055
FXUS62 KCAE 171847
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
147 PM EST FRI JAN 17 2025
SYNOPSIS
MOISTURE INCREASES TONIGHT AND WIDESPREAD SHOWERS EXPECTED
SATURDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE EASTERN U.S.
BEHIND THE SYSTEM, EXPECT WELL BELOW NORMAL TEMPERATURES AS A
ANOMALOUSLY DEEP TROUGH AND SURFACE HIGH PUSHES AN ARCTIC AIR
MASS INTO THE CENTRAL AND EASTERN US. BY THE MIDDLE OF NEXT
WEEK, A COASTAL LOW WILL LIKELY INCREASE PRECIPITATION CHANCES
WITH SOME WINTRY POTENTIAL POSSIBLE BUT STILL UNCERTAIN.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGE(S):
- QUIET WEATHER CONTINUES INTO TONIGHT.
- CLOUDS INCREASE TONIGHT, WITH A SLIGHT CHANCE FOR RAIN IN THE
CSRA AROUND DAYBREAK.
HIGH PRESSURE AND WEAK RIDGING OVER THE AREA THIS AFTERNOON HAVE
BROUGHT BRIGHT SUNNY SKIES AND NEAR NORMAL TEMPERATURES. THE
HIGH PRESSURE AND RIDGING ARE EXPECTED TO SHIFT EASTWARD THROUGH
THE REST OF THE AFTERNOON INTO TONIGHT.
AN UPPER TROUGH AND ASSOCIATED COLD FRONT CURRENTLY OVER THE
CENTRAL CONUS MOVE TOWARD THE REGION TONIGHT. BECAUSE OF THIS,
EXPECT INCREASING CLOUD COVER TO DEVELOP OVERNIGHT, KEEPING
TEMPERATURES MORE MILD COMPARED TO THE PAST FEW NIGHTS. LOWS ARE
EXPECTED TO BE IN THE MID 30S TO LOWER 40S. LATEST GUIDANCE HAS
SLOWED THE ONSET OF PREFRONTAL PRECIPITATION TONIGHT, SO HAVE
DELAYED THE START OF PRECIPITATION TO THE AREA. HOWEVER, A
SLIGHT CHANCE OF SHOWERS BEGINS TO ENTER THE UPPER CSRA NEAR
DAYBREAK.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/
KEY MESSAGE(S):
- WIDESPREAD SHOWERS MOVE THROUGH SATURDAY, WITH SOME
REDEVELOPMENT POSSIBLE SUNDAY.
- A STRONG COLD FRONT PUSHES THROUGH SUNDAY, BRINGING BREEZY
CONDITIONS AND MUCH COLDER TEMPS OVERNIGHT.
SATURDAY AND SATURDAY NIGHT: THE AFOREMENTIONED TROUGH AND
FRONT CONTINUE WORKING THEIR WAY TOWARD THE AREA ON SATURDAY. A
SHORTWAVE EMBEDDED WITHIN THE LARGER TROUGH IS EXPECTED TO BRING
WIDESPREAD LIGHT TO MODERATE SHOWERS TO THE AREA THROUGH THE
DAY. PRECIPITATION AMOUNTS ARE FORECAST RANGE FROM A TENTH OR
TWO OF AN INCH IN THE NORTHERN MIDLANDS TO NEAR A HALF INCH IN
THE CSRA. MOST OF THIS SHOULD FALL IN THE MID MORNING TO EARLY
AFTERNOON BEFORE TAPERING OFF FOR A WHILE SATURDAY EVENING AND
OVERNIGHT. WARM AIR ADVECTION IS EXPECTED TO HELP KEEP
TEMPERATURES NEAR NORMAL.
SUNDAY AND SUNDAY NIGHT: THE UPPER TROUGH AND SURFACE FRONT ARE
FORECAST TO MOVE THROUGH THE REGION ON SUNDAY, ALLOWING FOR THE
POTENTIAL FOR REDEVELOPMENT OF SOME SHOWER ACTIVITY. THE HIGHEST
CHANCES FOR SHOWER ACTIVITY ON SUNDAY IS FOR THE EASTER
MIDLANDS. ANOTHER TENTH OF AN INCH OF RAIN IS POSSIBLE ON
SUNDAY. IN ADDITION TO THE POTENTIAL FOR RAINFALL, BREEZY
CONDITIONS ARE EXPECTED JUST AHEAD OF AND BEHIND THE STRONG COLD
FRONT AS IT MOVES THROUGH THE REGION. BEHIND THE FRONT, STRONG
COLD AIR ADVECTION MOVES INTO THE REGION AND A STRONG HIGH
PRESSURE FILTERS INTO THE SOUTHEAST. THIS IS LIKELY TO USHER IN
MUCH COLDER WEATHER BEGINNING SUNDAY NIGHT AS LOWS FALL TO 10-15
DEGREES BELOW NORMAL.
