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000
FXUS62 KGSP 111855
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
255 PM EDT TUE MAR 11 2014

.SYNOPSIS...
DRY AND WARM HIGH PRESSURE WILL MOVE OFF THE CAROLINA COAST TONIGHT
AS A LOW PRESSURE SYSTEM APPROACHES FROM THE WEST. AN ASSOCIATED
COLD FRONT WILL PUSH THROUGH THE AREA ON WEDNESDAY FOLLOWED BY COOL
HIGH PRESSURE ON THURSDAY. DRIER...MILD HIGH PRESSURE WILL RETURN
FOR THE END OF THE WORK WEEK.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 215 PM EDT...SHORTWAVE TROUGH CURRENTLY OVER SERN TX IN THE SRN
STREAM WILL SLIDE ALONG THE GULF COAST TONIGHT. THE TROUGH WILL
CONTINUE TO PRODUCE ABUNDANT CIRRUS ACRS THE CENTRAL GULF STATES THIS
AFTN...EVENTUALLY SPREADING INTO OUR CWFA FROM THE SOUTHWEST BY
EVENING. OTHERWISE THIS AFTN SKIES WILL REMAIN MOSTLY CLEAR AND
TEMPERATURES IN THE UPPER 60S TO MID 70S. DEWPOINTS APPEAR TO HAVE
MIXED OUT BUT STABILIZED...MITIGATING ANY FURTHER DROP IN RH THOUGH
KEEPING IT IN THE NEAR CRITICAL 25-30 PERCENT RANGE.

MEANWHILE A DEEPENING SFC LOW ASSOCIATED WITH A STRONG UPPER WAVE
WILL MOVE INTO THE OH/TN VALLEYS BY TMRW MRNG. MODEST LLVL SW FLOW
WILL PRECEDE THIS SYSTEM ACRS THE SOUTHEAST. ABUNDANT MIDLEVEL
MOISTURE WILL ADVECT INTO THE REGION BEGINNING LATE EVENING...QUICKLY
FOLLOWED WITH ADDITIONAL MOISTURE IN THE LLVLS. A KEY INGREDIENT IS
MISSING IN ISENTROPIC UPGLIDE...WITH BOTH ISENTROPIC CHARTS AND
TRADITIONAL ISOBARIC FIELDS SHOWING NEUTRAL OR EVEN COLD ADVECTION.
HOWEVER DPVA WITH THE SRN STREAM WAVE LOOKS MORE THAN CAPABLE OF
DRIVING PRECIP ON ITS OWN. THE CAA NEARER THE SFC COULD BE DUE TO A
COLD POOL ASSOCIATED WITH THE PRECIP SHIELD. AT ANY RATE...SOME
UPSLOPE WILL COME INTO PLAY THOUGH THIS IS MAINLY THOUGHT TO BE IN
THE SW MTNS GIVEN THE DEEP SW TO WSW FLOW. QPF IS PRETTY LIGHT ON
MOST GUIDANCE WHICH COULD BE DUE TO THE LACK OF GOOD LLVL FORCING.

AFTER DAYBREAK...SRN SHORTWAVE WILL MOVE TO THE ATLANTIC COAST AND
SUPPORT DIMINISHES FOR PRECIP OVER THE PIEDMONT. HOWEVER...BY THIS
TIME THE SFC LOW WILL BEGIN TO CROSS THE CENTRAL APPALACHIANS AND
LLVL WIND FIELDS RAMP UP. SFC FRONT WILL NOT CROSS UNTIL LATE
AFTERNOON KEEPING THE FA IN THE WARM SECTOR THRU DIURNAL PEAK TEMPS.
INSTABILITY DIFFERS SOMEWHAT BETWEEN NAM/GFS AS ONE MIGHT
EXPECT...WITH THE SREF MEMBERS BASICALLY SUPPORTING A BLEND OF ALL
THREE MODELS. MODEST CAPE OF 100-200 J LOOKS LIKELY IN PARTS OF THE
AREA. SHEAR IS NO PROBLEM WITH CONSENSUS SUPPORTIVE OF A LOW END
SEVERE /HSLC/ THREAT...IF THE INSTABILITY IS REALIZED. FREQUENT GUSTS
OF 25-30 KT ARE LIKELY FROM MID MORNING THRU THE END OF THE DAY. AT
LEAST A FEW WIND GUSTS OF 35-40 KT ARE POSSIBLE IN ALL AREAS...MAYBE
A BIT HIGHER. A WIND ADVY MAY BE NEEDED AND ISSUED OVERNIGHT TONIGHT.

