Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 271746
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1246 PM EST SAT DEC 27 2014

.SYNOPSIS...
A SERIES OF SMALL LOW PRESSURE WILL MOVE NORTHEAST ALONG A COLD
FRONT AS THE FRONT SLOWLY CROSSES OUR REGION FROM THE WEST THROUGH
MONDAY. COOLER HIGH PRESSURE WILL BUILD OVER OUR REGION IN THE MID
TO LATTER PART OF THE WEEK. ANOTHER LOW PRESSURE WILL GET ORGANIZED
OVER TEXAS AND REACH OUR AREA NEXT WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
1145 AM EST UPDATE...LATEST RADAR TREND SHOWS AREAS OF LIGHT PRECIP
CURRENTLY OVER THE NORTH-CENTRAL GA LIFTING NORTHEAST TOWARDS NE GA
AND SW MTNS ZONES AS OF LATE MORNING HOURS. LATEST MESO-SCALE MODELS
INCLUDING THE RAP AND HRRR SUGGEST THAT THE AFOREMENTIONED FEATURE
WILL REACH THE NE GA AND SW MTN ZONES BY AROUND 18Z AND DRIES OUT
TOWARD 21Z. HENCE...HAVE KEPT THE LOW-END CHANCE POPS OVER THE
EXTREME WESTERN TIER OF THE CWA...BEFORE RAMPING DOWN TO THE SLIGHT
CHANCE RANGE BY 21Z. POPS THEN RAMP UP FROM WEST TO EAST THROUGH
TONIGHT AS DEEPER GULF MOISTURE ARRIVES. AS FOR THE PRECIP
TYPE...HAVE MENTIONED SHOWERS THROUGH SUNDAY... WITH CHANCE OF
THUNDER...OVER THE WESTERN PORTIONS OF THE CWA AS MODELS SUGGEST
THAT SOME DEGREE OF ELEVATED INSTABILITY (100-200J/KG MUCAPE)WILL BE
PRESENT ON SUN AFTERNOON. HAVE RAISED THE QPF THRU SUN AFTERNOON PER
LATEST GUIDANCE.

845AM EST UPDATE...THE LATEST REGIONAL RADARS SHOW AREAS OF LIGHT
RETURNS OVER PORTIONS OF NE GA AND THE EXTREME WESTERN NC MTNS AS OF
THIS MORNING...IN LIGHT OF A WEAK UPPER DISTURBANCE LIFTING NE
ACROSS THE WESTERN ZONES OF THE CWA. ALSO...AREAS OF LIGHT PRECIP
CURRENTLY OVER AL AND PORTIONS OF NW GA WILL MOVE
EASTWARD...REACHING NE GA AND SW MTNS BY AROUND 18Z TODAY.
HOWEVER...LATEST HRRR SUGGESTS THIS FEATURE WILL WEAKEN AS IT ENTERS
OUR CWA ATT. HENCE...SLIGHT CHANCE TO THE LOW END CHANCE POPS WERE
WARRANTED THERE THROUGH THE MORNING HOURS INTO EARLY PART OF THIS
AFTERNOON. WITH TEMPS WARMING UP ABOVE THE FREEZING LEVEL...SHRA WAS
MENTIONED IN THE WX GRID.

AS OF 630 AM...LIGHT RETURNS ON REGIONAL 88DS ARE BEGINNING TO LIFT
NE OF THE AREA. THERE WAS ACTUALLY A LITTLE LIGHT SLEET REPORTED
UNDERNEATH SOME OF THIS ACTIVITY ACROSS THE MTNS EARLIER...WHICH IS
SURPRISING CONSIDERING THE VERY DRY SUBCLOUD LAYER (WITH CLOUDS
BASES AT AROUND 10 KFT). WITH RADAR EHCOES DIMINISHING...WILL
CONTINUE TO FEATURE A PRECIPITATION-LESS FORECAST THIS MORNING.
TEMPS SHOULD WARM TO AROUND 50 ACROSS THE PIEDMONT/FHILLS AND MTN
VALLEYS BY LATE MORNING.

