123
FXUS62 KCAE 161922
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
222 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 /THROUGH TONIGHT/
KEY MESSAGE(S):
- DENSE FOG POSSIBLE TONIGHT.
FLAT UPPER RIDGE CENTERED OVER FLORIDA. LOW AMPLITUDE UPPER
TROUGH OVER THE UPPER MIDWEST MOVING TOWARD THE GREAT LAKES/OHIO
VALLEY THIS EVENING AND NORTHEAST BY MORNING. GENERALLY
SOUTHWEST FLOW ALOFT AS RIDGE AXIS MOVES OFF THE COAST. SURFACE
RIDGE CENTERED ACROSS THE WESTERN CAROLINAS. LOW CLOUDINESS THIS
MORNING HAS ERODED ACROSS MUCH OF THE AREA. EXPECT MAINLY CLEAR
SKIES EARLY THIS EVENING. TEMPERATURES ARE RISING INTO 60S
ACROSS CENTRAL AND EASTERN AREAS WITH 50S IN THE PIEDMONT. A FEW
AREAS WILL RISE TO NEAR 70, WELL ABOVE NORMAL FOR THIS TIME OF
YEAR, MAINLY IN THE SOUTHEAST MIDLANDS DUE TO WARM ADVECTION.
CLEAR SKIES AND NEAR CALM WINDS THIS EVENING LEADING TO STRONG
NOCTURNAL COOLING EARLY. GUIDANCE IS FAIRLY CONSISTENT TONIGHT
WITH WIDESPREAD FOG DEVELOPMENT BY AROUND MIDNIGHT WITH SUPPORT
FROM THE NBM, LAMP AND HRRR. FOG MAY BE DENSE. STAYED CLOSE TO
THE NBM FOR OVERNIGHT LOWS WITH UPPER 40S TO LOW 50S.
SHORT TERM /TUESDAY 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 /19Z MONDAY THROUGH SATURDAY/
VFR CONDITIONS THROUGH THE EARLY EVENING. LIFR RESTRICTIONS
EXPECTED AFTER 05Z DUE TO DENSE FOG DEVELOPMENT.
HIGH PRESSURE ACROSS THE AREA. LOW CLOUDS FROM THE MORNING HAVE
ERODED. EXPECT AT MOST A FEW STRATO-CU CLOUDS THIS AFTERNOON BUT
MAINLY CLEAR THROUGH AT LEAST 00Z. WINDS LIGHT AND VARIABLE.
GUIDANCE IS CONSISTENT WITH DEVELOPING FOG AFTER 05Z WITH CLEAR
SKIES ALOFT, SHALLOW LOW-LEVEL MOISTURE AND NEAR CALM WINDS.
THE CONFIDENCE IS RELATIVELY HIGH FOR DENSE FOG. WENT WITH LIFR
AT ALL TERMINALS AFTER 05Z THROUGH 12Z TUESDAY, THEN SLOW
IMPROVEMENT WITH VFR BY 15Z.
EXTENDED AVIATION OUTLOOK...POTENTIAL FOR SHOWERS AND ASSOCIATED
RESTRICTIONS WEDNESDAY INTO THURSDAY.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
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