Severe Thunderstorm Warning 154, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
235 PM EDT WED JUL 8 2015

.SYNOPSIS...
UPPER RIDGE WILL CONTINUE TO STRENGTHEN OVER THE SOUTHEAST THROUGH
THE WEEKEND...BEFORE SLIDING WEST BY EARLY NEXT WEEK. SHOWER AND
THUNDERSTORM CHANCES WILL FAVOR THE AFTERNOON AND EVENING WITH THE
BEST CHANCES RESIDING OVER THE HIGH TERRAIN. A MID LEVEL TROUGH IS
EXPECTED TO DIG EAST OF THE MISSISSIPPI RIVER BY THE MIDDLE OF NEXT
WEEK. TEMPERATURES WILL REMAIN ABOVE NORMAL.

&&

.NEAR TERM /THROUGH TONIGHT/...
AT 215 PM...WIDELY SCT/SCT THUNDERSTORMS CURRENTLY OVER THE
MOUNTAINS WERE MOVING EASTWARD AND WILL EVENTUALLY AFFECT THE
ADJACENT FOOTHILLS AND PIEDMONT AREAS DURING THE LATE AFTERNOON AND
EARLY EVENING HOURS. MID LEVEL DRY AIR IS EVIDENT IN THE SOUNDINGS
SO SOME GUSTY WINDS AND POSSIBLY EVEN A COUPLE SEVERE MICROBURSTS
ARE NOT OUT OF THE QUESTION. CONVECTIVE ACTIVITY SHOULD QUICKLY WANE
WITH THE LOSS OF HEATING THIS EVENING PER CAMS.

FOR THE OVERNIGHT...WEAK BOUNDARY SHOULD STAY NORTH OF THE AREA AS
THE BERMUDA HIGH BUILDS WESTWARD. THEREFORE...MOSTLY CLEAR
CONDITIONS ARE ANTICIPATED. WITH THE CLEAR CONDITIONS...MOUNTAIN
VALLEY FOG IS A GOOD BET AND ALSO AROUND SOME OF THE LAKES EARLY
THURSDAY. OVERNIGHT LOWS WILL BE ABOVE CLIMO WITH LOW TO MID 70S
OUTSIDE OF THE MOUNTAINS...WITH 60S MOUNTAINS.

ON THURSDAY...THE UPPER ANTICYCLONE IS FORECAST TO REGTROGRADE
WESTWARD. MODEL SOUNDINGS DEPICT WARM MID LEVELS AND CONSIDERABLE
LOW LEVEL CIN. HENCE...CONVECTION WILL BE SUPPRESSED. THE ONLY PLACE
WHERE PARCELS MAY HAVE A CHANCE TO BREAK THE CAP IS ALONG THE SPINE
OF THE MOUNTAINS ADJACENT TO TN. HENCE...HAVE SOME ISOLATED TYPE
POPS THERE DURING THE MID TO LATE AFTERNOON HOURS. THURSDAY WILL BE
ANOTHER HOT DAY WITH TEMPS WELL ABOVE CLIMO. HIGHS ARE FORECAST IN
THE MID TO UPPER 90S MOST PIEDMONT LOCATIONS AND MID TO UPPER 80S
MOUNTAIN VALLEYS.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
AS OF 205 PM WEDNESDAY...THE UPPER PATTERN CONTINUES TO SHOW A
RETROGRADING SUBTROPICAL RIDGE ACROSS THE DEEP SOUTH. THIS KEEPS THE
CWFA UNDER THE INFLUENCE OF THE RIDGE ON FRI. HOWEVER BY SATURDAY...
HEIGHTS BEGIN TO SLOWLY FALL AS THE CENTER OF THE RIDGE MOVES WEST
AND NWLY FLOW DEVELOPS ALLOWING WEAK SHORTWAVES TO MOVE INTO OR
TOWARD THE AREA. THE SURFACE PATTERN SHOWS A GENERAL MTN RIDGE AND
FALL LINE LEE TROF EACH DAY. HOWEVER...A WEAK BOUNDARY DOES APPEAR
TO SLIDE INTO THE AREA FRI AND LINGER ON SAT. THIS BOUNDARY COULD
PROVIDE A BOUNDARY LAYER FOCUS FOR CONVECTIVE INITIATION...ESPECIALLY
ON SAT WHEN SHORTWAVE ACTIVITY INCREASES. THAT SAID...FCST SOUNDINGS
ARE NOT VERY IMPRESSIVE INSTABILITY-WISE WITH RELATIVELY LOW DEW
POINTS DUE TO THE W TO NW LOW LEVEL FLOW AND WARM MID LEVEL TEMPS.
HOWEVER...PW VALUES ARE FCST IN INCREASE THRU THE PERIOD WHICH COULD
LEAD TO BETTER CHC OF CONVECTION. GIVEN THE UNCERTAINTY...WILL KEEP
POP NEAR A CLIMO TREND WITH BEST CHC ACROSS THE MTNS AND ADD THE
I-40 CORRIDOR WHERE THE WEAK BOUNDARY LINGERS AND ANY OUTFLOW
BOUNDARIES FROM OVERNIGHT MCS ACTIVITY WOULD MOVE THRU.

