Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 262048
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
448 PM EDT SAT JUL 26 2014

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN DOMINATE ACROSS THE AREA THROUGH SUNDAY.
A COLD FRONT WILL REACH THE AREA EARLY MONDAY MORNING AND PUSH
THROUGH BY THE LATE AFTERNOON. HIGH PRESSURE WILL REGAIN CONTROL ON
TUESDAY...LASTING THROUGH MID-WEEK WITH BELOW NORMAL TEMPERATURES
EXPECTED. WARM/MOIST EASTERLY FLOW WILL RETURN TOWARDS THE END OF
THE WEEK LEADING TO INCREASED PRECIPITATION CHANCES ON FRIDAY AND
SATURDAY.

&&

.NEAR TERM /THROUGH SUNDAY/...
AS OF 445 PM EDT...THE LATE AFTERNOON UPDATE WAS NEEDED ONLY FOR
MINOR ADJUSTMENT IN HOURLY TEMPS...AS LATE AFTN VALUES WERE RUNNING
A TOUCH COOLER THAN FORECAST. OTHERWISE...THE UPPER RIDGE AXIS
OVERHEAD WILL BEGIN A RETREAT TONIGHT INTO SUNDAY...AS A
SIGNIFICANT/ANOMALOUSLY STRONG SHORT WAVE TROUGH DIGS OUT OF THE
NORTHERN PLAINS TOWARD THE OHIO VALLEY REGION. AS THIS WAVE AND
ATTENDANT FRONTAL ZONE INTERACT WITH A RATHER POTENT COMBINATION OF
STRONG BUOYANCY AND UNSEASONABLY STRONG SHEAR PARAMETERS...A
WELL-ORGANIZED MCS IS EXPECTED TO DEVELOP ACROSS THE CORN BELT LATE
THIS AFTERNOON...AND RACE E/SE OVERNIGHT. SOME SHORT TERM AND HI RES
MODEL GUIDANCE ARE SIGNALING A POTENTIAL THAT REMNANTS OF THIS
CONVECTIVE ACTIVITY COULD APPROACH OUR NORTHERN AND WESTERN ZONES
SUNDAY MORNING. UNCERTAINTY REMAINS HIGH ATTM...SO POPS WILL BE
MAINTAINED AT A SLIGHT CHANCE DURING THIS TIME...BEGINNING AROUND
THE END OF THE SUNDAY PERIOD.

BY TOMORROW AFTERNOON...HOT AND RELATIVELY MOIST CONDITIONS ARE
EXPECTED TO BE IN PLACE...WITH HIGHS OF 90-95 EXPECTED IN MOST MTN
VALLEY AND PIEDMONT/FOOTHILL LOCATIONS. WITH THE UPPER RIDGE IN FULL
RETREAT...FORECAST SOUNDINGS ARE UNCAPPED AND FAIRLY UNSTABLE...WITH
CAPE EXCEEDING 2000 J/KG. OF PARTICULAR INTEREST IS THE INCREASING
WIND FIELDS THAT WILL BE SEEN ACROSS THE AREA IN RESPONSE TO STRONG
HEIGHT FALLS TO OUR NORTHWEST. IN FACT...0-3 KM SHEAR IS UPWARDS OF
30 KTS ACROSS THE WESTERN ZONES BY LATE AFTERNOON...PRACTICALLY
UNHEARD OF THIS TIME OF YEAR AROUND THESE PARTS. NEVERTHELESS...
MODEL QPF RESPONSE IS QUITE MUTED. HOWEVER...CONSIDERING THE
POTENTIAL FOR UPSLOPE INITIATION NEAR THE TN BORDER IN THE
UNSTABLE AND STRONG LOW LEVEL W/SW FLOW REGIME...AND THE OUTSIDE
POSSIBILITY OF CELLS ORGANIZING INTO CLUSTERS GIVEN THE ROBUST
LOW-LEVEL SHEAR...FELT THE NEED TO CARRY 30-50 POPS ACROSS THE MTNS
TOMORROW AFTERNOON...WITH SLIGHT CHANCES ACROSS MUCH OF THE
PIEDMONT/FOOTHILLS. ISOLATED SEVERE STORMS WILL CERTAINLY BE OF
INCREASING CONCERN AS SUNDAY WEARS ON.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AS OF 215 PM SATURDAY...FOR SUNDAY NIGHT AND MONDAY THE FEATURE OF
INTEREST REMAINS THE ERN CONUS TROUGH AMPLIFYING AS A SHORTWAVE MOVES
ACRS THE ERN GREAT LAKES...WITH ATTENDANT SFC LOW AND UNSEASONABLY
STRONG COLD FRONT. PREFRONTAL CONVECTION WILL PROGRESS ACRS THE OH/TN
VALLEYS LATE SUNDAY GIVEN EXCEPTIONAL BUOYANCY AND INCREASINGLY
STRONG H5 FLOW BENEATH THE DIGGING TROUGH.

