218
FXUS62 KGSP 161921
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
221 PM EST MON DEC 16 2024
SYNOPSIS
DRIER TODAY WITH RAIN CHANCES RETURNING FOR THE MOUNTAINS TONIGHT
INTO TUESDAY AHEAD OF AN APPROACHING COLD FRONT. WELL ABOVE NORMAL
TEMPERATURES RETURN TUESDAY INTO WEDNESDAY, WITH A COLD FRONT
INCREASING RAIN CHANCES AREA-WIDE WEDNESDAY AFTERNOON AND EVENING.
DRIER AND COOLER CONDITIONS ARE EXPECTED BEHIND THE FRONT THROUGH
THE WEEKEND, OUTSIDE OF NORTHWEST FLOW SNOW SHOWERS IN THE WESTERN
NORTH CAROLINA MOUNTAINS FRIDAY AFTERNOON INTO SATURDAY MORNING.
NEAR TERM /THROUGH TUESDAY/
AS OF 147 PM EST MONDAY: EXTENSIVE LOW CLOUDS CONTINUE TO BLANKET
MOST OF THE FCST AREA EARLY THIS AFTERNOON, BUT WERE THINNING
ACROSS THE MTNS. MEANWHILE, THE MIXING EDGE OVER THE MIDLANDS OF
SC WAS WORKING NORTHWESTWARD TOWARD THE UPSTATE AND SRN PIEDMONT
OF NC, SO THE RACE IS ON TO ELIMINATE THE CLOUDS AND SEE THE SUN
FROM GREENWOOD TO CHESTER AND MONROE. DON'T GET YOUR HOPES UP IN
THE AREA BETWEEN I-85 AND THE MOUNTAINS, AS IT IS HIGHLY LIKELY
THAT AREA WILL REMAIN SOCKED IN WITH THE LOW OVERCAST UNTIL MAYBE
RIGHT AROUND SUNSET. TEMPS WILL BE MODULATED BY WHERE WE MANAGE
TO THIN OUT THE CLOUDS.
AS IS TYPICALLY THE CASE WITH REMNANT COOL POOLS AT THIS TIME OF
THE YEAR, ONCE THE SUN GOES DOWN THE LOW CLOUDS WILL EXPAND AGAIN
WITH SOME LIGHT UPSLOPE FLOW. A ZONAL FLOW ALOFT IS EXPECTED
TO STRING OUT A WEAK COLD FRONT TO THE NW OVERNIGHT. SOME WEAK
FORCING ALOFT IS EXPECTED TO SKIRT THE NC MTNS AS IT MOVES ACROSS
THE GREAT VALLEY AND THEN PAST JUST TO OUR NORTH OVERNIGHT, AND
THE GUIDANCE RESPONDS WITH SOME PRECIP CHANCES MAINLY ALONG THE
TN BORDER REGION LATE TONIGHT THAT PEAK WITH SOME LIKELY RAIN
OVER THE SMOKIES. THIS SHOULD NOT POSE ANY P-TYPE ISSUE, AS THE
LOW CLOUD BLANKET WILL KEEP DIURNAL RANGES SMALL AND TEMPS ON
THE ORDER OF 10-15 DEGREES ABOVE NORMAL. LOW LEVEL MOISTURE WILL
REMAIN PLENTIFUL EAST OF THE MOUNTAINS, SO THE BIG QUESTION IS,
DO WE DEVELOP ANY DENSE FOG LATE THIS EVENING, AND IF SO, HOW
EXTENSIVE DOES IT GET? THE SITUATION IS NOT IDEAL, WITH A LACK OF
MID/UPPER DRYING AND MOISTURE LAPSE RATES NOT EXACTLY FAVORABLE,
SO THE CURRENT THINKING IS WE WILL HAVE MORE OF THE LOW STRATUS AND
LESS OF THE DENSE FOG. THE FRONT, AS IT WERE, SHOULD LAY OUT ACROSS
THE FCST AREA ON TUESDAY WITH THE UPPER FLOW BECOMING MORE WSW,
BUT WHAT MEAGER FORCING THERE IS SHOULD MOVE OUT TO THE EAST BY
THE MIDDLE PART OF THE DAY. THAT WILL LEAVE US WITH A RAIN CHANCE
IN THE MORNING TO EARLY AFTERNOON, MAINLY OVER THE HIGHER TERRAIN
WHEN THE TAIL END OF THE VORTICITY MOVES PAST, BUT NOT A LOT OF
POTENTIAL FOR ANYTHING MORE THAN PASSING VERY LIGHT RAIN. THE
POSITION OF THE FRONT AND TRACK OF THE VORT SUGGESTS THE AREA
S/E OF I-85 WILL STAY DRY. THE TREND HAS BEEN FOR LESS COVERAGE
AND AN EARLIER DEPARTURE AS WELL, SO PRECIP PROBS ARE CURTAILED
TO THE FAR WESTERN PART BY THE END OF THE DAY. TEMPS WILL ONCE
AGAIN BE TRICKY BECAUSE OF THE TRAPPED REMNANT COOL POOL. LOW
CLOUDS AND FOG SHOULD DELAY THE WARMUP THROUGH THE LATE MORNING,
BUT IT APPEARS THAT WITH THE FRONT LAYING OUT WE WILL SEE ENOUGH
SFC WARM ADVECTION AND MIXING TO EVENTUALLY ELIMINATE THE COLD POOL
IN THE AFTERNOON, SO A NICE REBOUND ABOVE NORMAL IS STILL EXPECTED.
SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/
AS OF 130 PM EST MONDAY...
KEY MESSAGES:
1) TRENDING DRIER TUESDAY EVENING INTO WEDNESDAY MORNING WITH RAIN
HOLDING OFF UNTIL LATE WEDNESDAY AFTERNOON/EVENING
2) WELL ABOVE NORMAL TEMPERATURES LINGER THROUGH WEDNESDAY NIGHT
3) DRIER AND COOLER ON THURSDAY WITH THE SUNSHINE RETURNING
A COLD FRONT WILL APPROACH OUT OF THE WEST TUESDAY EVENING INTO
WEDNESDAY AFTERNOON BEFORE TRACKING ACROSS THE FORECAST AREA
WEDNESDAY EVENING INTO WEDNESDAY NIGHT. THE 12Z CAMS DEPICT MOSTLY
DRY CONDITIONS TUESDAY NIGHT INTO EARLY WEDNESDAY AFTERNOON, SO WENT
WITH LOWER POPS THAN THE PREVIOUS FORECAST HAD. CAMS SHOW THE BEST
TIMING FOR WILL BE LATE WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT
AHEAD OF AND ALONG THE FRONTAL BOUNDARY. HAVE THE HIGHEST POPS
CONFINED TO THE WESTERN NORTH CAROLINA MOUNTAINS WITH LOWER POPS
ELSEWHERE FOR NOW BASED ON THE LATEST CAM AND GLOBAL MODEL GUIDANCE
TRENDS. ALL LIQUID PRECIP IS EXPECTED WITH TEMPS TRENDING WELL ABOVE
NORMAL THROUGH WEDNESDAY NIGHT. LOWS TUESDAY NIGHT WILL END UP ~20
DEGREES ABOVE NORMAL THANKS TO INCREASING CLOUD COVER. HIGHS ON
WEDNESDAY WILL REMAIN WELL ABOVE NORMAL (~15 DEGREES) THANKS TO
STRONG SW'LY FLOW AHEAD OF THE FRONT. BREEZY SW WINDS CAN BE
EXPECTED AHEAD OF THE FRONT AREA-WIDE ON WEDNESDAY. WINDS WILL
GRADUALLY TURN NW BEHIND THE FRONT, WITH GUSTS LINGERING ACROSS THE
MOUNTAINS THROUGH WEDNESDAY NIGHT BEFORE TAPERING OFF AROUND
DAYBREAK THURSDAY. LOWS WEDNESDAY NIGHT WILL BE COOLER, BUT STILL
~10-12 DEGREES ABOVE NORMAL.
DRIER CONDITIONS ARE EXPECTED BEHIND THE FRONT BY EARLY THURSDAY
MORNING THANKS TO SFC HIGH PRESSURE BUILDING IN FROM THE WEST. HIGHS
ON THURSDAY WILL BE NOTICEABLY COOLER BEHIND THE FRONT, DESPITE THE
RETURN OF SUNSHINE, BUT WILL STILL END UP ~3-6 DEGREES ABOVE NORMAL.
LOWS THURSDAY NIGHT WILL DROP INTO THE 30S IN MOST AREAS BUT TEMPS
WILL STILL END UP ~5-8 DEGREES ABOVE NORMAL THANKS TO PARTLY CLOUDY
SKIES.
LONG TERM /FRIDAY THROUGH MONDAY/
AS OF 200 PM EST MONDAY...