MODEL CONSENSUS IS FOR A CRASH IN TEMPS BEHIND THE FRONT...WITH THE
TENN BORDER ZONES SEEING TEMPS FALL ENOUGH FOR A SNOW MENTION VERY
LATE IN THE AFTN...THOUGH THIS IS UNLIKELY TO BE ASSOCIATED WITH CAPE
AND ANY ACCUMULATION WOULD NOT OCCUR UNTIL LATER.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 230 PM TUESDAY...THE MAIN FOCUS FOR THE SHORT RANGE WILL BE
THE POST-FRONTAL AIR MASS WEDNESDAY NIGHT. THICKNESSES DROP
RAPIDLY SUCH THAT ANY REMAINING PRECIP OVER THE MTNS SHOULD
QUICKLY CHANGE TO SNOW FROM HIGH ELEVATIONS TO THE VALLEY FLOORS
BY MID EVENING. THE MODELS ARE IN GOOD AGREEMENT WITH A NW FLOW OF
LOW LEVEL MOISTURE GENERATING SNOW SHOWERS IN THE UPSLOPE AREAS
NEAR THE TN BORDER THROUGH THE EARLY MORNING HOURS ON THURSDAY.
THE NEW GUIDANCE SUGGESTS THAT SOME SNOW SHOWER ACTIVITY COULD
PERSIST BEYOND SUNRISE. PRECIP AMTS HAVE TRENDED SLIGHTLY HIGHER
AS WELL...WITH SOME SUPPORT FROM THE PASSAGE OF ANOTHER SHORT WAVE
EARLY THURSDAY MORNING. A CONSENSUS QPF BETWEEN THE PREVIOUS FCST
AND A BLEND OF THE HPC/SREF/GFS/NAM YIELDS ADVISORY LEVEL SNOW
AMOUNTS. IF THE FCST DOES NOT CHANGE...A WINTER WX ADVISORY MAY BE
ISSUED FOR THE ZONES THAT BORDER TENNESSEE FOR WEDNESDAY NIGHT.
WINDS WILL REMAIN STRONG BEHIND THE FRONT WEDNESDAY
EVENING...PERHAPS WITH ADVISORY LEVEL GUSTS AT ELEVATIONS ABOVE
3500 FEET. A WIND ADVISORY MIGHT BE ISSUED FOR HIGH ELEVATIONS IF
THE FCST DOES NOT CHANGE. EAST OF THE MTNS...IT SHOULD BE BRISK
AND COLD WITH TEMPS DROPPING BELOW FREEZING.

THE REST OF THE FORECAST IS QUIET IN COMPARISON. THE UPPER TROF AXIS
SHOULD MOVE OFF THE EAST COAST ON THURSDAY FOLLOWED BY AN UPPER TROF
BUILDING IN FROM THE WEST THURSDAY NIGHT AND DAMPENING ON FRIDAY.
THIS WILL SUPPORT ANOTHER DRY HIGH PRESSURE AIR MASS MOVING ACROSS
THE FCST AREA THROUGH THE REMAINDER OF THE PERIOD. THERE IS SOME
CONCERN ON THURSDAY THAT PORTIONS OF THE FCST AREA WILL FLIRT WITH
RED FLAG FIRE CONDITIONS BECAUSE OF A VERY LOW RH IN THE AFTERNOON
AND SOME LINGERING WIND GUSTS OVER THE MTNS. OTHERWISE...TEMPS WILL
BE WELL BELOW NORMAL ON THURSDAY BUT SHOULD MODERATE FOR THURSDAY
NIGHT AND THEN BACK TO NEAR NORMAL ON FRIDAY.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 2 PM EDT TUE...THE UNCERTAINTY IN THE SAT THROUGH TUE PERIOD
REMAINS QUITE HIGH...WITH SIGNIFICANT MODEL SPREAD ON JUST ABOUT
EVERY SALIENT FEATURE. SHORTWAVE ENERGY APPROACHING THE REGION IN
GENERALLY ZONAL FLOW ALOFT DAMPENS OUT STRONGLY ON THE ECMWF/CMC AS
IT APPROACHES THE AREA...BUT IS MUCH MORE AMPLIFIED ON THE
GFS...ALONG WITH BETTER MOISTURE.  WILL LEAN TOWARD THE CONSENSUS
WEAKER WAVE SOLUTION...WITH THE ASSOCIATED DEPICTION OF MAINLY
CLOUDS FRI NIGHT THROUGH SAT...BUT LITTLE IN THE WAY OF
PRECIPITATION.

