307
FXUS62 KCHS 170539
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1239 AM EST FRI JAN 17 2025
SYNOPSIS
HIGH PRESSURE WILL PREVAIL THROUGH 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 THIS MORNING/
CLEAR SKY WITH LIGHT SW WINDS SHOULD CONTINUE ACROSS THE
FORECAST AREA TONIGHT. TEMPERATURES APPEAR ON PACE TO REACH THE
LOW 30S INLAND TO THE MID TO UPPER 30S ALONG THE COAST BEFORE
DAYBREAK FRIDAY MORNING.
SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY/
HIGH PRESSURE WILL GIVE WAY TO AN APPROACHING COLD FRONT
SATURDAY AS A SERIES OF NORTHERN STREAM SHORTWAVES PROPAGATE
ACROSS THE NORTHERN CONUS. RAIN CHANCES WILL INCREASE QUICKLY
SATURDAY AHEAD OF THE COLD FRONT AS BUILDING MOISTURE
CHARACTERIZED BY PWATS >1" COMBINE WITH FORCING GENERATED BY
PASSING SOUTHERN STREAM SHORTWAVE ENERGY AND THE LEFT EXIT
REGION OF A POWER 150 KT SUBTROPICAL JET. IT APPEARS MOST AREAS
WILL RECEIVE A SOLID 0.75-1.50" INCH OF RAIN WITH THIS SYSTEM
AND CATEGORICAL POPS 90-100% WERE MAINTAINED. FLOODING IS NOT
ANTICIPATED TO BE AN ISSUE. RAIN CHANCES WILL SLOWLY DIMINISHING
SATURDAY NIGHT INTO SUNDAY AS THE FRONT PUSHES OFFSHORE. HIGHS
EACH DAY WILL WARM INTO THE UPPER 50S/LOWER 60S AWAY FROM THE
COAST WITH OVERNIGHT LOWS DROPPING INTO THE MID-UPPER 30S FRIDAY
NIGHT WITH UPPER 40S/LOWER 50S SATURDAY NIGHT.
LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/
THERE REMAINS MUCH UNCERTAINTY THE SYSTEM THAT WILL IMPACT THE
REGION DURING THE MID-WEEK AS A COLD, ARCTIC AIRMASS SETTLES
OVER THE REGION. WHAT IS KNOWN IS THERE IS HIGH PROBABILITY FOR
TEMPERATURES TO AVERAGE WELL BELOW NORMAL LEVELS FOR MID-JANUARY
WITH HIGHS BOTH TUESDAY AND WEDNESDAY LIKELY REMAINING SOLIDLY
IN THE 30S WITH MINIMUM WIND CHILLS FALLING INTO THE 10-20
DEGREE RANGE AT NIGHT. THIS IS WELL WITHIN COLD WEATHER ADVISORY
CRITERIA (11-20 DEGREES). IN FACT, THERE ARE SIGNALS THAT SOME
LOCATIONS COULD SEE WIND CHILLS DROP BELOW 10 DEGREES WHICH IS
DIPPING INTO EXTREME COLD WARNING TERRITORY (10 DEGREES OR
COLDER).
WHAT IS MORE UNCERTAIN IS HOW THE PRECIPITATION PATTERN WILL
EVOLVE MONDAY NIGHT THROUGH WEDNESDAY MORNING WHEN TEMPERATURES
WILL BE AT THE COLDEST. MUCH WILL BE DEPENDENT ON HOW FAR SOUTH
AND OFFSHORE LOW PRESSURE TRACKS OFF THE SOUTHEAST U.S. COAST IN
RESPONSE TO AN IMPRESSIVE UPPER TROUGH PROPAGATING ACROSS THE
EASTERN CONUS. GIVEN THE AMOUNT OF COLD AIR IN PLACE, IT REMAINS
QUITE REASONABLE THAT VARYING DEGREES OF ACCUMULATING WINTER
WEATHER COULD OCCUR OVER SOUTHEAST SOUTH CAROLINA AND SOUTHEAST
GEORGIA WITH SPECIFICS ON P- TYPES, INTENSITY AND POSSIBLE
ACCUMULATIONS REMAINING HIGHLY UNCERTAIN THIS FAR OUT. WHILE A
FEW OF THE OPERATIONAL RUNS OF THE VARIOUS LONG-TERM GUIDANCE
HAVE TRENDED DRIER OVER THE PAST FEW CYCLES, MANY OF THEIR
ACCOMPANYING ENSEMBLE COUNTERPARTS REMAIN QUITE WET AND COLD.
