Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 041438
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
938 AM EST THU FEB 4 2016

.SYNOPSIS...
A COLD FRONT WILL CONTINUE TO SLIDE EAST OF THE AREA THROUGH
MORNING LIKELY STALLING ALONG THE ATLANTIC COASTLINE LATER TODAY.
THE FRONT WILL FINAL SLIDE OUT TO SEA ON FRIDAY WITH DRIER HIGH
PRESSURE PREVAILING THROUGH SATURDAY.  A COASTAL LOW COULD SPREAD
A FEW SHOWERS INTO THE AREA FROM THE SOUTHEAST ON SUNDAY BEFORE A
MORE POTENT UPPER DISTURBANCE AND ASSOCIATED SURFACE COLD FRONT
SPILL IN FROM THE NORTHWEST MONDAY MORNING LEADING TO ELEVATED
PRECIPITATION CHANCES THROUGH MIDWEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 945 AM...STILL NOT REALLY SEEING MUCH OF A CHANGE ACROSS THE
FCST AREA. VISIBLE SATELLITE IMAGERY SUPPORTS THE IDEA THAT A
SIGNIFICANT CONTRAST IN AIR MASSES REMAINS ACROSS THE WESTERN
CAROLINAS. THE NC MTNS...AWAY FROM THE TN BORDER...HAVE CLEARED
OUT...WHILE THE PIEDMONT REMAINS SOCKED IN WITH LOW/MID LEVEL OVC.
WILL REMOVE THE REMAINING FOG WITH THE UPDATE...BUT WILL HAVE TO
KEEP A CHANCE OF SHOWERS ON THE SOUTHEAST FRINGE OF METRO CLT INTO
THE AFTERNOON AS RADAR TRENDS SUPPORT THE WRN EDGE OF PRECIP
CONTINUING TO SKIRT THAT REGION.

THE BOUNDARY IS GOING TO MAINTAIN ITS SLOW DELIBERATE PACE UNTIL THE
UPPER TROUGH AXIS...CURRENTLY OVER THE CENTRAL CONUS BEGINS ITS PUSH
OVER THE SOUTHEAST...ENABLING CYCLOGENESIS OFF THE SOUTHEAST COAST
LATER TODAY. THUS...THE FIRST PROBLEMATIC PART OF THE FORECAST IS
TODAY/S MAX TEMPS...AS GUIDANCE HAS THUS FAR BEEN GENERALLY TOO
AGGRESSIVE IN PUSHING THE COOLER AIR INTO THE FORECAST AREA. JUST AS
AN EXAMPLE...RAW MODEL MAX TEMP FORECASTS AT KAVL RANGE FROM 40 TO
50 TODAY. BASED ON THE LATEST TRENDS...THE GUIDANCE THAT IS CLOSER
TO 50 APPEARS LESS WRONG THAN THE COOLER GUIDANCE...AND WE ARE
FORECASTING MAXES FAIRLY CLOSE...OR JUST ABOVE CLIMO IN MOST AREAS.
TEMPS SHOULD EVENTUALLY FLAT LINE OR BEGIN TO FALL ACROSS THE MTNS
LATER TODAY...AS COLD ADVECTION INTENSIFIES WEST OF THE DEVELOPING
CYCLONE.

THE NEXT ISSUE IS WHAT TO DO WITH POPS...ESPECIALLY THIS EVENING AS
THAT COLD ADVECTION IS DEVELOPING. SOME OF THE GUIDANCE TENDS TO
DEVELOP A BIT OF A DEFORMATION ZONE ACROSS THE INTERIOR CAROLINAS
THIS EVENING...AS THE BASE OF THE UPPER TROUGH AND ATTENDANT
NEUTRALLY-TILTED SHORT WAVE PASSES SOUTH OF THE AREA. THIS ALLOWS
FOR A LITTLE LIGHT PRECIP TO DEVELOP AS FAR WEST AS THE MTNS. THIS
SCENARIO IS ESPECIALLY PROMINENT IN THE GFS. TAKING A LOOK AT GEFS
OUTPUT...THE OPERATIONAL GFS IS THE ONLY MEMBER THAT DEVELOPS PRECIP
OVER THE MOUNTAINS TONIGHT...WHILE THE OTHER MEMBERS ARE A LITTLE
MORE IN LINE WITH THE DETERMINISTIC MODEL EAST OF THE MTNS. THERE IS
ALSO SUPPORT FOR THIS SCENARIO FROM THE CANADIAN AND TO A LESSER
EXTENT THE ECMWF. OPTED THEREFORE TO PULL SLIGHT CHANCE POPS ALMOST
TO THE BLUE RIDGE THIS EVENING FOR A VERY LIGHT QPF EVENT. PARTIAL
THICKNESS PROGS INDICATE A RAIN/SNOW SCENARIO...WITH MOSTLY RAIN IN
THE PIEDMONT/FOOTHILLS (POSSIBLY MIXING WITH FLURRIES LATE TONIGHT).
IF PRECIP MANAGES TO DEVELOP OVER THE MTNS...IT WOULD BE SNOW.
AGAIN...THIS IS A LOW PROBABILITY/LOW QPF SITUATION. OTHERWISE...
WITH COLD ADVECTION OVERSPREADING THE AREA...MIN TEMPS ARE EXPECTED
TO BE A SOLID 5 DEGREES BELOW CLIMO TONIGHT.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
AS OF 230 AM EST THURSDAY...THE SHORT TERM FCST PERIOD INITIALIZES
ON FRIDAY MORNING WITH THE UPPER PATTERN HIGHLIGHTED BY A POTENT
SHORTWAVE TROF PASSING ATOP THE MID ATLANTIC...WHILE SHORTWAVE
RIDGING BUILDS WESTWARD OVER THE MID/LOWER MS RIVER VALLEY.  AT THE
SURFACE...A QUASISTATIONARY FRONTAL AXIS WILL RESIDE ALONG THE
ATLANTIC COASTLINE...HOWEVER WILL BE ON THE MOVE RATHER QUICKLY AS
THE POTENT H5 WAVE MOVES OVERHEAD.  A BROAD REGION OF SURFACE HIGH
PRESSURE BENEATH THE A FORE MENTIONED UPPER SHORTWAVE RIDGE AXIS
WILL CONTINUE MARCHING EAST THROUGH THE DAY ON FRIDAY...EVENTUALLY
SETTLING ATOP NORTHEAST GA AND THE WESTERN CAROLINAS BY SATURDAY
MORNING.