KEY MESSAGES:
1) COOLING TREND CONTINUES INTO THE WEEKEND, WITH WELL BELOW NORMAL
TEMPERATURES RETURNING ON SATURDAY
2) DRY THROUGH THE LONG TERM OUTSIDE OF NW FLOW SNOW SHOWERS IN THE
WESTERN NC MOUNTAINS FRIDAY INTO EARLY SATURDAY
2 GUSTY WINDS MAY DEVELOP FRIDAY INTO SATURDAY, ESPECIALLY ACROSS
THE MOUNTAINS
A MOSTLY DRY COLD FRONT WILL TRACK ACROSS THE WESTERN CAROLINAS AND
NORTHEAST GEORGIA ON FRIDAY, ALLOWING GUSTY NW WINDS TO DEVELOP
ACROSS THE MOUNTAINS. GUSTY WINDS WILL LINGER THROUGH FRIDAY NIGHT
BEFORE GRADUALLY TAPERING OFF SATURDAY. THE LATEST GLOBAL MODEL
GUIDANCE AGREE THAT THERE WILL BE ENOUGH MOISTURE BEHIND THE FRONT
FOR NW FLOW SNOW SHOWERS TO DEVELOP FRIDAY AFTERNOON INTO EARLY
SATURDAY MORNING ALONG THE NC/TN BORDER. THE NBM DID END UP WITH
SOME VERY LIGHT SNOWFALL ACCUMS (A FEW TENTHS OF AN INCH) THIS
FORECAST CYCLE. THE LREF 90TH PERCENTILE ACCUMULATED SNOWFALL ONLY
SHOWS UP TO AN INCH ALONG THE TN BORDER FRIDAY INTO EARLY SATURDAY
SO NOT ANTICIPATING A MAJOR NW FLOW SNOW EVENT. DRY CONDITIONS ARE
EXPECTED ELSEWHERE THANKS TO SFC HIGH PRESSURE BUILDING INTO THE
REGION BEHIND THE FRONT AND LINGERING THROUGH THE REST OF THE
FORECAST PERIOD. WE WILL HAVE ONE MORE DAY OF ABOVE NORMAL TEMPS ON
FRIDAY AHEAD OF THE FRONT BEFORE WELL BELOW NORMAL TEMPS RETURN
BEHIND THE FRONT THIS WEEKEND INTO EARLY NEXT WEEK.
AVIATION /20Z MONDAY THROUGH SATURDAY/
AT KCLT AND ELSEWHERE: A TYPICAL SITUATION ACROSS THE REGION THIS
AFTERNOON WITH A REMNANT COOL POOL AND EXTENSIVE LOW CLOUDS LEFTOVER
FROM A COLD AIR DAMMING WEDGE. KAVL SHOULD STAY MAINLY VFR THRU THE
EVENING, BUT A TEMPORARY MVFR CEILING IS POSSIBLE. ON THE OTHER
END OF THE COOL POOL IS KCLT, WHICH STILL HAS A SHOT AT BRIEF
IMPROVEMENT IN THE LATE AFTERNOON. UNTIL THEN, LIFR CEILING WILL
PERSIST WITH IFR/MVFR HOLES. THE REST OF THE TERMINALS WILL STAY IN
THE CLOUDS FOR THE DURATION WITH CONTINUED LIFR/IFR CEILING. EVEN
KCLT WILL SEE A RETURN OF THE IFR TO LIFR CEILING ONCE THE SUN
GOES DOWN, WHICH IS A SAFE BET IN THESE CIRCUMSTANCES. WIND WILL
REMAIN LIGHT S. THE BIG QUESTION FOR TONIGHT IS HOW BAD DOES THE
CEILING/VIS GET? THE SET-UP IS NOT EXACTLY THE BEST FOR DENSE FOG,
BUT SOME OF THE GUIDANCE SUGGESTS A PERIOD OF VLIFR EAST OF THE
MOUNTAINS IN THE LATE EVE TO PRE-DAWN HOURS. WE WILL RESIST THIS
FOR THE TIME BEING BECAUSE OF CONFIDENCE ISSUES, AND BECAUSE OFTEN
THE GUIDANCE BACKS OFF AS THE WOULD-BE EVENT DRAWS NEAR. AT ANY
RATE, WIDESPREAD LIFR IS EXPECTED, WITH A VERY SLOW IMPROVEMENT
ONCE AGAIN OWING TO A LACK OF ANY STRONG MECHANISM TO DISLODGE
THE ENTRENCHED LOW CLOUDS AND COOL TEMPS.
OUTLOOK: RESTRICTIONS MAY NOT CLEAR OUT UNTIL TUESDAY AFTERNOON. AN
UNSETTLED PATTERN CONTINUES THROUGH THE REST OF THE WEEK AS
MULTIPLE STORM SYSTEMS PUSH INTO REGION LIKELY LEADING TO PERIODS
OF ASSOCIATED RESTRICTIONS.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...AR
NEAR TERM...PM
SHORT TERM...AR
LONG TERM...AR
AVIATION...PM
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