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Area Forecast Discussion

783
FXUS62 KGSP 010857
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
357 AM EST SUN MAR 1 2015

.SYNOPSIS...
COLD HIGH PRESSURE WILL PERSIST THROUGH TODAY. MOISTURE WILL
INCREASE AHEAD OF AN APPROACHING COLD FRONT WHICH WILL CROSS THE
AREA ON MONDAY. CANADIAN HIGH PRESSURE BUILDS BACK IN TUESDAY...WITH
ANOTHER MOIST COLD FRONT AFFECTING THE REGION LATE WEDNESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AT 300 AM EST SUNDAY...A BROAD UPPER TROUGH WAS OVER CENTRAL
CANADA AND THE UPPER MIDWEST THIS MORNING...WHILE A CLOSED UPPER
LOW WAS OFF THE S CA COAST. NEARLY ZONAL FLOW EXTENDED FROM N
MEXICO TO THE CAROLINA COAST. BY MONDAY MORNING THE NORTHERN
TROUGH PROGRESSES TO EASTERN CANADA....WHILE THE UPPER LOW REMAIN
OFF CA. SLIGHT AMPLIFICATION OF A RIDGE TAKES PLACE BETWEEN THESE
THE FEATURES OVER THE PLAINS...BUT THE FLOW OVER THE SOUTHEAST
REMAINS BASICALLY ZONAL.

AT THE SURFACE...COLD AIR DAMMING WEAKENS FROM S TO N OVER THE
CAROLINAS AND N GA TODAY...BUT NOT BEFORE ISENTROPIC UPGLIDE
PRODUCES PRECIPITATION ACROSS THE AREA. WITH THE TOP OF THE MOIST
LAYER TO WARM FOR ICE NUCLEATION...AND SURFACE TEMPERATURES COOLING
BELOW FREEZING ACROSS MOST OF OUR AREA...FREEZING RAIN CAN BE
EXPECTED ACROSS ALL BUT OUR SOUTHERN MOST COUNTIES. LIGHT RAINFALL
AMOUNTS WILL KEEP THIS FROM BECOMING AN ICE STORM...BUT THE IMPACTS
WILL BE SUFFICIENT FOR THE CURRENT WINTER WEATHER ADVISORY AND
FREEZING RAIN ADVISORY TO REMAIN IN EFFECT...WITH PERHAPS SOME
MODIFICATION IN THE SOUTHERN TIER. PRECIPITATION WILL CHANCE TO ALL
RAIN THIS AFTERNOON...ENDING THE ICING. HIGH TEMPERATURES WILL RUN
NEARLY 40 DEGREES BELOW NORMAL TODAY.

A COLD FRONT WILL APPROACH FROM THE NE TONIGHT...PRECEDED BY ONLY
LIGHT PRECIPITATION IN AN ABSENCE OF UPGLIDE. PRECIPITATION CHANCES
AND AMOUNTS WILL BE BEST IN THE NC MOUNTAINS BORDERING TN WHERE THE
COLD FRONT WILL MAKES ITS ARRIVAL TOWARD DAYBREAK. THERMAL PROFILES
SUPPORT AN ALL RAIN EVENT. MODEL GUIDANCE SUGGESTS MINIMUM
TEMPERATURES AS WARM OR WARMER IN THE MOUNTAINS THAN IN THE FOOTHILLS
AND PIEDMONT...WITH VALUES AROUND 8 DEGREE ABOVE NORMAL IN THE
FORMER...AND AROUND NORMAL IN THE LATER.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 315 AM...SOME LINGERING LIGHT PRECIP WILL REMAIN POSSIBLE
ACROSS THE WESTERN MTNS EARLY MONDAY...AS PLENTY OF MOISTURE REMAINS
ACROSS THE SOUTHERN APPALACHIAN/TENN VALLEY REGION WITHIN A W/NW
FLOW. HOWEVER...PROFILES WILL REMAIN QUITE WARM...AS BAROCLINIC ZONE
BECOMES INCREASINGLY ORIENTED PARALLEL TO QUASI-ZONAL FLOW
ALOFT...WITH THE BETTER COLD ADVECTION PASSING WELL NORTH OF THE
FORECAST AREA. THEREFORE...ANY PRECIP WOULD BE LIGHT RAIN OR
DRIZZLE. THE NAM...(AND OTHER MODELS TO A MUCH LESSER EXTENT) HAS
BEEN VERY CONSISTENT IN DEVELOPING AN AREA OF PRECIP ACROSS NORTH GA
AND THE SC PIEDMONT TOMORROW...PERHAPS ASSOCIATED WITH CONVERGENCE
NEAR TERRAIN BLOCKED-INDUCED SURFACE LOW AND WIND SHIFT ASSOCIATED
WITH THE LEADING EDGE OF THE COLD FRONT. AGAIN...THE NAM IS THE
ONLY MODEL THAT IS OVERLY EXCITED ABOUT THIS...AND THERE IS LITTLE
SUPPORT FROM THE SREF FOR THIS...BUT A LOW POPS STILL SEEMS
WARRANTED IN LIGHT OF THE NAMS CONSISTENCY.

