Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 200601
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
201 AM EDT SUN APR 20 2014

.SYNOPSIS...
A MOIST LOW PRESSURE SYSTEM WILL CONTINUE MOVING OFF THE SOUTH
CAROLINA COAST THROUGH SUNDAY. HIGH PRESSURE WILL BRIEFLY BUILD IN
MONDAY...BEFORE A COLD FRONT PUSHES ACROSS THE REGION ON TUESDAY. A
BROAD AND DRY AREA OF HIGH PRESSURE WILL THEN BUILD IN FROM THE
NORTH WEDNESDAY AND LINGER THROUGH THE END OF THE WEEK.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 155 AM EDT...REGIONAL RADARS SHOW ONE LAST TRAINING BAND
MOVING THROUGH THE SOUTHEAST SIDE OF CHARLOTTE EARLY THIS MORNING.
ALL MESOSCALE MODELS DEPICT COVERAGE SLOWLY DIMINISHING THROUGH THE
EARLY MORNING HOURS AS THE DEFORMATION ZONE DISSIPATES AND SLIPS
EAST. MEANWHILE...WATER VAPOR IMAGERY SHOWS THE SWIRLING UPPER LOW
MOVING OVER THE OFFSHORE WATERS EAST OF SAVANNAH EARLY THIS MORNING.
AS THIS UPPER VORTEX MOVES FARTHER OFFSHORE TODAY...RIDGING WILL
BUILD IN FROM THE WEST. GRADUAL SCATTERING WILL ALLOW TEMPS TO
REBOUND DESPITE THE LINGERING SFC HIGH PRES ZONE REMAINING IN PLACE.
THE NAM HAS MORE EASTERLY FLOW MOISTURE AT 850 MB TONIGHT...BUT THE
PREFERRED GFS/ECM CAMP KEEP THE MOISTURE CONFINED MORE TO THE
COASTAL PLAIN. EXPECT MAXES IN THE 60S THIS AFTN AND MINS IN THE 40S
TONIGHT.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
AS OF MIDDAY SATURDAY...SHORT UPPER RIDGE REMAINS OVER THE FA SUNDAY
NIGHT AS DEEP LOW MOVES OFF THE SOUTHEAST COAST...MAINTAINING
NORTHERLY LLVL FLOW INTO MONDAY. WRAPAROUND MOISTURE FROM THE LOW
LINGERING OVER THE ERN HALF OF THE FA LATE SUNDAY THUS GETS SHUNTED
OFF TO THE SOUTH OVERNIGHT...WHILE SOME LLVL MOISTURE DOES ADVECT
INTO THE WRN FA AS THE FLOW BACKS. THIS MOIST LAYER IS SHALLOW ON
PROG SOUNDINGS. CONVECTION ACRS THE FA WILL LIKELY REMAIN CAPPED BY
SUBSIDENCE WITHIN THE RIDGE MON AFTN. HOWEVER...LATE MONDAY THE RIDGE
COLLAPSES AS TROUGH SWINGS INTO THE OHIO VALLEY. SOME OF THE 09Z SREF
MEMBERS INDICATED THE CAP WILL BREAK AS EARLY AS MON EVENING...AND
SOME SFC BASED INSTABILITY COULD BE REALIZED IF THAT SCENARIO
HAPPENED EARLY ENOUGH. MORE LIKELY THOUGH...THE INVERSION DISSOLVES
CLOSER TO TUE MRNG AS THE TROUGH DIGS IN AHEAD OF IMPENDING FROPA.
POPS WILL BE REINTRODUCED INTO THE MTNS EARLY TUE MRNG AS FRONTAL
MOISTURE SPREADS IN WITH WEAK UPSLOPING.

DECENT SFC BASED CAPE DOES DEVELOP OVER THE FA AHEAD OF THE FRONT ON
TUESDAY. NONE OF THE SHEAR PARAMETERS LOOK THREATENING FOR SEVERE
WX...AND WITH THE STRONGER FORCING BEING WELL TO OUR NORTH THE QPF IS
LIGHT ON ALL THE CONSULTED GUIDANCE. BEST INSTABILITY IS SHOWN OVER
THE NC PIEDMONT...WITH MODEL CONSENSUS SHOWING CAPE PEAKING AROUND
1000 J. DCAPE IS ALSO FAIRLY HIGH ON GFS WHICH HAS FAIRLY HIGH CLOUD
BASES...SO THERE MAY BE A LOW-END PULSE STORM WIND THREAT. POPS
DIMINISH LATE TUE FOLLOWING THE DIURNAL PEAK AND AS THE FRONT
DEPARTS. VERY SHALLOW MOISTURE ON NW FLOW TUE NIGHT MIGHT PRODUCE
SOME ADDITIONAL SHOWERS IN THE MTNS. WINDS MAY ALSO BE MODERATELY
GUSTY IN THE HIGHER TERRAIN TUE AND TUE NIGHT.

