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Area Forecast Discussion

452
FXUS62 KGSP 272347
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
747 PM EDT SUN JUL 27 2014

.SYNOPSIS...
A COLD FRONT WILL APPROACH THE CAROLINAS LATE TONIGHT AND PUSH EAST
ACROSS THE REGION ON MONDAY. IN ITS WAKE...CANADIAN HIGH PRESSURE
WILL DOMINATE THE SURFACE PATTERN THROUGH MIDWEEK LEADING TO WELL
BELOW NORMAL TEMPERATURES AND PLEASANT CONDITIONS. PRECIPITATION
CHANCES WILL RAMP BACK UP AGAIN ON THURSDAY AND FRIDAY AS ATLANTIC
MOISTURE SPREADS OVER THE REGION AND LOW LEVEL WINDS BECOME MORE
EASTERLY.

&&

.NEAR TERM /THROUGH MONDAY/...
730 PM EDT UPDATE...SEVERE STORMS OVER ERN TN ARE HAVING A HARD TIME
MAINTAINING ORGANIZATION AND SUPERCELLUAR STRUCTURE AS THEY APPROACH
THE SMOKIES AND NRN MTN SPINE COUNTIES. STILL...THERE IS ENUF
INSTABILITY AND SHEAR COMBO TO HELP MAINTAIN STRONG COLD POOL
OUTFLOWS AS THESE STORMS MOVE EAST ACROSS THE COMPLEX TERRAIN.
EXPECT DOWNSLOPING FLOW EAST OF THE FHILLS TO LIMIT STORM COVERAGE
AND INTENSITY THROUGH THE EVENING. WILL COUNT ON THE PREFRONTAL TROF
AXIS TO WARRANT A POP INCREASE AFT 08Z OR SO. POPS WERE THUS ADJ UP
EAST ACROSS THE NC ZONES FROM 08Z THROUGH DAYBREAK.

430 PM EDT UPDATE...ORGANIZED UPSTREAM CONVEC REMAINS VIGOROUS AND
SEVERE ACROSS ERN TN AND SE/RN KY. BASEBALL SIZE HAIL HAS BEEN
REPORTED IN KY AND A FEW TOR WARNINGS HAVE BEEN ISSUED BY MRX AND
JKL. THIS ACTIVITY IS ALIGNED A PREFRONTAL TROF WITH A -8 C H5 COLD
POOL...SOME DISCREET CELLS HAVE ALSO BEEN FORMING...WITH A LONG
LASTING TORNADIC SUPERCELL NOW MOVING INTO SW VA. LOW LEVEL THETA/E
HAS INCREASED THE MOST ACROSS THE WRN NC ZONES THE PAST COUPLE HRS
AND WILL ANTICIPATE INCREASING INSTABILITY ACROSS THE MTNS THROUGH
THE NEXT UPDATE. EFFECTIVE SHEAR REMAINS ABOVE 40 KTS JUST WEST OF
THE CWFA ATTM...HOWEVER THIS AREA OF SHEAR WILL MOVE INTO THE NRN
MTNS AFT 22Z. THUS...THE ATMOS WILL BE PRIMED FOR A CONTINUED SEVERE
AND POSSIBLY A TORNADO THREAT AS THE CONVEC ACTIVITY DEVELOPS
INTO OUR AREA BETWEEN 22Z-23Z. NOT MANY CHANGES WERE NEEDED TO THE
FCST GRIDS WITH MINOR TWEAKS MADE TO SKY AND T/TD. WILL STILL CARRY
THE DMG WIND AND LG HAIL MENTION ACROSS THE NRN MTNS FOR LATER THIS
AFTERNOON AND EVENING.