OTHERWISE...MONDAY SHOULD FINALLY SEE SEASONAL TEMPS ACROSS MUCH OF
THE UPSTATE AND NORTHEAST GA...WHILE THE MTNS AND NORTHERN ZONES
WILL REMAIN COOL DUE TO COLD ADVECTION/DEVELOPING WEDGE...AS 1030+
MB SURFACE HIGH MOVES QUICKLY ACROSS THE OHIO VALLEY...AND SETTLES
NEAR THE DELMARVA BY TUE MORNING. THIS WILL RESULT IN ANOTHER VERY
COOL/COLD AIR DAMMING DAY ON TUE...WHEN MAX TEMPS IN THE 40S ARE
EXPECTED...EXCEPT PERHAPS ACROSS THE FAR WESTERN MTNS AND THE LOWER
PIEDMONT. MEANWHILE...UPGLIDE PRECIP CHANCES WILL INCREASE AGAIN MON
NIGHT INTO EARLY TUE...AS LARGE SCALE WAA REGIME DEVELOPS IN
RESPONSE TO A DEVELOPING PLAINS CYCLONE. THERE COULD BE ANOTHER
ROUND OF FREEZING RAIN TUE MORNING...ALTHOUGH THIS WOULD BE CONFINED
TO A VERY SMALL AREA...PRIMARILY THE EASTERN ESCARPMENT REGION OF
NORTH CAROLINA.

LIGHT PRECIP CHANCES WILL PERSIST INTO TUE NIGHT...ESP ACROSS THE
MTNS AND THE NORTHERN ZONES...AS THE MID-LEVELS WILL BEGIN TO DRY
AND THE WEDGE BEGIN TO ERODE ACROSS SOUTHERN AREAS. MEANWHILE...
STRONG FRONTOGENESIS IS EXPECTED TO DEVELOP TUE NIGHT/EARLY WED
ACROSS THE TENN AND OHIO VALLEY REGION...BUT HEAVIER PRECIP
ASSOCIATED WITH THIS IS EXPECTED TO REMAIN WEST OF OUR AREA THROUGH
12Z WED.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 340 AM...STILL MIXED SIGNALS REGARDING THE POTENTIAL FOR HEAVY
RAIN ACROSS THE FORECAST AREA DURING MID-WEEK...AS STRONG FRONTAL
ZONE MIGRATES ACROSS THE REGION. BASED UPON GLOBAL MODEL CLUES...
MUCH SEEMS TO HINGE ON THE POTENTIAL DEVELOPMENT OF A SURFACE WAVE
ACROSS THE SOUTHEAST AS THE FRONT PROGRESSES ACROSS THE CAROLINAS
AND GEORGIA WED INTO WED NIGHT. INTERESTINGLY...ALTHOUGH THE ECMWF
AND GFS DEVELOP A WAVE OF SIMILAR STRENGTH ACROSS THE CAROLINAS
DURING THIS TIME...THE LOW LEVEL FORCING AND QPF RESPONSE IS QUITE
DIFFERENT...WITH THE GFS DEVELOPING A BAND OF HEAVIER PRECIP ACROSS
THE FORECAST AREA...WHILE THE ECMWF MAINTAINS A VERY MUTED QPF
RESPONSE. NEVERTHELESS...THE POTENTIAL FOR HEAVY RAIN IS STILL THERE
IN LIGHT OF WELL-ABOVE NORMAL PWATS AND A SLOW MOVING/STRONG FRONTAL
ZONE.