UPSTREAM...DIGGING ENERGY MOVING SE OF THE ROCKIES SAT NIGHT THROUGH
SUNDAY GETS INCREASINGLY UNCERTAIN HANDLING WITH TIME. THE FEATURE
MAY START OUT AS A RELATIVELY IN PHASE TROUGH AXIS FROM THE NRN
PLAINS TO W TX. HOWEVER...THE NRN AND SRN STREAMS SHOULD BECOME
QUICKLY OUT OF PHASE SUNDAY NIGHT THROUGH MONDAY...WITH A SRN STREAM
CUTOFF LOW POSSIBLE OVER NRN MEXICO...WHILE THE PROGRESSIVE NRN
STREAM SWINGS QUICKLY E TO THE APPALACHIANS. THE MODEL DIFFS ARE
STARK WITH THIS FEATURE. THE CMC IS FASTEST AND MOST AMPLIFIED WITH
THE NRN STREAM WAVE...THE GFS IS A LITTLE SLOWER...WHILE THE ECMWF
IS THE SLOWEST. THE ONE POINT OF AGREEMENT IS THAT SFC HIGH PRES
SHOULD BUILD EAST FROM THE GREAT LAKES TO THE NE THROUGH MON. THIS
SHOULD ALLOW COOLER TEMPERATURES TO SPILL SWD INTO THE REGION. A
CONSENSUS OF THE ENSEMBLE SOLUTIONS REVEALS SFC LOW PRES MOVING
ALONG A FRONTAL ZONE DRAPED ALONG THE GULF COAST SUNDAY...WRAPPING
TO A LOW SOMEWHERE OFF THE SE COAST THROUGH MON. MOST MODELS HAVE
JUST ENOUGH COULD AIR SPILLING INTO THE NRN MTNS FOR POSSIBLE PTYPE
ISSUES EARLY MON...AND THEN AGAIN MON NIGHT N OF INTERSTATE 40 AS
THE LOW MOVES UP THE COAST. WILL KEEP POPS IN THE CHANCE RANGE AND
FEATURE MAINLY RAIN...EXCEPT FOR A NRN TIER RAIN/SNOW MIX EARLY
MONDAY AND MONDAY NIGHT...WITH DRYING INTO TUE.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
AT KCLT...WEAK S/W TROF WILL CROSS THE DEEP SOUTH OVERNIGHT INTO
EARLY WED...WITH STRONGER AND DEEPER TROF MOVING THRU THE OHIO
VALLEY DURING THE DAY AND PUSHING A COLD FRONT TOWARD THE REGION.
SOME DEGREE OF LLVL MOISTURE ADVECTION WILL PRECEDE THE
FRONT...CONCURRENT WITH FORCING FROM THE SRN TROF. PRECIP LIKELY BY
DAYBREAK...LASTING THRU MOST OF THE MRNG. WITH THE NEAR SFC FORCING
REMAINING RATHER UNIMPRESSIVE AND MODELS HAVING TRENDED LATER IN THE
MRNG WITH THE HEAVIEST PRECIP...BOTTOMED OUT CIGS AT MVFR. MVFR VSBY
LIKELY DURING SHOWERS. SWLY WINDS WILL BEGIN TO RAMP UP AFTER
DAYBREAK BUT WSHFT WITH FROPA NOT EXPECTED UNTIL AFTER 18Z. FREQUENT
GUSTS OF 25-30KT LIKELY BY LATE MRNG...WITH A NONZERO CHANCE OF TSRA
TOWARD MIDDAY.

ELSEWHERE...SWLY LLVL FLOW WILL BRING INCREASING MOISTURE BEGINNING
THIS EVENING...WITH CIGS DROPPING AFTER MIDNIGHT AND BOTTOMING OUT
AT IFR OVER THE SW MTNS AND THE SC TAF SITES AROUND OR A LITTLE
AFTER DAYBREAK CONCURRENT WITH NEAR 100 PERCENT POPS. KAVL AND KHKY
STAND A BETTER CHANCE OF STAYING LOW MVFR. SW WINDS WILL BECOME
QUITE GUSTY AFTER DAYBREAK WITH GUSTS OF 25-30 KT LIKELY EVERYWHERE
BY MIDDAY...POSSIBLY UP TO 40 KT IN THE HIGH ELEVS OF THE MTNS. A
SLIGHT CHANCE OF THUNDER EXISTS AFTER ABOUT 15Z AT ALL SITES...BUT
WILL OMIT THIS FROM TAF FOR NOW.

OUTLOOK...A STRONG COLD FRONT WILL SWEEP ACROSS THE REGION WEDNESDAY
AFTERNOON...FOLLOWED BY GUSTY NORTHWEST WINDS THROUGH THURSDAY
MORNING. DRY HIGH PRESSURE WILL REMAIN OVER THE WESTERN CAROLINAS
THROUGH THE REMAINDER OF THE WORK WEEK.

CONFIDENCE TABLE...

            19-01Z        01-07Z        07-13Z        13-19Z
KCLT       HIGH 100%     HIGH 100%     HIGH  87%     HIGH  95%
KGSP       HIGH 100%     HIGH 100%     HIGH  91%     HIGH  84%
KAVL       HIGH 100%     HIGH 100%     HIGH  93%     HIGH  92%
KHKY       HIGH 100%     HIGH 100%     HIGH  88%     HIGH  90%
KGMU       HIGH 100%     HIGH 100%     HIGH  86%     HIGH  86%
KAND       HIGH 100%     HIGH 100%     HIGH  81%     MED   79%

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...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JOH
NEAR TERM...WIMBERLEY
SHORT TERM...PM
LONG TERM...HG
AVIATION...WIMBERLEY