467
FXUS62 KCAE 181129
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
629 AM EST SAT JAN 18 2025
SYNOPSIS
WIDESPREAD SHOWERS ARE EXPECTED TODAY AS A COMPLEX LOW PRESSURE
SYSTEM MOVES INTO THE EASTERN U.S. A STRONG COLD FRONT WILL MOVE
THROUGH THE AREA BY MIDDAY SUNDAY WITH STRONG GUSTY WINDS IN ITS
WAKE THROUGH THE AFTERNOON. BEHIND THE FRONT, VERY COLD AIR WILL
BEGIN TO SPREAD ACROSS THE REGION. WELL BELOW NORMAL
TEMPERATURES ARE EXPECTED NEXT WEEK AS AN ANOMALOUSLY DEEP
TROUGH AND SURFACE HIGH PUSHES AN ARCTIC AIR MASS INTO THE
CENTRAL AND EASTERN US. ON TUESDAY, A COASTAL LOW WILL LIKELY
INCREASE PRECIPITATION CHANCES WITH WINTRY POTENTIAL INCREASING,
BUT THE DETAILS REMAIN UNCERTAIN.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGE(S):
- DREARY WEATHER EXPECTED THROUGHOUT THE DAY TODAY
- TWO WAVES OF RAINFALL EXPECTED - ONE THIS MORNING, AND ANOTHER
TONIGHT AS THE SURFACE LOW REORGANIZES
A FAIRLY DREARY AND WET DAY IS AHEAD ACROSS THE FORECAST AREA AS A
SHORTWAVE TROUGH PUSHES THROUGH THE AREA. CLOUDS OVERSPREAD THE
REGION QUICKLY OVERNIGHT AHEAD OF THIS, AND THESE ARE AIDING IN
KEEPING TEMPS ELEVATED IN THE LOW TO MID 40S ACROSS THE AREA AT THIS
TIME. RAIN IS FAIRLY WIDESPREAD TO OUR WEST UNDERNEATH RELATIVELY
ROBUST DIFFLUENCE ALOFT AHEAD OF THE TROUGH AXIS. THIS IS OVERCOMING
SOMEWHAT MARGINALS PWS THAT REMAIN AROUND OR JUST ABOVE 1" EVEN IN
THE IMMEDIATE WARM SECTOR OF THE APPROACHING LOW PRESSURE SYSTEM.
LATEST HI-RES GUIDANCE SUGGESTS THAT RAIN WILL APPROACH THE WESTERN
FA BEFORE 12Z AND SHOULD GENERALLY LAST THROUGH ABOUT 18Z AS THIS
FIRST BOUT OF SYNOPTIC SCALE ASCENT PUSHES EASTWARD. IT MAY TAKE A
BIT FOR THE PRECIP TO BEGIN MAKING IT TO THE GROUND, THOUGH, AS THE
LOW-LEVELS REMAIN QUITE DRY ACROSS THE FORECAST AREA. A LULL IS
EXPECTED THIS AFTERNOON BUT DURING THIS TIME VERY LOW CLOUDS ARE
LIKELY TO DEVELOP. HIGHS REALLY SHOULD BE MUTED THIS AFTERNOON,
LIKELY ONLY MAKING IT INTO THE LOW OR MID 50S ACROSS THE AREA AFTER
THE RAIN MOVES OUT.
ANOTHER SHORTWAVE IS CURRENTLY DIGGING ACROSS THE CENTRAL ROCKIES
AND IS EXPECTED TO INFLUENCE OUR WEATHER TONIGHT, AS WELL. THIS IS
FORECAST TO PHASE WITH THE INITIAL SHORTWAVE AS THE OVERALL LONGWAVE
TROUGH THAT CONTAINS BOTH AMPLIFIES AND DIGS THROUGH THE EASTERN
HALF OF THE CONUS. AS A RESULT, LIFT IS EXPECTED TO QUICKLY INCREASE
AGAIN TONIGHT, WITH A SURFACE LOW DEVELOPING NEAR THE FORECAST AREA.
PWS ARE FORECAST TO RAPIDLY INCREASE TO THE 1.0"-1.25" RANGE AS THIS
OCCURS AND WIDESPREAD SHOWERS ARE LIKELY TO DEVELOP AGAIN AFTER 00Z
AS A RESULT. LOW CLOUDS WILL CONTINUE TO ACCOMPANY THIS, MAKING FOR
A DREARY EVENING AS WELL. OVERALL, PRECIP TOTALS SHOULD REMAIN UNDER
AN INCH BETWEEN BOTH EVENTS. CLOUDS ARE EXPECTED TO HANG AROUND ALL
NIGHT, WITH LOWS FALLING ONLY INTO THE UPPER 40S.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/
KEY MESSAGE(S):
- A STRONG COLD FRONT PUSHES THROUGH SUNDAY, BRINGING BREEZY
CONDITIONS AND MUCH COLDER TEMPS OVERNIGHT.
- THE COLDEST AIRMASS SO FAR THIS SEASON WILL MOVE INTO MONDAY
WITH TEMPERATURES NEAR 20 DEGREES BELOW NORMAL.
