582
FXUS62 KCHS 201809
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
109 PM EST TUE JAN 20 2026
WHAT HAS CHANGED
THE AVIATION SECTION HAS BEEN UPDATED FOR THE 18Z TAF ISSUANCE.
COLD TEMPERATURES FOR WEDNESDAY MORNING CONTINUE TO BE
ADDRESSED IN KEY MESSAGE 1. THE POTENTIAL FOR A WINTER WEATHER
EVENT REMAINS ADDRESSED IN KEY MESSAGE 2. ADDED KEY MESSAGE 3 TO
ADDRESS THE COLD WEATHER EARLY NEXT WEEK.
KEY MESSAGES
- 1) COLD TEMPERATURES IN THE MID TO UPPER 20S ACROSS INLAND
AREAS WEDNESDAY MORNING.
- 2) WIDESPREAD PRECIPITATION IS EXPECTED TO OCCUR THIS
WEEKEND, BRINGING INCREASING POTENTIAL FOR A MULTI-DAY WINTER
WEATHER EVENT ACROSS PORTIONS OF THE REGION.
- 3) VERY COLD TEMPERATURES WILL OCCUR EARLY NEXT WEEK.
DISCUSSION
KEY MESSAGE 1: COLD TEMPERATURES IN THE MID TO UPPER 20S ACROSS
INLAND AREAS WEDNESDAY MORNING.
DRY HIGH PRESSURE WILL MOVE FROM THE CENTRAL APPALACHIANS TO
THE MID ATLANTIC REGION OVERNIGHT, THEN MOVE TO THE NORTHEAST
OVER THE ATLANTIC ON WEDNESDAY. EXPECT VERY LIGHT NORTHEAST FLOW
THROUGH THE OVERNIGHT, WITH CIRRUS PASSING ALOFT. THIS WILL
YIELD LOW TEMPERATURES IN THE MID TO UPPER 20S INLAND, WITH MID
TO UPPER 30S ALONG THE IMMEDIATE COASTLINE. GIVEN THAT WINDS
WILL BE LIGHT TO CALM, WIND CHILL VALUES WILL REMAIN CLOSE TO
THE AIR TEMPERATURE. MINIMUM WIND CHILL VALUES ARE EXPECTED TO
BE IN THE MID TO UPPER 20S AWAY FROM THE COAST, SO A COLD
WEATHER ADVISORY WILL NOT BE NEEDED.
KEY MESSAGE 2: WIDESPREAD PRECIPITATION IS EXPECTED TO OCCUR
THIS WEEKEND, BRINGING INCREASING POTENTIAL FOR A MULTI-DAY
WINTER WEATHER EVENT ACROSS PORTIONS OF THE REGION.
GUIDANCE CONTINUES TO SHOW A MULT-DAY WINTER WEATHER EVENT
DEVELOPING THIS WEEKEND AND POTENTIALLY LINGERING INTO EARLY
NEXT WEEK. THE PERIOD OF WINTER WEATHER BEGINS LATE SATURDAY AS
THE CENTER OF A ARCTIC AIR MASS REACHES NEW ENGLAND. THIS DRY
AND COLD AIR MASS SHOULD RIDGE SOUTHWEST ACROSS THE SOUTHEAST
U.S LATE SATURDAY, WITH COLD AIR DAMMING STRENGTHENING THROUGH
THE NIGHT. GIVEN THE APPROACH OF A BROAD H5 TROUGH AND UPPER
DIVERGENCE ASSOCIATED WITH A 180 KT JET OVER THE MID-ATLANTIC, A
LOW IS FORECAST TO DEVELOP OFF THE GA/SC COAST. AS THE LOW
DEVELOPS, DEEP ISENTROPIC LIFT WILL DEVELOP OVER THE WEDGED HIGH
PRESSURE, PRODUCING WIDESPREAD PRECIPITATION. GUSTY NORTHEAST
WINDS AND WET-BULB EFFECTS SHOULD RESULT IN TEMPERATURES TO
COOL INTO THE 30S ACROSS INLAND SC LOWCOUNTRY INTO SE GA. BY
LATE SATURDAY NIGHT, SFC TEMPERATURES ARE FORECAST TO DROP INTO
THE UPPER 20S FROM BERKELEY COUNTY WEST TO JENKINS COUNTY.
