422
FXUS62 KCHS 212204
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
504 PM EST WED JAN 21 2026
WHAT HAS CHANGED
THE AVIATION SECTION WAS UPDATED FOR THE 22/00Z TAF CYCLE.
KEY MESSAGES
- 1) WIDESPREAD PRECIPITATION IS EXPECTED TO OCCUR THIS
WEEKEND, BRINGING THE POTENTIAL FOR A WINTER WEATHER EVENT
ACROSS PORTIONS OF THE REGION.
- 2) VERY COLD TEMPERATURES WILL OCCUR EARLY NEXT WEEK.
DISCUSSION
KEY MESSAGE 1: WIDESPREAD PRECIPITATION IS EXPECTED TO OCCUR
THIS WEEKEND, BRINGING THE POTENTIAL FOR A WINTER WEATHER EVENT
ACROSS PORTIONS OF THE REGION.
FOCUS ON THE FORECAST REMAINS THE POTENTIAL FOR A WINTER
WEATHER EVENT ACROSS PORTIONS OF SOUTHEAST SOUTH CAROLINA AND
GEORGIA THIS WEEKEND. THE OVERALL SYNOPTIC PATTERN REMAINS
FAIRLY CONFIDENT, HOWEVER THERE ARE MANY DETAILS IN THE
EVOLUTION OF THIS PATTERN THAT ARE NOT CERTAIN. THIS IS CAUSING
A FAIRLY HIGH SPREAD IN MODEL GUIDANCE ON P-TYPES LOCATION AND
TIMING.
SYNOPTIC PATTERN/DIAGNOSIS:
ON THURSDAY, A DECAYING OMEGA BLOCK WILL BE LOCATED ACROSS
ALASKA WITH TWO UPPER LEVEL LOWS UNDERCUTTING THE BLOCK (FORMING
A QUASI REX BLOCK). THE UPPER LEVEL LOW OF CONCERN WILL BE
LOCATED JUST SOUTHWEST OF CALIFORNIA. SIMULTANEOUSLY, A LONG
WAVE TROUGH WILL BE CENTERED SOUTHWEST OF THE HUDSON BAY WITH A
TRAILING SHORTWAVE EXTENDING ACROSS SASKATCHEWAN AND ALBERTA.
HOW THIS SHORTWAVE INTERACTS WITH THE CUTOFF LOW IS THE LINCHPIN
TO HOW THIS WEEKEND UNFOLDS FOR THE CENTRAL/ EASTERN UNITED
STATES. THE GENERAL IDEA IS THAT THE SHORTWAVE WILL DIVE
SOUTHEAST OUT OF CANADA AND THEN BEGIN TO PICKUP THE CLOSED LOW
IN THE MAIN FLOW. BY LATE SATURDAY/ EARLY SUNDAY, THE CLOSED LOW
WILL OPEN UP WITH FRAGMENTS OF PV EJECTING EAST/ NORTHEAST. AS
THIS OCCURS, SURFACE LOW PRESSURE WILL FORM SOMEWHERE ACROSS THE
SOUTHERN UNITED STATES OR NORTHERN GULF. OVER THE CANADIAN
MARITIMES, A CLOSED LOW WILL BE EJECTING EAST AND WILL HELP PUSH
A SURFACE COLD FRONT THROUGH THE AREA SATURDAY. AS WINDS NEAR
THE SURFACE TURN FROM THE NORTHEAST AND LOW LEVEL FLOW REMAINS
OUT OF THE SOUTHWEST, ISENTROPIC UPGLIDE WILL COMMENCE. THIS
WORKING IN TANDEM WITH THE FRAGMENTS OF PV MOVING OVERHEAD WILL
QUICKLY CAUSE VERTICAL PROFILES TO SATURATE WITH PRECIPITATION
BEGINNING LATE SATURDAY MORNING/ EARLY SATURDAY AFTERNOON. ON
SUNDAY, SURFACE LOW PRESSURE WILL EJECT NORTHEAST WITH
PRECIPITATION CONTINUING ACROSS THE REGION. THE MAIN UNCERTAINTY
WILL BE THE TRACK OF THE SURFACE LOW. MORE ON THIS BELOW.
MONDAY MORNING, A SURFACE COLD FRONT WILL SWEEP THROUGH ALL
ZONES WITH PRECIPITATION COMING TO AN END FROM WEST TO EAST.
MODEL CONFIDENCE:
THE LATEST 00Z EPS AND GEPS HAVE SEEN A REAL TRANSLATION
NORTHWARDS OF THE FREEZING RAIN, SLEET, AND SNOW PRECIPITATION
TYPES WITH THE 00Z GEFS STILL HOLDING ON TO THE COLDER SOLUTION.