- A COLD WEATHER ADVISORY MAY BE NEEDED MONDAY NIGHT.
SUNDAY AND SUNDAY NIGHT...THE HIGHLY AMPLIFIED UPPER TROUGH FROM
THE UPPER MIDWEST SOUTH THROUGH THE MISSISSIPPI VALLEY WILL BE
BE SHIFTING INTO THE EASTERN CONUS. A LOW PRESSURE AREA WILL BE
NEAR THE REGION IN THE MORNING BUT WILL BE LIFTING TO THE
NORTHEAST. A FEW LINGERING SHOWERS POSSIBLE IN THE MORNING BUT
ONCE THE STRONG COLD FRONT MOVES THROUGH AROUND NOON, EXPECT
DRIER AIR TO BEGIN ADVECTING INTO THE AREA. STRONG COLD
ADVECTION WILL DEVELOP IN THE AFTERNOON WITH STRONG MIXING.
WESTERLY WINDS 15 TO 25 MPH WITH GUSTS TO 30-35 MPH ARE EXPECTED
AS THE PRESSURE GRADIENT TIGHTENS BETWEEN THE LOW OFF THE MID
ATLANTIC COAST AND A VERY STRONG RIDGE IN THE MIDWEST. TEMPS
MAXING OUT NEAR 60 DEGREES BUT COLDER AIR WILL BE SPREADING IN
DURING THE LATE AFTERNOON HOURS. COLD ADVECTION CONTINUES
THROUGH THE OVERNIGHT WITH TEMPERATURES FALLING INTO THE 20S AS
THE ARCTIC AIR MASS OVER THE MIDWEST BUILDS EAST.
MONDAY AND MONDAY NIGHT...THE ARCTIC AIR MASS (1040 MB HIGH
PRESSURE SITUATED TO THE NORTH) WILL BE BUILDING OVER THE AREA.
THIS IS INDICATED BY THE VERY LOW DEW POINTS, IN THE SINGLE
DIGITS. EC EFI AND NAEFS CONTINUES TO SHOW THIS AIRMASS WITH A
CHARACTERISTIC "HIGHLY ANOMALOUS BUT LIKELY NOT HISTORIC"
SIGNAL. TEMPERATURES WILL STRUGGLE STAYING IN THE 30S ACROSS
MUCH OF THE REGION WITH FULL INSOLATION DUE TO CONTINUED STRONG
COLD ADVECTION. NOTE 850MB TEMPERATURES AROUND -10C IN THE
AFTERNOON. WIND CHILL TEMPERATURES ARE EXPECTED TO FALL INTO THE
TEENS MONDAY NIGHT NEAR THE COLD WEATHER ADVISORY CRITERION.
LONG TERM /TUESDAY THROUGH FRIDAY/
KEY MESSAGE(S):
-CONFIDENCE IS INCREASING FOR IMPACTS FROM A WINTER STORM LATE
TUESDAY INTO WEDNESDAY.
THE LATEST 00Z MODEL GUIDANCE HAS TRENDED FURTHER INLAND WITH
THE WINTRY PRECIPITATION, MAINLY SNOW LATE TUESDAY INTO
WEDNESDAY. THE CANADIAN MODEL CONTINUES TO BE THE MOST
AGGRESSIVE WITH THIS STORM BUT THE LATEST GFS AND ECMWF ARE
SUGGESTING A STRONGER AND MORE PHASED SYSTEM (EARLIER IN TIME)
BETWEEN THE NORTHERN STREAM TROUGH MOVING OUT OF THE NORTHERN
PLAINS AND THE TROUGH MOVING OUT OF THE DESERT SOUTHWEST. THE
BASE OF THE UPPER TROUGH MOVES INTO THE GULF OF MEXICO. THIS
LEADS TO SURFACE LOW DEVELOPMENT IN THE GULF OF MEXICO WHICH
TRACKS EAST ACROSS FLORIDA TO OFF THE GA/SC COAST TUESDAY NIGHT.
THE ECMWF LOW CENTER IS CLOSER TO THE COAST THAN THE GFS. THE
ECMWF ENSEMBLES HAVE TRENDED MORE TOWARD THE CANADIAN ENSEMBLES
WITH A GREATER THREAT OF WINTRY PRECIPITATION. THE MODELS
CONTINUE TO POINT TO HIGHER PROBABILITIES OF ACCUMULATING SNOW
SOUTH AND EAST OF I-20, BUT NOTE PROBABILITIES APPEAR TO BE
INCREASING TO THE NORTHWEST.