LONG TERM /MONDAY THROUGH THURSDAY/
KEY MESSAGE(S):
- THE COLDEST AIRMASS SO FAR THIS SEASON WILL MOVE INTO MONDAY.
- POTENTIAL FOR SNOW AND WINTRY MIX CONTINUES TO INCREASE FOR PARTS
OF THE AREA TUESDAY INTO WEDNESDAY.
THE EXTREMELY COLD, DRY ARCTIC AIRMASS WILL SETTLE INTO THE FORECAST
AREA BY MONDAY WITH HIGH AND LOW TEMPS RUNNING 20+ DEGREES BELOW
AVERAGE, WITH SURFACE DEW POINTS INTO THE SINGLE DIGITS OR BELOW 0
F. DEPENDING ON THE TIMING OF THE SURFACE WINDS, WE WILL LIKELY
APPROACH COLD WEATHER ADVISORY CRITERIA BOTH MONDAY MORNING AND
AGAIN TUESDAY MORNING AS WIND CHILLS FALL INTO THE LOW-MID TEENS. EC
EFI AND NAEFS CONTINUES TO SHOW THIS AIRMASS WITH A CHARACTERISTIC
"HIGHLY ANOMALOUS BUT LIKELY NOT HISTORIC" SIGNAL.
THINGS START TO MOVE QUICKLY AS WE GET INTO TUESDAY AFTERNOON WITH
THE MUCH DISCUSSED WINTER SYSTEM. THE STRONG SURFACE HIGH WILL SINK
SOUTH AND EAST INTO THE CENTRAL US AS THE BROAD MID-UPPER LEVEL
TROUGH DRAGS INTO THE GOM. THE CORRESPONDING SURFACE LOW THAT WILL
DEVELOP ACROSS THE NORTHERN GOM WILL SLIDE DUE EASTWARD INTO FLORIDA
AND THEN UP THE CAROLINA COAST. OVERALL, GUIDANCE HAS TRENDED
SLIGHTLY MORE NORTHWESTERLY WITH THE EXPECTED LOW TRACK AND BRINGS
THE PRECIP SHIELD FURTHER INTO EASTERN GA AND SC. AS OF THE 12Z RUNS
ON FRIDAY, THERE IS NOTABLY MORE GUIDANCE CONSENSUS AND CONFIDENCE
IN SOME WINTRY PRECIP IMPACTS ACROSS PORTIONS OF EASTERN SC AND
SOUTHEAST GA. HOWEVER, THE EXTENT OF THESE IMPACTS ARE QUITE
UNCERTAIN, WITH A LARGE SPECTRUM FROM NUISANCE TO DISRUPTIVE
POSSIBLE. 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 AT LEAST MINOR IMPACTS,ESPECIALLY
SOUTH OF I-20, BUT UNTIL THE SYNOPTIC SCALE FLOW IS RESOLVED BETTER
ALOFT (HOPEFULLY SATURDAY 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 /18Z FRIDAY THROUGH WEDNESDAY/
VFR CONDITIONS THROUGH THE TAF PERIOD.
HIGH PRESSURE MOVES EAST THIS AFTERNOON, WITH A COLD FRONT
APPROACHING FROM THE WEST LATE THIS WEEKEND. THE NEXT 24 HOURS
WILL REMAIN MOSTLY VFR, ALTHOUGH CLOUDS WILL BE ON THE INCREASE
LATER TONIGHT. MOSTLY CLEAR SKIES THROUGH THIS AFTERNOON, THEN
BROKEN TO OVERCAST UPPER TO MID LEVEL CLOUDINESS MOVES IN AFTER
SUNSET. VFR CEILINGS WILL HOWEVER CONTINUE OVERNIGHT AND INTO
SATURDAY MORNING. RAINFALL SHOULD BE MOVING INTO THE CSRA SITES
BY SUNRISE, THEN INTO THE MIDLANDS BETWEEN 13Z-15Z. VISIBILITIES
IN THE RAIN EXPECTED TO DROP TO MVFR THROUGH THE DAY AT ALL
SITES. NEAR THE END OF THE 24 HOUR FORECAST PERIOD, CONFIDENCE
INCREASING FOR IFR CEILINGS, ESPECIALLY AT AGS/DNL, SO HAVE
INTRODUCED THOSE CONDITIONS ACROSS THE CSRA BY 16Z SATURDAY.
WINDS LIGHT AND OUT OF THE EAST THIS AFTERNOON, THEN MOSTLY
LIGHT AND VARIABLE FROM SUNSET ONWARD INTO SATURDAY. WINDS MAY
BECOME MORE SOUTHERLY LATE IN THE PERIOD AS THE SYSTEM MOVES
THROUGH.
EXTENDED AVIATION OUTLOOK
RESTRICTIONS ARE EXPECTED ON
SATURDAY AFTERNOON AS A LOW PRESSURE SYSTEM WORKS ITS WAY
THROUGH THE REGION.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
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