TAKING A LOOK AT THE WPC CLUSTER ANALYSIS REVEALS THAT THE GEFS
NOW IS THE LEAST DISPERSIVE WITH 67% OF GEFS MEMBERS IN CLUSTER
2 WITH ONLY 18% OF EPS AND 10% OF GEPS MEMBERS A PART OF THAT
CLUSTERING. MEANING THE EPS AND GEPS NOW APPEAR MUCH CLOSER IN
THE SOLUTION SPACE. THE ISSUE APPEARS TO BE WITH THE DEVELOPMENT
OF THE SURFACE LOW AND HOW IT EVOLVES. THE GEFS SOLUTIONS SHOW
A STRONG CAD IN PLACE WITH SURFACE LOW PRESSURE FORMING OFF OF
THE SOUTHEAST SOUTH CAROLINA COAST. THE LATEST RUN OF THE EPS
AND GEPS SHOWS A MUCH WEAKER CAD IN PLACE WITH SURFACE LOW
PRESSURE MOVING OVER CENTRAL GEORGIA AND SOUTH CAROLINA,
EFFECTIVELY PUTTING THE REGION TEMPORARILY IN A WARM SECTOR.
THIS CHANGE IN THE EPS FROM A COLDER ENSEMBLE SUITE TO A WARMER
ENSEMBLE SUITE IS NOT COMPLETELY UNEXPECTED. TAKING A LOOK AT
THE WPC ENSEMBLE SENSITIVITY ANALYSIS WEBPAGE REVEALS THAT MOST
OF THE MODEL SPREAD IS COMING FROM THE SHORTWAVE DIVING SOUTH
OUT OF CANADA AS WELL AS HOW MID-LEVEL HEIGHTS RESPOND TO THAT
INCOMING WAVE OVER THE CENTRAL/ EASTERN UNITED STATES. MOST OF
THESE DETAILS WILL NOT BE RESOLVED UNTIL FRIDAY. THIS MEANS THAT
CHANGES IN DETERMINISTIC AND ENSEMBLE MEMBERS (POSSIBLY DRASTIC
AT TIMES) ARE POSSIBLE OVER THE NEXT 24 TO 48 HRS.
POTENTIAL IMPACTS/TIMING:
COLDER/GEFS SOLUTION: PRECIPITATION STARTING LATE SATURDAY
MORNING WITH FREEZING RAIN POSSIBLE SATURDAY EVENING INTO SUNDAY
MORNING. THIS COLDER SOLUTION WOULD FAVOR THE POTENTIAL FOR
FREEZING RAIN TO THE SOUTH CAROLINA COAST AND AREAS OF INLAND
GA. PRECIPITATION WOULD THEN COME TO AN END LATE MONDAY MORNING.
WARMER/EPS AND GEPS SOLUTION: PRECIPITATION STARTING SATURDAY
AFTERNOON WITH A WARM FRONT AND SURFACE LOW PRESSURE MOVING
OVERHEAD SUNDAY EVENING. A BRIEF BREAK IN THE PRECIPITATION
WOULD BE POSSIBLE WITH THIS SOLUTION SUNDAY AFTERNOON. THE
CHANCES FOR FREEZING RAIN WOULD BE CONFINED TO FAR INLAND
BERKELEY, DORCHESTER, COLLETON, AND ALLENDALE COUNTIES.
CONFIDENCE ON WHICH SOLUTION SET, OR A BLEND OF THE TWO,
ACTUALLY OCCURS IS LOW. NOW IS THE TIME TO PREPARE FOR THE
POTENTIAL FOR MINOR IMPACTS FROM A WINTER STORM.
KEY MESSAGE 2: VERY COLD TEMPERATURES WILL OCCUR EARLY NEXT
WEEK.
ARCTIC HIGH PRESSURE WILL SETTLE OVERHEAD THROUGH THE FIRST
PART OF NEXT WEEK WITH SOME OF THE COLDEST TEMPERATURES OF THE
SEASON POSSIBLE.
MONDAY NIGHT/TUESDAY MORNING: LOW TEMPERATURES IN THE UPPER
TEENS TO LOWER 20S WITH WIND CHILLS IN THE LOWER TO MIDDLE TEENS
ARE CURRENTLY FORECAST FOR TUESDAY MORNING. COLD WEATHER
ADVISORIES APPEAR LIKELY AT THIS POINT WITH PROBABILITIES OF
MEETING OR EXCEEDING CRITERIA AT 50 - 75%.
TUESDAY NIGHT/WEDNESDAY MORNING: WEDNESDAY MORNING LOW
TEMPERATURES WILL BE IN THE LOWER TO MID 20S WITH MORNING WIND
CHILLS IN THE UPPER TEENS TO LOWER 20S. CONFIDENCE ON NEEDING A
COLD WEATHER ADVISORY IS LESS FOR TUESDAY NIGHT/ WEDNESDAY
MORNING WITH PROBABILITIES OF MEETING OR EXCEEDING CRITERIA AT
20 TO 50%.
IT SHOULD BE NOTED THAT MODEL CONFIDENCE IS FAIRLY HIGH AT THIS
RANGE WITH THE IQR (OR CORE 50% OF GUIDANCE) ONLY SHOWING A 3 -
6 DEGREE SPREAD FOR LOWS TUESDAY AND WEDNESDAY MORNINGS OF NEXT
WEEK. HOWEVER, CHANGES IN THE SYNOPTIC PATTERN MENTIONED IN KEY
MESSAGE 1 WILL HAVE IMPACTS ON THE TIMING OF THE COLD AIR FOR
TUESDAY INTO WEDNESDAY AND IF COLD AIR PERSISTS INTO THE LATER
HALF OF THE NEXT WORK WEEK.
