Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 302015
AFDGSP

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

.SYNOPSIS...
AN APPROACHING FRONTAL BOUNDARY AND UNSETTLED AIRMASS WILL SUPPORT
NUMEROUS THUNDERSTORMS THIS AFTERNOON/EVENING...SOME STRONG TO
SEVERE. THIS ACTIVE 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 WEDNESDAY/...
AS OF 415 PM EDT TUESDAY...INITIAL ROUND OF CONVECTION ASSOCIATED
WITH A WEAK UPPER IMPULSE CONTINUES TO SLIDE EAST ACROSS THE NC/SC
PIEDMONT AT THIS TIME.  CURRENTLY NONE OF THE CONVECTION IS AT
SEVERE LIMITS...HOWEVER STRONG STORMS DO EXIST.
MEANWHILE...CLUSTERS OF THUNDERSTORMS SLIDING THROUGH EAST TN
CONTINUE TO MOVE TOWARDS/INTO THE NC HIGH TERRAIN. IN ADDITION...NEW
CONVECTION IS STARTING TO FIRE OVER PORTIONS OF NORTHCENTRAL GA.
LATEST SPC MESOANALYSIS DOES INDICATE ENOUGH INSTABILITY REMAINS
PRESENT OVER THE REGION TO SUPPORT ENHANCED/ORGANIZED CONVECTION IN
THE NEAR TERM.  THEREFORE WILL CONTINUE THE CURRENT WW AS IS FOR
THIS UPDATE.  MADE ADJUSTMENTS TO POPS/SKY TO ACCOUNT FOR MOST
RECENT RADAR/SAT COVERAGE.  ALSO TWEAKED TEMPS/DEWS TO BETTER
REFLECT LATEST SURFACE OBS.  NO OTHER SIG CHANGES WERE MADE WITH
THIS UPDATE.

PREVIOUS DISCUSSION...

AS OF 245 PM...SEVERE THUNDERSTORM WATCH 373 IN EFFECT FOR THE CWA
UNTIL 9 PM EDT THIS EVENING. A VERY MESSY CONVECTIVE SITUATION IS
UNFOLDING ACROSS THE CWA AT THIS TIME. CLUSTERS OF STRONG TO SEVERE
STORMS WILL PUSH EAST ACROSS THE FOOTHILLS AND PIEDMONT THROUGH
EARLY THIS EVENING. THESE STORMS WILL BE SUPPORTED BY MODERATE
INSTABILITY AND DCAPES BETWEEN 1000 TO 1500 J/KG ACROSS THE UPSTATE
OF SC. FORECAST SOUNDINGS INDICATE THAT CONDITIONS ACROSS THE FA
WILL MAINTAIN BULK SHEAR AROUND 3KTS...FAVORING MULTICELL STORMS.
LATE THIS AFTERNOON INTO THE EVENING...ANOTHER BAND OF STRONG TO
SEVERE STORMS WILL APPROACH THE NC MTNS FROM EASTERN TN. THIS SECOND
BAND IS PRIMARILY SUPPORTED BY AN ADVANCING S/W...NICELY SEEN ON
RECENT W/V IMAGES. THIS LINE OF CONVECTION IS FORECAST TO TRACK SE
ACROSS THE MTNS...LIKELY DISSIPATING EAST OF THE MTNS LATE THIS
EVENING. THE REST OF THE NIGHT...SHRA AND TSRA MAY REMAIN ACROSS THE
TN BORDER COUNTIES...WITH AREAS EAST REMAINING GENERALLY DRY. MIN
TEMPERATURES ARE FORECAST TO RANGE CLOSE TO NORMS.

ON WEDNESDAY...CONDITIONS WILL REMAIN SIMILAR TO TODAY...BUT OVERALL
ALL PARAMETERS ARE FORECAST TO RANGE A LITTLE WEAKER. HIGH
TEMPERATURES ARE FORECAST TO PEAK 3 TO 4 DEGREES COOLER THAN TODAY.
THEREFORE...CAPE VALUES SHOULD PEAK BETWEEN 1000 TO 1500 J/KG. IN
ADDITION...BULK SHEAR IS FORECAST TO FAVOR VALUES WITHIN THE LOW 20
KTS. HOWEVER...SOUNDINGS CONTINUE TO APPEAR WITH AN INVERTED V
ACROSS THE REGION. GFS TIMES A WEAK VORT MAX TO PASS ACROSS THE
REGION DURING THE AFTERNOON. I WILL FORECAST POPS CATE NEAR THE TN
LINT TO SOLID CHC EAST. SPC DAY 2 OUTLOOK HIGHLIGHTS MOST OF THE
AREA UNDER MARGINAL RISK FOR SEVERE STORMS.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 215 PM TUESDAY...AN UPPER TROUGH WILL CONTINUE ACROSS THE
EAST THROUGH THE END OF THE WEEK...BUT EVOLVING INTO SPLIT FLOW
REGIME WITH THE MAIN AXIS OF THE WESTERLIES THROUGH THE GREAT LAKES
AND NEW ENGLAND...WITH A SOUTHERN EXTENSION THEN FROM THE CENTRAL
U.S INTO THE SOUTHERN APPALACHIANS. A NUMBER OF EMBEDDED SHORT WAVES
WILL MOVE THROUGH THE TROUGH AND AFFECT THE AREA. THEREFORE...THE
SENSIBLE WEATHER WILL REMAIN UNSETTLED.

