346
FXUS62 KCAE 190035
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
735 PM EST WED DEC 18 2024
SYNOPSIS
SHOWERS AND THUNDERSTORMS WILL DIMINISH THROUGH THE EVENING
FOLLOWED BY A FRONT CROSSING THE AREA OVERNIGHT. THURSDAY AND
FRIDAY LOOK MOSTLY CLOUDY AND COOLER. A SECOND FRONT CLEARS
SKIES OUT LATE FRIDAY INTO FRIDAY NIGHT, FOLLOWED BY SEVERAL
DAYS OF COLD WEATHER WITH SUBFREEZING TEMPERATURES AT NIGHT. A
WARMING TREND IS EXPECTED TOWARDS CHRISTMAS ALONG WITH THE NEXT
CHANCE OF RAIN.
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
KEY MESSAGE(S):
- ISOLATED SHOWERS AND THUNDERSTORMS AHEAD OF A COLD FRONT
- PATCHY DENSE FOG POSSIBLE TONIGHT.
SHOWERS AND THUNDERSTORMS, SUPPORTED BY AN UPPER LEVEL
SHORTWAVE, WILL PERSIST INTO THE EARLY EVENING. DEEP LAYER SHEAR
OF 20 TO 30 KTS AND CAPE VALUES AROUND 1000 J/KG WILL SUPPORT
ORGANIZED THUNDERSTORMS. LOW FREEZING LEVELS AND ROTATING
UPDRAFTS WILL AID IN HAIL FORMATION. OVERALL THE SEVERE THREAT
FOR THE REMAINDER OF THE NEAR TERM IS LOW AS THE AIRMASS
STABILIZES.
THE FRONT APPEARS TO MOVE SLOWLY THROUGH THE AREA, PROBABLY
LINGERING NEAR THE EASTERN MIDLANDS EVEN AFTER SUNRISE. LOW-
LEVEL MOISTURE REMAINS HIGH OVERNIGHT, AND MIXING LIMITED EVEN
WITH THE WEAK FRONT MOVING THROUGH. SO, STRATUS AND FOG EXPECTED
AS UPPER LEVELS CLEAR OUT. THE FOG MAY DEVELOP BEFORE MIDNIGHT
AND MIX OUT NEAR OR BEFORE 12Z. STAYED CLOSE TO THE NBM FOR
OVERNIGHT LOWS MAINLY LOW TO MID 50S.
SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/
KEY MESSAGE(S):
- CLOUDY AND COOLER CONDITIONS EXPECTED THURSDAY.
- DECREASING CLOUDINESS BEHIND A COLD FRONT ON FRIDAY WITH SIMILAR
DAYTIME TEMPERATURES TO THURSDAY.
THE COLD FRONT EXITS THE FORECAST AREA EARLY THURSDAY MORNING WITH
PWATS FALLING IN ITS WAKE. HOWEVER, GUIDANCE REMAINS BULLISH ON
LOCKING MOISTURE INTO THE LOWEST LEVELS OF THE ATMOSPHERE, KEEPING
PARTLY TO MOSTLY CLOUDY SKIES AROUND UNTIL A SECOND COLD FRONT
ARRIVES ON FRIDAY TO CLEAR THINGS OUT. THE PASSAGE OF TWO SHORTWAVES
DURING THE PERIOD COULD SPARK A FEW LIGHT SHOWERS, BUT THE CHANCE OF
ACCUMULATING PRECIPITATION ON THURSDAY AND FRIDAY IS LOW, LESS
THAN 20 PERCENT, SO KEPT THE FORECAST DRY WITH THIS PACKAGE.
DAYTIME TEMPERATURES ARE SIMILAR BOTH DAYS, ABOUT 10 TO 15
DEGREES COOLER THAN TODAY, WITH FORECAST HIGHS IN THE MID-50S TO
MID-60S. THE CLOUDS LIMIT COOLING THURSDAY NIGHT WITH LOWS IN
THE LOWER TO MID 40S. IT WON'T BE UNTIL FRIDAY NIGHT THAT CAA
TAKES OVER BEHIND THE SECOND COLD FRONT. DESPITE THE COLD
ADVECTION AND CLEARING SKIES, SURFACE WINDS MAY STAY UP AT NIGHT
LIMITING RADIATIONAL COOLING. CURRENT THINKING IS THAT
TEMPERATURES WILL FALL INTO THE UPPER 20S TO MID-30S BY DAYBREAK
SATURDAY.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
KEY MESSAGE(S):
- COLD AND DRY CONDITIONS LIKELY THROUGH MONDAY.