PRECIPITATION MAY TRANSITION FROM A COLD RAIN, TO A MIX OF RAIN
AND SLEET, THEN AS FREEZING RAIN. ACCUMULATIONS ARE POSSIBLE,
ESPECIALLY ON ELEVATED SURFACES ACROSS NORTHERN DORCHESTER AND
BERKELEY COUNTIES BY SUNDAY MORNING.
ON SUNDAY, THE COASTAL LOW SHOULD CONTINUE TO TRACK NORTHEAST
OFF THE CAROLINA COAST. SFC WINDS MAY TURN FROM THE NORTH,
STRENGTHENING THE COLD AIR DAMMING ACROSS THE REGION. HIGH
TEMPERATURES ON SUNDAY WERE COOLED SIGNIFICANTLY, LIMITING
VALUES TO THE 30S ACROSS THE INLAND TIER OF COUNTIES, ELSEWHERE
TEMPERATURES IN THE 40S ARE POSSIBLE. THESE TEMPERATURES MAY
NEED TO BE COOLED FURTHER WITH FUTURE UPDATES. TEMPERATURES
SUNDAY NIGHT SHOULD COOL SHARPLY AFTER SUNSET, WITH SUB-FREEZING
TEMPERATURES PUSHING TO THE COAST ACROSS THE LOWCOUNTRY AND
POTENTIAL TO THE I-16 CORRIDOR OF SE GA. FORECAST SOUNDINGS
WITHIN THE COLD AIR SUNDAY NIGHT FEATURES A WARM NOSE CENTER AT
H85 WITH COLD BL. FREEZING RAIN IS EXPECTED ACROSS THE SC
LOWCOUNTRY, WITH A MIXTURE OF RAIN/FREEZING RAIN SOUTH TO I-16.
THE FORECAST BECOME MORE UNCERTAIN BY SUNDAY NIGHT AND BEYOND.
GFS INDICATES A MUCH SLOWER SCENARIO WITH A CLOSED H5 LOW,
OPENING TO A WAVE OVER THE SOUTHERN PLAINS, POTENTIALLY KEEP
PRECIP OVER THE FORECAST AREA INTO EARLY NEXT WEEK. FORTUNATELY,
GFS AND ECMWF AI MODELS INDICATE A FASTER SCENARIO, OPENING THE
WAVE AS FAR WEST AS BAJA, RESULTING IN DRY AIR TO EACH THE
FORECAST AREA BY MONDAY. AT THIS TIME, PRECIP IN THE FORECAST
WILL END DURING THE DAYLIGHT HOURS ON MONDAY.
THE PROBABILISTIC WINTER STORM SEVERITY INDEX (WSSI-P) SHOWS
CHANCES OF MINOR WINTER STORM IMPACTS ACROSS THE ENTIRE AREA,
WITH EVEN A 20-40% CHANCE OF MODERATE IMPACTS ESPECIALLY NORTH
OF I-16. ICE ACCUMULATION APPEARS TO BE THE PRIMARY THREAT. WE
WILL ALSO NEED TO BE ON THE LOOKOUT FOR TEMPS/WIND CHILLS
APPROACHING COLD WEATHER ADVISORY CRITERIA SUNDAY NIGHT AND
BEYOND.
KEY MESSAGE 3: VERY COLD TEMPERATURES WILL OCCUR EARLY NEXT
WEEK.