SCT CONVECTION MAY BE ONGOING WED EVENING BUT SHOULD WANE DUE TO
LOSS OF HEATING AND THE PASSAGE TO THE EAST OF A WEAK SHORT WAVE.
HOWEVER...CONVECTION IS EXPECTED TO RAMP UP AGAIN ON THURSDAY
AFTERNOON AS ANOTHER MORE POTENT WAVE APPROACHES AND MOVES THROUGH
THE REGION THU EVENING. WILL RAMP DOWN POPS SOME THU NIGHT BUT SCT
SHRA/TSRA MY CONTINUE OVERNIGHT. FRIDAY SHOULD ALSO SEE NUMEROUS
SHOWERS/THUNDERSTORMS AS YET ANOTHER UPPER WAVE ARRIVES.

IN REGARD TO SEVERE POTENTIAL...SPC HAS THE AREA IN A MARGINAL RISK
FOR THURSDAY AS WIND FIELDS REMAIN STRONGER THAN USUAL FOR THIS TIME
OF YEAR. HOWEVER...FORECAST CAPES ARE ON THE DOWN TREND AS DEEP
LAYER MOISTURE OVERSPREADS THE AREA. LOCALLY HEAVY RAIN MAY BECOME
MORE OF A CONCERN DURING THE LATE WEEK TIME FRAME AS PWATS INCREASE
TO AROUND 2 INCHES. THE FORECAST WILL FEATURE ABOVE CLIMO POPS WITH
MAX TEMPS A LITTLE BELOW CLIMO DUE TO INCREASED CLOUDS COVER AND
PRECIP.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 230 PM TUESDAY...THE EXTENDED PERIOD BEGINS FRIDAY NIGHT WITH
THE PERSISTENT LONGWAVE TROUGH OVER THE EASTERN CONUS CONTINUING TO
DEAMPLIFY. A DIFFUSE BOUNDARY WILL HUG THE BASE OF THE TROUGH...AND
OSCILLATE OVER THE SOUTHERN APPALACHIANS OVER MUCH OF THE WEEKEND.
FOR INDEPENDENCE DAY...BOTH GLOBAL MODELS ARE NOW KEYING ON A SMALL
SHORTWAVE RIDGE MOVING OVER THE CWFA DURING THE DAY. THOUGH THERE IS
UNCERTAINTY IN THE AMPLITUDE...PLACEMENT AND TIMING OF THE
FEATURE...IT MAY AFFORD SOME LEVEL OF PROTECTION FOR THE PIEDMONT
AND FOOTHILLS ZONES AND KEEP THE BEST PRECIP COVERAGE OVER THE
HIGHER TERRAIN IN THE AFTERNOON. POPS WOULD THEREFORE BE NEAR CLIMO
FOR OUR EASTERN ZONES...AND JUST ABOVE CLIMO FOR THE WESTERN ZONES.
AT THIS POINT...IT APPEARS THAT A LACK OF ANY IMPRESSIVE INSTABILITY
OR FORCING OVER THE PIEDMONT/FOOTHILLS WILL ALLOW ANY DIURNAL SHOWER
OR THUNDERSTORM ACTIVITY THAT DOES FORM OUTSIDE OF THE MOUNTAINS TO
DISSIPATE SHORTLY AFTER SUNSET. THE BOUNDARY WILL BE IN CLOSER
PROXIMITY TO OUR AREA ON SUNDAY...SO COVERAGE OF DIURNAL SHOWERS AND
STORMS IS EXPECTED TO BE HIGHER THAN SATURDAY. MONDAY AND TUESDAY
WILL BOTH FEATURE SOME BERMUDA HIGH INFLUENCE...AND POPS WILL REMAIN
NEAR CLIMO THROUGH THE BEGINNING OF THE WORK WEEK BEFORE ANOTHER
LONG WAVE TROUGH AND ASSOCIATED FRONTAL BOUNDARY SWEEPS THROUGH BY
THE MIDDLE OF NEXT WEEK.

MAX TEMPS WILL BE ABOUT A CATEGORY ABOVE AVERAGE FOR THE ENTIRE
MEDIUM RANGE...WITH LOWS BEGINNING NEAR AVERAGE AND SLOWLY RISING TO
A CATEGORY ABOVE AVERAGE BY THE END OF THE PERIOD.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
AT KCLT AND ELSEWHERE...SEVERE THUNDERSTORM WATCH UNTIL
1Z. WIDESPREAD MODERATE INSTABILITY COMBINED WITH A PASSING MID
LEVEL FEATURE WILL SUPPORT NUMEROUS THUNDERSTORMS ACROSS THE REGION
THROUGH MID EVENING. STORMS WILL MOVE EAST ACROSS THE WESTERN
CAROLINA BETWEEN 25-35 MPH. THE ENVIRONMENT MAY SUPPORT DAMAGING
WIND GUSTS AND LARGE HAIL. I WILL HIGHLIGHT EACH TAF WITH TEMPO AND
FM FOR TSRA THROUGH EARLY THIS EVENING. CONVECTION COVERAGE WILL
DECREASE DIUNRALLY TONIGHT. PRE DAWN FOG APPEARS POSSIBLE ACROSS
KAVL...EXPECTING WET SOIL. CONDITIONS SUPPORTIVE OF THUNDERSTORMS
WILL REMAIN FOR WED. I WILL INCLUDE A PROB30 DURING THE LATE MORNING
FOR TERMINALS WEST OF THE I-77 CORRIDOR.

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       MED   77%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     MED   72%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH  88%     HIGH 100%     HIGH 100%
KAND       HIGH  88%     HIGH  88%     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...CDG/NED
SHORT TERM...LG
LONG TERM...LEV
AVIATION...NED


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