330
FXUS62 KCHS 132349
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
649 PM EST SAT DEC 13 2025
SYNOPSIS
HIGH PRESSURE WILL PREVAIL TONIGHT, THEN AN ARCTIC COLD FRONT
WILL SWEEP THROUGH SUNDAY. DRY HIGH PRESSURE WILL THEN BUILD
OVERHEAD FOR MUCH OF THE COMING WEEK.
NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
ALOFT, A ZONAL FLOW PREVAILS FOR MUCH OF THE NIGHT IN ADVANCE
OF THE DIGGING TROUGH ACROSS THE MIDWEST. AT THE SFC, THE
ATLANTIC HIGH WILL EXTEND ACROSS THE SOUTHEAST, WHILE SOME
TROUGHING DEVELOPS NORTH AND INLAND OVERNIGHT. ALTHOUGH THE
PRESSURE GRADIENT REMAINS MODEST BETWEEN THESE FEATURES,
CONDITIONS WILL REMAIN NOTICEABLY MORE MILD THAN THE PREVIOUS
NIGHT WHILE A LIGHT SOUTHWESTERLY WIND ADVECTS WARMER AIR INTO
THE REGION WELL IN ADVANCE OF A COLD FRONT. ONLY POTENTIAL
HAZARD TO HIGHLIGHT OVERNIGHT IS THE LOW (10% OR LESS) RISK FOR
SOME PATCHY FOG AWAY FROM THE IMMEDIATE COAST. FAILURE TO
DECOUPLE FOR AN EXTENDED PERIOD, AND INCREASING CLOUDS LATE,
SHOULD PRECLUDE ANY DENSE FOG THREAT.
SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/
..BITTER COLD TEMPERATURES LATER SUNDAY INTO TUESDAY
SUNDAY: TIMING OF ARCTIC COLD FRONT SUNDAY COMING INTO BETTER
AGREEMENT, CROSSING THE AREA LATE MORNING. HIGH TEMPERATURES OF
60-65 WILL LIKELY BE REACHED MIDDAY, WITH STRONG CAA ENSUING BY
EARLY AFTERNOON. A FEW SHOWERS ARE EXPECTED IMMEDIATELY AHEAD
OF THE FRONT, BUT RAINFALL RATES WILL BE MODEST AND TOTAL
RAINFALL WILL REMAIN .25 IN OR LESS ACROSS THE AREA. WEST-
SOUTHWEST WINDS IN THE MORNING WILL VEER SHARPLY TO NORTHWEST
AND INCREASE BEHIND THE FRONT BY MIDDAY. WIND GUSTS OF 20-30 MPH
ARE POSSIBLE EARLY-TO-MID-AFTERNOON, WITH A LAKE WIND ADVISORY
NOW IN EFFECT FOR LAKE MOULTRIE SUNDAY AFTERNOON THROUGH SUNDAY
NIGHT.
BY SUNDAY NIGHT, A STRONG ARCTIC SURFACE RIDGE WILL BUILD FROM
THE NORTHWEST, KEEPING NORTHWEST TO NORTH WINDS THROUGH THE
NIGHT. TEMPERATURES EXPECTED TO DROP INTO THE UPPER TEENS WELL
INLAND, AND LOWER TO MID 20S ELSE WHERE, WARMEST NEAR THE COAST.
ENSEMBLE SUITES ARE IN GOOD AGREEMENT, MAKING WINDCHILL VALUES
OF 5-15 EARLY MONDAY MORNING (AWAY FROM THE WATER) A HIGH
PREDICTABILITY, HIGH CONFIDENCE FORECAST. CURRENTLY, HIGHEST
PROBS (30-50%) FOR WIND CHILL VALUES LESS THAN 10F EXIST ACROSS
THE SC LOWCOUNTRY AND INTERIOR SE GA, WHICH PROBS ARE LOWER (20%
OR LESS) ALONG THE GA COAST. THE CURRENT CONFIGURATION OF
EXTREME COLD WATCHES AND COLD WEATHER ADVISORIES REFLECT THESE
PROBABILITIES.
