000
FXUS62 KGSP 180622
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
222 AM EDT TUE JUN 18 2013

.SYNOPSIS...
WEAK UPPER LEVEL DISTURBANCES WILL CROSS THE AREA FROM THE WEST
THROUGH MID WEEK AS A ZONE OF RELATIVELY ABUNDANT MOISTURE LAYS
DRAPED ACROSS THE AREA. SLIGHTLY DRIER HIGH PRESSURE WILL BUILD INTO
THE REGION THROUGH FRIDAY...WITH WARMER BERMUDA HIGH PRESSURE
DOMINATING THROUGH THE WEEKEND.

&&

.NEAR TERM /THROUGH TODAY/...
10 PM UPDATE...CLUSTER OF STORMS IN THE CENTRAL PART OF THE CWFA
HOLDING THEIR OWN AND PRODUCING WIDESPREAD HEAVY RAINFALL. LATEST
RAP RUN SEEMS TO HAVE PICKED UP ON THIS CLUSTER EARLIER IN ITS
EVOLUTION BUT SHOWS IT DIMINISHING OVER THE NEXT COUPLE OF HOURS.
MESOANALYSIS SHOWS LESSER INSTABILITY OUT AHEAD OF THE CLUSTER...AND
RECENT TRENDS IN COMPOSITE REFLECTIVITY SUGGEST IT IS LOSING STEAM.
OTHERWISE...POPS HAVE BEEN LOWERED TO SCHC UNTIL CLOSER TO DAYBREAK
WHEN BETTER MOISTURE AND FORCING MOVE IN FROM THE WEST.

PREV DISCUSSION...
THIS AFTERNOON THROUGH TONIGHT...THE OVERALL CONV COVERAGE IS
BEGINNING TO PICK UP ACROSS THE CWFA WITH A DEFINITE MINIMA SEEN
OVER THE UPSTATE AND FAR ERN ZONES. SOME CELLS HAVE BECOME FAIRLY
STRONG AND A COUPLE COULD REACH SEVERE CRITERIA...MAINLY FOR LARGE
HAIL...AS THE AFTERNOON PROGRESSES. THE UPPER LEVEL VORT ACTIVITY IS
RATHER WEAK AND ILL DEFINED OVER THE CWFA...BUT WILL COUNT ON
GENERAL EASTWARD DEVELOPMENT OF STORMS THROUGH THE EVENING. THINGS
WILL BEGIN TO WANE AFT SUNSET AND LOSS OF SBCAPE...HOWEVER UPPER
POCKETS OF PVA WILL TRAVERSE THE DEEPLY MOIST AIRMASS AND ISOL/SCT
-SHRA/TSTMS ARE NOT OUT OF THE QUESTION THROUGH DAYBREAK. MIN TEMPS
WILL BE HELD A COUPLE CATS OR SO ABOVE NORMAL IN THIS ENVIRONMENT.

A SHARPENING H5 S/W WILL MOVE INTO TN TOMORROW AND CREATE A GOOD
AMOUNT OF DYNAMIC OMEGA...ABOUT TWICE AS MUCH VV/S AS TODAY.
THUS...WILL ANTICIPATE GOOD COVERAGE OF SHOWERS AND STORMS EARLY
ON...ESP ACROSS THE NC MTNS WHERE CAT POPS ARE ADVERTISED AFT 15Z.
DEEP LAYERED SHEAR WILL BE ABOUT 10 KTS HIGHER TOMORROW...BUT SBCAPE
MAY ACTUALLY BE LOWER DUE TO ALL THE CLOUD COVER. YET...STILL THINK
A BETTER POTENTIAL EXISTS FOR SVR STORMS TOMORROW AFTERNOON AS THE
DEFINED S/W CROSSES OVERHEAD DURING MAX HEATING. MAX TEMPS WILL BE
SIMILAR TO TODAY/S...OR RIGHT AROUND NORMAL.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
AT 215 PM EDT MON...THERE IS GOOD MODEL CONSENSUS THAT A WEAK AREA
OF LOW PRESSURE AND ASSOCIATED WEAK COLD FRONT WILL CROSS THE AREA
FROM WEST TO EAST TUE NIGHT. HOWEVER...THERE ARE SOME MINOR TIMING
DIFFERENCES. THE 12Z GFS IS A LITTEL STRONGER WITH THE SURFACE LOW
AND FASTER WITH THE SYSTEMS MOVEMENT. THE 12Z NAM IS SIMILAR TO THE
SREF IN REGARD TO TIMING...SO HAVE LEANED MORE TOWARD A NAM
SOLUTION. HENCE...WE EXPECT NUMEROUS SHOWERS/THUNDERSTORMS TO AFFECT
THE WESTERN CAROLINAS AND NE GA TUE NIGHT. THE HIGHEST QPF AND POPS
SHOULD BE OVER NORTHERN SECTIONS CLOSER TO THE BEST UPPER FORCING.
WITH PWATS AROUND 2 INCHES...SOME LOCALLY HEAVY RAIN IS CERTAINLY A
POSSIBILITY. HOWEVER...DO NOT BELIEVE THAT THE FLOOD THREAT IS MORE
THAN ISOLATED AT THIS POINT.

