Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 160853
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
353 AM EST TUE DEC 16 2014

.SYNOPSIS...
A COLD FRONT WILL MOVE ACROSS THE CAROLINAS TODAY. HIGH PRESSURE
WILL SPREAD BACK OVER THE REGION WEDNESDAY. A WEAK WEATHER SYSTEM
ALOFT WILL SPREAD CLOUDS AND PERHAPS SOME SPOTTY LIGHT SHOWERS IN
THE MOUNTAINS ON THURSDAY. ANOTHER LOW WILL DEVELOP TO OUR SOUTHWEST
ON FRIDAY AND INCREASE CHANCES FOR WIDESPREAD PRECIPITATION GOING
INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 345 AM EST TUESDAY...UPPER RIDGE THAT HAS PREVIOUSLY BEEN IN
CONTROL OF THE WEATHER ACROSS THE SOUTHERN/CENTRAL APPS HAS SHIFTED
ENTIRELY OUT TO SEA AHEAD OF AN APPROACHING UPPER/SFC TROF AXIS AND
COLD FRONT.  PRIMARY UPPER SHORTWAVE PASSING THROUGH THE MEAN TROF
BASE CONTINUES TO PUSH EAST ACROSS THE LOWER TN RIVER VALLEY.  IN
RESPONSE...LATEST RADAR IMAGERY INDICATES MULTIPLE BANDS OF PRECIP
AHEAD OF THE FRONT MOVING INTO...AND THROUGH THE FCST AREA THIS
MORNING.  AT THIS TIME THE FRONT IS LOCATED ALONG THE I65 CORRIDOR
STRETCHING FROM SOUTHCENTRAL INDIANA SOUTHWARD TOWARDS THE GULF OF
MEXICO.

