532
FXUS62 KCAE 180544
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
1244 AM EST SAT JAN 18 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 /UNTIL 6 AM THIS MORNING/
KEY MESSAGE(S):
- CLOUDS INCREASE OVERNIGHT, WITH A SLIGHT CHANCE FOR RAIN IN
THE CSRA AROUND DAYBREAK.
UPPER TROUGH IS DIGGING INTO THE SOUTHERN PLAINS WITH A WEAK
RIDGE AXIS SHIFTING OFFSHORE THIS EVENING, LEADING TO SOUTHWEST
FLOW DEVELOPING AND INCREASING MOISTURE. THIS IS ALREADY EVIDENT
WITH THE INCREASING CLOUDINESS IN THE UPPER LEVELS, ALTHOUGH,
THE 00Z SOUNDING UPSTREAM FROM PEACHTREE CITY INDICATES A
SUBSTANTIAL LAYER OF DRY AIR BELOW 15,000 FEET WITH PWATS AROUND
A QUARTER INCH. AS THE TROUGH DIGS FARTHER SOUTH, STRONGER
MOISTURE TRANSPORT FROM THE GULF OF MEXICO WITH LOWERING CLOUD
DECKS AND THE POTENTIAL FOR SHOWER CHANCES IN THE CSRA AROUND
DAYBREAK, ALTHOUGH THE HIGHER CHANCES FOR RAIN WILL BE AFTER DAY
BREAK. WITH THE INCREASING CLOUDS, EXPECT LOW TEMPERATURES TO
BE WARMER THAN LAST NIGHT WITH LOWS IN THE MID-30S NORTH TO
AROUND 40 IN THE CSRA.
SHORT TERM /6 AM THIS MORNING 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 FRIDAY/
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
0F. 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 /06Z SATURDAY THROUGH WEDNESDAY/
WIDESPREAD RESTRICTIONS EXPECTED FOR MUCH OF THE PERIOD.
HIGH CLOUDS HAVE INCREASED GRADUALLY THIS EVENING, WITH A
GRADUAL THICKENING AND LOWERING EXPECTED OVER THE COMING HOURS.
THESE SHOULD GENERALLY REMAIN VFR THROUGH 12Z AS EVEN UPSTREAM
OBS CLOSER TO THE RAIN SUGGEST THAT CLOUDS ARE ONLY 5KFT TO
8KFT. AS WE GET INTO THE DAY & RAIN BEGINS OVERSPREADING THE
REGION, THOUGH, WE WILL LIKELY SEE THE ATMOSPHERE QUICKLY
MOISTEN UP AT ALL TAF SITES. THE BULK OF THE RESTRICTIONS ARE
FORECAST BY GUIDANCE TO DEVELOP NEAR THE TAIL END OF THE
PRECIPITATION BY MID MORNING, 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 TO LIFR CEILINGS
DEVELOPING BY 00Z AT ALL SITES, LASTING THROUGH THE REMAINDER OF
THE PERIOD (AND INTO THE NEXT TAF PERIOD MORE THAN LIKELY).
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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