- SEVERAL NIGHTS OF SUBFREEZING TEMPERATURES EXPECTED.
- TEMPERATURES MODERATE TOWARDS THE END OF THE PERIOD.
THE EXTENDED PERIOD WILL OPEN WITH STRONG TROUGHING IN PLACE ACROSS
THE EASTERN CONUS, BEING REPLACED BY RIDGING EARLY NEXT WEEK.
MEANWHILE, SURFACE HIGH PRESSURE CENTERED TO OUR NORTH WILL BE IN
CONTROL OF OUR WEATHER FOR MOST OF THE PERIOD, RESULTING IN SEVERAL
DAYS OF COLD AND DRY CONDITIONS. TEMPERATURES WILL CONTINUE TO
DECREASE THIS WEEKEND WITH THE COLDEST DAYS EXPECTED SUNDAY AND
MONDAY. CONFIDENCE REMAINS HIGH THAT THERE WILL BE SEVERAL NIGHTS OF
SUBFREEZING TEMPERATURES. THE PRIMARY QUESTION WILL BE HOW COLD WE
GET AND IF A COLD WEATHER ADVISORY WILL BE NEEDED AT ANY POINT IN
THE EXTENDED. WITH HIGH PRESSURE TO OUR NORTH AND NOT DIRECTLY
OVERHEAD, SURFACE WINDS MAY REMAIN HIGH ENOUGH TO PREVENT IDEALIZED
RADIATIONAL COOLING KEEPING VALUES OUT OF ADVISORY CRITERIA.
HAVING SAID THAT, THE MOST LIKELY PERIOD FOR A CWA WILL BE
SUNDAY NIGHT INTO MONDAY MORNING, WHEN WIND CHILL VALUES ARE
FORECAST TO BE IN THE 10 TO 20 DEGREE RANGE. REGARDLESS,
PREPARATIONS FOR AN EXTENDED PERIOD OF COLD WEATHER SHOULD BE
MADE, ESPECIALLY FOR THOSE WHO WILL BE TRAVELING AWAY FROM HOME
AHEAD OF THE CHRISTMAS HOLIDAY. SPEAKING OF CHRISTMAS,
TEMPERATURES ARE EXPECTED TO MODERATE DURING THE MIDDLE OF NEXT
WEEK BUT MAY COME AT THE PRICE OF ANOTHER CHANCE OF RAIN ON OR
AROUND CHRISTMAS DAY.
AVIATION /01Z THURSDAY THROUGH MONDAY/
RESTRICTIONS LIKELY TONIGHT AND THURSDAY MORNING.
WITH ABUNDANT MOISTURE ACROSS THE AREA, WE SHOULD SEE FOG
DEVELOP EARLY TONIGHT AHEAD OF A WEAK COLD FRONT. PATCHY FOG
MAY DEVELOP AS EARLY AS 02Z, ESPECIALLY AT CAE WHICH RECEIVED
RAINFALL, AND SPREAD IN SPATIAL EXTENT THROUGH THE NIGHT. THE
FRONT WILL MOVE THROUGH THE AREA LATE TONIGHT AND THURSDAY
MORNING. ONCE THE FRONT MOVES THROUGH AND DRIER AIR FILTERS INTO
THE AREA, WE SHOULD SEE VISIBILITIES IMPROVE PRIOR TO 12Z.
CONTINUED A PERIOD OF IFR/LIFR TONIGHT, FOLLOWED BY SLIGHTLY
IMPROVED CONDITIONS BY 12Z. EXPECT MVFR CEILINGS THROUGH
THURSDAY MORNING UNTIL THE DRY AIR MIXES OUT THE LOWER CLOUDS.
WINDS THURSDAY FROM 5 TO 10 KNOTS OUT OF THE NE.
EXTENDED AVIATION OUTLOOK...RESTRICTIONS POSSIBLE FRIDAY
MORNING, OTHERWISE NO SIGNIFICANT IMPACTS TO AVIATION.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
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