THE MAIN STORY OF THE LATTER MEDIUM RANGE WILL BE THE RETURN OF
UNSEASONABLY COLD AIR...AS STRONG SHORT WAVE EJECTING FROM THE
PLAINS ALLOWS FOR THE RETURN OF THE EASTERN LONG WAVE TROUGH.

&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
AT KCLT...GUIDANCE DISCREPANCIES YIELD LOW CONFIDENCE ON TIMING AND
VALUES OF CIGS AND VSBYS THIS FORECAST. A BLENDED APPROACH BRING
VSBY DOWN TO MVFR BY DAWN AS FREEZING RAIN SETS UP OVER THE
AREA...WITH A RETURN TO VFR BY MIDDAY...THEN MVFR TONIGHT. THE SAME
APPROACH BRINGS A LOW VFR CIG DOWN TO MVFR BEFORE DAWN...THEN BACK
TO LOW VFR THIS EVENING...THEN TO IFR LATE THIS EVENING. WINDS WILL
FAVOR THE NE IN COLD AIR DAMMING TODAY...BACKING TO THE SW THIS
EVENING AS THE COLD AIR WEDGE ERODES. FREEZING PRECIPITATION WOULD
CHANGE TO RAIN IN THE MORNING...WITH AS MUCH AS SEVEN TENTHS OF AN
INCH OF ICE ACCRETION. RAIN WOULD TAPER OF DURING THE EVENING.

ELSEWHERE...GUIDANCE VARIES CONSIDERABLY ON CIGS AND VSBYS AND THEIR
TIMING...YIELDING LOW CONFIDENCE. USING A BLENDED APPROACH...CIGS
WILL FALL TO MVFR OVERNIGHT WHILE FREEZING RAIN SETS UP AT ALL SITES
BUT KAND...WHERE RAIN WILL FALL. CIGS RISE TO VFR AT SC SITES AND
KAVL THIS EVENING...BUT FALL TO IFR AT KHKY. AN MVFR CIG MAY RETURN
TO KAND VERY LATE IN THE FORECAST. FOOTHILL VSBYS WOULD FALL TO MVFR
IN THE MORNING IN RAIN INDUCED FOG. BY THE TIME KAVL GOES TO MVFR
VSBY AT MIDDAY...SC SITES RETURN TO VFR. BY LATE AFTERNOON NC SITES
GO VFR...THEN IN THE EVENING ALL SITE RETURN TO MVFR. FREEZING
PRECIPITATION CHANGE TO RAIN IN THE MORNING...WITH ICE TOTALS
GENERALLY A LITTLE MORE THAN 5 TENTHS OF AN INCH...EXCEPT AT KAND
WHERE ONLY RAIN FALLS. RAIN WOULD TAPER OFF DURING THE EVENING.

OUTLOOK...CAD REGIME WILL WEAKEN LATE SUN INTO MON WITH ANOTHER
CANADIAN HIGH SLIDING NORTH OF THE CAROLINAS. AS THE HIGH MOVES NE
OF THE REGION...ANOTHER BRIEF CAD PATTERN IS POSSIBLE. PERIODS OF
PRECIP AND FLIGHT RESTRICTIONS THUS ARE LIKELY TUE-WED. A COLD FRONT
WILL MOVE THROUGH THE REGION BY THU BRINGING WET WEATHER AND
POSSIBLE RESTRICTIONS.

CONFIDENCE TABLE...

            13-19Z        19-01Z        01-07Z        07-12Z
KCLT       HIGH  95%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   74%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       MED   77%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...FREEZING RAIN ADVISORY UNTIL NOON EST TODAY FOR GAZ010-017.
NC...FREEZING RAIN ADVISORY UNTIL NOON EST TODAY FOR NCZ048-051>053-
     059-062>065-068>072-082-507>510.
     WINTER WEATHER ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR
     NCZ033-035>037-049-050-056-057-501>506.
SC...FREEZING RAIN ADVISORY UNTIL NOON EST TODAY FOR SCZ001>003-
     005>010-012>014.

&&

$$
SYNOPSIS...SBK
NEAR TERM...JAT
SHORT TERM...JDL
LONG TERM...ARK/JDL
AVIATION...JAT



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