AVIATION /22Z WEDNESDAY THROUGH MONDAY/
22/00Z TAF DISCUSSION:
KCHS/KJZI/KSAV: VFR THROUGH 23/00Z.
EXTENDED AVIATION FORECAST: THERE IS A LOW END PROBABILITY FOR
SOME FOG ACROSS THE AREA FRIDAY MORNING, OTHERWISE VFR WILL
PREVAIL THROUGH FRIDAY. EXPECT INCREASING CHANCES OF MVFR AND
IFR CONDITIONS THROUGH THE WEEKEND AS A STORM SYSTEM IMPACTS THE
AREA. THERE CONTINUES TO BE A THREAT FOR A PERIOD OF WINTER
PRECIPITATION, PRIMARILY BEGINNING LATE SATURDAY NIGHT AND INTO
SUNDAY AND MAINLY AT KCHS AND KJZI.
MARINE
TONIGHT: QUIET CONDITIONS WILL CONTINUE WITH LIGHT NORTHERLY
FLOW THROUGH THE OVERNIGHT. WIND SPEEDS 10-15 KT SHOULD
DIMINISHING TO 5-10 KT. SEAS WILL MOSTLY AVERAGE 2-3 FEET, BUT
COULD BE UP TO 4 FEET IN THE OUTER REACHES OF THE GEORGIA
OFFSHORE WATERS.
THURSDAY AND FRIDAY: CONTINUED QUIET CONDITIONS ACROSS THE
LOCAL WATERS FOR THE LATE WEEK TIME PERIOD. WIND SPEEDS SHOULD
BE NO MORE THAN 10 KNOTS THROUGHOUT, WITH SEAS 2-3 FEET ACROSS
THE NEARSHORE WATERS AND UP TO 4 FEET IN THE OUTER WATERS.
FRIDAY NIGHT THROUGH MONDAY: OVERALL, EXPECT HAZARDOUS MARINE
CONDITIONS TO OCCUR THIS WEEKEND. A STRONG COLD FRONT IS
FORECAST TO PUSH ACROSS THE WATERS FRIDAY NIGHT AS HIGH PRESSURE
BUILDS IN ACROSS INLAND AREAS. THIS WILL DRIVE A STRONG
NORTHEAST SURGE BEGINNING LATE FRIDAY NIGHT WHICH WILL CONTINUE
THROUGH SATURDAY AND INTO SATURDAY NIGHT. AS WE HEAD INTO
SUNDAY, AN AREA OF LOW PRESSURE IS EXPECTED TO DEVELOP JUST
OFFSHORE AND LIFT TO THE NORTHEAST INTO SUNDAY NIGHT. FINALLY A
COLD FRONT WILL SWEEP THROUGH FROM THE WEST BY MONDAY. WINDS AND
SEAS WILL RAMP UP TO SOLID SMALL CRAFT ADVISORY (SCA)
CONDITIONS EARLY SATURDAY MORNING ACROSS ALL WATERS. AS OF NOW,
PEAK WINDS LOOK TO OCCUR LATE SATURDAY. PEAK WIND GUSTS ARE
CURRENTLY FORECAST TO BE AROUND 30 KNOTS, THROUGH THERE
CONTINUES TO BE SOME SUPPORT FOR POTENTIAL GALES IN THE
CHARLESTON COUNTY WATERS. THERE COULD BE A BIT OF A LULL IN
CONDITIONS (MAINLY WINDS) LATE SUNDAY AS THE GRADIENT DIMINISHES
WHEN THE SURFACE LOW PULLS AWAY FROM THE AREA. HOWEVER, WINDS
SHOULD RAMP BACK UP A BIT FOR MONDAY AS THE COLD FRONT FROM THE
WEST MOVES THROUGH.
IN SUMMARY, SMALL CRAFT ADVISORIES (SCA) WILL LIKELY BE NEEDED
FOR ALL WATERS (POSSIBLY CHARLESTON HARBOR AS WELL) FROM LATE
FRIDAY NIGHT THROUGH MONDAY FOR BOTH WIND AND SEA CONDITIONS.
THERE IS STILL A LOW CHANCE FOR A PERIOD OF GALES IN THE
CHARLESTON COUNTY WATERS IN THE LATE SATURDAY TIME PERIOD AND IT
IS POSSIBLE THAT A GALE WATCH/WARNING COULD EVENTUALLY BE
NEEDED.
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 TODAY OR THURSDAY TO RESTORE FULL SERVICE.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
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