233
FXUS62 KCAE 170259
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
959 PM EST MON DEC 16 2024
SYNOPSIS
WARM AND DRY CONDITIONS ARE EXPECTED AS MID-LEVEL RIDGING
DEVELOPS ACROSS THE SOUTHEAST. A FRONT WITH SOME SCATTERED
SHOWERS IS EXPECTED ON WEDNESDAY, WITH A STEADY COOL DOWN
EXPECTED FOLLOWING THIS FRONT INTO THE WEEKEND. WELL BELOW
AVERAGE TEMPS ARE LIKELY SUNDAY AND INTO EARLY NEXT WEEK.
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
KEY MESSAGE(S):
- DENSE FOG DEVELOPING ACROSS THE WRN MIDLANDS AND NR CSRA
- DENSE FOG POSSIBLE TONIGHT ACROSS THE REMAINDER OF THE CWA
BASED ON OBSERVATIONS AND SATELLITE DATA, A DENSE FOG ADVISORY
HAS BEEN ISSUED FROM FAIRFIELD COUNTY SOUTH/SOUTHWEST INTO THE
NORTHERN CSRA COUNTIES. ADDITIONAL COUNTIES MAY NEED TO BE ADDED
OVERNIGHT. WILL CONTINUE TO MONITOR.
CLEAR SKIES AND NEAR CALM WINDS THIS EVENING
HAVE LEAD TO STRONG NOCTURNAL COOLING. THE GUIDANCE HAS
CONTINUED TO INDICATE WIDESPREAD FOG DEVELOPMENT. THE FOG HAS
ALREADY FORMED ACROSS PORTION OF THE UPSTATE AND INTO THE
WESTERN MIDLANDS AND NORTHERN CSRA. TRENDS AND ATMOSPHERIC
CONDITIONS INDICATE ADDITIONAL AREAS OF FOG DEVELOPMENT ACROSS
THE MIDLANDS AND CSRA AROUND MIDNIGHT. THIS IS SUPPORTED BY THE
NBM, LAMP AND HRRR. FOG MAY BECOME DENSE ACROSS THE ENTIRE CWA.
STAYED CLOSE TO THE NBM FOR OVERNIGHT LOWS WITH UPPER 40S TO
LOW 50S.
SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/
KEY MESSAGE(S):
- WARM AND DRY TUESDAY. AN APPROACHING FRONT WILL DEVELOP SOME
SHOWERS FOR WEDNESDAY.
FOLLOWING A FOGGY START ACROSS MOST OF THE AREA, BROAD HEIGHT
RISES WILL CONTINUE ACROSS THE REGION ON TUESDAY BUT THE 500MB
RIDGING ALOFT WILL STEADILY FLATTEN OUT AND BECOME MORE ZONAL.
WITH THE 850MB AND SURFACE RIDGING OFFSHORE, STRENGTHENING
SOUTHWESTERLY WILL DEVELOP ACROSS OUR AREA TUESDAY. ANY RESIDUAL
FOG-STRATUS SHOULD EASILY BE SCOURED OUT THROUGHOUT THE MORNING
DUE TO THIS INCREASING FLOW. BETWEEN THE RIDGING ALOFT,
SOUTHWESTERLY FLOW, AND 850MB TEMPS 8-12 C, A WARM DAY IS IN
STORE WITH HIGHS INTO THE LOW- MID 70'S EXPECTED.
A QUICKLY DIVING 500MB SHORTWAVE WILL DRIVE A BROAD COLD FRONT
INTO THE EASTERN US AS WE MOVE INTO WEDNESDAY. THE ASSOCIATED
STRENGTHENING FLOW AHEAD OF THE FRONT WILL INCREASE MOISTURE
CONVERGENCE AND PWAT'S WILL PUSH BACK TO AROUND 1.0" BY
WEDNESDAY MORNING. THERE IS NOT A LARGE RESERVOIR OF MOISTURE
AVAILABLE TO THE SOUTHWEST HOWEVER, HENCE WHY PWAT'S ONLY RISE
TO AROUND 1.0" FOR MOST OF THE AREA. THE DETERMINISTIC GUIDANCE
HAS COME INTO MUCH BETTER AGREEMENT WITH THE PRECIP DEPICTION
FOR THIS SYSTEM, WITH DEVELOPING PREFRONTAL, ISENTROPICALLY
FORCED SHOWERS THROUGHOUT THE DAY BUT THEN VERY LITTLE, IF ANY,
PRECIP FROM THE FRONTAL FORCING ITSELF LATER WEDNESDAY
AFTERNOON; THIS IS AGAIN PRIMARILY A RESULT OF THE RELATIVELY
WEAK MOISTURE CONVERGENCE BUT ALSO A LACK OF SYNOPTIC SCALE
FORCING OVER OUR AREA. IN THE PREFRONTAL WAVE OF PRECIP, WE
COULD SEE AN ISOLATED THUNDERSTORM IN THE DEEPEST MOISTURE
ACROSS THE EASTERN MIDLANDS; GEFS AND EC DEVELOPS SOME LOW END
SURFACE BASED INSTABILITY BETWEEN 300-500 J/KG BUT MID-LEVEL
LAPSE RATES ARE VERY WEAK. THE FRONT SHOULD PUSH THROUGH THE
AREA LATE WEDNESDAY AND OVERNIGHT THURSDAY, SHIFTING WINDS OUT
OF THE NORTHWEST BY THURSDAY MORNING.
