774
FXUS62 KGSP 171736
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1236 PM EST TUE DEC 17 2024
SYNOPSIS
TEMPERATURES WILL BE SEVERAL DEGREES ABOVE NORMAL THROUGH WEDNESDAY,
WITH A STRONG COLD FRONT APPROACHING FROM THE WEST AND INCREASING
RAIN CHANCES AREA-WIDE WEDNESDAY AFTERNOON AND EVENING. COOLER
CONDITIONS ARE EXPECTED BEHIND THE FRONT THROUGH THE WEEKEND WITH
TEMPERATURES SEVERAL DEGREES BELOW NORMAL SUNDAY AND MONDAY.
NEAR TERM /THROUGH TONIGHT/
AS OF 1230 PM EST TUESDAY: MADE SOME MINOR TWEAKS TO POPS THROUGH
TODAY BASED ON THE LATEST CAM GUIDANCE AND RADAR TRENDS. ALSO
LOWERED POPS TONIGHT AS CAMS GENERALLY SHOW DRY CONDITIONS.
OTHERWISE, SEEING SOME BREAKS IN CLOUD COVER THIS AFTERNOON BUT
THICKER CLOUD COVERAGE IS GRADUALLY APPROACHING OUT OF THE WEST. SO,
ANY SUNSHINE WILL BE FAIRLY SHORT LIVED. MOST OF THE RAIN HAS
DISSIPATED ACROSS THE FORECAST AREA BUT A FEW LIGHT ISOLATED SHOWERS
ARE FLOATING AROUND PER THE LATEST KGSP RADAR LOOPS.
OTHERWISE, CHANCE POPS ARE BEING MAINTAINED FOR THE MOUNTAINS MAINLY
AS A RESULT OF UPSLOPE LIFT; STILL EXPECT THE SFC FRONT WILL STALL
FROM EAST TN TO SOUTHWEST VA AND KEEP THE FOOTHILLS/PIEDMONT IN THE
NEUTRAL TO VERY WEAK WAA REGIME. TEMPERATURES STILL SHOULD REBOUND
INTO THE 60S, EVEN WHERE THE EFFECTS OF THE COLD POOL AND STRATUS
HANG ON THE LONGEST. MOST PIEDMONT AREAS WILL RISE INTO THE UPPER
60S.
THE APPROACH OF A SHORTWAVE INTO THE OZARK REGION STILL IS EXPECTED
TO BACK LOW LEVEL FLOW TO SOUTHERLY AND REACTIVATE THE STALLED
FRONT. THE BEST RESULTING FORCING APPEARS OVER THE NORTHERN PART
OF THE CWA, SO POPS TAPER A BIT IN THE MOUNTAINS FOR A TIME AND
INCREASE TO A SOLID SLIGHT-CHANCE IN AREAS NORTH OF I-40 OVERNIGHT
TONIGHT, AND IN OUR EAST WHERE MOIST MARITIME AIR MAY ADVECT. THE
COLD POOL NOT BEING LIKELY TO GO COMPLETELY AWAY TODAY, AND WITH
LIGHT WINDS AND NEAR-SFC WARM/MOIST ADVECTION, AREAS OF FOG ARE
EXPECTED ACROSS MOST OF THE PIEDMONT ONCE AGAIN. ANOTHER DENSE FOG
ADVISORY MAY BE NEEDED BUT PER USUAL WE WOULD SEEK TO ISSUE THAT
THIS EVENING ONCE WE HAVE CONFIDENCE EXACTLY WHERE. MINS AGAIN
WILL BE CONSIDERABLY ABOVE NORMAL, MOSTLY NEAR 50.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
AS OF 150 AM EST TUESDAY: LONGWAVE UPPER TROUGH WILL DIG ACROSS
FROM THE CENTRAL CONUS TO THE EASTERN SEABOARD DURING THE DAY
WEDNESDAY, WHILE THE STALLED FRONT DRAPED OVER THE AREA BEGINS TO
LIFT NORTH OVERNIGHT TUESDAY INTO WEDNESDAY AS WEAK CYCLOGENESIS
WILL UNDERWAY NEAR THE BASE OF THE TROUGH AND ACTIVATE A SURFACE