A LOW AMPLITUDE RIDGE WILL PERSIST ALONG THE EAST COAST TODAY...
BEFORE MOVING OFF THE COAST BY THE END OF THE PERIOD...AS AN
UPSTREAM TROUGH BEGINS TO EJECT FROM TEXAS/THE SOUTHERN PLAINS.
TODAY WILL SEE A VARYING DEGREE OF MID/HIGH LEVEL CLOUD COVER ACROSS
THE WESTERN CAROLINAS AND NORTHEAST GEORGIA...RESULTING IN PARTLY
CLOUDY SKIES ACROSS MUCH OF THE AREA. MAX TEMPS WILL AVERAGE AROUND
10 DEGREES ABOVE CLIMO.

RAIN CHANCES INCREASE TONIGHT...AS A WEAK FRONTAL ZONE AND
ASSOCIATED WEAK LOW PRESSURE MOVE ACROSS THE TENN VALLEY. RESULTANT
ISENTROPIC LIFT/LOW LEVEL CONVERGENCE AND WEAK MID-LEVEL SHORT WAVE
TROUGH SHOULD SUPPORT RAIN MOVING INTO THE WESTERN ZONES BY MIDNIGHT
OR SO. RAIN CHANCES DIMINISH TOWARD THE SOUTHEAST...AS THE BEST
FORCING IS EXPECTED TO LIFT NORTHEAST ACROSS THE CWA BETWEEN 06 AND
12Z. POPS WILL RANGE FROM CATEGORICAL ACROSS THE MOUNTAINS/NC
FOOTHILLS/NORTHWEST UPSTATE...TO THE LOW END OF LIKELY ACROSS THE
SOUTHEAST ZONES. RAINFALL AMOUNTS THROUGH 12Z SHOULD RANGE FROM A
QUARTER TO HALF INCH ACROSS THE MOUNTAINS AND ADJACENT FOOTHILLS...
TO LESS THAN A QUARTER INCH ACROSS MUCH OF THE PIEDMONT. MIN TEMPS
WILL BE WELL ABOVE NORMAL.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 300 AM SAT...ON SUNDAY THE FAIRLY BROAD FRONTAL ZONE WILL
EXTEND FROM QUEBEC SWWD TO THE WRN GULF COAST...BISECTING THE TENN
VALLEY JUST TO OUR WEST. AT LEAST ONE WEAK WAVE IS PROGGED TO RIDE UP
THE FRONT DURING THE DAY AS A RESULT OF CYCLONIC UPPER FLOW OVER THE
BOUNDARY CONTAINING EMBEDDED WEAK VORTICES. THOUGH SUCH A WAVE WOULD
LIKELY PROVIDE LOCAL ENHANCEMENT TO LLVL WARM/MOIST ADVECTION AHEAD
OF THE FRONT...THE EXISTENCE OF ONE IS IN QUESTION GIVEN THE POOR
AGREEMENT AND CONSISTENCY FROM GUIDANCE ON HOW THIS OCCURS. OVERALL
THE FORCING SUNDAY IS JUST NOT ALL THAT IMPRESSIVE. LITTLE TO NO
INSTABILITY IS PROGGED OVER THE CWFA AND THOUGH A GOOD SLUG OF
MOISTURE TRANSPORT IS PRESENT ON NAM/GFS PROGS THE LLVL LIFT IS
LIMITED. AT ANY RATE...THRU SUNDAY THE FRONT REMAINS NEARLY
STATIONARY ACRS THE SOUTHEAST...THE PARENT LOW CONTINUING TO PROGRESS
EWD WITH THE ACTIVE NRN STREAM WHILE THE BROAD SRN STREAM TROUGH IS
HELD OFF BY THE BERMUDA HIGH. IT APPEARS THE FRONT WILL NOT ACTUALLY
ENTER THE AREA UNTIL MONDAY MRNG...WITH A DISTINCT 500MB SHORTWAVE
ACCOMPANYING IT AS WELL AS UPPER DIVERGENCE ASSOC WITH RR QUAD OF A
JET STREAK.

TWO PEAKS OF PRECIP ACTIVITY ARE SUGGESTED WHEN THE TOTAL FORCING IS
MAXIMIZED...SUNDAY MRNG AND THEN EARLY MON MRNG. HOWEVER IT IS
DIFFICULT TO PICK OUT A POINT BETWEEN WHERE A LULL SHOULD BE
BETWEEN...WITH THE OVERALL PATTERN REMAINING FAVORABLE FOR AT LEAST
LIGHT PRECIP. WILL CONTINUE TO ADVERTISE LIKELY POPS MOST OF THE AREA
THROUGHOUT SUNDAY...BUT CONCENTRATING MORE QPF CLOSE TO THE
AFOREMENTIONED PEAKS. DESPITE CLOUDS AND RAIN...IN THE WARM AIRMASS
TEMPS SHOULD TOP OUT 5-9 DEGREES ABOVE NORMAL SUN AFTN...WITH MINS
MON MRNG BEING EVEN MORE ABOVE NORMAL...UPPER 40S AND LOWER 50S. MAX
TEMPS MONDAY WILL BE SLIGHTLY WARMER THAN SUNDAY OVER THE PIEDMONT
WITH THE FRONT NOT YET HAVING AN IMPACT.