LATEST NEAR TERM GUIDANCE CONTINUES TO AGREE ON EASTWARD ADVECTION
OF THESE PREFRONTAL PRECIP BANDS THROUGH MORNING.  THUS THE FCST
FEATURES INCREASING LIKELY LEVEL POPS ACROSS SOUTHWEST
NC...NORTHEAST GA...AND THE WESTERN UPSTATE.  ELSEWHERE...POPS WILL
INCREASE FROM THE WEST THROUGH MID/LATE MORNING ALBEIT TOPPING OUT
AT SOLID CHANCE LEVELS.  SKIES WILL REMAIN OVERCAST PRE FROPA BEFORE
SCT OUT THIS AFTERNOON AS THE FRONT SLIDES THROUGH.  WINDS ALONG AND
AHEAD OF THE FRONT WILL INCREASE OUT OF THE SOUTHWEST WITH GUSTING
LIKELY...BEFORE VEERING SHARPLY TO THE NORTHWEST THIS EVENING.  AS
POPS DECREASE ACROSS THE EAST THIS AFTERNOON...POPS WILL REMAIN
ELEVATED ALONG THE SPINE OF THE APPS WHERE INCREASING NW FLOW
PROMOTES SHOWER ACTIVITY.  THROUGH THE OVERNIGHT TEMPERATURES WILL
FALL ALLOWING THIS SHALLOW MOIST LAYER TO YIELD A FEW SNOW SHOWERS
WITH NO ACCUMULATION EXPECTED.  HIGHS TODAY WILL REMAIN JUST ABOVE
NORMAL DESPITE PRECIP AND MOSTLY CLOUDY SKIES.  ALTHOUGH
TEMPERATURES ARE EXPECTED TO COOL INTO WEDNESDAY MORNING AMIDST WEAK
COLD ADVECTION...FCST FEATURES MORNING LOWS NEAR NORMAL.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 135 AM TUESDAY...ONGOING LIGHT NW FLOW PRECIP ACROSS THE NC
MTNS AT THE BEGINNING OF THE PERIOD WILL DISSIPATE BEFORE NOON.
ALTHOUGH TEMPS AND THICKNESSES ARE RELATIVELY WARM...THE FCST
SOUNDINGS SHOW WET BULBS ARE BELOW FREEZING. THEREFORE...EXPECT
PRECIP TO BE RAIN OR SNOW SINCE ANY FORCING WILL MOISTEN AND COOL
THE COLUMN ABOVE THE SFC. EITHER WAY...NO SIGNIFICANT ACCUMS ARE
EXPECTED. THE LOW CLOUDS AND GUSTY NW WINDS MAY LINGER THRU THE DAY
HOWEVER. OUTSIDE OF THE MTNS...CLEAR SKIES AND LIGHT WINDS WILL
PREVAIL. HIGHS WILL BE NEAR NORMAL ACROSS THE MTNS AND A FEW DEGREES
ABOVE NORMAL ELSEWHERE. A LOW AMPLITUDE RIDGE DEVELOPS WED
NITE...THEN A WEAKENING SHORT WAVE WILL CROSS THE AREA THU....WITH
THE RIDGE REBUILDING THU NITE. HIGH PRESSURE TRIES TO BUILD IN WED
NITE...BUT A WEAK BOUNDARY WILL LINGER ACROSS THE AREA. THE SHORT
WAVE COULD CREATE A WEAK SFC WAVE ALONG THIS BOUNDARY THU.
HOWEVER...THERE IS LITTLE IN THE WAY OF DEEP FORCING ASSOCIATED WITH
THESE FEATURES. IN ADDITION...MOISTURE WILL BE LIMITED AS WELL. BEST
CHC FOR PRECIP WILL BE ACROSS THE MTNS WHERE WLY FLOW COULD WRING
OUT SOME RAINFALL. EVEN THERE...ONLY A SLIGHT CHC OF LIQUID PRECIP
IS WARRANTED. THERE WILL BE A SIGNIFICANT AMOUNT OF CLOUDS ACROSS
THE AREA HOWEVER. THE CLOUDS MOVE EAST THU NITE AS THE WAVE MOVES
EAST AND THE BOUNDARY DISSIPATES. LOWS WED NITE WILL BE A LITTLE
ABOVE NORMAL THEN FALL TO NEAR NORMAL THU NITE. HIGHS THU WILL BE
NEAR NORMAL.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 350 AM TUESDAY...THE MEDIUM RANGE GUIDANCE IS COMING INTO
BETTER AGREEMENT REGARDING THE OVERALL PATTERN. HOWEVER...
TEMPERATURES...THERMAL STRUCTURES...AND THE RESULTANT SENSIBLE WX
ARE STILL IN QUESTION. A SRN STREAM SHORT WAVE CROSSES THE AREA SAT
AS AN OPEN WAVE AND MOVES EAST OF THE AREA SUN. AT THE SFC...A
MILLER A TYPE SFC LOW PRESSURE SYSTEM APPROACHES THE AREA SAT AS A
NON-CLASSICAL TYPE COLD AIR DAMMING HIGH PRESSURE DEVELOPS OVER THE
AREA. THE SFC LOW MOVES ALONG THE GULF COAST SAT NITE THEN EAST OF
THE AREA SUN...WHILE THE DAMMING HIGH EVENTUALLY WEAKENS AND
DISSIPATES. THE AIR MASS IN THE DAMMING REGION IS NOT VERY COLD AND
THE HIGH IS TRANSIENT. THE GFS...ITS ENSEMBLE MEAN...AND THE
CANADIAN MODEL ARE RELATIVELY WARM...SUGGESTING LIQUID PRECIP FOR
ALL BUT THE NRN MTNS WHERE SNOW WOULD FALL. THE ECMWF IS COLDER...
AND SUGGESTS A WINTRY MIX IS POSSIBLE ACROSS THE NRN TIER AND MAYBE
EVEN SOUTH TO THE I-85 CORRIDOR. GIVEN ALL THE DIFFERENCES...HAVE
KEPT THE PREVIOUS FCST TRENDS AND HAVE GONE WITH A RAIN/SNOW MIX
WHERE SFC TEMPS WARRANT. THE PRECIP ENDS OUTSIDE OF THE MTNS SUNDAY
BUT SOME NW FLOW SNOW COULD LINGER THRU THE DAY ACROSS THE NC MTNS.
AS THERE IS SO MUCH UNCERTAINTY...THE FCST WILL REMAIN IN FLUX UNTIL
BETTER CONTINUITY DEVELOPS...AND EVERYONE SHOULD STAY UP TO DATE
WITH THE LATEST FORECASTS.

ANOTHER SRN STREAM SHORT WAVE APPROACHES THE AREA MONDAY...BUT
AGAIN...THERE IS A DISCREPANCY WITH THE TIMING AND POSITION OF THE
WAVE AND THE ASSOCIATED SFC LOW. THEREFORE...HAVE CONTINUED THE DRY
FCST.