LOW ALONG THE ATTENDANT FRONTAL BOUNDARY, WHICH IN TURN ALLOWS FOR
WARM FRONTAL ACTIVATION TO TAKE PLACE WITHIN THE STALLED FRONT. DEEP
LAYER SOUTHWESTERLY FLOW SUGGESTS THAT VERTICAL PROFILES GRADUALLY
BECOME SATURATED, BUT DRY AIR ABOVE THE BOUNDARY LAYER MAY PUT A
CAP IN WIDESPREAD SHOWER/THUNDERSTORM COVERAGE, ESPECIALLY SINCE
THE ASSOCIATED DPVA LAGS BEHIND THE FRONT, WITH NOT MUCH EVIDENCE
FOR PRE-FRONTAL FORCING AS THE COLD FRONT ENTERS THE CFWA WEDNESDAY
AFTERNOON/EVENING. AS A RESULT, LOW-END POPS AND LIGHT QPF RESPONSE
FOR LOCATIONS EAST OF THE MOUNTAINS ON WEDNESDAY BEFORE THE FROPA
OCCURS. STILL EXPECT OROGRAPHICALLY ENHANCED PRECIPITATION TO
DEVELOP ACROSS THE MOUNTAINS AHEAD AND ALONG THE FRONT WILL ALLOW
FOR CONVECTION TO INITIATE DURING THE DAY WEDNESDAY, WITH ALL LIQUID
P-TYPES AS TEMPERATURES ARE WAY TOO WARM ALONG AND AHEAD OF THE COLD
FRONT. THE COLD FRONT WILL COMPLETE A FULL FROPA LATER WEDNESDAY
EVENING, BUT NORTHWEST FLOW PRECIP MAY PERSIST IMMEDIATELY BEHIND
THE FRONT ALONG THE NC/TN BORDER AS THE ASSOCIATED VORT LOBE LAGS
BEHIND WITH FALLING TEMPERATURES. THE COLD AIR WILL CHASE THE PRECIP
AND MAY PROVIDE ONLY A BRIEF PERIOD FOR SNOW BEFORE DRY AIR
ENTRAINMENT FILTERS IN, WITH LITTLE TO NO SNOW ACCUMULATION
EXPECTED. COMPRESSIONAL WARMING AHEAD OF THE FRONT AND BEING
SITUATED WITHIN THE WARM SECTOR AHEAD OF THE ATTENDANT COLD FRONT
WILL LEAD TO AFTERNOON HIGHS ON WEDNESDAY TOPPING OUT 10-15 DEGREES
ABOVE NORMAL.
WEAK HIGH PRESSURE MOVES IN BEHIND THE FRONT WEDNESDAY NIGHT INTO
THURSDAY WITHOUT ANY SIGNIFICANT HEIGHT FALLS. THE SENSIBLE WEATHER
WILL BE QUIET, BUT THE AIRMASS REMAINS RATHER MILD CONSIDERING A
COLD FRONT PASSAGE DURING THE MONTH OF DECEMBER. AFTERNOON HIGHS
WILL BE AT OR SLIGHTLY ABOVE NORMAL FOR MOST LOCATIONS. A STRONG
SHORTWAVE TROUGH AND ASSOCIATED SURFACE LOW WILL BE BARRELING
TOWARDS THE MIDWEST AND OH VALLEY THURSDAY NIGHT, IN AN ALBERTA
CLIPPER TYPE FASHION. RAPID HEIGHT FALLS WILL ACCOMPANY THIS
SHORTWAVE TO GO ALONG WITH WEAK MOISTURE ADVECTION AHEAD OF THE
TROUGH, WHICH SHOULD PRODUCE OROGRAPHICALLY ENHANCED CLOUD COVER
ALONG THE NC/TN BORDER THURSDAY NIGHT, BUT NOT ENOUGH TO SQUEEZE
OUT MEASURABLE POPS. OTHERWISE, OVERNIGHT LOWS THURSDAY WILL BE
SLIGHTLY ABOVE NORMAL AS THE BOUNDARY LAYER STRUGGLES TO FULLY
DECOUPLE AND INCREASING CLOUD COVER MOVES IN ACROSS THE AREA AHEAD
OF THE SHORTWAVE AS A SHALLOW LOW-LEVEL MOISTURE LAYER LINGERS
UNDERNEATH A NOCTURNAL INVERSION.