BASED ON THE CLIMATOLOGY AND TYPICAL MODEL BIASES, THERE IS A
NORTHWARD CAP ON HOW FAR THE PRECIP SHIELD SHOULD BE ABLE TO
LIFT INTO SC BASED ON THE POSITIONING AND STRENGTH OF THE
SURFACE HIGH IN THE TN VALLEY. SO A SUPPRESSED LOW WITH HIGHER
CHANCES FOR SNOW- WINTRY PRECIP ALONG I-20 AND I-95, AS COMPARED
TO I-85, REMAINS FAVORED. BUT THE TYPICAL NORTHWESTWARD DRIFT
IN CYCLOGENESIS ACROSS GUIDANCE REMAINS POSSIBLE AS MODELS COME
INTO BETTER DEPICTIONS OF THE SURFACE HIGH POSITION AND
STRENGTH. ADDITIONALLY, LIKE WE SAW IN THE LAST WINTRY PRECIP
EVENT, GUIDANCE WILL UNIFORMLY STRUGGLE IN DEPICTING THE
STRENGTH AND TIMING OF THE WARM ADVECTION ALONG THE DEVELOPING
WARM FRONT ALOFT AND THIS ADDS SOME UNCERTAINTY IN PRECIP TYPE,
ESPECIALLY CLOSER TO THE COAST. ITS TOO FAR OUT FOR ANY
SPECIFICS ON IMPACTS, BUT ITS WORTH NOTING THE POTENTIAL FOR AN
IMPACTFUL WINTER STORM.
SO CONFIDENCE IS INCREASING IN IMPACTS INTO THE CENTRAL MIDLANDS
(POPS HAVE BEEN RAISED ALL AREAS) AND ESPECIALLY SOUTH OF I-20,
BUT UNTIL THE SYNOPTIC SCALE FLOW IS RESOLVED BETTER ALOFT
(HOPEFULLY LATER TODAY OR SUNDAY), SPECIFICS ON THE EXTENT WILL
REMAIN UNCLEAR. REGARDLESS OF ANY WINTRY PRECIP IMPACTS, AN
IMPACTFUL COLD AIRMASS WILL SETTLE INTO THE AREA THROUGH
THURSDAY. HIGH TEMPS WILL REMAIN IN THE 30'S FOR MULTIPLE DAYS
IN A ROW ALONG WITH OVERNIGHT LOWS IN THE TEENS. SO FROZEN PIPES
AND RELATED IMPACTS ARE EXPECTED FROM MONDAY ONWARD.
AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
WIDESPREAD RESTRICTIONS EXPECTED FOR MUCH OF THE PERIOD.
RAIN HAS BEGUN TO APPROACH AND OVERSPREAD THE TAF SITES FROM
WEST TO EAST, WITH LIGHT RAIN BEING REPORTED AT SITES ACROSS THE
WESTERN MIDLANDS AND CSRA. MORE WIDESPREAD RAIN IS EXPECTED TO
PUSH IN OVER THE NEXT COUPLE OF HOURS. THE BULK OF THE
RESTRICTIONS ARE FORECAST BY GUIDANCE TO DEVELOP NEAR THE TAIL
END OF THE PRECIPITATION BY MIDDAY, WITH MVFR SETTLING IN
SOMETIME IN THE 15Z-18Z TIMEFRAME AS RAIN PUSHES EASTWARD. BEST
FORCING SHOULD BE TO OUR EAST AT THIS TIME, WITH SOME SUBSIDENCE
NOTED IN FORECAST SOUNDINGS. AS A RESULT, CLOUDS ARE EXPECTED
TO LOWER QUICKLY AFTER THE INITIAL ONSET OF MVFR. THIS MAY OCCUR
QUICKER THAN WHAT IS EXPLICITLY FORECAST IN THE TAFS, WITH
CLOUDS LIKELY DROPPING TO IFR AND THEN LIFR BY THE EVENING
HOURS. DESPITE A RAPID INCREASE IN UPPER-LEVEL ASCENT BY THE END
OF THIS TAF PERIOD, THERE LOOKS TO BE LITTLE TO SCOUR OUT THE
CEILING RESTRICTIONS. SCATTERED TO NUMEROUS SHOWERS ARE AGAIN
EXPECTED TO DEVELOP AS A SURFACE LOW QUICKLY ORGANIZES ACROSS
WESTERN GA AND SC TONIGHT. ADDITIONALLY, A PW SURGE IS PROBABLE
TONIGHT IN ASSOCIATION WITH THE AFORMENTIONED SURFACE LOW. ALL
OF THESE FACTORS YIELD PRETTY HIGH CONFIDENCE IN IFR OR LIFR
CEILINGS DEVELOPING BY 00Z AT ALL SITES, LASTING THROUGH THE
REMAINDER OF THE PERIOD. WINDS ARE TRICKY TODAY. THEY SHOULD
SHIFT OUT OF THE SOUTHEAST OVER THE NEXT SEVERAL HOURS, LIKELY
BECOMING VARIABLE AFTER THIS MORNING'S RAIN. THEN, THEY LOOK TO
AGAIN SHIFT SOUTHERLY OR SOUTHEASTERLY AGAIN AS THE SURFACE LOW
GETS GOING THIS EVENING. GENERALLY, WINDS SHOULD STAY IN THE
5-10 KNOT RANGE THROUGHOUT THE PERIOD.
EXTENDED AVIATION OUTLOOK
EXPECTING CEILING RESTRICTIONS TO
CONTINUE INTO SUNDAY MORNING. COLD FRONT IS FORECAST TO PASS
THROUGH THE AREA BY SUNDAY AFTERNOON, WHICH SHOULD IMPROVE
CONDITIONS. GUSTY WINDS ARE EXPECTED WITH THIS COLD FRONT.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
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