HIGHS WILL BE NEARLY STEADY IN THE 90S OUTSIDE OF THE MTNS AND 80S
OVER THE MTN VALLEYS...WITH LOWS NEARLY STEADY SEVERAL DEGREES ABOVE
NORMAL.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 230 PM WEDNESDAY...FOR THE FORECAST ON SUNDAY AND MONDAY WE
USED A BLEND OF THE GFS AND THE ECMWF BUT FAVORED THE ECMWF FOR
TUESDAY AND WEDNESDAY. BOTH SOLUTIONS SHOW A VERY LARGE 500MB RIDGE
OVER THE SOUTHERN PLAINS ON SUNDAY.  HEIGHTS ACROSS THE WESTERN
CAROLINAS AND NE GEORGIA WILL REMAIN SLIGHTLY ABOVE 590DM THROUGH
THE DAY.  AT THE SURFACE...THE REGION WILL BE COVERED BY A BROAD AND
WEAK AREA OF HIGH PRESSURE.  FORECAST SOUNDINGS INDICATE A
SIGNIFICANT INVERSION AROUND 650MB SUNDAY AFTERNOON.  AS A
RESULT...A THIN LAYER OF INHIBITION SHOULD REMAIN ACROSS THE AREA
THROUGH THE LATE AFTERNOON...WEAKEST OVER THE MOUNTAINS.  GIVEN HIGH
TEMPERATURES ARE 3-5 DEGREES ABOVE NORMAL AND AFTERNOON DEWPOINTS IN
THE LOWER TO MID 60S...WEAK INSTABILITY WILL EXIST ABOVE THE
INVERSION.  MONDAY WILL BE VERY SIMILAR TO SUNDAY WITH SLIGHTLY MORE
AVAILABLE MOISTURE AND A WEAKER INVERSION.  BOTH DAYS WILL START OFF
DRY WITH GENERALLY MOSTLY SUNNY SKIES.  BY THE AFTERNOON WE WILL
FAVOR THE MOUNTAINS WITH SLIGHT CHANCE TO CHANCE POPS...GREATER
COVERAGE EXPECTED ON MONDAY.

THE MID-LEVEL PATTERN CHANGES DURING THE PERIOD ON TUESDAY AND
WEDNESDAY AS A TROUGH DIGS INTO THE MID-MISSISSIPPI RIVER VALLEY.
CONDITIONS ON TUESDAY BEGIN TO MODIFY FROM A HOT AND DRY START TO
THE WORK WEEK...WITH PWS RISING TO 1.8 INCHES.  IN ADDITION...CAPE
VALUES ACROSS THE REGION...ESPECIALLY ACROSS THE MOUNTAINS...WILL
INCREASE WITH LOWER VALUES OF INHIBITION.  POPS ON TUESDAY WILL
RANGE FROM 40 PERCENT ACROSS THE RIDGES TO MID- TO UPPER-30S ACROSS
THE VALLEYS AND THE PIEDMONT.  ON WEDNESDAY...TROUGH AXIS SHOULD AT
LEAST AMPLIFY ACROSS THE CENTRAL CONUS...WITH THE GFS SHOWING A WELL-
DEVELOPED CLOSED LOW.  OVERALL...WEDNESDAY SHOULD HAVE CLOUDIER
CONDITIONS WITH COOLER HIGH TEMPERATURES...RANGING WITHIN A DEGREE
OR TWO OF NORMAL.  LATE WEDNESDAY AFTERNOON POPS SHOULD GENERALLY
RANGE IN THE 40S WITH SOME LIKELY VALUES ACROSS THE HIGHEST RIDGES.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
AT KCLT...MAIN CONCERN IS WHETHER CONVECTION MOVING OFF THE
MOUNTAINS WILL AFFECT THE AIRFIELD DURING THE LATE AFTERNOON HOURS.
EXPECT THAT ACTIVITY WILL BE WIDELY SCT SO ELECTED TO KEEP THE
MENTION OF THUNDER OUT OF THE TAF FOR NOW. DID MENTION VCSH AT 22Z
ALONG WITH A WIND SHIFT TO THE NW ANTICIPATING EXPECTING AN OUTFLOW
BOUNDARY. ANY THREAT OF THUNDER SHOULD END BY 01Z WITH WINDS BACKING
TO THE SW AGAIN AT LESS THAN 5 MPH.

ELSEWHERE...RADAR SHOWS SCT CONVECTION DEVELOPING OVER THE MOUNTAINS
WITH A STORM MOVING JUST N OF KAVL. WILL CARRY TEMPO TSRA AT KAVL
UNTIL 21Z. ELSEWHERE...CONFIDENCE NOT HIGH ENOUGH TO PUT IN A
TEMPO...BUT DID MENTION VCTS AT KGSP/KGMU AND KHKY FROM 20-22Z.
OTHERWISE...VFR EXCEPT SOME VALLEY FOG MAY RESTRICT VSBYS TO 3 MILES
OR LESS AT KAVL EARLY ONN THURSDAY...AND SOME FOG VCNTY LAKE
HARTWELL MAY AFFECT KAND AROUND SUNRISE.

OUTLOOK...ISOLATED TO SCATTERED AFTN/EVENING THUNDERSTORMS ARE
EXPECTED OVER THE AREA THRU THIS WEEKEND...MAINLY IN THE MTNS...WITH
ASSOCIATED RESTRICTIONS UNDER THE HEAVIEST SHOWERS. LOW CLOUDS AND
FOG COULD DEVELOP IN THE MORNING AT PLACES THAT HAVE SHOWER ACTIVITY
THE DAY BEFORE...AND IN DAILY IN MTN AND RIVER VALLEYS. !--NOT SENT--

!--NOT SENT--!

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH  97%     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  97%     HIGH  94%

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...JMP/NED
NEAR TERM...LG
SHORT TERM...RWH
LONG TERM...JMP/NED
AVIATION...LG

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