ON WED...THE FRONT IS FORECAST TO MOVE EAST OF THE I-77 CORRIDOR
DURING THE MORNING. HENCE...WILL HAVE SCATTERED POPS IN THAT AREA
EARLY...BUT WILL TAKE THE MENTION OF PRECIP OUT OF THE FORECAST BY
MIDDAY. ON WED AFTERNOON...THE GFS AND THE CMC BRING WINDS
AROUND TO AN UPSLOPE COMPONENT OVER THE MOUNTAINS AND RESPOND WITH
SOME QPF THERE. THE NAM IS ESSENTIALLY DRY. WILL COMPROMISE AT THIS
POINT WITH JUST SOME VERY LOW END POPS OVER THE MOUNTAINS.

WITH CONTINUING LIGHT UPSLOPE FLOW ADVERTISED BY THE GLOBAL MODELS
WED NIGHT...CAN`T RULE OUT AT LEAST SOME WIDELY SCATTERED SHOWERS
CONTINUING OVER THE MOUNTAINS. ON THU...EXPECT THAT SCATTERED SHOWERS
AND THUNDERSTORMS WILL DEVELOP OVER THE MOUNTAINS DURING THE
AFTERNOON AS THE WEAK UPSLOPE FLOW CONTINUES ALONG WITH WEAKLY
DIVERGENT FLOW ALOFT. USED THE ALL-BLEND GUIDANCE WHICH KEEPS MAX
TEMPS A CATEGORY OR SO BELOW AVERAGE.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 110 PM EDT MONDAY...HEIGHTS WILL SLOWLY BUILD FROM THE WEST
FROM THURSDAY NIGHT INTO THE WEEKEND AS THE CENTER OF THE UPPER
RIDGE SHIFTS EAST FROM TEXAS TO SOMEWHERE OVER THE SE
STATES...DEPENDING ON WHICH MODEL YOU REFERENCE. A LIGHT EASTERLY
LOW LEVEL FLOW FRIDAY AND SATURDAY WILL SHIFT TO LIGHT SOUTHWEST BY
LATE SUNDAY INTO MONDAY. LIGHT WIND ALL THE WAY UP TO AROUND 500MB
WITH AROUND 10 KTS AT 500MB AND GENERALLY LESS DOWN TO THE SURFACE
FROM DAY 5 THROUGH NEW DAY 7. SURFACE HIGH PRESSURE CENTERED NEAR
NEW JERSEY THURSDAY NIGHT WILL RIDGE DOWN THROUGH THE CAROLINAS WITH
THE COOLER THAN NORMAL TEMPERATURES. THE CENTER OF THIS HIGH WILL
DRIFT TO NEAR BERMUDA LATE IN THE WEEKEND AND EARLY NEXT WEEK
PROVIDING A CHANGE IN AIRMASS COMBINED WITH INCREASING INFLUENCE OF
THE UPPER RIDGE BUILDING FROM THE WEST. CAPE VALUES ON FRIDAY AND
SATURDAY WILL BE A LITTLE HIGHER OVER THE MTNS...1000 TO 1600 ON THE
GFS FRIDAY. CAPE VALUES DROP OFF VERY LOW SUNDAY AND MONDAY. VARYING
LEVELS OF LOW LEVEL MOISTURE THROUGHOUT THE MEDIUM RANGE WILL SERVE
FOR THE PRODUCTION OF PM SHOWERS AND T-STORMS. TEMPERATURES A BIT
WARMER AT END OF THE WEEKEND AND START OF NEXT WEEK.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
AT KCLT...BORDERLINE VFR/MVFR CONDITIONS WILL PREVAIL THROUGH THE
OVERNIGHT HOURS BEFORE CIGS GRADUALLY LOWER TO SOLID MVFR LEVELS.
AS UPPER LEVEL SHORT WAVE TROF APPROACHES AROUND MID MORNING...AMPLE
MOISTURE IN THE BOUNDARY LAYER WILL PROMPT A REORGANIZATION OF OVC
MVFR CIGS AND SCATTERED SHOWER DEVELOPMENT.  PRECIPITATION COVERAGE
WILL CONTINUE TO INCREASE THROUGH THE LATE MORNING HOURS ACROSS THE
REGION THUS STARTED WITH VCSH AND GAVE WAY TO -SHRA BY AROUND 14Z.
CIGS WILL INCREASE TO VFR LEVELS LATE TOMORROW MORNING AS THE
ATMOSPHERE HEATS.  FURTHERMORE...INCREASING INSTABILITY THROUGH THE
COLUMN...AND CONVERGENCE ALONG A PASSING FRONTAL BOUNDARY WILL ALLOW
FOR SOME THUNDERSTORM DEVELOPMENT TOMORROW AFTERNOON.  WITH
THAT...INCLUDED A PROB30 GROUP FROM 18-24Z FOR MVFR VISB WITH
TSRA.  THE FRONT WILL LIKELY NOT REACH KCLT UNTIL AROUND THE 02Z
TIMEFRAME SHIFTING WINDS TO A NORTHERLY COMPONENT.  WINDS ALONG AND
JUST AHEAD OF THE FRONT COULD BE GUSTY WITH READINGS IN THE 20KT
RANGE NOT BEING OUT OF THE QUESTION.

