Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 011527
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1027 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/...
AS OF 1025 AM EST SUNDAY...PER LACK OF PRECIP...AND WARMER
TEMEPRATURES ACROSS THE ADVISORY AREAS...DECIDED TO CAN ENTIRE FZRA
ADV ALONG WITH PORTIONS OF THE WINTER WX ADV ACROSS THE NORTHERN NC
MOUTNAINS.  CONTINUED WITH WINTER WX ADV ALONG AND NORTH OF
INTERSTATE 40 OVER THE NC PIEDMONT WHERE TEMPS REMAIN AT OR JUST
BELOW FREEZING AND SOME LIGHT RA/DZ PERSISTS.  OTHERWISE...TWEAKED
TEMPS/DEWS IN THE NEAR TERM AND LEFT THE REMAINDER OF THE FCST AS
IS.

PREVIOUS DISCUSSION...

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 CHANGE 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 /16Z SUNDAY THROUGH THURSDAY/...
AT KCLT...GUIDANCE DISCREPANCIES CONTINUE TO YIELD LOW CONFIDENCE ON
TIMING AND VALUES OF CIGS AND VSBYS...STARTING WITH POOR
INITIALIZATION THIS MORNING. THE FORECAST WILL START OUT WITH
OBSERVED VALUED...THEN FOLLOW A BLENDED APPROACH THAT BRINGS THE CIG
DOWN FROM MVFR TO IFR BY THIS EVENING...GENERALLY KEEPING IT THERE
OVERNIGHT. VSBY FALLS TO MVFR OR EVEN IFR AT TIMES BEFORE MIDDAY...
WITH BRIEF IMPROVEMENT TO VFR SUGGESTED THIS AFTERNOON... BEFORE
FALLING BACK TO MVFR OVERNIGHT. NE WINDS WILL BACK TO SW THIS
EVENING AS THE COLD AIR WEDGE WEAKENS. FREEZING RAIN THIS MORNING
WILL CHANGE OVER TO RAIN BY MIDDAY...WITH A DIMINISHING TREND
THEREAFTER.

ELSEWHERE...GUIDANCE CONTINUES TO VARY ON CIGS AND VSBYS AND THEIR
TIMING...WITH A POOR HANDLE ON THE CURRENT SITUATION YIELDING LOW
CONFIDENCE. THE FORECAST WILL START WITH OBSERVED VALUES...THEN A
WITH A BLENDED APPROACH...CIGS WILL FALL TO IFR BY THIS EVENING.
SOME BRIEF MIDDAY IMPROVEMENT TO VFR IS SUGGESTED AT KAVL...WITH IFR
OCCURRING MUCH LATER THERE TONIGHT. VSBY IS EXPECTED TO BECOME
RESTRICTED BY MIDDAY...FOLLOWED BY AFTERNOON IMPROVEMENT...AND THEN BACK
TO RESTRICTED OVERNIGHT. SURFACE WINDS WILL BACK FROM NE TO SW
TONIGHT AS THE COLD AIR WEDGE WEAKENS OVER OUR AREA. FREEZING RAIN
WILL CHANGE OVER TO RAIN BY MIDDAY...DIMINISHING THEREAFTER...HOWEVER
AN APPROACHING FRONT WILL KEEP RAIN CHANCES HIGHER AT KAVL
OVERNIGHT.

OUTLOOK...ANOTHER CANADIAN HIGH SLIDES NORTH OF THE CAROLINAS EARLY
IN THE WEEK. AS THE HIGH MOVES NE OF THE REGION...ANOTHER BRIEF CAD
PATTERN IS POSSIBLE. PERIODS OF PRECIP AND FLIGHT RESTRICTIONS 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...NONE.
NC...WINTER WEATHER ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR
     NCZ035>037-056-057-502-504.
SC...NONE.

&&

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



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