ARCTIC AIR IS FORECAST TO SPREAD ACROSS THE REGION MONDAY NIGHT
INTO TUESDAY MORNING. USING A BLEND OF GUIDANCE, MIN
TEMPERATURES ARE FORECAST TO RANGE IN THE TEENS WEST OF I-95
WITH LOW TO MID 20S ALONG THE COAST. NORTH TO NORTHWEST WINDS
MAY REMAIN ACROSS THE REGION, POSSIBLY AROUND 10 MPH. THE
COMBINATION OF COLD TEMPERATURES AND WIND MAY RESULT IN
WIDESPREAD WIND CHILL VALUES IN THE TEENS.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
VFR CONDITIONS WILL PREVAIL AT KCHS, KJZI, AND KSAV THROUGH 18Z
WEDNESDAY.
EXTENDED AVIATION FORECAST: VFR THROUGH FRIDAY. PERIODS OF MVFR
AND/OR IFR CONDITIONS POSSIBLE WITH A RAIN AND/OR MIX OF FROZEN
PRECIP OVER THE WEEKEND.
MARINE
TONIGHT: WITH HIGH PRESSURE TO THE NORTH AND NORTHEAST, WE
SHOULD SEE WINDS TURN MORE NORTHEASTERLY OVERNIGHT WITH SPEEDS
INCREASING INTO THE 10-15 KNOT RANGE. SEAS SHOULD AVERAGE 2-3
FEET THROUGH THE NIGHT, WITH UP TO 4 FEET IN THE OUTER GA
WATERS.
WEDNESDAY THROUGH FRIDAY: OVERALL, QUIET CONDITIONS EXPECTED TO
PREVAIL ACROSS THE LOCAL WATERS. WIND SPEEDS SHOULD REMAIN NO
HIGHER THAN 10 KNOTS DURING THIS PERIOD WITH SEAS MOSTLY IN THE
2-4 FT RANGE.
FRIDAY NIGHT THROUGH THE WEEKEND: THE WEEKEND CONTINUES TO BE
THE PERIOD OF GREATEST CONCERN ACROSS THE LOCAL WATERS. A STRONG
COLD FRONT IS EXPECTED TO PASS THROUGH FROM THE NORTH FRIDAY
NIGHT AS HIGH PRESSURE BUILDS INLAND. THEN SATURDAY NIGHT INTO
SUNDAY, AN AREA OF LOW PRESSURE IS EXPECTED TO DEVELOP OFFSHORE
AND TRACK AWAY TO THE NORTHEAST. BEHIND THE FRONT FRIDAY NIGHT
AND THROUGH THE DEVELOPMENT OF THE OFFSHORE LOW SATURDAY NIGHT,
THE COASTAL WATERS WILL LIKELY BECOME SITUATED WITHIN AN AREA OF
ENHANCED GRADIENT AND STRENGTHENING NORTHEAST FLOW. THE
POTENTIAL FOR FREQUENT GUSTS INTO THE 25-30 KNOT RANGE CAN BE
EXPECTED ACROSS ALL WATERS, WITH SEAS QUICKLY RAMPING UP INTO
THE 6-10 FT RANGE (HIGHEST FROM AROUND 10 NM AND OUT). SMALL
CRAFT ADVISORIES WILL ALMOST CERTAINLY BE NEEDED FOR ALL WATERS
BEGINNING FRIDAY NIGHT AND CONTINUING THROUGH THE END OF THE
WEEKEND. THERE CONTINUES TO BE A LOW PROBABILITY FOR GALE FORCE
GUSTS IN THE CHARLESTON COUNTY WATERS.
EQUIPMENT
THE BEAUFORT/GREEN POND NOAA WEATHER RADIO TRANSMITTER (WXJ-23)
IS OPERATING AT LOW POWER WITH DIMINISHED SERVICE. REPAIRS ARE
SCHEDULED TO BE MADE WEDNESDAY OR THURSDAY TO RESTORE FULL
SERVICE.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
BSH/NED
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