ELSEWHERE...PREVAILED LOW END MVFR CIGS THROUGH THE FIRST PERIOD OF
THE TAF CYCLE DUE TO CONVECTIVE CLOUD DEBRIS ACROSS THE REGION.
BEYOND THAT...CIGS WILL RAISE SLIGHTLY ON TUESDAY MORNING BUT
SHOULD REMAIN AT MVFR LEVELS.  CIGS WILL FINALLY REBOUND TO VFR
CONDITIONS LATE MORNING AS THE BOUNDARY LAYER WARMS.
FURTHERMORE...KEPT SOME MENTION OF VCSH AT ALL SITES AS SCATTERED
LIGHT SHOWERS CONTINUE ACROSS THE REGION.  BY MID TO LATE
MORNING...UPPER LEVEL SHORTWAVE WILL MOVE IN...AND INSTABILITY WILL
HAVE INCREASED SOMEWHAT ALLOWING FOR SOME THUNDERSTORM ACTIVITY TO
DEVELOP.  THE WINDOW FOR THUNDERSTORMS LOOKS TO BE A LITTLE NARROWER
FOR THE SOUTH CAROLINA SITES..THUS HANDLED THEM WITH TEMP GROUPS.
FOR KAVL AND KHKY...DECIDE TO GO WITH A PROB30 AS MODEL GUIDANCE
INDICATES INSTABILITY SHOULD REMAIN HIGHER LATER INTO THE DAY AS THE
FRONT APPROACHES.  NEAR THE END OF THE PERIOD...THE FRONT WILL MOVE
THROUGH WESTERN NORTH CAROLINA BY AROUND 00Z...AND CONTINUE PUSHING
TO THE SOUTHEAST REACHING THE SOUTH CAROLINA SITES BY AROUND 03-04Z
WEDNESDAY.  WINDS ALONG AND JUST AHEAD OF THE FRONT COULD BE GUSTY
WITH READINGS IN THE 20KT RANGE NOT BEING OUT OF THE QUESTION.

OUTLOOK...CONDITIONS WILL IMPROVE SOMEWHAT TUE NIGHT AS DRIER AIR
FILLS IN BEHIND A COLD FRONT.  A MODERATELY UNSTABLE ATMOSPHERE
COMBINED WITH EASTERLY FLOW MAY LEAD TO SHOWER AND THUNDERSTORM
DEVELOPMENT MIDWEEK...CAUSING SPOTTY RESTRICTIONS.

CONFIDENCE TABLE...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       HIGH  83%     HIGH  91%     HIGH 100%     HIGH  93%
KGSP       HIGH  81%     HIGH  88%     HIGH  96%     HIGH  94%
KAVL       HIGH  86%     HIGH  91%     HIGH  91%     HIGH  80%
KHKY       HIGH  88%     HIGH  80%     HIGH  92%     HIGH  90%
KGMU       MED   72%     HIGH  96%     HIGH  96%     HIGH  89%
KAND       HIGH  85%     HIGH  81%     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...DEO
NEAR TERM...SBK/WIMBERLEY
SHORT TERM...LG
LONG TERM...DEO
AVIATION...CDG