Area Forecast Discussion
Issued by NWS Greer, SC

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205
FXUS62 KGSP 040842
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
342 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/...
THE LATEST SURFACE ANALYSIS INDICATES THE COLD FRONT IS ROUGHLY
BISECTING THE FORECAST AREA...AND CREEPING ALONG TO THE EAST. UNTIL
THE FRONT SHIFTS EAST...LIGHT/VRBL WINDS NEAR THE BLUE RIDGE WILL
RESULT IN POCKETS OF DENSE FOG THROUGH DAYBREAK. THE BOUNDARY IS
GOING TO MAINTAIN ITS 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 /09Z THURSDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE (EXCEPT KAVL)...FORECAST CONFIDENCE IN
TRENDS OVER THE NEXT 6 HOURS IS WELL BELOW AVERAGE FOR THIS SET OF
TAFS...DUE TO A NUMBER OF COMPETING FACTORS. MOISTURE CONTENT OF THE
AIR MASS REMAINS QUITE HIGH OVER THE PIEDMONT EARLY THIS MORNING.
HOWEVER...COOLER AND DRIER AIR IS FILTERING IN FROM THE
WEST...ALTHOUGH THE COOLING IS SOMEWHAT OUTPACING THE DRYING...AS
EVIDENCED BY AREAS OF IFR (AND WORSE) CONDITIONS IN THE FOOTHILLS.
MEANWHILE...SW WINDS CONTINUE AT 5-10 KTS...BUT THESE ARE EXPECTED
TO DIMINISH LATER...CREATING THE POTENTIAL FOR FOG/LOW STRATUS
FORMATION IN THE STILL-MOIST AIR MASS. ON THE OTHER HAND...MID-LEVEL
CLOUDS ARE ALREADY PUSHING INTO THE AREA FROM THE SW...WHICH WOULD
TEND TO PREVENT FOG/LOW STRATUS DEVELOPMENT. AGAIN...CONFIDENCE IS
LOW...BUT OUR BEST GUESS IS FOR IMPROVEMENT IN THE FOOTHILLS...AND A
RETURN TO AT LEAST IFR CONDITIONS AT KCLT BY AROUND 08Z. DUE TO THE
INHERENT UNCERTAINTY...JUDICIOUS USE OF TEMPOS HAS BEEN MADE.
OTHERWISE...VFR CONDITIONS SHOULD RETURN AT MOST TERMINALS BY NO
LATER THAN MID-MORNING...ALTHOUGH PERIODS OF MVFR CIGS WILL REMAIN
POSSIBLE AT KCLT THROUGH MUCH OF THURSDAY. WINDS SHOULD GRADUALLY
TURN TOWARD THE NE BY LATE MORNING OR SO.

AT KAVL...NW WINDS HAVE DEVELOPED AT THE TERMINAL...WHICH HAS PUSHED
DRIER AIR UP THE VALLEY. THESE FACTORS ARE EXPECTED TO PRECLUDE
DEVELOPMENT OF ANY FOG OR VERY LOW STRATUS THIS MORNING. HOWEVER...
STRATUS AT THE LOW END OF MVFR IS PROBABLE...AND AT THE HIGH END OF
IFR IS POSSIBLE. OTHERWISE...VFR IS EXPECTED TO RETURN BY
NOON...WITH OCCASIONALLY GUSTY NW WINDS CONTINUING THROUGH THE
DAY.

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...

            08-14Z        14-20Z        20-02Z        02-06Z
KCLT       HIGH  86%     HIGH  92%     HIGH  85%     HIGH  93%
KGSP       HIGH  91%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       LOW   55%     MED   77%     HIGH 100%     HIGH 100%
KHKY       HIGH  80%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH  91%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       MED   74%     HIGH 100%     LOW   56%     HIGH 100%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE 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
SHORT TERM...CDG
LONG TERM...CDG
AVIATION...JDL



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