Severe Thunderstorm Warning 146, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1223 PM EDT TUE JUN 30 2015

.SYNOPSIS...
MER TEMPERATURES ARE EXPECTED FOR THE NEXT COUPLE OF DAYS BEFORE
A FRONTAL BOUNDARY APPROACHES BY MID WEEK...INCREASING CHANCES FOR
SHOWERS AND THUNDERSTORMS. THIS UNSETTLED PATTERN IS EXPECTED TO
PERSIST THROUGH THE WEEKEND...WITH TYPICAL SUMMERTIME AFTERNOON
SHOWERS AND THUNDERSTORMS DEVELOPING EACH DAY AND HIGH TEMPERATURES
WARMING TO ABOVE NORMAL BY EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1215 PM...KGSP RADAR INDICATED THAT A CLUSTER OF THUNDERSTORMS
WAS PUSHING EAST ACROSS EXTREME NE GA...MOVING AT 25 MPH. STRONG
MORNING INSOLATION HAS RESULTED IN TEMPS TO REACH WELL INTO THE U80S
EAST OF THE MTNS. CAPES ACROSS THE REGION HAVE RISEN TO 2000 J/KG
ACROSS THE LAKELANDS...WITH DCAPE ABOVE 1000 J/KG. THE STORMS
EXITING NRN GA SHOULD CONTINUE TO STRENGTHEN AS THEY MOVE
EAST...POSSIBLY YIELDING SVR WIND GUSTS. I WILL UPDATE THE FORECAST
TO THE LATEST TRENDS.

AS OF 1010 AM...LATEST SATELLITE AND RADAR IMAGES INDICATED A WEAKEN
TREND IN THE BAND OF SHOWERS AND THUNDERSTORMS ACROSS THE NC MTNS.
RECENT SPC ANALYSIS INDICATED CIN VALUES REMAIN AROUND 100 J/KG WITH
CAPES ABOVE 500 J/KG ACROSS THE SC UPSTATE AND NE GA. MORNING
CONVECTION SHOULD CONTINUE TO WEAKEN THROUGH THE REMAINDER OF THE AM.

CONDITIONS WILL BECOME MARGINALLY TO MODERATELY UNSTABLE THIS
AFTERNOON...AS DEWPOINTS RANGE IN THE MID 60S WITH TEMPS IN THE U80S
TO L90S. IN ADDITION...FORECAST SOUNDINGS INDICATE THAT 0-6 KM BULK
SHEAR MAY PEAK AROUND 30 KTS...WITH EHI VALUES AROUND .5. ALSO...TT
ARE FORECAST TO RANGE IN THE MID 50S WITH SWEAT GREATER THAN 400.
CAMS AND THE FORECAST ENVIRONMENT SUPPORT A SCENARIO OF A BROKEN BAND
OF THUNDERSTORMS DEVELOPING ALONG THE EAST FACING SLOPES OF THE
APPALACHIANS AND NORTHERN GA. ONCE THE LINE FORMS...STEERING FLOW
AND COLD POOL DEVELOPMENT SHOULD RESULT IN A QUICK MOTION TO THE
EAST. DCAPE VALUES ACROSS THE UPSTATE AND SOUTHERN PIEDMONT MAY
RANGE ABOVE 1000 J/KG. AS THE LINE TRACKS EAST AND
ORGANIZES...SEVERE WIND GUSTS WILL BECOME THE PRIMARY CONCERN. I
HAVE UPDATED THE FORECAST AND HWO TO HIGHLIGHT THE AFTERNOON-EARLY
EVENING RISK FOR SEVERE WEATHER.

0940 UTC UPDATE...POPS HAVE BEEN RAISED ALONG THE TN BORDER PER
RADAR TRENDS.

0830 UTC UPDATE...POPS AND QPF WERE ADJUSTED BASED ON RADAR TRENDS
AND FOR A BETTER FIT WITH NEIGHBORING OFFICES.

AT 230 AM EDT TUESDAY...AN ANOMALOUS UPPER TROUGH AXIS WAS LOCATED
OVER EASTERN NORTH AMERICA THIS MORNING...WITH A RIDGE OVER THE
WESTERN PORTION OF THE CONTINENT. A SHORTWAVE MOVING THROUGH THE
BASED OF THIS TROUGH WILL APPROACH THE SOUTHERN APPALACHIANS THIS
AFTERNOON...CROSSING THE MOUNTAINS TONIGHT. ANOTHER SHORTWAVE WILL
APPROACH THE MOUNTAINS FROM THE WEST TOWARD DAWN ON WEDNESDAY.