COOL WEDGY TEMPS CONTINUE ACRS THE AREA SUNDAY NIGHT...BUT TEMPS
REBOUND TO SLIGHTLY ABV CLIMO FOR MON AND TUE.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 145 PM SATURDAY...STRONG LATITUDINAL UPPER RIDGING WILL
DEVELOP TO THE WEST EARLY WED AND PUSH EAST OVER THE FCST AREA
THROUGH THU. THIS WILL BRING DOWN A STRONG CANADIAN SFC HIGH AND
ALLOW FOR DEEP LAYERED DRYING WHILE THE HIGH SETTLES INTO AN ATL
RIDGE CONFIG THU. THERE WILL BE SOME MEASURE OF AN AIRMASS MIX WED
MAINLY ACROSS THE ERN ZONES WHERE MAX TEMPS WILL PROBABLY BE HELD A
COUPLE DEGREES BELOW NORMAL ACROSS THE NW PIEDMONT. DOWNSLOPE FLOW
WILL AIDE IN WARMER THAN NORMAL TEMPS ACROSS THE REST OF THE
NON/MTNS...WHILE THE MTNS VALLEYS REACH RIGHT AROUND NORMAL. THE
LLVL FLOW VEERS S/LY THU AND ALLOWS A BETTER MODIFICATION OF SFC
BASED THETA/E AND TEMPS/TDS WILL RESPOND A COUPLE DEGREES WARMER.
ALL IN ALL...BOTH DAYS SHOULD MOSTLY SUNNY AND PLEASANT WITH TD/S
REMAINING BELOW 50 F MOST LOCALES.

THE UPPER RIDGE AXIS SHIFTS EAST THU NIGHT AS AN H5 LOW DEEPENS
ACROSS THE UPPER MIDWEST. THE OP MODELS DISAGREE ON THE TIMING AND
NATURE OF THIS LOW WITH THE 12Z GFS CLOSING IT OFF AND PRODUCING A
SLOWER SYNOPTIC PATTERN BY ABOUT 12 HRS THAN THE 00Z ECMWF. THE GEFS
MEAN HEIGHTS/MSLP ARE A PRETTY GOOD COMPROMISE AS FAR AS TIMING AND
THIS WAS GIVEN THE MOST WEIGHT IN THE FCST. THERE ARE ALSO NOTABLE
DIFFERENCES WITH THE AMOUNT OF THE GOM RIDGING AND AVAILABLE MOIST
FLUX AHEAD OF THE SFC FRONT FRI. THE ECMWF SETS UP A STRONGER LLVL
RIDGE AND THUS DISRUPTS THE MOIST GOM FLOW MORESO THAN THE
GFS...LEAVING A DRY FROPA BY FRI NIGHT. IN ANY CASE THERE SHOULD BE
ENOUGH ISEN LIFT MOISTURE TO PRODUCE ISOL PREFRONTAL SHOWERS
BEGINNING EARLY FRI WITH AN INCREASE TO SCT COVERAGE ACROSS THE NC
MTNS BY THE AFTERNOON. MODEL SOUNDINGS SHOW THE PRESENCE OF ELCAPE
ON THE ORDER OF A COUPLE HUNDRED JOULES FRI AFTERNOON...SO THUNDER
MENTION WILL BE MAINTAINED THROUGH THE EVENING PERIOD. DONT SEE
ENOUGH IN THE DYNAMICS TO SUSPECT A SEVERE POTENTIAL ATTM AS UPPER
FORCING REMAINS WEAK AND SHEAR LEVELS ARE MODERATE AT BEST. MAX
TEMPS WILL CONTINUE TO INCREASE A COUPLE DEGREES EACH DAY.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
AT KCLT...MAINLY LIGHT RAIN IN THE LINGERING DEFORMATION ZONE NEAR
THE AIRFIELD WILL CONTINUE THROUGH 09Z BEFORE DISSIPATING. LOW LEVEL
DRY AIR ADVECTING IN ON NE FLOW IS KEEPING ALL CIGS AND VSBY VFR
EVEN IN THE BETTER PRECIPITATION...SO WILL RIDE ON VFR THROUGH THE
MORNING HOURS. OCCASIONAL GUSTS ARE LIKELY IN THE NE FLOW...BUT WITH
BETTER GUSTS DEVELOPING THROUGH THE DAY WITH MIXING. WILL ALLOW VFR
CIGS TO SCATTER OUT BY 16Z AND THEN LEAN TOWARD LESS CLOUDS AS
INDICATED ON THE GFS/ECM THROUGH THE EVENING HOURS.

ELSEWHERE...ALL LINGERING DEFORMATION ZONE PRECIPITATION SHOULD
REMAIN EAST OF THE FOOTHILL AND MTN TAF SITES THROUGH THE EARLY
MORNING HOURS. IN ADDITION...SLIGHTLY DRIER AIR ADVECTING IN ON NE
FLOW IS KEEPING VSBY AND CIGS AT VFR LEVELS AND THIS SHOULD PERSIST.
KAVL TO KAND ARE THE SITES OF MOST CONCERN. KAVL WILL BE SHELTERED
TO THE DRIER NE FLOW...AND KAND WILL SEE SLIGHTLY LESS BOUNDARY
LAYER DRYING. THESE LOCATIONS COULD EXPERIENCE BRIEF MVFR CONDITIONS
BUT CONFIDENCE IS TOO LOW TO FEATURE AT THE MOMENT. EXPECT
OCCASIONAL GUSTS ON NE FLOW AT THE UPSTATE TAF SITES
TODAY...ESPECIALLY THIS AFTN WITH MIXING.

OUTLOOK...DRY HIGH PRES WILL DEVELOP THROUGH MONDAY. A FAIRLY WET
FRONTAL SYSTEM IS EXPECTED ON TUE...WITH DRYING RETURNING MID WEEK.

CONFIDENCE TABLE...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
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%     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...SBK
NEAR TERM...HG
SHORT TERM...WIMBERLEY
LONG TERM...SBK
AVIATION...HG






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