LONG TERM /THURSDAY THROUGH MONDAY/
KEY MESSAGE(S):
- A GENERAL COOL DOWN IS EXPECTED THROUGH THE WEEKEND. THE
COLDEST AIR OF THE SEASON WILL LIKELY PUSH IN FOR SUNDAY AND
INTO MONDAY.
BROAD TROUGHING ALOFT IS EXPECTED TO SETTLE IN ACROSS THE
EASTERN CONUS THROUGHOUT THE LONG TERM PERIOD WITH WELL BELOW
AVERAGE TEMPS EXPECTED BY LATE IN THE WEEKEND. A SERIES OF SHARP
SHORTWAVES WILL PUSH IN FROM THE NORTHWEST, DRIVING SOME
REINFORCING FRONTS INTO THE AREA AND DIGGING THE TROUGH FURTHER.
WELL BELOW AVERAGE TEMPS WILL THEN LIKELY DEVELOP FOR SATURDAY
ALONG WITH EXTREMELY DRY AIR AS PWAT'S FALL TO AROUND 0.25".
DETERMINISTIC AND ENSEMBLE GUIDANCE ARE ALL IN GOOD AGREEMENT
OVER THIS INITIAL SLUG OF COLD, DRY AIR WITH ONLY A 5 DEGREE
INTERQUARTILE RANGE IN THE NBM MEMBERS FOR HIGH TEMPS ON
SATURDAY (MEDIAN OF 49 F), DESPITE BEING DAY 5. ANOTHER
REINFORCING SHORTWAVE IS EXPECTED SUNDAY AND INTO MONDAY WHICH
MUCH OF THE GUIDANCE CONTINUES TO HIT AT. BASED ON THE GEFS AND
ECE, MEAN 850 MB ANOMALIES PUSH OVER -15 C BY SUNDAY MORNING AND
INTO MONDAY. EC AND GEFS ENSEMBLE PERCENTILES ARE HIGHLIGHTING
THIS TIME PERIOD WITH TEMPS AND HEIGHTS BELOW IN THE 1-10TH
PERCENTILE; MUCH THE SAME FOR THE EC EFI, WITH THE ENTIRE
HIGHLIGHTED, BUT NOT NOTABLE SOT AT THIS TIME. SO THE ENSEMBLE
SOLUTION WOULD SUGGEST A COLD, BUT NOT QUITE THREATENING
RECORDS, TYPE OF EVENT WITH DAYTIME HIGHS IN THE 40'S AND
OVERNIGHT LOWS IN THE 20'S, MAYBE INTO THE 10'S. AS AN FYI,
CURRENT FORECASTED WIND CHILLS ARE BELOW 20 F WHICH IS NEAR COLD
WEATHER ADVISORY CRITERIA (A NEW PRODUCT FOR 2024).
AVIATION /03Z TUESDAY THROUGH SATURDAY/
LIFR RESTRICTIONS EXPECTED AFTER 06Z DUE TO DENSE FOG
DEVELOPMENT.
HIGH PRESSURE GENERALLY REMAINS IN CONTROL ACROSS THE AREA. WITH
LINGERING LOW LEVEL MOISTURE, MODERATELY HIGH CONFIDENCE IN
LIFR VISIBILITIES AND CEILINGS DEVELOPING AT THE COLUMBIA AND
AUGUSTA TERMINALS AFTER MIDNIGHT. A BIT MORE QUESTIONABLE AS TO
THE RESTRICTIONS THAT DEVELOP AT OGB WITH GUIDANCE TRENDING MORE
TOWARDS TEMPORARY MVFR RESTRICTIONS POSSIBLE BUT BACKING OFF TO
THE OVERALL POTENTIAL FOR WIDESPREAD RESTRICTIONS. RESTRICTIONS
LIKELY DIMINISH BY MID TO LATE MORNING. OVERALL THROUGHOUT THE
TAF PERIOD, WINDS EXPECTED TO REMAIN LIGHT AND VARIABLE.
EXTENDED AVIATION OUTLOOK...POTENTIAL FOR SHOWERS AND ASSOCIATED
RESTRICTIONS WEDNESDAY INTO THURSDAY.
CAE WATCHES/WARNINGS/ADVISORIES
SC...DENSE FOG ADVISORY UNTIL 8 AM EST TUESDAY FOR SCZ018-020-021-
025-026.
GA...DENSE FOG ADVISORY UNTIL 8 AM EST TUESDAY FOR GAZ040-063-064.
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
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