LOW LEVEL MOISTURE AHEAD OF THE FIRST SHORTWAVE WILL MOVE EAST ACROSS
OUR AREA TODAY...FOLLOWED MY MODEST DRYING TONIGHT. MODELS FORECAST
SOUNDINGS SHOW SUBSTANTIAL SHEAR AND INSTABILITY DEVELOPING WITH
DAYTIME HEATING...SUPPORTING ROBUST CONVECTION THAT SHOULD ONLY
GRADUALLY DIMINISH THIS EVENING. INITIALLY PLENTY OF DRY AIR WILL BE
AVAILABLE ALOFT FOR EVAPORATIVE COOLING...BUT AS THE MID AND UPPER
LEVELS MOISTEN...ONLY THE LOWEST LEVELS WILL REMAIN DRY. STEERING
FLOW WILL KEEP CELLS MOVING...AND WITH LOW LEVEL FLOW NEARLY
PARALLEL TO THE BLUE RIDGE...UPSLOPE FLOW WILL BE LIMITED.
NEVERTHELESS...HEAVY DOWNPOURS COULD ACCOMPANY SOME OF THE
THUNDERSTORMS. TEMPERATURES WILL RUN NEAR NORMAL.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 245 AM TUESDAY...THE SHORT TERM FCST PICKS UP AT 12Z ON
WEDNESDAY WITH THE PERSISTENT UPPER TROF AXIS OVER THE FCST AREA AND
UPPER RIDGING IN PLACE OVER THE WESTERN CONUS. AS WE MOVE INTO
THURS...THE TROF BEGINS TO DEAMPLIFY AND LIFT NE WHILE VARIOUS LOBES
OF SHORTWAVE ENERGY STREAM ACROSS THE FCST AREA. THIS IS EXPECTED TO
CONTINUE INTO FRI AS THE PERIOD ENDS.