MULTIPLE SUPERCELLS HAVE DEVELOPED ALONG AND AHEAD OF A PRE-FRONTAL
TROUGH ACROSS EASTERN KENTUCKY THIS AFTERNOON. EXPECT CONVECTION TO
CONTINUE TO DEVELOP TOWARD THE SOUTHWEST THROUGH THE AFTERNOON...
LIKELY CONSOLIDATING INTO AN ORGANIZED MCS THAT WILL APPROACH
WESTERN NC BY EARLY EVENING. WITH THAT IN MIND...STILL EXPECT THE
PRIMARY THREAT OVER OUR AREA TO BE DAMAGING DOWNBURST WINDS...
ALTHOUGH WOULD NOT BE SURPRISED TO SEE AN ISOLATED TORNADO...
ESPECIALLY IF THE PRE-FRONTAL/DISCRETE SUPERCELL CURRENTLY SOUTHEAST
OF JKL MANAGES TO HOLD TOGETHER INTO OUR AREA. SEVENTY POPS WILL BE
CONTINUED ACROSS THE NRN NC MTNS...AND HAVE ALSO ADDED A MENTION OF
DAMAGING WINDS AND LARGE HAIL TO THE FORECAST SUITE IN THESE AREAS.
THE SHORT TERM MODELS CONTINUE TO DISSIPATE ANY CONVECTION EAST OF
THE MTNS THIS EVENING...PROBABLY DUE TO A DEVELOPING STRONG WESTERLY
DOWNSLOPE FLOW. HOWEVER...STRONG/COLD POOL-DRIVEN CONVECTION OFTEN
/DOES NOT CARE/ ABOUT DOWNSLOPE FLOW...AND SOME OF THE MESOSCALE
MODELS ARE BEGINNING TO PICK UP ON THE POTENTIAL FOR AN MCS TO BLAST
THROUGH THE FHILLS/PIEDMONT OF NC THIS EVENING. THEREFORE...HAVE
BEGUN TO STEP INTO HIGHER POPS EAST OF THE BLUE RIDGE IN NC THIS
EVENING. THE SEVERE WEATHER THREAT IS EXPECTED TO WIND DOWN BY LATE
EVENING...OR EARLY IN THE OVERNIGHT...ALTHOUGH THERE WILL BE A
CONTINUED POTENTIAL FOR CONVECTION ACROSS THE WESTERN MTNS THROUGH
THE NIGHT...AS THE ACTUAL COLD FRONT APPROACHES AND W RATHER STOUT
W/NW UPSLOPE FLOW DEVELOPS. WITH COLD ADVECTION HOLDING OFF UNTIL
TOMORROW...AND THE EXPECTATION THAT SURFACE WINDS WILL REMAIN
SOMEWHAT ELEVATED TONIGHT...EXPECT MIN TEMPS TO BE ABOUT 5 DEGREES
ABOVE CLIMO.

MONDAY WILL SEE THE ONSET OF COLD ADVECTION OVER THE MTNS...WHERE
MAXES ARE EXPECTED TO TOP OUT A LITTLE BELOW CLIMO. MEANWHILE...
DESPITE FALLING THICKNESSES...DOWNSLOPE WARMING SHOULD YIELD HIGHS
VERY CLOSE TO CLIMATOLOGICAL NORMS EAST OF THE MTNS. CANNOT RULE OUT
SOME NW UPSLOPE FLOW SHOWERS ACROSS THE WESTERN MTNS DURING THE
AFTERNOON...BUT WILL CONTINUE WITH A POP FORECAST JUST A SHADE BELOW
SLIGHT CHANCE.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF 130 PM SUNDAY...NWLY FLOW WILL PREVAIL IN THE LOW- TO
MID-LEVELS MONDAY NIGHT WITH THE AXIS OF A DEEP ERN CONUS TROUGH
EXTENDING FROM ERN ONTARIO SWD INTO SC/GA. COOL AIR WILL CONTINUE TO
FILTER INTO THE REGION AT THIS TIME AS CONTINENTAL HIGH PRESSURE
SETTLES IN ACRS THE INLAND SOUTH. HIGH LLVL RH IS NOTED ON GFS/NAM IN
THE COLD-ADVECTIVE FLOW INTO THE MTNS...REMINISCENT OF THE COOL
SEASON. THE MOIST LAYER IS SO SHALLOW ONLY THE MOST FAVORED UPSLOPE
AREAS LOOK TO HAVE ANY MENTIONABLE CHANCE OF PRECIP.