MEANWHILE...SPLIT FLOW OVER THE PLAINS STATES WILL ATTEMPT TO
PHASE INTO A SINGLE FULL LATITUDE TROF...LIKELY MOVING OVER THE
ARKLATEX BY DAYBREAK ON SATURDAY.  THIS BROAD AREA OF H5 HEIGHT
FALLS WILL ADVECT EAST ALL THE WHILE CONTINUING TO DEEPEN AS IT
SPREADS OVER THE NORTHEAST GULF COAST INTO MIDDAY SATURDAY.  AT THAT
TIME...GUIDANCE FAVORS SIGNIFICANT SFC PRESSURE FALLS ACROSS THE FL
PENINSULA THEN EASTWARD OVER THE WATERS OF THE WESTERN ATLANTIC.
SAID SURFACE LOW PRESSURE WILL DEEPEN THROUGH THE OVERNIGHT INTO
SUNDAY MORNING WITH SOME MODEL DISCONTINUITY PRESENT AS TO ITS
EVENTUAL TRACK...AND HOW THAT RELATES TO THE SOUTHERN APPALACHIANS.
ECMWF/CMC SOLUTIONS ARE WETTER AND SIGNIFICANTLY FURTHER INLAND THAN
THAT OF THE GFS...WHICH IF WAS TO VERIFY...WOULD YIELD NOTHING MORE
THAN INCREASED CLOUDINESS.  HOWEVER...THE FORMER WOULD FAVOR LOW
END PRECIP CHANCES ALONG/EAST OF THE I77 CORRIDOR THROUGH MIDDAY
SUNDAY...WITH THERMAL PROFILES BARELY SUPPORTING A RASN MIX AT
PRECIP ONSET.  THUS THE FCST FAVORS SUCH SOLUTION WITH SLIGHT
CHANCE POPS HIGHLIGHTED WITH A BRIEF SHOT AT A FEW FLURRIES.
THE ENTIRE SYSTEM LOOKS TO EJECT EAST THROUGH THE DAYLIGHT HOURS
ON SUNDAY ALLOWING FOR DRYING AND ANOTHER BRIEF ROUND OF HIGH
PRESSURE INTO SUNDAY NIGHT.  TEMPERATURES THROUGH THE SHORT TERM
PERIOD WILL REMAIN JUST A FEW DEGREES BELOW CLIMO ON AVERAGE.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
AS OF 300 AM EST THURSDAY...THE MEDIUM RANGE FCST PERIOD KICKS
OFF ON SUNDAY NIGHT AS A BRIEF ROUND OF DEEP LAYER RIDGING SETS
UP ATOP THE SOUTHERN APPALACHIANS AS A POTENT H5 SHORTWAVE EJECTS
INTO THE WESTERN ATLANTIC.  HOWEVER...A FAST MOVING CLIPPER TYPE
SYSTEM DIVING THROUGH THE UPPER MIDWEST WILL SWEEP INTO THE SOUTHERN
APPALACHIANS BY MONDAY MORNING PACKING A MODEST AMOUNT OF MOISTURE
ALONG ITS SURFACE COLD FRONT.  BEYOND THIS POINT...AND REALLY
THROUGH THE REMAINDER OF THE PERIOD...THE PATTERN REMAINS DOMINATED
BY A BROAD/DEEP LONGWAVE TROF WHILE A SERIES OF REINFORCING H5
SHORTWAVES PASS THROUGH THE MEAN FLOW ALOFT.  THIS WILL LIKELY
SPELL A FAIRLY PROLONGED NWFS SETUP ACROSS THE SOUTHERN APPS WITH
SOME OF THE A FORE MENTIONED FRONTAL MOISTURE BREAKING CONTAINMENT
INTO THE NC/SC PIEDMONT AS WELL AS NE GA LEADING TO A FEW SN
SHOWERS...SPECIFICALLY ON MONDAY INTO TUESDAY.  ANY NWFS COULD
PERSIST FOR A FEW DAYS LEADING TO MODEST ACCUMULATIONS ACROSS THE
MTNS AS FLOW/MOISTURE ARE CONTINUOUSLY REINFORCED.  ALONG WITH THE
PRECIP...THE AIRMASS ASSOCIATED WITH THIS SYSTEM LOOKS RATHER COLD
AS BOTH THE GFS/ECMWF SHOVE ANY CRITICAL THICKNESS VALUES WELL
SOUTH OF THE CWFA...MORE SPECIFICALLY...THE 540DM LINE LOOKS TO
PUSH AS FAR SOUTH AS JACKSONVILLE FL.  CLOSER TO HOME...GUIDANCE
IS STARTING TO SHOW SIGNS OF THE RETURN TO WINTER LIKE TEMPERATURES
AS A CONSENSUS OF HIGHS BY MIDWEEK RANGE FROM THE MID 30S TO LOWER
40S ON AVERAGE...WITH LOWS BY WEDNESDAY/THURSDAY MORNINGS IN THE
TEENS TO MID 20S ON AVERAGE.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
AT KCLT...THERE IS A BETTER-THAN-GOOD CHANCE THAT THE CURRENT LOW
LMVFR CIGS WILL LOWER TO IFR...AT LEAST PERIODICALLY OVER THE NEXT
2-3 HOURS. IN ADDITION...HIGH SURFACE MOISTURE CONTENT COULD RESULT
IN SOME REDUCED VISBY...SO 3SM/BR HAS BEEN INCLUDED AS WELL. AFTER
THAT...EXPECT CIGS TO SETTLE IN THE 020-030 RANGE AND PERSIST
THROUGH MUCH ABOUT MID-AFTERNOON...THEN BECOMING VFR. VFR SHOULD
LAST THROUGH THE END OF THE PERIOD...BUT PERIODS OF MVFR ARE
POSSIBLE OVERNIGHT. OTHERWISE...WINDS ARE EXPECTED TO BECOME LIGHT
NW BY THE END OF THE MORNING...THEN TURN TOWARD THE N/NE AND
INCREASE TO 5-10 KTS DURING THE AFTERNOON. SMALL CHANCES FOR -RA
CREEP INTO THE FORECAST BY THIS EVENING...AND CONTINUING THROUGH THE
OVERNIGHT...BUT CHANCES ARE TOO LOW TO INCLUDE IN THE TAF ATTM.

