Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 160605
AFDGSP

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

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO MOVE EAST OF THE AREA OVERNIGHT.
A COLD FRONT WILL MOVE ACROSS THE CAROLINAS TONIGHT INTO TUESDAY.
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 TODAY/...
AS OF 100 AM EST TUESDAY...TWEAKED POPS ACROSS THE REGION TO ACCOUNT
FOR LATEST NEAR TERM RADAR TRENDS.  MADE SLIGHT ADJUSTMENTS TO
TEMPERATURES/DEWPOINTS TO REFLECT LATEST OBSERVATIONS.  EXPECTING
WINDS TO BEGIN TO INCREASE SHORTLY AS THE SURFACE TROF APPROACHES
FROM THE WEST.  THUS...CURRENT PATCHY FOG ACROSS PORTIONS OF THE SC
PIEDMONT IS NOT FCST TO EXPAND FURTHER.  OTHERWISE...CURRENT FCST
REMAINS ON TRACK.

PREVIOUS DISCUSSION...

0330 UTC UPDATE...POPS WERE ADJUSTED BASED ON THE LATEST RADAR
TRENDS...RESULTING IN AN INCREASE FROM THE UPPER SAVANNAH RIVER
VALLEY TO THE CENTRAL NC MOUNTAINS.

AT 830 PM EST MONDAY...AN UPPER RIDGE WAS LOCATED ALONG THE EAST
COAST...WHILE A CLOSED UPPER LOW WAS LOCATED OVER THE MID MS RIVER
VALLEY. A COLD FRONT ASSOCIATED WITH THIS LOW WAS CROSSING THE MID
AND LOWER MS RIVER VALLEY...WHILE SURFACE HIGH PRESSURE LINGERED
ALONG THE EASTERN SEABOARD. PRECIPITATION AHEAD OF THE COLD FRONT
WAS ENTERING THE THE SW MOUNTAINS OF NC...AND APPROACHING THE
MOUNTAINS OF NE GA.

CLOUDS COVER WILL CONTINUE OT INCREASE AND LOWER AS THE FRONT
APPROACHES...WITH PRECIPITATION SPREADING EAST ACROSS THE AREA.
MODEL SOUNDING SHOW THAT INSTABILITY AHEAD OF THE FRONT SHOULD NOT BE
SUFFICIENT FOR CONVECTION IN OUR AREA OVERNIGHT. PRECIPITATION
AMOUNTS ARE EXPECTED TO BE RATHER LIGHT...AS GULF INFLOW REMAINS
LIMITED. WINDS COULD BE RATHER GUSTY AT HIGH ELEVATIONS OF THE NC
MOUNTAINS TONIGHT...BUT SHOULD REMAIN BELOW ADVISORY CRITERIA.
MINIMUM TEMPERATURES WILL RUN AROUND 7 DEGREES ABOVE NORMAL DUE TO
CLOUD COVER.