H7 HEIGHTS BOTTOM OUT AROUND DAYBREAK TUE AND INCREASE SLIGHTLY
THEREAFTER. THIS CREATES A CAPPING INVERSION THAT WILL RESTRICT DEEP
CONVECTION TUE AFTN...BUT THE MAJOR MODELS VARIOUSLY STILL DEVELOP
SMALL AMOUNTS OF QPF IN THE FA. BY WED THERE IS LITTLE REAL CHANGE IN
THE PATTERN...BUT THE FLOW REGIME BECOMES VERY WEAK IN THE LOWER
TROPOSPHERE AND MODEL PROFILES SHOW THE INVERSION WEAKENING AS WELL.
A GREATER PROPORTION OF GUIDANCE PRODUCES QPF IN THE HIGHER
TERRAIN...BUT THIS MAY BE OVERDONE GIVEN RECENT POST-FRONTAL
PERFORMANCE. ALSO...GIVEN THE CONTINUED SLIGHT HEIGHT RISES I WILL
CURRENTLY FAVOR THE INVERSION HOLDING FAST. THUS NO QPF IS IN THE
FCST FOR WED. MAX TEMPS WILL BE NEAR 10 DEGREES BELOW CLIMO...
TRENDING UPWARD SLIGHTLY FROM TUE TO WED. MIN TEMPS HOWEVER WILL BE
SLIGHTLY COOLER WED MRNG WITH WINDS BEING LIGHTER OVERNIGHT.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 140 PM EDT SUNDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
THURSDAY WITH BROAD AND DEEP UPPER TROFFING IN PLACE OVER THE
EASTERN CONUS WHILE AN EQUALLY IMPRESSIVE UPPER RIDGE IS IN PLACE
OVER THE WEST. THE LONG RANGE GUIDANCE CONTINUES TO SUGGEST THAT WE
WILL REMAIN IN THIS AMPLIFIED PATTERN INTO THE WEEKEND WITH SOME
AMOUNT OF DEAMPLIFICATION LIKELY OVER THE WEEKEND. COMPARED TO
PREVIOUS FCSTS...ITS LOOKING LESS CERTAIN THAT THE NORTHERN STREAM
UPPER FLOW WILL COMPLETELY CUTOFF THE TROF AND ALLOW A CLOSED LOW TO
DEVELOP OVER THE WEEKEND. THE LATEST GFS ENSEMBLE RUN HAS ABOUT HALF
OF THE MEMBERS COMPLETELY CUTTING THE TROF OFF AND HALF MAINTAINING
SOME DEGREE OF TROFFING.

AT THE SFC...CANADIAN HIGH PRESSURE WILL CONTINUE TO SLIDE
SOUTHEASTWARD AND WEAKEN ON THURS AS BNDRY LYR FLOW REMAINS NLY TO
WEAK AND VRB. BY EARLY 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 SOUTHWEST. THIS UPSLOPE POTENTIAL
COUPLED WITH UPPER LVL DIVERGENCE COURTESY OF THE UPPER TROF AND
POSSIBLY THE CLOSED UPPER LOW IF IT ACTUALLY DEVELOPS...WILL IMPROVE
OUR CHANCES FOR WIDESPREAD SHOWERS AND TS FOR THE REST OF THE MEDIUM
RANGE. OTHERWISE...NO SIGNIFICANT CHANGES WERE MADE TO THE
TEMPERATURE FCST WITH VALUES EXPECTED TO REMAIN WELL BELOW NORMAL
FOR LATE JULY/EARLY AUGUST.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AT KCLT...NO FLIGHT RESTRICTIONS OUTSIDE OF CONVECTIVE ACTIVITY. FOR
NOW WILL COUNT ON DOWNSLOPING FLOW TO LIMIT THE COVERAGE DOWNSTREAM
OF CURRENT MTN MCS ACTIVITY AND WILL GO GO WITH A TEMPO TSRA AFT 02Z
THRU 06Z. THE LATEST HRRR DEVELOPS A DECENT AMOUNT OF CONVECTION
ASSOCIATED WITH THE PRE/FRONTAL TROF SCHED TO CROSS THE TERMINAL
ARND 08Z OR SO. LLVL WINDS WILL REMAIN STRONG ENUF TO OFFSET A VSBY
THREAT ARND DAYBREAK. LOW END WIND GUST ARE ANTICIPATED TOMORROW
AFTERNOON AHEAD OF THE MAIN FROPA.

ELSEWHERE...THE NC TAF SITES WILL EXPERIENCE BOUTS OF VCTS AND
PERHAPS PREVAILING TSRA THIS EVENING INTO THE EARLY OVERNIGHT. WINDS
COULD BECOME QUITE VARIABLE AND GUSTY WITH ANY NEARBY OUTFLOW.
EXPECT THINGS TO SETTLE DOWN A BIT AFT 03Z THEN PICK BACK UP AS
PREFRONTAL TROF WORKS INTO THE AREA ARND 06Z THROUGH 09Z. NO EARLY
MORNING FLIGHT RESTRICTIONS AT ANY TAF SITE AS BL WINDS REMAIN
FAIRLY STRONG. LOW END GUSTS SHOULD DEVELOP AT ALL SITES BY THE
MIDDLE OF MON AFTERNOON.

OUTLOOK...DRY CONDITIONS WILL RETURN BY MONDAY AFTERNOON WITH VFR
CONDITIONS EXPECTED TO REMAIN THROUGH MID WEEK. MOISTURE WILL BEGIN
RETURNING BY LATE IN THE WEEK...WITH INCREASING CHANCES FOR LOW
CLOUDS AND PRECIP.

CONFIDENCE TABLE...

            23-05Z        05-11Z        11-17Z        17-23Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH  86%     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...JDL/SBK
SHORT TERM...WIMBERLEY
LONG TERM...JPT
AVIATION...SBK






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