MONDAY: DEEP RIDGING IS SHOWN BY ALL MODELS TO SETTLE OVER THE
REGION, WITH LIGHTER WINDS AND MOSTLY SUNNY/SUNNY SKIES. DESPITE
FULL SUN, GUIDANCE CONTINUES TO HOLD HIGH TEMPERATURES IN THE
UPPER 30S TO MID-40S, 15 TO 20 DEGREES BELOW NORMAL! MONDAY
NIGHT, HIGH PRESSURE WILL START CENTERED OVER THE REGION, THEN
SLOWLY SHIFT OFFSHORE BY LATE NIGHT. LIGHT WINDS, CLEAR SKIES
AND DRY LOW LEVELS SHOULD ALLOW FOR STRONG RADIATIONAL COOLING.
VERY COLD TEMPERATURES AGAIN EXPECTED, WITH LOWS AROUND 20 WELL
INLAND, TO THE MID 20S TO NEAR 30 CLOSER TO THE COAST.
TUESDAY: THIS PERIOD BEGINS THE MODERATION IN TEMPERATURES, WITH THE
SURFACE RIDGE SHIFTING FURTHER OFFSHORE, ALLOWING FOR LOW LEVEL
WINDS TO VEER TO SOUTHWEST BY AFTERNOON. UNDER MOSTLY SUNNY SKIES,
HIGHS REBOUNDING INTO THE 50S ALL AREAS, WHICH IS STILL A TAD BELOW
NORMAL.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
ALL GLOBAL AND BLENDED MODEL SOLUTIONS SHOW THAT THE LARGE
SCALE/SYNOPTIC PATTERN SHIFTS TO ZONAL, WITH MODERATING TEMPERATURES
THROUGH THE PERIOD. TUESDAY NIGHT WILL BE THE COLDEST PERIOD, WITH
FREEZING TEMPERATURES AGAIN EXPECTED INLAND, AND MID TO UPPER 30S
CLOSER TO THE COAST. THEN WEDNESDAY THROUGH SATURDAY, TEMPERATURES
CONTINUE TO WARM, WITH TEMPERATURES NEAR NORMAL ON WEDNESDAY, TO
ABOVE NORMAL THURSDAY THROUGH SATURDAY. THE BIGGEST FORECAST ISSUE
FOR THIS PERIOD WILL BE HOW TO HANDLE THE MODEL DIFFERENCES WITH
CHANCES FOR PRECIP. LATE IN THE PERIOD. SOME MODELS INDICATE THE
POTENTIAL FOR ANOTHER COLD FRONT TO APPROACH THE AREA LATER THURSDAY
AND EARLY FRIDAY, BUT TIMING AND AMOUNT OF DEEP LAYER MOISTURE VARY
BETWEEN MODELS. FOR NOW, THE MOST LIKELY SCENARIO IS FOR A
WEAKENING COLD FRONT TO BRING LIMITED PRECIPITATION TO THE AREA
FRI/SAT, WITH DRY HIGH PRESSURE RETURNING THEREAFTER.
AVIATION /00Z SUNDAY THROUGH THURSDAY/
00Z TAFS: HIGH PRESSURE WILL PREVAIL TONIGHT, BRINGING VFR WITH
LIGHT WINDS. AN ARCTIC COLD FRONT WILL QUICKLY MOVE THROUGH OUR
AREA ON SUNDAY. A FEW SHOWERS WITH MVFR CEILINGS ARE POSSIBLE
FOR A FEW HOURS DURING THE DAY AT KCHS AND KJZI. SINCE
PROBABILITIES ARE AROUND 30%, WE HANDLED THIS WITH A PROB30
GROUP. FURTHER SOUTH AT KSAV, NO SHOWERS ARE EXPECTED. THOUGH,
CEILINGS SHOULD STILL DROP TO MVFR FOR A FEW HOURS. VFR RETURNS
TO ALL OF THE TAF SITES BY THE LATE AFTERNOON. ADDITIONALLY,
THERE WILL BE A QUICK WIND SHIFT TO THE NW AND THE WINDS WILL
BECOME VERY GUSTY.