STEERING FLOW COULD TAKE SOME OF THE UPSTREAM ACTIVITY INTO THE
APPALACHIANS SUNDAY EVENING...BUT THERE IS A GREATER THREAT OF
ACTIVITY ACCOMPANYING THE SFC FRONT INTO THE WNC MTNS. MODEL
CONSENSUS BRINGS HAS THIS HAPPENING OVERNIGHT CONCURRENT WITH AXIS OF
THE AFOREMENTIONED SHORTWAVE. MID TO UPPER LEVEL FLOW IS QUITE
IMPRESSIVE FOR LATE JULY...AND MTN RIDGES ARE LIKELY TO EXPERIENCE A
FEW STRONG NONCONVECTIVE GUSTS. NAM IS PRODUCING SOME FAIRLY SCARY
HODOGRAPHS WITH OVER THE MTNS WHILE ALSO ALLOWING FREE CONVECTION FOR
NEAR-SFC PARCELS. GFS AND MOST SREF WIND PROFILES SHOW WINDS NEARLY
AS STRONG THOUGH CONVECTION IS CAPPED. NOT SURE WHAT TO MAKE OF THE
NAM BEING DIFFERENT BUT IT COULD COME AS A RESULT OF BETTER TERRAIN
RESOLUTION...ACCOUNTING FOR UPSLOPE COOLING ALOFT. SPC HAS KEPT MOST
OF OUR MTNS AND NRN FOOTHILLS IN THE DAY 2 SLIGHT RISK AREA...WITH
THE FRINGE OF THE 30 PERCENT PROBS ALONG THE TN/NC BORDER. THIS LOOKS
APPROPRIATE. FOR ME...CONFIDENCE IS MAINLY LIMITED BY THE DIFFERING
PROFILES BETWEEN THE MODEL CAMPS.

LATER ON MONDAY...EARLIER GUIDANCE HAD INDICATED THE FRONT WOULD BE
SLOW ENOUGH IN MOVING OUT OF THE MTNS THAT OUR PIEDMONT ZONES WOULD
BE ABLE TO DESTABILIZE. WITH SHEAR PARAMETERS CONTINUING TO BE
IMPRESSIVE...THIS SUGGESTED A SEVERE THREAT THERE AT LEAST THRU
MID-AFTN. HOWEVER THE SOLUTIONS FROM THE 06Z-12Z MODEL CYCLES PUSH
THE FRONT INTO THE CENTRAL NC AND THE SC MIDLANDS BY MIDDAY. THIS
MITIGATES OUR SEVERE RISK AND LIMITS POPS AS WELL. THOUGH THE FROPA
WILL ONLY HAVE A MODEST IMPACT ON AFTN TEMPS...AN ELEVATED WARM LAYER
SUGGESTS CONVECTIVE TEMPS WILL BE MUCH WARMER THAN THE NEAR-NORMAL
MAX TEMPS.  WINDS WILL BE SOMEWHAT GUSTY ACRS THE CWFA...ESP ON
RIDGETOPS WHERE 30-35 KT GUSTS ARE POSSIBLE.

WIND PROFILES CALM APPRECIABLY MONDAY AFTN AND REMAIN SO THRU
TUESDAY...AND THE COOLER/DRIER AIR WILL BRING TUE MRNG MIN TEMPS DOWN
A CATEGORY OR TWO BELOW NORMAL. TUESDAY WILL BE THE FIRST DAY OF A
MUCH-ANTICIPATED PERIOD OF TEMPS REMINISCENT OF EARLY FALL...HIGHS IN
THE 70S ACRS MUCH OF THE MTNS AND LOWER 80S PIEDMONT. CAPPED PROFILES
SUGGEST A DRY FCST FOR TUE AS WELL.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 145 PM EDT SATURDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
WEDNESDAY WITH DEEP UPPER TROFFING IN PLACE OVER THE EASTERN CONUS
WHILE AN EQUALLY STEEP UPPER RIDGE IS IN PLACE OVER THE WEST. NO
MAJOR PATTERN CHANGES ARE EXPECTED AS THIS TROF WILL REMAIN LARGELY
IN PLACE THRU FRI WITH SOME DEAMPLIFICATION LIKELY OVER THE WEEKEND.
IN FACT...BOTH THE GFS AND ECMWF SUGGEST THAT THE NORTHERN STREAM
UPPER FLOW WILL CUTOFF THE TROF AND SOME SORT OF CLOSED LOW COULD
DEVELOP BEYOND DAY 7.

