESSURE
TRACKS OFF THE SOUTHEAST U.S. COASTLINE. THE 00Z GFS/ECMWF/CMC
DETERMINISTIC MODEL RUNS SUGGEST SNOW COULD BE THE MAIN P-TYPE
WITH THIS SYSTEM. POPS WERE INCREASED A BIT FOR TUESDAY AND
WEDNESDAY MORNING TO 40-60%. MOST OF THE MODELS ARE IN AGREEMENT
THAT MOST OF THE PRECIPITATION SHOULD END BY WEDNESDAY
AFTERNOON. HOWEVER, PLENTY OF UNCERTAINTY REMAINS REGARDING THE
AMOUNT OF ANY FROZEN/FREEZING PRECIPITATION WE MIGHT RECEIVE.
WELL BELOW NORMAL TEMPERATURES IS AN ASPECT THAT WE CAN SPEAK
ABOUT WITH HIGH CONFIDENCE, AND IT WILL BE VERY COLD. IN FACT,
THERE ARE SIGNALS THAT SOME LOCATIONS COULD SEE WIND CHILLS DROP
BELOW 10 DEGREES ON TUESDAY NIGHT AND WEDNESDAY NIGHT WHICH IS
DIPPING INTO EXTREME COLD WARNING TERRITORY (10 DEGREES OR
COLDER). WE COULD EVEN APPROACH RECORD LOW TEMPERATURES AT
KCHS/KCXM/KSAV ON THURSDAY.
AVIATION /15Z FRIDAY THROUGH TUESDAY/
VFR CONDITIONS WILL PREVAIL AT KCHS, KJZI, AND KSAV THROUGH 12Z
SATURDAY. LIGHT RAIN SHOWERS SHOULD DEVELOP OVER THE TERMINALS
DURING THE HOURS SATURDAY MORNING.
EXTENDED AVIATION OUTLOOK: FLIGHT RESTRICTIONS ARE LIKELY
SATURDAY 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 NIGHT AS A POTENTIAL
WINTER STORM IMPACTS THE REGION. THERE IS A CHANCE FOR FREEZING
OR FROZEN PRECIPITATION IMPACTING ALL TERMINALS DURING THIS TIME
PERIOD.
MARINE
HIGH PRESSURE WILL BUILD OVER THE MARINE ZONES THIS AFTERNOON,
THEN WILL GRADUALLY WEAKEN TONIGHT. THIS PATTERN WILL YIELD
CHANGING WIND DIRECTIONS, SPEEDS SHOULD REMAIN BETWEEN 5 TO 10
KTS. WAVE HEIGHTS ARE FORECAST TO REMAIN BETWEEN 1 TO 2 FT.
SATURDAY THROUGH WEDNESDAY: SOUTHERLY/SOUTHWESTERLY WINDS BEGIN TO
INCREASE AHEAD OF THE APPROACHING COLD FRONT TO 10 TO 15 KT ON
SATURDAY. BEHIND THE COLD FRONT, WINDS BECOME NORTHWESTERLY AND PICK
UP TO 20 TO 25 KT WITH GUSTS UP TO 30 KT. SMALL CRAFT ADVISORIES
APPEAR LIKELY FOR SUNDAY NIGHT THROUGH MONDAY MORNING. SEAS WILL
PEAK 3-5 FT OVER THE NEARSHORE WATERS OUT 20 NM AND 4-6 FT OVER THE
GEORGIA OFFSHORE WATERS OUT 20-60 NM. ANOTHER SURGE WILL OCCUR
MONDAY NIGHT INTO TUESDAY AS THE PRESSURE GRADIENT TIGHTENS BETWEEN
INLAND HIGH PRESSURE AND A DEVELOPING LOW OFFSHORE. NORTH TO
NORTHEAST WINDS 20-25 KT WITH GUSTS TO 30 KT WILL OCCUR DURING THIS
TIME WITH SEAS 2-4 FT WITHIN 20 NM AND 5-8 FT OVER THE GEORGIA
OFFSHORE WATERS OUT 20-60 NM. SMALL CRAFT ADVISORIES APPEAR LIKELY
AGAIN FOR MONDAY NIGHT THROUGH WEDNESDAY AFTERNOON FOR ALL MARINE
ZONES EXCEPT FOR THE OUTER GEORGIA WATERS WHICH WILL PROBABLY NEED A
GALE WARNING. SOME WINTER PRECIPITATION COULD FALL OVER THE COASTAL
WATERS MONDAY NIGHT INTO TUESDAY.
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...BSH/NED
SHORT TERM...DENNIS
LONG TERM...DENNIS
AVIATION...DENNIS/NED
MARINE...DENNIS/NED
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