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FXUS62 KCAE 181902
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
202 PM EST WED DEC 18 2024
SYNOPSIS
ANOTHER WARM AFTERNOON IS EXPECTED WITH SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS AHEAD OF AN APPROACHING COLD FRONT. 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 /THROUGH TONIGHT/
KEY MESSAGE(S):
- SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS THIS AFTERNOON
AND EVENING AHEAD OF AN APPROACHING COLD FRONT.
- PATCHY DENSE FOG POSSIBLE TONIGHT.
A POSITIVELY TILTED STRONG UPPER TROUGH IN THE MISSISSIPPI
VALLEY THIS AFTERNOON WILL MOVE EAST AND DRIVE A WEAK COLD FRONT
THROUGH THE REGION TONIGHT. MOISTURE, ESPECIALLY IN THE LOW-
LEVELS HAS INCREASED ACROSS THE AREA WITH PRECIPITABLE WATER IN
THE 1 TO 1.25 INCH RANGE. A FEW SHOWERS HAVE DEVELOPED IN WEAK
WARM ADVECTION PATTERN AIDED BY WEAK SHORT WAVE TROUGHS IN
SOUTH- WESTERLY FLOW ALOFT. STRATUS AND FOG WAS SLOW TO ERODE
THROUGH THE MORNING, IN FACT, STRATUS AND PATCHY FOG STILL BEING
REPORTED IN THE AGS AREA. SATELLITE TRENDS SUGGEST STRATUS IS
MIXING OUT WITH CUMULUS FIELD IN THE SOUTHEAST MIDLANDS WHERE
STRONGER DIABATIC HEATING HAS OCCURRED. SB CAPE 1500 J/KG IN
THAT REGION. MIXED LAYER CAPE IN THE 500-1000 J/KG. MESO-
ANALYSIS AND FORECAST MODEL SOUNDINGS CONFIRM DEEP LAYER SHEAR
30-35 KTS. SO, CAN'T RULE OUT A STRONG THUNDERSTORM MAINLY IN
THE SOUTHEAST MIDLANDS THIS AFTERNOON AND EVENING WHERE STRONGER
INSTABILITY WILL BE LOCATED. CAM MODELS SUPPORT SCATTERED
CONVECTIVE COVERAGE INTO THE EVENING THEN PUSHING TO THE EAST
AND DIMINISHING. 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 /THURSDAY 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 /19Z WEDNESDAY THROUGH MONDAY/
MVFR CONDITIONS IMPROVING TO VFR THIS AFTERNOON BUT IFR OR LIFR
RESTRICTIONS EXPECTED OVERNIGHT WITH STRATUS/FOG RE-
DEVELOPMENT.
HIGH LOW-LEVEL MOISTURE ACROSS THE AREA. SATELLITE SHOWING
LINGERING STRATUS/STRATO-CU RESULTING IN MAINLY MVFR CONDITIONS,
ALTHOUGH IFR CONDITIONS REMAIN IN THE AGS TERMINAL AREA. THINK
SLIGHT IMPROVEMENT THROUGH 00Z AS LOWER CLOUDS MIX OUT, BUT IN
GENERAL EXPECT MVFR CEILINGS AND IMPROVED VISIBILITY THROUGH THE
AFTERNOON AND EARLY EVENING. A WEAK COLD FRONT WILL MOVE THROUGH
THE AREA LATE TONIGHT AND THURSDAY MORNING. GUIDANCE INDICATES A
RE-DEVELOPMENT OF STRATUS AND OR FOG TONIGHT, POSSIBLY BEFORE
06Z AND CONTINUING THROUGH THE OVERNIGHT AT LEAST THROUGH 09Z.
SOME GUIDANCE SUGGESTS THE VISIBILITIES WILL IMPROVE PRIOR TO
12Z AS THE FRONT MOVES THROUGH THE AREA. SO A PERIOD OF IFR/LIFR
TONIGHT, FOLLOWED BY SLIGHTLY IMPROVED CONDITIONS BY 12Z. WINDS
WILL BE SOUTHWEST 5 TO 10 KNOTS THIS AFTERNOON THEN LIGHT. A
WIND SHIFT NORTH-NORTHEAST AFTER 12Z 5 TO 10 KNOTS TO MIX OUT
ANY LOWER CLOUDS/FOG.
EXTENDED AVIATION OUTLOOK...PATCHY FOG OR LOW CEILINGS POSSIBLE
FRIDAY MORNING OTHERWISE NO SIGNIFICANT IMPACTS TO AVIATION.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
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