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000
FXUS62 KGSP 270245
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1045 PM EDT SAT JUL 26 2014

.SYNOPSIS...
HIGH PRESSURE WILL WEAKEN ACROSS THE AREA THROUGH SUNDAY.  A COLD
FRONT WILL REACH THE AREA SUNDAY NIGHT AND PUSH EAST ACROSS THE
REGION ON MONDAY. HIGH PRESSURE WILL REGAIN CONTROL ON
TUESDAY...LASTING THROUGH MID WEEK...WITH BELOW NORMAL TEMPERATURES
EXPECTED. 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 1040 PM EDT...IR IMAGERY NOW SHOWS COLD CLOUD TOP TEMPERATURES
OF MINUS 65 C ATOP THE MCS OVER THE LOWER OH VALLEY LATE THIS
EVENING. CORFIDI VECTOR STEERING FLOW CONTINUES TO DRIVE THIS SYSTEM
SOUTHEAST TOWARD THE SRN APPALACHIANS APPALACHIANS OVERNIGHT...WITH
ARRIVAL TIMING NOW LOOKING TO BE AS EARLY AS 07Z TO 08Z. WESTERN
MTNS POPS HAVE BEEN ADJUSTED UP ACCORDINGLY FOR THE EARLY MORNING
HOURS. ALL OF THE MESOSCALE MODELS THAT HAVE CAPTURED THIS UPSTREAM
CONVECTION HAVE IT WEAKENING AS IT APPROACHES THE MTN CHAIN IN THE
PRE/DAWN HOURS...AND THIS CONTINUES TO LOOK REASONABLE GIVEN THE
CINH SHOWING UP IN MTN/FOOTHILL MODEL PROFILES THROUGHOUT THE EARLY
MORNING HOURS. LOW END SCT POPS HAVE BEEN ADVERTISED ALONG THE TN
BORDER COUNTIES AFTER 08Z...WITH LOW END CHANCES THEN INCREASING
SLIGHTLY INTO THE ADJACENT FOOTHILLS THROUGH MID MORNING BEFORE THE
REMNANTS DISSIPATE. THE DEBRIS CLOUDS WITH THIS SYSTEM SHOULD
PRECLUDE MUCH MORNING FOG...EXCEPT PERHAPS IN THE LITTLE TN VALLEY
OF THE SW MTNS.

BY TOMORROW AFTERNOON...HOT AND RELATIVELY MOIST CONDITIONS ARE
EXPECTED TO BE IN PLACE...WITH HIGHS OF 90 TO 95 EXPECTED IN MOST
MTN VALLEY AND PIEDMONT/FOOTHILL LOCATIONS...IF THE DEBRIS CLOUDS
SCATTER QUICKLY ENOUGH. FORECAST SOUNDINGS BECOME INCREASINGLY
UNCAPPED AND UNSTABLE...WITH CAPE VALUES EXCEEDING 2000 J/KG AND 850
TO 500 MB LAPSE RATES STEEPENING ABOVE 6.5 DEG C/KM. OF PARTICULAR
INTEREST IS THE INCREASING WIND FIELD THAT DEVELOPS ACROSS THE AREA
IN RESPONSE TO STRONG HEIGHT FALLS TO OUR NW. SFC TO 3 KM SHEAR
SHOULD INCREASE TO NEAR 30 KT ACROSS THE WESTERN ZONES BY LATE
AFTERNOON...VALUES HIGHLY UNSEASONABLE FOR OUR AREA. STILL...THE QPF
RESPONSE ON MOST MODELS REMAINS QUITE MUTED THROUGH LATE DAY.
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...WILL CARRY 30 TO 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. EXPECT GUSTS OF 20 TO 25 MPH
WITH MIXING AS THE PRES GRADIENT IMPROVES AS WELL.

&&

.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 /03Z SUNDAY THROUGH THURSDAY/...
AT KCLT...AN MCS THAT MOVED THROUGH THE CENTRAL APPALACHIANS EARLIER
THIS EVENING SENT SOME DEBRIS CLOUDS DOWN TOWARD THE KCLT AIRFIELD.
SCT TO BKN HIGH CLOUDS HAVE RESULTED AND SHOULD LINGER INTO THE
EARLY OVERNIGHT. THE DEBRIS CLOUDS WILL COMBINE WITH BOUNDARY LAYER
DRYING EXPERIENCED TODAY TO LIKELY KEEP LOW CLOUDS AND RESTRICTIONS
FROM FORMING OVERNIGHT. ANOTHER MCS MOVING THROUGH THE LOWER OH
VALLEY THIS EVENING COULD MAKE A RUN INTO THE SRN APPALACHIANS
OVERNIGHT...BUT WITH PROBABLY LITTLE MORE THAN MID AND HIGH CLOUDS
REACHING THE KCLT TERMINAL AREA. THE FORECAST WILL THUS REMAIN DRY
AS THESE SYSTEMS DISSIPATE...AND ANY UPSTREAM CONVECTION WITH THE
NEXT APPROACHING FRONT STAYS WEST OF THE PIEDMONT THROUGH LATE
SUNDAY. LIGHT SW WINDS WILL INCREASE WITH MIXING AND AN INCREASING
PRES GRADIENT ON SUNDAY. GUSTS OF 18 KT OR BETTER ARE LIKELY BY MID
TO LATE AFTN.

ELSEWHERE...EXPECT AN INCREASE IN MID AND HIGH DEBRIS CLOUDS FROM A
SERIES OF MCS/S MOVING THROUGH AND TOWARD THE APPALACHIANS TONIGHT.
MESOSCALE MODELS DEPICT VERY LITTLE ACTIVITY SURVIVING THE TRIP...SO
NO SHOWERS OR THUNDERSTORMS WILL BE FEATURED THROUGH SUNDAY
MORNING...BUT KAVL WOULD SEE THE BEST CHC OF SHRA/TSRA IF SOMETHING
DID MAKE IT. WILL ONLY ADVERTISE MVFR FOG AT KAVL GIVEN THE EXPECTED
HIGH CLOUDS. WSW FLOW WILL INCREASE THROUGH SUNDAY AS THE PRESSURE
GRADIENT IMPROVES FROM FALLING HEIGHTS TO THE WEST. A CLUSTER OF
ORGANIZED CONVECTION MAY COME TOGETHER NEAR THE SRN APPALACHIANS
TOWARD THE END OF THE CURRENT TAF PERIOD JUST AHEAD OF AN
APPROACHING COLD FRONT...BUT ONLY PROB30 AT KAVL AFTER 21Z IS
WARRANTED THUS FAR. EXPECT GUSTS OF 20 KT OR BETTER AT THE UPSTATE
TAF SITES FROM MID TO LATE AFTN IN THE INCREASING GRADIENT FLOW.

OUTLOOK...SCATTERED TO NUMEROUS THUNDERSTORMS ARE EXPECTED TO
ACCOMPANY THE COLD FRONT AS IT MOVES INTO THE SOUTHERN APPALACHIANS
SUNDAY NIGHT AND CROSSES THE REGION INTO MONDAY. VFR CONDITIONS WILL
RETURN BY LATE MONDAY...THEN LINGER THROUGH AT LEAST MID WEEK.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-02Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  97%     HIGH  82%     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...HG
NEAR TERM...HG
SHORT TERM...WIMBERLEY
LONG TERM...JPT
AVIATION...HG