AT THE SFC...CANADIAN HIGH PRESSURE WILL BRING COOLER AND DRIER AIR
TO THE CAROLINAS BY THE END OF THE SHORT TERM PERIOD. CONDITIONS
WILL REMAIN QUIET THRU AT LEAST EARLY THURS AS THE HIGH SLOWLY
SLIDES SOUTHEASTWARD AND BNDRY LYR FLOW REMAINS NLY TO WEAK AND VRB.
ON FRI...THE MODELS CONTINUE TO VEER THE FLOW MORE FROM THE EAST TO
NE AND MOVE A LARGE PLUME OF DEEPER LYR MOISTURE OVER THE CWFA FROM
THE SOUTH. THIS COUPLED WITH THE UPPER TROF POSSIBLY MORPHING INTO A
CLOSED LOW CENTERED TO OUR WEST WILL SIG IMPROVE OUR CHANCES FOR
WIDESPREAD SHOWERS AND TS NEXT WEEKEND. OTHERWISE...TEMPS SHOULD
REMAIN WELL BELOW NORMAL FOR LATE JULY/EARLY AUGUST WITH POPS
RAMPING UP TOWARDS THE END OF THE FCST PERIOD.

&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
AT KCLT...MAINLY SCT CUMULUS IN THE 040-045 RANGE ARE EXPECTED
THROUGH LATE AFTN...AS DRIER AIR GRADUALLY PUSHES INTO THE AREA FROM
THE SOUTHWEST. THIS SHOULD ALSO KEEP ANY CONVECTION WELL EAST OF THE
TERMINAL THROUGH THE END OF THE PERIOD. THANKS TO THE DRIER AIR...WE
DO NOT ANTICIPATE A RECURRENCE OF THIS MORNING/S FOG/LOW STRATUS
OVER THE TERMINAL SUNDAY MORNING. WINDS SHOULD REMAIN SW AT 5-10 KTS
LATER THIS AFTERNOON...DIMINISHING THIS EVENING BEFORE INCREASING
AGAIN BY THE END OF THE PERIOD.

ELSEWHERE...ALTHOUGH DRIER AIR IS PUSHING INTO THE AREA...STILL
CANNOT RULE OUT VALLEY FOG/LOW STRATUS CAUSING RESTRICTIONS AT KAVL
SUNDAY MORNING...BUT THE POTENTIAL CERTAINLY APPEARS CONSIDERABLY
LESS THAN THIS MORNING. HAVE OPTED TO FORECAST A 5SM THERE DURING
THE PRE-DAWN HOURS. OTHERWISE...VFR CONDITIONS ARE EXPECTED AT ALL
TERMINALS THROUGH THE PERIOD. THERE IS AN OUTSIDE CHANCE THAT
ORGANIZED CONVECTION APPROACHING FROM THE NORTHWEST COULD PASS NEAR
KHKY AND PERHAPS KAVL SUNDAY MORNING...BUT CERTAINLY NOT A HIGH
ENOUGH PROBABILITY TO INCLUDE A TAF MENTION ATTM.

OUTLOOK...SCATTERED TO NUMEROUS THUNDERSTORMS ARE EXPECTED TO RETURN
TO THE AREA IN ADVANCE OF A COLD FRONT SUNDAY AFTERNOON...WITH THE
POTENTIAL CONTINUING THROUGH AT LEAST MONDAY MORNING. CHANCES FOR
STORMS WILL BE MUCH HIGHER OVER THE MTNS DURING THIS TIME. VFR
CONDITIONS WILL RETURN BY LATE MONDAY...THEN LINGER THROUGH AT LEAST
MID WEEK.

CONFIDENCE TABLE...

            20-02Z        02-08Z        08-14Z        14-20Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH  89%     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...JPT
NEAR TERM...HG/JDL
SHORT TERM...WIMBERLEY
LONG TERM...JPT
AVIATION...HG/JDL





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