PREVIOUS DISCUSSION...IN CONJUNCTION WITH A RATHER FAST EASTWARD
TRANSLATION OF VORT LOBE ON TUESDAY...A NARROW BAND OF CONVERGENCE
SHOULD SUPPORT A ROUND OF SHOWERS FOR MOST FOOTHILL AND PIEDMONT
LOCALES FROM DAYBREAK UNTIL ABOUT EARLY AFTERNOON BEFORE LLVL FLOW
VEERS TO WESTERLY. SMALL SHOWERS WILL BE MAINTAINED ACRS THE
MOUNTAINS THROUGH THE BALANCE OF THE AFTERNOON AS STEEPER LAPSE
RATES ASSOCIATED WITH UPPER LEVEL COOL POOL SWINGS THROUGH. WESTERLY
FLOW WILL AID IN CLEARING EAST OF THE BLUE RIDGE TUESDAY AFTERNOON
WITH MAXIMUM TEMPERATURES STILL SVRL CATEGORIES ABOVE THE MID-
DECEMBER CLIMO.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
AS OF 200 PM MONDAY...UPPER FLOW WILL FEATURE A COUPLE FAST MOVING
SYSTEMS IN THE SHORT TERM TO DEAL WITH. AT THE ONSET OF THE
PERIOD... A SHORT WAVE FOLLOWING THE MAIN UPPER TROUGH WILL QUICKLY
MOVE THROUGH WESTERN NC TUE EVENING. THIS WILL AID IN DEVELOPING
SOME NW FLOW PRECIP...WHICH THE MODELS LIMIT TO THE NORTHERN
MOUNTAINS. PROFILES INITIALLY FAVOR ALL LIQUID...BUT COULD
CHANGEOVER TO SOME LIGHT IP/ZR BEFORE ENDING. WEAK HIGH PRESSURE
THEN NOSES OVER THE AREA ON WED PRODUCING A QUIET WEATHER DAY. ON
THU...A FAST MOVING SHORT WAVE EMBEDDED IN THE ZONAL FLOW IS
FORECAST TO TRAVERSE THE REGION. THE MODELS HINT AT A WEAK SFC WAVE
DEVELOPING ALONG THE OLD FRONTAL BOUNDARY DRAPED ACROSS THE DEEP
SOUTH. HOWEVER...THE SYSTEM WILL BE MOISTURE CHALLENGED WITH NO
OPPORTUNITY FOR GULF INFLOW. HENCE...PRECIP SHOULD BE LIGHT AND
SPOTTY WITH ANY MEASURABLE PRECIP CONFINED TO THE MOUNTAINS. THERE
COULD BE SOME MINOR PYTPE CONCERNS EARLY ON THU IF ANY PRECIP
DEVELOPS IN THE PREDAWN HOURS OVER THE MOUNTAINS. HOWEVER AS
MENTIONED PREVIOUSLY...AMOUNTS WILL BE LIGHT. USED A MODEL CONSENSUS
TO POPULATE GRIDS. MAX TEMPS ARE EXPECTED TO BE NEAR CLIMO ON WED
AND THEN A LITTLE BELOW CLIMO ON THU WITH INCREASED CLOUD COVER.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 225 PM EST MONDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
FRIDAY WITH WEAK UPPER RIDGING TO OUR SOUTH AND A DEPARTING CLOSED
H5 LOW OVER NORTHERN NEW ENGLAND. BY EARLY SAT...A SOUTHERN STREAM
UPPER TROF WILL MAKE ITS WAY EASTWARD AND APPROACH THE FCST AREA BY
EARLY SAT. BEYOND THIS POINT...THE LONG MODELS CONTINUE TO DIVERGE
QUITE A BIT WRT THE AMPLITUDE AND TRACK OF THE TROF. THE LATEST 12Z
GFS...AND TO A LESSER EXTENT THE 12Z CANADIAN...REMAIN MUCH LESS
AMPLIFIED WITH THE SYSTEM WHILE THE OLDER 00Z RUN OF THE ECMWF STILL
TRIES TO CUT OFF THE TROF LATE SAT/EARLY SUN AS IT MOVES OVER THE
FCST AREA. THE REMAINDER OF THE MEDIUM RANGE IS ALSO UNCLEAR AS THE
GFS TRIES TO KEEP SOME BROAD SOUTHERN STREAM TROFFING TO OUR SW THRU
MON...WHILE THE ECMWF REESTABLISHES UPPER RIDGING OVER THE GULF OF
MEX BY DAY 7.

AT THE SFC...CANADIAN HIGH PRESSURE WILL BE OVER THE REGION AT THE
START OF THE PERIOD AND SHOULD REMAIN CENTERED TO OUR NORTH THROUGH
THE DAY ON FRI. MAJOR DISCREPANCIES PERSIST BETWEEN THE OPERATIONAL
MODELS WRT THE EVOLUTION OF THE LOW THAT DEVELOPS TO OUR SW LATE
FRI/EARLY SAT. THE 12Z GFS HAS A POORLY DEVELOPED SYSTEM THAT MOVES
ACROSS THE CWFA FASTER THAN THE ECMWF OR CANADIAN SOLUTIONS. THE GFS
LOW LVL PROFILES ARE ALSO WARMER WITH MOSTLY LIQUID PRECIP FOR SAT
AND SUN EXCEPT FOR THE NORTHERN MTS. ALL THE MODELS SUGGEST THAT
THINGS SHOULD BE DRY AGAIN BY LATE SUN WITH BROAD HIGH PRESSURE
BUILDING BACK OVER THE REGION. I AM STILL LEANING MORE TOWARDS AN
ECMWF TYPE SOLUTION WHICH WOULD PRODUCE MORE FROZEN PRECIP FOR AT
LEAST THE NORTHERN HALF OF THE CWFA. OF COURSE...IF THE TRACK OF THE
LOW TRENDS MORE NORTHWARD IN THE COMING DAYS...THEN MORE LIQUID
PRECIP WOULD BE LIKELY. TEMPERATURES SHOULD REMAIN BELOW NORMAL
THROUGH THE PERIOD.

&&

.AVIATION /06Z 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...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       HIGH 100%     HIGH  88%     HIGH  87%     HIGH 100%
KGSP       HIGH  98%     HIGH  95%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  91%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH  92%     HIGH 100%     HIGH 100%
KGMU       HIGH  97%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  95%     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...LG
NEAR TERM...CDG/CSH/JAT
SHORT TERM...LG
LONG TERM...JPT
AVIATION...CDG



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