PROGRESSION OF THE UPPER PATTERN IS STILL PRETTY SLOW THRU MON
NIGHT...WITH THE CWFA NEAR THE INFLECTION POINT BETWEEN THE PLAINS
TROUGH AND THE ATLANTIC RIDGE. POPS DECLINE ONLY GRADUALLY THRU THE
END OF THE PERIOD WITH MOST OF THE GUIDANCE INDICATING SOME QPF
CONTINUING ON THE BACK SIDE OF ANOTHER FRONTAL WAVE DEVELOPING NEAR
THE GA/SC COAST. COLDER AIR WILL BEGIN TO RETURN TO ALL AREAS ON THE
ENSUING NLY FLOW MON NIGHT...THOUGH MIN TEMPS WILL STILL BE AROUND 10
DEGREES ABOVE CLIMO.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 200 AM SAT...QUASI-ZONAL UPPER FLOW CONTINUES OVER THE SUN BELT
TUESDAY EVEN AS A POLAR TROUGH MOVES INTO THE CONUS AND SHEARS INTO
TWO SHORTWAVES TO OUR NORTH AND WEST. ONE WAVE MOVES OVER THE GREAT
LAKES AND CONTRIBUTES TO GENTLE HEIGHT FALLS OVER THE SOUTHEAST
MID-WEEK...WHILE THE OTHER CUTS OFF OVER THE SOUTHWEST AND LEADS TO
THE DEVELOPMENT OF A SFC LOW OVER THE SRN PLAINS OR ARKLATEX BY THE
END OF THE WEEK. CONFLUENCE DOWNSTREAM OF THE SW TROUGH WILL PRODUCE
A SPRAWLING SFC HIGH WHICH WILL SPREAD ACRS THE OH VALLEY AND SRN
STATES TUE NIGHT THRU FRI. THIS WILL BRING SEASONABLY COOL CONDITIONS
FOR OUR AREA WITH TEMPS A SHADE BELOW CLIMO. MOST OF THE PERIOD LOOKS
DRY BEFORE POPS START RAMPING UP THU NIGHT AHEAD OF THE DEVELOPING
LOW.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AT KCLT AND ELSEWHERE...VFR CONDITIONS WILL CONTINUE AT LEAST THRU
TONIGHT. CONSIDERABLE CLOUDINESS WILL SPREAD IN FROM THE WEST THIS
AFTERNOON THRU THRU TONIGHT AS MOIST SWLY FLOW ALOFT DEVELOPS. AS
DEEPER GULF MOISTURE ASSOCIATED WITH A WAVE OF LOW APPROACHES FROM
THE SW...MVFR CLOUDS WITH PRECIP WILL SPREAD ACROSS THE AREA FROM
WEST TO EAST LATE TONIGHT THRU EARLY SUN MORNING. LATEST GUIDANCE IS
SUPPORTIVE OF IFR VSBY/CIGS WITH ONGOING SHRA THRU 18Z SUN...AS A
WAVE OF LOW PASSES JUST TO OUR NORTH. LIGHT SW WINDS SHOULD PREVAIL
THRU THE PERIOD...EXECPT KAVL WHERE S WINDS WILL VEER TO THE NORTH
BY SUN AFTERNOON.

OUTLOOK...PERIODS OF RAIN AND FLIGHT RESTRICTIONS ARE EXPECTED
THROUGHOUT SUNDAY...MONDAY...AND MONDAY NIGHT BEFORE GRADUAL
IMPROVEMENT OCCURS THROUGHOUT TUESDAY. DRY HIGH PRESSURE SHOULD
RETURN BY MID-WEEK.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     LOW   53%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     MED   70%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  80%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     MED   70%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     MED   70%

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...DEO
NEAR TERM...JDL/JOH
SHORT TERM...WIMBERLEY
LONG TERM...ARK/WIMBERLEY
AVIATION...JOH



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