LONG TERM /FRIDAY THROUGH TUESDAY/
AS OF 315 AM EST TUESDAY: SHORTWAVE TROUGH WILL BE IN THE MIDST OF
SWEEPING ACROSS THE EAST COAST ON FRIDAY, WITH THE AXIS PUSHING
EAST OF THE AREA BY FRIDAY NIGHT. NORTHWEST FLOW PRECIP IS
EXPECTED TO DEVELOP BEHIND THE TROUGH AS MECHANICAL LIFT ON THE
FAVORABLE NORTHWEST FACING SLOPES ALONG THE NC/TN BORDER WILL BE
IN PLAY. PROFILES FROM VARIOUS MODEL GUIDANCE WILL BE COLD ENOUGH
TO SUPPORT SNOW, BUT NOT ALL PROFILES SHOW ENOUGH SATURATION TO
TAP INTO THE DENDRITIC GROWTH ZONE. THIS WILL LIMIT ANY DECENT
SNOWFALL ACCUMULATIONS CONSIDERING THE ANTECEDENT DRY CONDITIONS
PRIOR TO THE SHORTWAVE PASSAGE AND FOR THE POTENTIAL OF RIME ICE
TO LIMIT OVERALL SNOWFALL AMOUNTS AS WELL. DETERMINISTIC MODELS
AND ENSEMBLE MEAN BARELY SHOW UP TO AN INCH OF SNOW BEFORE WINDS
SHIFT MORE NORTH TO NORTHEASTERLY SATURDAY NIGHT AS THE SURFACE
HIGH MOVES ACROSS THE GREAT LAKES AND ESSENTIALLY SHUTS OFF ANY
NORTHWEST FLOW PRECIP. EXPECT TEMPERATURES TO DIP 5-10 DEGREES BELOW
NORMAL OVER THE WEEKEND AS COLDER AIR ALOFT SETTLES OVERHEAD AND CAA
FILTERS IN BEHIND THE SHORTWAVE ON SATURDAY. SUNDAY INTO THE EARLY
PART OF NEXT WEEK, MODEL GUIDANCE SHOW A WEDGE-LIKE CONFIGURATION
FROM A SYNOPTIC STANDPOINT AS A STRONG SURFACE HIGH (~1035-1040MB)
SETS UP SHOP OVER THE NORTHEASTERN CONUS AND NORTHEASTERLY FLOW
NOSES INTO THE REGION.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
AT KCLT AND ELSEWHERE: MOSTLY DRY CONDITIONS EXPECTED THROUGH THE
18Z TAF PERIOD. WIND DIRECTION WILL BE NW ACROSS MOUNTAINS AND SW
EAST OF THE MOUNTAINS THROUGH THE PERIOD. WIND SPEEDS WILL RANGE
FROM ~4-9 KTS TODAY, BECOMING LIGHT TO CALM THIS EVENING INTO
TONIGHT. CALM WINDS AND LINGERING LOW-LEVEL MOISTURE WILL ALLOW FOR
ANOTHER ROUND OF LOW STRATUS AND DENSE FOG TO DEVELOP AGAIN
OVERNIGHT INTO WEDNESDAY MORNING SO HAVE LIFR TO IFR CIGS AND VSBYS
MENTIONED AT MOST TERMINALS. DID GO WITH VLIFR VSBYS AT KHKY AS
CONFIDENCE IS HIGHEST THAT THIS TERMINAL WILL SEE DENSE FOG. ANY FOG
THAT DEVELOPS SHOULD LIFT BETWEEN 14Z AND 16Z. A COLD FRONT WILL
APPROACH OUT OF THE WEST THROUGH TOMORROW MORNING BEFORE TRACKING
ACROSS THE FORECAST AREA TOMORROW AFTERNOON. HIGH-RES MODEL GUIDANCE
SOURCES ARE NOT IN GOOD AGREEMENT REGARDING THE ONSET TIMING OF RA
TOMORROW AFTERNOON/EVENING BUT OVERALL THEY DO AGREE THAT RAIN
SHOULD HOLD OFF UNTIL AFTER THE 18Z TAF FORECAST PERIOD. WIND SPEEDS
WILL GRADUALLY INCREASE AHEAD OF THE FRONT ON WEDNESDAY RANGING FROM
~7-10 KTS. SOME LOW-END GUSTS CANNOT BE ENTIRELY RULED OUT TOMORROW
AFTERNOON BUT DID NOT MENTION IN THE TAFS THIS CYCLE WITH THIS
POTENTIAL BEING TOWARDS THE END OF THE FORECAST PERIOD.
OUTLOOK: RAIN AND ASSOCIATED RESTRICTIONS MAY LINGER THROUGH
WEDNESDAY NIGHT. DRIER CONDITIONS ARE EXPECTED THURSDAY INTO THE
WEEKEND AS DRY HIGH PRESSURE BUILDS INTO THE REGION. COULD NOT RULE
OUT SOME PERIODIC CIG RESTRICTIONS THROUGH THE WEEKEND BUT IT SHOULD
BE DRY ENOUGH TO PROHIBIT FOG FORMATION.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...DEO
NEAR TERM...AR/WIMBERLEY
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...WIMBERLEY
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