561
FXUS62 KCAE 181010
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
510 AM EST WED DEC 18 2024
SYNOPSIS
DENSE FOG TO START THE DAY AS A COLD FRONT APPROACHES THE
REGION THIS AFTERNOON. THERE IS A CHANCE FOR SHOWERS AND
ISOLATED THUNDERSTORMS DURING THE LATE AFTERNOON AND EVENING
HOURS. COLD AND DRY CONDITIONS THEN DOMINATE FOR THE REMAINDER
OF THE WEEK AND INTO EARLY NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGE(S):
- WIDESPREAD DENSE FOG EXPECTED THROUGH DAYBREAK.
- SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON AHEAD OF AN
APPROACHING COLD FRONT.
A DEEP UPPER LEVEL TROUGH TO OUR WEST IS INDUCING SOUTHWEST FLOW
ACROSS THE REGION THIS MORNING. AS THE UPPER TROUGH AMPLIFIES,
MOISTURE AND CLOUD COVER WILL INCREASE. A FEW STRONGER ECHOES ARE
STARTING TO SHOW UP ON RADAR IMAGERY THIS MORNING, LIKELY DUE TO A
WEAK SHORTWAVE QUICKLY TRAVERSING THE AREA. SATELLITE PWAT ESTIMATES
ARE AROUND 1-1.25", AND SURFACE DEWPOINTS ARE IN THE MID TO
UPPER 50S ACROSS MOST OF THE AREA. DENSE FOG HAS DEVELOPED
ACROSS THE MAJORITY OF THE MIDLANDS AND PORTIONS OF THE CSRA,
AND CONTINUES TO ADVECT TOWARD THE UPSTATE. VISIBILITIES OF LESS
THAN 1/4 TO 1/2 MILE ARE EXPECTED, AND A DENSE FOG ADVISORY IS
IN EFFECT FOR THE ENTIRE AREA THROUGH 10 AM THIS MORNING. LOW
TEMPERATURES THIS MORNING WILL BE A LITTLE MILDER THAN THE
PREVIOUS NIGHT, IN THE LOW TO MID 50S.
THE UPPER TROUGH WILL CROSS THE MISSISSIPPI AND TENNESSEE VALLEYS
TODAY, WITH STRENGTHENING SOUTHWEST FLOW ALOFT. THE ATTENDANT COLD
FRONT IS NOT EXPECTED TO CROSS THE FORECAST AREA UNTIL TONIGHT.
MOISTURE ADVECTION AHEAD OF THE FRONT COMBINED WITH DAYTIME HEATING
AND SOME PRE-FRONTAL CONVERGENCE SHOULD LEAD TO ISOLATED TO
SCATTERED SHOWERS AND A FEW THUNDERSTORMS, AS HREF MEAN SBCAPE
VALUES ARE BETWEEN 250 AND 700 J/KG. SOME OF THIS POTENTIAL COULD BE
TEMPERED BY RESIDUAL LOW CLOUD COVER LEFT OVER FROM THIS MORNING, SO
THERE REMAINS SOME UNCERTAINTY IN THUNDERSTORM COVERAGE. CAM
SOLUTIONS ARE IN BETTER AGREEMENT THAT THE TIMING FOR PRECIP WILL BE
LATE THIS AFTERNOON AND THIS EVENING, ENDING BY MIDNIGHT. THERE IS
ALSO GOOD AGREEMENT THAT PRECIP ASSOCIATED DIRECTLY WITH THE FRONT
WILL BE LIMITED, AS MANY MODELS HAVE CONVECTION WEAKENING
CONSIDERABLY BEFORE THE FRONT REACHES OUR AREA. GIVEN ALL OF THESE
FACTORS, RAINFALL AMOUNTS WILL BE LIMITED TO JUST A FEW HUNDREDTHS
OF AN INCH TO PERHAPS TWO TENTHS OF AN INCH IN THE HEAVIER SHOWERS
OR THUNDERSTORMS. A WARM DAY IS EXPECTED DESPITE THE ABUNDANT
CLOUDINESS WITH FORECAST HIGHS IN THE UPPER 60S TO LOWER 70S.
TEMPERATURES FALL INTO THE MID-40S TO MID-50S AT NIGHT. EARLY
GUIDANCE IS THAT ANOTHER ROUND OF FOG OR LOW STRATUS IS
POSSIBLE TONIGHT, BUT IT SHOULDN'T BE NEARLY AS WIDESPREAD OR
DENSE AS THIS MORNING.
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/
KEY MESSAGE(S):
- THURSDAY & FRIDAY LOOK COOLER AND CLOUDIER BEHIND THE COLD
FRONT.
SYNOPTIC PATTERN WILL BE ACTIVE BUT SHOULDN'T RESULT IN ACTIVE
SENSIBLE WEATHER. COLD FRONT FROM WEDNESDAY SHOULD BE THROUGH THE
REGION BY THURSDAY MORNING, WITH SLIGHTLY COOLER AND DRIER WEATHER
IN PLACE. TRANSIENT SHORTWAVE RIDGING AND SURFACE HIGH PRESSURE ARE
FORECAST TO MOVE THROUGH THE AREA, WITH HIGHS IN THE UPPER 50S AND
LOWER 60S ACROSS THE AREA. CLOUDS ARE FORECAST TO BUILD BACK IN ON
THURSDAY NIGHT AS A STRONGER AND SHARPER SHORTWAVE QUICKLY
APPROACHES THE AREA FROM THE NORTHWEST. THIS SHOULD KEEP TEMPS IN
THE MID 40S ACROSS THE AREA. LIGHT SHOWERS ARE POSSIBLE ON FRIDAY
MORNING AS VERY STRONG TROUGHING PUSHES SOUTHEASTWARD THROUGH THE
EASTERN CONUS ON FRIDAY. LOW PRESSURE SYSTEM AND COLD FRONT ARE
FORECAST TO PUSH THROUGH DURING THE AFTERNOON AND EVENING HOURS,
BEGINNING THE SHIFT TOWARDS MUCH COLDER TEMPS OVER THE WEEKEND.