FOR NOW...HAVE HIGHS NEAR NORMAL FRI...DROPPING WELL BELOW NORMAL
SAT...THEN BACK TO A LITTLE BELOW NORMAL SUN AND MON. ABOVE NORMAL
LOWS FRI NITE FALL BELOW NORMAL BY SUN NITE.

&&

.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
AT KCLT...A MIXTURE OF VFR/MVFR CONDITIONS WILL PREVAIL THROUGH THIS
TAF CYCLE.  TAF INITIALIZES VFR WITH CALM WINDS BENEATH OVC HIGH
LEVEL CIRRUS STREAMING IN FROM THE WEST.  AS MOISTURE INCREASES FROM
THE WEST ASSOCIATED WITH FRONTAL INTRUSION EXPECTING CIGS TO LOWER
TO LOW VFR BY MID MORNING...WITH FURTHER DERTERIORATION EXPECTED AS
SHRA MOVES IN JUST AFTER DAYBREAK.  WITH THAT TAF FEATURES SHRA AND
MVFR CIGS AMIDST INCREASING SOUTHERLY FLOW AROUND 14Z.  MODELS
INDICATE RATHER QUICK CLEARING BEHIND THE SHRA...HOWEVER OPTED TO
INCLUDE AT LEAST SCT LOW CLOUDS UNTIL THE FRONT PASSES LATE IN THE
AFTERNOON WHEN SKIES IMPROVE SIGNIFICANTLY.  WINDS WILL INCREASE
JUST AHEAD OF THE FRONT WITH GUSTS LIKELY BY LATE MORNING...LASTING
THROUGH THE AFTERNOON BEFORE FLOW VEERS NORTHWESTERLY BEHIND THE
FRONT WITH GUSTS BEING PERSISTANT.

ELSEWHERE...MUCH THE SAME AS KCLT ABOVE WITH A MIXTURE OF VFR/MVFR
PREVAILING AT ALL SITES WITH THE POSSIBLE EXCEPTION OF KHKY WHERE
MVFR CIGS ARE QUESTIONABLE.  ASIDE FOR A BRIEF 1HR TEMPO FOR CURRENT
SHRA AT THE SC SITES...TAFS INITIALIZE WITH NO WX BENEATH LOW VFR
CIGS AND INCREASING SOUTHERLY WINDS.  CIGS WILL LOWER AS SHRA MOVES
THROUGH THE REGION BY MID/LATE MORNING WITH MVFR CIGS FEATURED
EVERYWHERE WITH THE EXCEPTION OF KHKY WHERE MVFR IS BORDERLINE PER
GUIDANCE...THUS LEFT OUT AT THIS TIME.  CIGS WILL LIFT BY LATE
MORNING AS SHRA EXITS EAST WITH WINDS INCREASING AHEAD OF THE FRONT
WITH GUSTS LIKELY AT ALL SITES.  WINDS WILL VEER NORTHERLY BEHIND
THE FRONT WITH GUSTS CONTINUING THROUGH THE REMAINDER OF THE DAY
INTO THE EVENING.

OUTLOOK...DRY HIGH PRESSURE WILL SPILL IN LATE ON TUESDAY BEHIND THE
FROPA...LASTING THROUGH MIDWEEK.  ANOTHER SYSTEM WILL APPROACH FROM
THE WEST NEAR WEEKS END ONCE AGAIN INCREASING PRECIP/RESTRICTION
CHANCES.  SOME WINTRY PRECIP IS POSSIBLE ACROSS THE NC
MOUNTAINS/FOOTHILLS AFFECTING BOTH KAVL AND KAND SATURDAY MORNING.
WINTRY PRECIP IS NOT EXPECTED AT THIS TIME FOR ANY OTHER TAF SITES.

CONFIDENCE TABLE...

            09-15Z        15-21Z        21-03Z        03-06Z
KCLT       HIGH 100%     HIGH  91%     HIGH 100%     HIGH 100%
KGSP       HIGH  97%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH  91%     HIGH 100%     HIGH 100%
KGMU       HIGH  97%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  91%     HIGH  94%     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...NONE.
SC...NONE.

&&

$$
SYNOPSIS...RWH
NEAR TERM...CDG
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...CDG


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