ELSEWHERE...THE AIR MASS HAS DRIED OUT QUITE A BIT OVER KAND...AND
ESP AT KAVL. EXPECT VFR CONDITIONS TO PERSIST THERE THROUGH THE
PERIOD. MEANWHILE...THE DRY AIR HAS REALLY STRUGGLED TO PUSH INTO
THE FOOTHILLS. KHKY MAY HAVE FINALLY CLEARED THE LIFR/VLIFR
CONDITIONS FOR GOOD...BUT WILL NEVERTHELESS ADVERTISE TEMPOS FOR
LIFR THROUGH THE FIRST HOUR. MEANWHILE...VLIFR CONDITIONS HAVE
DEVELOPED AT KGSP...AND LIFR HAS CREPT INTO KGMU. WILL KEEP AT LEAST
A TEMPO FOR LIFR THROUGH 14Z...BUT EXPECT CONDITIONS TO IMPROVE
CONSIDERABLY AFTER THAT...AS THE DRIER AIR FINALLY PUSHES OVER THESE
SITES. PERIODS OF MVFR CIGS COULD BE SEEN AT ANY OF THE TERMINALS
THIS AFTERNOON...AS SOME LOW LEVEL MOISTURE WILL REMAIN OVER THE
AREA.

OUTLOOK...LARGE HIGH PRESSURE WILL SLOWLY BUILD ACROSS THE REGION
THROUGH THE WEEKEND...GRADUALLY PUSHING OUT THE LINGERING MOISTURE
LATE THU INTO EARLY FRIDAY. UNRESTRICTED CONDITIONS ARE THEN
EXPECTED THROUGH THE WEEKEND. A STRONG UPPER AIR DISTURBANCE COULD
BRING ENOUGH MOISTURE TO WRING OUT A FEW RAIN OR SNOW SHOWERS ON
MONDAY.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       MED   73%     HIGH  84%     HIGH  98%     HIGH  87%
KGSP       HIGH  98%     HIGH 100%     HIGH  94%     HIGH  87%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  87%
KHKY       HIGH 100%     HIGH  98%     HIGH 100%     HIGH  87%
KGMU       HIGH 100%     HIGH 100%     HIGH  97%     HIGH  87%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  87%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...CDG
NEAR TERM...JDL/PM
SHORT TERM...CDG
LONG TERM...CDG
AVIATION...JDL


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