EXTENDED AVIATION OUTLOOK: GENERALLY VFR CONDITIONS ARE EXPECTED
SUNDAY NIGH THROUGH MID WEEK.
MARINE
TONIGHT: HIGH PRESSURE CONTINUES TO DOMINATE, THOUGH INCREASING
GRADIENT LATE AHEAD OF AN APPROACHING COLD FRONT WILL BRING
SLOWLY INCREASING WINDS. A FEW WIND GUSTS UP TO 20 KT ARE
POSSIBLE ACROSS NORTHERN SOUTH CAROLINA WATERS AND OUTER GEORGIA
WATERS BY THE PRE-DAWN HOURS. SEAS BECOME 2-3 FT OVERNIGHT IN
MOSTLY LOCAL WINDSWELL.
..HAZARDOUS MARINE CONDITIONS LATER SUNDAY INTO MONDAY
A STRONG ARCTIC COLD FRONT WILL MOVE THROUGH THE WATERS LATER
SUNDAY MORNING, LIKELY PASSING THROUGH THE ENTIRE REGION BY
MIDDAY. SOUTHWEST WINDS WILL VEER SHARPLY TO NORTHWEST AS THE
FRONT CROSSES, WITH GUSTS TO 35 KT POSSIBLE ACROSS THE COASTAL
WATERS WHERE A GALE WATCH IS NOW IN EFFECT SUNDAY AFTERNOON
THROUGH EARLY MONDAY MORNING. INSHORE WATERS, INCLUDING THE
CHARLESTON HARBOR, WILL ALSO SEE GUSTY CONDITIONS AS WINDS
READILY MIX OVER THE RELATIVELY WARMER WATERS SUNDAY EVENING AND
OVERNIGHT, WITH AN SCA IN EFFECT ACCORDINGLY. HAZARDOUS
CONDITIONS, ESPECIALLY FOR SEAS, ARE EXPECTED TO REMAIN THROUGH
LATER MONDAY, ESPECIALLY BEYOND 20 NM OFFSHORE. WINDS AND SEAS
ARE EXPECTED TO FALL BELOW ANY HIGHLIGHT LEVELS TUESDAY THROUGH
WEDNESDAY.
CLIMATE
RECORD LOW TEMPERATURES:
DECEMBER 15:
KCHS: 15/1962
KCXM: 23/1943
KSAV: 19/1962
RECORD LOW MAXIMUM TEMPERATURES:
DECEMBER 15:
KCHS: 39/1943
KCXM: 38/1904
KSAV: 38/1904
CHS WATCHES/WARNINGS/ADVISORIES
GA...EXTREME COLD WATCH FROM SUNDAY EVENING THROUGH MONDAY MORNING
FOR GAZ087-088.
COLD WEATHER ADVISORY FROM 10 PM SUNDAY TO 10 AM EST MONDAY
FOR GAZ099>101-114>119-137>141.
SC...EXTREME COLD WATCH FROM SUNDAY EVENING THROUGH MONDAY MORNING
FOR SCZ040-042>045-050-052.
COLD WEATHER ADVISORY FROM 10 PM SUNDAY TO 10 AM EST MONDAY
FOR SCZ047>049-051.
LAKE WIND ADVISORY FROM 4 PM SUNDAY TO 4 AM EST MONDAY FOR
SCZ045.
MARINE...SMALL CRAFT ADVISORY FROM 1 PM SUNDAY TO 9 AM EST MONDAY FOR
AMZ330.
GALE WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY MORNING FOR
AMZ350-352-354-374.
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
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