Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS62 KGSP 010009
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
809 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 800 PM EDT TUESDAY...OPTED TO REMOVE THE WESTERN TIER OF THE
FCST AREA FROM THE CURRENT WW AS THE ENVIRONMENT NO LONGER SUPPORTS
WIDESPREAD SVR CONVECTIVE POTENTIAL.  FURTHER EAST...THE ENVIRONMENT
IS ONLY A BIT MORE FAVORABLE...HOWEVER WITH CONVECTION ONGOING
DECIDED BEST TO CONTINUE WATCH THROUGH 9PM.  OTHERWISE...TWEAKED
TEMPS/DEWS/SKY TO ACCOUNT FOR MOST RECENT OBS/SAT TRENDS.

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 /00Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...VFR CONDITIONS WILL PREVAIL THROUGH THE TAF CYCLE WITH THE
EXCEPTION OF CONVECTION THIS EVENING...AND ON WED AFTN.  INITIALIZED
TAF WITH SW GUSTS UNDER FEW LOW VFR AND BKN MID LEVEL CLOUDS.
INCLUDED AN IMMEDIATE TEMPO TO ACCOUNT FOR UPSTREAM CONVECTIVE
LINE...AND ALSO FOR ITS OUTFLOW WHICH WILL LIKELY YIELD A NW WINDS
SHIFT AT THE AIRFIELD.  CONFIDENCE IN THE ARRIVAL OF THE CONVECTION
CONTINUES TO DECREASE AS RADAR TRENDS SHOW WEAKENING.
NEVERTHELESS...THE TEMPO REMAINS THROUGH 03Z...WHICH WILL LIKELY BE
TAILORED BACK OVER THE NEXT HOUR OR SO.  OTHERWISE...LIGHT/CALM SW
FLOW OVERNIGHT UNDER MID/HIGH CLOUDS WILL GIVE WAY TO INCREASING SW
GUSTS ON WEDNESDAY WITH INCREASING LOW VFR CU AND TSRA CHANCES.
THUS A PROB30 WAS INCLUDED FOR SUCH.

ELSEWHERE...ASIDE FOR LOW CONFIDENCE TSRA TEMPOS AT THE KGSP/KGMU
THROUGH THE EARLY EVENING...EXPECTING VFR TO PREVAIL AT ALL SITES
UNTIL MID/LATE MORNING.  AT THAT TIME...DUE TO MOIST
SURFACES...EXPECTING MVFR RESTRICTIONS IN THE FORM OF FOG AT
KAND/KHKY...ALONG WITH THE POSSIBLE IFR FOG/STRATUS AT KAVL.
CONFIDENCE IS LOW IN THE IFR...THUS KEPT KAVL AT MVFR FOR NOW
HOWEVER IT SHOULD BE NOTED THAT FURTHER LOWERING IS PROGGED BY SOME
GUID SOURCES.  BEYOND THAT...A REPEAT OF TODAY WITH LOW VFR CU
PREVAILING AND TSRA CHANCES INCREASING INTO THE AFTERNOON HOURS.
WINDS WILL REMAIN SW AT ALL SITES ASIDE FOR KAVL WHERE WINDS REMAIN
JUST NORTH OF WEST.  EXPECTING ALL SITES TO SEE LIGHT GUSTING ON
WEDNESDAY AS THE MIXED LAYER DEEPENS...WITH A POSSIBLE EXCEPTION AT
KHKY.

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...

            00-06Z        06-12Z        12-18Z        18-00Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     MED   63%     HIGH  87%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH  86%     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...CDG


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.