Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 292018
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
418 PM EDT MON JUN 29 2015

.SYNOPSIS...
THE NEXT COUPLE OF DAYS WILL FEATURE A WARMING AND MOISTENING TREND
BEFORE A FRONTAL BOUNDARY APPROACHES BY THE MIDDLE OF THE
WEEK...DRIVING RAIN AND THUNDERSTORM CHANCES UP. AND UNSETTLED
WEATHER PATTERN WILL PERSIST THROUGH THE WEEKEND...WITH TYPICAL
SUMMERTIME  AFTERNOON SHOWERS AND THUNDERSTORMS DEVELOPING EACH DAY
AND HIGH TEMPERATURES WARMING TO NEAR NORMAL BY NEXT WEEK.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 415 PM EDT MONDAY...LATEST VISIBLE SAT IMAGERY CONTINUES TO
INDICATE A MODESTLY UNSTABLE ENVIRONMENT ACROSS THE WESTERN NC MTNS
AND THE UPPER SAVANNAH RIVER VALLEY WHERE WIDESPREAD CU PERSISTS.
FURTHER EAST OVER THE NC/SC PIEDMONT REGIONS MUCH LESS COVERAGE IS
OBSERVED.  MOST RECENT CAM GUID FAVORS THE CURRENT POP FCST WHICH
EMPHASIZES ISOLATED/SCATTERED SHOWERS ACROSS THE NC HIGH TERRAIN
THIS AFTERNOON/EVENING...THUS NO CHANGES WERE MADE TO POPS.  DID
TWEAK TEMPS/DEWS AND SKY TO ACCOUNT FOR MOST RECENT TRENDS AND LEFT
THE REMAINDER OF THE FCST AS IT WAS FOR THIS UPDATE.

PREVIOUS DISCUSSION...

AS OF 225 PM...LATEST SATELLITE IMAGE INDICATED A BAND OF DEBRIS
CLOUDS ACROSS THE NC MTNS...WITH A SHALLOW CU FIELD ACROSS THE NC
AND NRN SC FOOTHILLS AND PIEDMONT. A FEW SHRA TO ISO TSRA MAY REACH
THE TN BORDER COUNTIES OF NC BEFORE DISSIPATING THIS EVENING. AT 2
PM...A LIGHT CLUSTER OF SHRA WAS LOCATED NEAR THE INTERSECTION OF
GA/AL/TN STATE LINES. AT 2 PM...SPC CAPE ANALYSIS INDICATED 100 TO
200 J/KG ACROSS THE EXTREME WESTERN NC MTNS...WHICH AGREES QUITE
WELL WITH THE 12Z NAM. I EXPECT THAT UPSTREAM CONVECTION WILL
SURVIVE TO REACH THE TN BORDER...ALONG WITH A FEW SHRA/TSRA
DEVELOPING OVER THE NC RIDGES...I WILL HIGHLIGHT WITH CHC TO SCHC
POPS AFTER 20Z. SHRA/TSRA MAY TRACK SLOWLY EAST...BUT SHOULD
DISSIPATE BEFORE REACHING THE FOOTHILLS. THE REST OF THE NIGHT...A
FEW SHRA MAY CONTINUE TO BRUSH THE TN LINE...I WILL INDICATE SCHC
POPS. PARTLY TO MOSTLY CLOUDY SKY WITH LIGHT SW WINDS SHOULD RESULT
IN MIN TEMPERATURES TO RANGE WITHIN A DEGREE OR TWO OF NORMAL.