CLOUDS LIKELY CLEAR BY FRIDAY AFTERNOON BUT BREEZY WESTERLY OR WEST-
NORTHWESTERLY WINDS LOOK TO AID IN KEEPING HIGHS UP AROUND 60F FOR
MOST, WITH TEMPS FALLING OFF QUICKLY DURING THE AFTERNOON AS THE
FRONT PUSHES THROUGH. COLD AIR ADVECTION WILL DRIVE LOWS ON FRIDAY
NIGHT, WITH TEMPS FALLING INTO THE LOW TO MID 30S BY SATURDAY
MORNING.
LONG TERM /SATURDAY THROUGH TUESDAY/
KEY MESSAGE(S):
- THE EXTENDED IS COLD AND DRY AS TEMPERATURES DECLINE THROUGH
THE PERIOD.
- SEVERAL NIGHTS OF SUBFREEZING TEMPERATURES ARE EXPECTED.
- WARM UP SHOULD BEGIN BY THE MIDDLE OF NEXT WEEK
MUCH COOLER THAN NORMAL TEMPS EXPECTED SATURDAY THROUGH MONDAY, WITH
TEMPS GRADUALLY WARMING AS WE APPROACH CHRISTMAS EVE AND DAY. DEEP
TROUGHING IS FORECAST TO BE SET UP ACROSS THE EASTERN CONUS FOR MUCH
OF THIS PERIOD, WITH THE PATTERN SHIFTING GRADUALLY AS WE HEAD INTO
NEXT WEEK. THE INTENSE CONVERGENCE ALOFT SHOULD AID IN SUPPORTING A
STRONG SURFACE HIGH PRESSURE SETTLING INTO THE REGION OVER THE
WEEKEND AND INTO NEXT WEEK. THE CENTER OF THIS WILL LIKELY SET UP
OVER THE MID-ATLANTIC, WITH A SURFACE RIDGE AXIS SETTING UP
SOUTHEAST OF THE APPALACHIANS. THE AIRMASS ASSOCIATED WITH THIS IS
ARCTIC IN ORIGIN, AND AS SUCH HIGHS AND LOWS WILL LIKELY BE WELL
BELOW NORMAL. LOOK FOR HIGHS IN THE 40S SUNDAY AND MONDAY, WITH
UPPER 40S OR LOW 50S EXPECTED ON SATURDAY AND TUESDAY. OVERNIGHT
LOWS WILL BE THE STORY, THOUGH, AS TEMPS WILL LIKELY APPROACH THE
UPPER TEENS AND LOW 20S ON SUNDAY NIGHT AND MONDAY NIGHT. WE'LL BE
ON THE SOUTHERN END OF THIS HIGH PRESSURE, SO SURFACE WINDS ARE
EXPECTED TO STAY UP NEAR 5-8 MPH POTENTIALLY. THIS COULD RESULT IN
WIND CHILLS AS LOW AS 10-15F ON MONDAY MORNING, WHICH WOULD BE IN
OUR COLD WEATHER ADVISORY CRITERIA. IT IS SOMETHING TO WATCH AS
THERE IS LITTLE ELSE EXPECTED IN THE LONG TERM PERIOD WITH THE DRY
HIGH PRESSURE HANGING AROUND. WEATHER LOOKS TO GET MORE ACTIVE BY
THE MIDDLE OF NEXT WEEK; HOWEVER, GUIDANCE IS LIKELY TO STRUGGLE
WITH THAT SYSTEM GIVEN THE COMPLEXITY OF THE SYNOPTIC SETUP AT A
HEMISPHERIC LEVEL RIGHT NOW. CONFIDENCE IS RELATIVELY HIGH THAT
WE'LL BEGIN TO WARM UP ON TUESDAY AND WEDNESDAY OF NEXT WEEK,
THOUGH.
AVIATION /09Z WEDNESDAY THROUGH SUNDAY/
IFR TO LIFR RESTRICTIONS EXPECTED THROUGH MID-MORNING.
LOW LEVEL MOISTURE HAS INCREASED WHICH HAS LED TO WIDESPREAD
IFR/LIFR CIG/VSBY RESTRICTIONS. IMPROVEMENT IS LIKELY BY MID TO
LATE MORNING WITH LIGHT SOUTHWESTERLY WINDS. MVFR CONDITIONS ARE
EXPECTED BY MIDDAY, RETURNING TO VFR THIS AFTERNOON. SOME LIGHT
SHOWERS AND A FEW THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON AND
EVENING, BUT UNCERTAINTY AS TO THEIR COVERAGE SO HAVE LEFT THEM OUT
OF THE TAF. ANOTHER ROUND OF RESTRICTIONS IS POSSIBLE TONIGHT, BUT
THEY MAY NOT BE AS WIDESPREAD.
EXTENDED AVIATION OUTLOOK...PATCHY FOG AND LOW CEILINGS
POSSIBLE THURSDAY AND FRIDAY MORNING.
CAE WATCHES/WARNINGS/ADVISORIES
SC...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR SCZ016-018-
020>022-025>031-035-037-038-041-115-116-135>137.
GA...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR GAZ040-
063>065-077.
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