Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 152316
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
616 PM EST MON DEC 15 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 TUESDAY/...
2315 UTC UPDATE...WINDS WERE UPDATED TO INCORPORATE THE LATEST NAM
DATA...PRESERVING GUSTS OVERNIGHT AT THE HIGHEST ELEVATIONS OF THE
NC MOUNTAINS IN SOUTHERLY PREFRONTAL FLOW. POPS WERE ADJUSTED TO
ACCOUNT FOR A SLIGHTLY FASTER ARRIVAL OF A PRECIPITATION BAND AHEAD
OF THE APPROACHING COLD FRONT IN SE TN.

AT SOME POINT THIS EVENING IN RESPONSE TO THE ENCROACHING SWLY LLVL
JET AND AIDED BY TERRAIN LIFT...SHOWERS SHOULD DEVELOP ACRS THE
NC/GA MTNS AND PROBABLY BECOME NUMEROUS ALL ACRS THE MOUNTAINS
OVERNIGHT AS UPPER WAVE APPROACHES. 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 /TUESDAY NIGHT 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 /23Z MONDAY THROUGH SATURDAY/...
AT KCLT...VFR. LOW CLOUDS AND PRECIPITATION ARE EXPECTED TO INCREASE
OVERNIGHT AND EARLY TUESDAY AHEAD OF AN APPROACHING COLD FRONT. A
GUIDANCE BLEND DOES NOT SUPPORT CIG IR VSBY RESTRICTIONS...EVEN
THOUGH THE PESSIMISTIC NAM DOES SUPPORT CIG RESTRICTIONS. S WINDS
WILL VEER SW ON TUESDAY AS THE FRONT APPROACHES...WITH GUSTS
INCREASING...THEN WSW AS THE FRONT MOVES THROUGH IN THE AFTERNOON.

ELSEWHERE...CLOUDS WILL LOWER AS A FRONT APPROACHES...WITH
INCREASING SHOWER CHANCES TONIGHT. EVEN THE PESSIMISTIC LAMP KEEPS
VSBY RESTRICTIONS CONFINED TO MOUNTAINS VALLEYS SW OF KAVL. CIG
RESTRICTIONS ARE SUPPORTED BY A MODEL BLEND AT ALL SITES BUT
KHKY...MAINLY AFTER DAYBREAK IN SC. RAPID IMPROVEMENT IS EXPECTED AS
THE FRONT MOVES THROUGH AT MIDDAY. S WINDS WILL VEER SW AHEAD OF THE
FRONT...WITH GUSTS PICKING UP...THEN VEER WSW IN THE AFTERNOON...
EXCEPT NW AT KAVL.

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.

CONFIDENCE TABLE...

            23-05Z        05-11Z        11-17Z        17-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  80%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     MED   75%     HIGH  90%

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...CSH/JAT
SHORT TERM...LG
LONG TERM...JPT
AVIATION...JAT



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