ON TUESDAY...IT APPEARS THAT THE REGION WILL RETURN TO SUMMER-LIKE
CONDITIONS. CONTINUED RETURN FLOW SHOULD RESULT IN DEWPOINTS TO
RANGE IN THE LOW TO MID 60S DURING THE AFTERNOON. USING A BLEND OF
GUIDANCE...HIGH TEMPERATURES ARE FORECAST TO RANGE FROM THE LOW 80S
WITHIN THE NC MTN VALLEYS TO AROUND 90 EAST. FORECAST SOUNDINGS
INDICATE THAT CAPE VALUES SHOULD RANGE FROM 1000 TO 2000 J/KG ACROSS
THE REGION...WITH LITTLE TO NO CIN. THE NEAR TERM MODELS INDICATE
THAT A MID LEVEL S/W WILL RIPPLE ACROSS THE SOUTHERN APPALACHIANS
DURING THE AFTERNOON. AS THE S/W APPROACHES...DEEP CONVECTION IS
FORECAST TO DEVELOP ACROSS THE MTNS BY MID DAY. COVERAGE ACROSS
FOOTHILLS AND PIEDMONT SHOULD INCREASE DURING THE AFTERNOON.
STEERING FLOW MAY YIELD EAST BOUND STORMS AROUND 15 M/S. I WILL
FORECAST HIGH CHC TO LIKELY POPS ACROSS THE MTNS...WITH SOLID CHC
POPS EAST. SPC DY2 HIGHLIGHTS MOST OF THE SOUTHEAST U.S. WITH A
MARGINAL RISK...5 PERCENT CHC FOR SEVERE STORMS.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
AS OF 2 PM MONDAY...SOME SEMBLANCE OF THE EAST COAST TROUGH WILL
PERSIST INTO LATE WEEK. HOWEVER...SOME WEAKENING IN THE PATTERN IS
FORECAST BY LATE THU AS AN UPPER LOW DEVELOPS IN EASTERN CANADA WITH
AN ENSUING SPLIT FLOW REGIME TO THE SOUTH. DURING THIS TIME...A
SERIES OF LOW PRESSURE SYSTEMS WILL MOVE THROUGH THE OHIO VALLEY
ALONG A QUASI-STATIONARY BOUNDARY. ALOFT A SERIES OF WEAK SHORT
WAVES ROTATING THROUGH THE UPPER TROUGH HAVE THE POTENTIAL TO
ENHANCE CONVECTION...ESPECIALLY IF THEY ARRIVE DURING THE OPTIMUM
DIURNAL CYCLE TIME.

IN REGARD TO THE SENSIBLE WEATHER IN THE SOUTHERN APPALACHIANS AND
THE WESTERN CAROLINAS...IT LOOKS LIKE THE PERIOD CAN CERTAINLY BE
CHARACTERIZED AS UNSETTLED. MODEL TIME HEIGHTS SHOW RATHER DEEP
LAYER MOISTURE WITH PWATS INCREASING TO NEAR 2 INCHES BY THURSDAY.
ALSO...THERE CERTAINLY ARE SOME DISAGREEMENTS IN THE MODEL DETAILS.
THE 12Z NAM IS A LITTLE FARTHER SOUTH WITH THE STORM TRACK AND
BRINGS THE LOWS THROUGH THE CENTRAL APPALACHIANS. THIS RESULTS IN
THE MODEL BRINGING WHAT LOOKS LIKE A MCS INTO THE NC MOUNTAINS BY
LATE WED WHICH PUSHES ACROSS THE MOUNTAINS WED NIGHT WITH AREAS OF
VERY GENEROUS QPF. THE GFS IS MUCH MORE MUTED WITH NOT NEARLY THE
QPF AS THE NAM. THE NAM APPEARS TO BE AN OUTLIER IN COMPARISON ALSO
WITH THE EC AND SREF...SO WILL LEAN TOWEARD THE GFS SOLUTION. THIS
WILL RESULT IN DIURNALLY ENHANCED SCT THUNDERSTORMS ON WED AFTERNOON
AND EVENING. WITH WIND FIELDS REMAINING STRONGER THAN USUAL FOR
EARLY JULY AND CAPES INCREASING TO >1000J...SOME SCT SEVERE STORMS
ARE OUT OF THE QUESTION. IT IS LOOKING LIKE THU COULD BE THE MORE
ACTIVE DAY IN REGARD TO OVERALL COVERAGE OF THUNDERSTORMS AS A SHORT
WAVE ROTATES THROUGH DURING THE AFTERNOON. WILL THEREFORE INCREASE
POPS TO NUMEROUS OVER A LARGE PORTION OF THE FORECAST AREA ON
THURSDAY AFTERNOON. TEMPS ARE FORECAST TO BE NEAR CLIMO EACH
DAY...EXCEPT A COUPLE DEGREES BELOW ON THU WESTERN PORTIONS DUE TO
MORE CLOUDS/PRECIP.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 230 PM MONDAY...THE MEDIUM RANGE BEGINS THURSDAY NIGHT AS A
WEAK SURFACE LOW/VORT MAX ROUNDS THE BASE OF THE LONGWAVE H5 TROUGH
TOWARDS THE SPINE OF THE SOUTHERN APPALACHIANS. THIS WILL KEEP POPS
ELEVATED EVEN INTO THE OVERNIGHT HOURS HEADING INTO FRIDAY MORNING.
OVERALL HEIGHTS BEGIN TO RISE AS THE UPPER TROUGH BREAKS DOWN ON
FRIDAY...THOUGH A BOUNDARY IN CLOSE PROXIMITY TO THE FORECAST AREA
AND PLENTIFUL SOUTHERN STREAM MOISTURE WILL KEEP POPS ELEVATED WELL
ABOVE CLIMO TO END THE WORK WEEK. THE AXIS OF ANOTHER H5 TROUGH AND
AN ASSOCIATED SPOKE OF VORTICITY WILL ARRIVE JUST IN TIME FOR PEAK
HEATING ON SATURDAY...WITH ACCOMPANYING POPS NEAR OR JUST ABOVE
NORMAL...THOUGH CONVECTION APPEARS TO FOLLOW A TYPICAL TREND OF
WANING SOMEWHAT AFTER SUNSET. THE TROUGH IS PROGRESSIVE IN LIFTING
OFF THE NORTHEAST CONUS LATE IN THE WEEKEND...LEAVING A NORMAL JULY
DIURNAL PATTERN OF POPS FOR EARLY NEXT WEEK.