ON WEDNESDAY...A LEE TROF WILL REDEVELOP OVER THE CWFA IN THE WAKE
OF A WEAK FROPA FROM EARLIER IN THE DAY. A LARGE PLUME OF DEEP LYR
MOISTURE WILL BEGIN TO OVERSPREAD THE CWFA FROM THE WEST BY LATE WED
AS THE LOW LVL FLOW REMAINS WEST TO SWLY. POPS WILL STEADILY RAMP UP
THRU THE DAY/EVENING FROM WEST TO EAST WITH SOME LOW END LIKELY
VALUES IN THE FAR WESTERN MTS. SPC CURRENTLY HAS A DAY 2 MARGINAL
RISK AREA EXTENDING INTO THE WESTERN HALF OF OUR CWFA VALID THRU 12Z
THURS. THIS MAKES SENSE WHEN CONSIDERING MODEL PROFILES GENERATE A
FAIR AMOUNT OF INSTABILITY AND SOME HEALTHY LOW LVL
SHEAR...ESPECIALLY OVER THE HIGHER TERRAIN. THIS IS LARGELY DUE TO A
POTENT LOOKING UPPER SHORTWAVE MOVING ACROSS WESTERN NC THURS
MORNING WITH SOME IMPRESSIVE MID TO UPPER LVL OMEGA ASSOCIATED WITH
IT AS WELL AS A STOUT 40 T0 50KT LOW LVL JET STREAK. THE MODELS KEEP
DEEP LYR MOISTURE OVER THE FCST AREA WELL INTO FRI WITH A CENTRAL
PLAINS LOW APPROACHING THE AREA BY THE END OF THE PERIOD 12Z FRI.
TEMPS START OUT AROUND CLIMO ON WED AND DROP A FEW DEGREES FOR THURS
WITH INCREASED CLOUD COVER AND POSSIBLE PRECIP.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 2 AM TUESDAY...THE MEDIUM RANGE FCST PICKS UP AT 12Z ON FRIDAY
WITH A DEAMPLIFICATION OF THE PERSISTENT UPPER TROF BY THE START OF
THE PERIOD. AS WE MOVE INTO THE WEEKEND HEIGHTS SLOWLY RISE AS THE
UPPER PATTERN FLATTENS OUT AND REMAINS THAT WAY THRU DAY 7. THE LONG
RANGE MODELS GENERATE MULTIPLE UPPER TROFS WITHIN THE NORTHERN
STREAM...YET THESE SYSTEMS AND THEIR ASSOCIATED ENERGY WILL REMAIN
WELL TO OUR NORTH. AT THE SFC...THE REGION WILL REMAIN FAIRLY
UNSETTLED THRU MOST OF THE PERIOD. ON FRIDAY...THE MODELS DEVELOP A
COMPLEX LOOKING LOW OVER THE FCST AREA AND ARE SLOW TO MOVE THE
SYSTEM NE. AS IT DOES MOVE WELL OFFSHORE ON SAT...ANOTHER SERIES OF
LOWS FORM IN ROUGHLY THE SAME AREA AND KEEP SOME DEGREE OF LEE
TROFFING OVER THE CWFA THRU THE END OF THE PERIOD. THE MODELS
GENERALLY AGREE THAT DEEP LYR MOISTURE WILL PERSIST OVER THE REGION
THRU MOST OF THE PERIOD WITH LOW LVL FLOW REMAINING OUT OF THE SOUTH
AND/OR SW MOST OF THE TIME. AS FOR THE SENSIBLE FCST...I KEPT THE
DIURNAL HIGH END CHANCES FOR CONVECTION EACH DAY/EVENING WITH SOME
LIKELY POPS OVER THE NC/TENN BORDER REGION FOR FRI AND SAT. TEMPS
START OUT AROUND CLIMATOLOGY ON FRI AND WARM THRU THE PERIOD WITH
HIGHS NEARLY A CATEGORY ABOVE NORMAL BY EARLY NEXT WEEK.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
AT KCLT...VFR. MODEL TIME HEIGHTS SUGGEST A LOW VFR CIG MOVING OVER
THE AREA AROUND MIDDAY AS THE REMAINS OF A COLD FRONT MOVE IN FROM
THE WEST. WINDS WILL FAVOR THE SW...BECOMING GUSTY DURING THE DAY.
CONVECTIVE CHANCES WARRANT A MENTION IN THE TAF THIS AFTERNOON AND
EVENING AS INSTABILITY IMPROVES WITH DAYTIME HEATING. A GUIDANCE
CONSENSUS IS NOT SUPPORTIVE OF A DAYBREAK FOG RESTRICTION WITH THIS
MORNING OR WEDNESDAY MORNING.

ELSEWHERE...VFR. CONVECTIVE ACTIVITY CROSSING THE MOUNTAINS MAY
STRUGGLE TO REACH KAVL THIS MORNING BEFORE INSTABILITY CAN RAMP UP.
ALTHOUGH A FEW GUIDANCE MEMBER FAVOR A DAYBREAK FOG RESTRICTION AT
KAVL...THE CONSENSUS DOES NOT. LOW VFR CIGS WILL OVERSPREAD THE
REGION STARTING IN THE MOUNTAINS...AND REACHING THE FOOTHILLS BY
LATE MORNING...AHEAD OF AN APPROACHING SURFACE BOUNDARY. CONVECTIVE
CHANCES ASSOCIATED WITH THE BOUNDARY WARRANT A MENTION FOR LATE
AFTERNOON AND EARLY THIS EVENING. WINDS WILL FAVOR THE SW...WITH
DAYTIME GUSTS...EXCEPT AT KAVL WHERE WINDS WILL CHANNEL UPVALLEY
FROM THE NW.

OUTLOOK...A LINGERING BERMUDA HIGH COMBINED WITH AN AMPLIFYING
LONGWAVE TROF OVER THE SOUTHEAST WILL GRADUALLY INCREASE MOISTURE
AND INSTABILITY THROUGH MOST OF THE WORK WEEK. THUNDERSTORM COVERAGE
MAY INCREASE EACH DAY THROUGH WEDNESDAY...WITH SCT TO NUM DIURNAL
THUNDERSTORMS LATE IN THE WEEK. RESTRICTIONS MAY OCCUR WITH PASSING
STORMS...AND EACH MORNING OVER AREAS OF WET SOIL.

CONFIDENCE TABLE...

            16-22Z        22-04Z        04-10Z        10-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     MED   61%
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...NED
SHORT TERM...JPT
LONG TERM...JPT
AVIATION...JAT

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