ALL NUMBER OF OUTCOMES REMAIN PLAUSIBLE RANGING FROM LITTLE TO
NO PRECIPITATION TO A FULL BLOWN WINTER STORM WITH SIGNIFICANT
IMPACTS; HOWEVER, NET ACCUMULATING SNOW AND FREEZING RAIN
PROBABILITIES ARE CREEPING UP WITH EACH FORECAST CYCLE. THE
OFFICIAL FORECAST REMAINS FAIRLY STEADY STATE WITH SOME MINOR
UPWARD ADJUSTMENTS IN POPS, SHOWING VARIOUS DEGREES OF A MIX OF
SNOW, FREEZING RAIN AND RAIN IN THE MONDAY NIGHT TO WEDNESDAY
MORNING TIME FRAME. RIGHT NOW, SLEET LOOKS THE BE THE LEAST
LIKELY P-TYPE TO OCCUR.
MOST OF THE PRECIPITATION SHOULD END WEDNESDAY MORNING. THERE
ARE SIGNALS THAT A WEAK WAVE OF LOW PRESSURE COULD DEVELOP
OFFSHORE WEDNESDAY NIGHT INTO THURSDAY AND WITH TEMPERATURES
STILL COLD, SOME LINGERING POCKETS OF FREEZING RAIN COULD OCCUR.
AVIATION /06Z FRIDAY THROUGH TUESDAY/
VFR CONDITIONS WILL PREVAIL AT KCHS, KJZI, AND KSAV THROUGH 06Z
SATURDAY.
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 MONDAY NIGHT INTO WEDNESDAY MORNING AS A POTENTIAL
WINTER STORM IMPACTS THE REGION. THERE IS A CHANCE FOR FREEZING
OR FROZEN PRECIPITATION IMPACTING ALL TERMINALS DURING THIS
TIME.
MARINE
TONIGHT: WE MAINTAIN THE SMALL CRAFT ADVISORIES FOR THE SOUTH
CAROLINA ATLANTIC WATERS AND FOR THE OUTER GEORGIA WATERS UNTIL
LATE. WE CONSIDERED DROPPING THE ADVISORY ON THE LOWER SOUTH
CAROLINA WATERS SINCE CONDITIONS OF LATE HAVE BEEN BELOW
ADVISORY THRESHOLDS. HOWEVER, WITH SOME STRONGER GEOSTROPHIC
WINDS AND A LITTLE WEAK COLD ADVECTION, WINDS COULD STRENGTHEN
AGAIN. IN GENERAL THERE WILL BE W OR WSW WINDS UP NEAR 15 OR 20
KT AND GUSTY MOST OF THE NIGHT, TURNING MORE TOWARD THE WNW AND
DROPPING ABOUT 5 KT OR SO LATE IN WAKE OF A SURFACE TROUGH. SEAS
WILL BE 4 FEET OR LESS THROUGHOUT, EXCEPT FOR A FEW 5 FOOTERS
OVER PARTS OF THE DISTANT CHARLESTON COUNTY WATERS AND BEYOND
50 NM OFF THE GEORGIA COAST.
FRIDAY THROUGH TUESDAY: NORTHWEST WINDS WILL SURGE BEHIND A
COLD FRONT SUNDAY NIGHT WITH SPEEDS REACHING 15-25 KT WITH GUSTS
TO 30 KT. SMALL CRAFT ADVISORIES ARE LIKELY DURING SUNDAY NIGHT
INTO 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 4-6 FT OVER THE GEORGIA OFFSHORE WATERS OUT
20-60 NM. SOME WINTER PRECIPITATION COULD FALL OVER THE COASTAL
WATERS MONDAY NIGHT INTO TUESDAY.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST EARLY THIS MORNING FOR
AMZ350-352-374.
NEAR TERM...NED
SHORT TERM...
LONG TERM...
AVIATION...NED
MARINE...
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