MAX TEMPS FOR THE MEDIUM RANGE WILL START NEAR AVERAGE AT THE END OF
THIS WEEK...THEN RISE TO JUST ABOVE CLIMO THIS WEEKEND AND THROUGH
NEXT WEEK. A TYPICAL MOIST SUMMERTIME AIRMASS WILL LIMIT THE DIURNAL
TEMPERATURE RANGE...KEEPING MIN TEMPS SLIGHTLY ABOVE NORMAL THROUGH
THE PERIOD.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
AT KCLT AND ELSEWHERE...LATEST SATELLITE IMAGE INDICATED A BAND OF
DEBRIS CLOUDS ACROSS THE NC MTNS...WITH A SHALLOW CU FIELD ACROSS
THE NC AND NRN SC FOOTHILLS AND PIEDMONT. A FEW SHRA TO ISO TSRA MAY
REACH THE TN BORDER COUNTIES OF NC BEFORE DISSIPATING THIS EVENING.
OTHERWISE...CONDITIONS ACROSS THE WESTERN CAROLINAS SHOULD REMAIN
QUIET...WITH A LIGHT SW CONTINUING THROUGH TONIGHT.

ON TUESDAY...CONDITIONS WILL BECOME MUCH MORE SUMMER-LIKE. THE
PASSAGE OF A MID LEVEL WAVE COMBINED WITH HIGHER LLVL DEWPOINTS WILL
YIELD AN ENVIRONMENT MORE SUITABLE FOR TSRAS. KAVL WILL SEE THE
GREATEST CHC DURING THE 18Z PACKAGE...I WILL HIGHLIGHT WITH A
PROB30. ELSEWHERE...TSRA SHOULD HOLD OFF UNTIL AFTER 18Z. IN
ADDITION...DEEP MIXING SHOULD YIELD MARGINAL WIND GUSTS DURING THE
AFTERNOON...KAND TO KGSP BEFORE 18Z.

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...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  89%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     MED   79%
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...LEV
NEAR TERM...CDG/NED
SHORT TERM...LG
LONG TERM...LEV
AVIATION...NED



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