Severe Thunderstorm Warning 523, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
255 PM EDT TUE JUL 5 2011

.SYNOPSIS...
A WEAK STATIONARY FRONT WILL SLOWLY DISSIPATE THROUGH WEDNESDAY...
ONLY TO BE REPLACED BY ANOTHER WEAK FRONT ON THURSDAY. THE PROXIMITY
OF THE FRONTS WILL MAINTAIN A GOOD CHANCE OF RAIN THROUGH THE END OF
THE WEEK.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AT 1850Z...A BAND OF CIRRUS LEVEL CLOUDS WAS LOCATED ACROSS THE CLT
METRO AREA. ACROSS THE MTNS...ENHANCED CU AND DEEP CONVECTION
EXISTED ACROSS THE RIDGES. OBS INDICATE THAT TEMPERATURES HAVE BEEN
HELD BACK DUE TO THE EXTENSIVE MORNING CLOUD COVER...ESPECIALLY
ACROSS NE GA AND THE UPSTATE OF SC. FOOTHILL AND PIEDMONT CU SHOULD
CONTINUE TO RAPIDLY DEVELOP THROUGH THE REST OF THE AFTERNOON. AFTER
20Z...COVERAGE OF SHRA AND TSRA WILL GRADUALLY INCREASE EAST OF THE
MTNS ACROSS THE FOOTHILLS AND PIEDMONT. GIVEN AN EXPECTED STORM
MOVEMENT FROM SW TO NE...IT APPEARS THAT LIKELY POPS ACROSS THE MTNS
WILL SPREAD EAST THROUGH LATE AFTERNOON...I WILL FAVOR VALUES AROUND
60 PERCENT. HIGHER COVERAGE EXPECTED ACROSS THE NC FOOTHILLS...I
WILL ADVERTISE POPS AROUND 70 PERCENT.

OBSERVED MORNING SOUNDINGS AT KGSO AND KFFC INDICATED THAT THE FZL
WAS AROUND 14.7 KFT...PLACING THE 55 DBZ CORE HEIGHT AROUND 26.5 KFT
AND THE 50 TO 55 DBZ AROUND 34 KFT. THE WBZ WAS LOCATED JUST ABOVE 13
KFT. PW VALUES WERE OBSERVED FROM 1.5 AT KGSO TO 1.7 AT KFFC. CAPE
VALUES ARE FORECAST TO RANGE FROM 1500 TO 2500 J/KG WITH A FEW
POCKETS NEAR 3000 J/KG. GIVEN THE HIGH FZL AND MARGINAL TO MODERATE CAPE IT
APPEARS THAT SEVERE HAIL WILL REMAIN ISOLATED AT BEST. THE DEEP
MOISTURE SHOULD YIELD DCAPE VALUES AROUND 500 J/KG. HOWEVER...TALL
LARGE CORES COULD RESULT IN DAMAGING WET MICROBURSTS...WHICH WILL
REMAIN THE PRIMARY HAZARD THIS AFTERNOON AND EVENING. HIGH MOISTURE
CONTENT AND POTENTIAL FOR MULTICELL CONVECTION MAY PRODUCE ISOLATED
AREAS OF EXCESSIVE RUNOFF. WE WILL CONTINUE TO HIGHLIGHT THE
POTENTIAL FOR DAMAGING MICROBURSTS AND HEAVY RAIN IN THE HWO.

CONVECTION SHOULD COME LARGELY TO AN END DURING THE EARLY MORNING
HOURS. ONLY A FEW ISO SHRA/TSRA MAY REMAIN OVERNIGHT...SUPPORTING
ONLY SCHC POPS. MIN TEMPERATURES SHOULD FALL WITHIN A DEGREE OR TWO
OF NORMAL.

WEDNESDAY...NEAR TERM TERM MODELS INDICATE THAT THE MID LEVEL TROF
AXIS WILL SLOWLY SLIDE EAST...POSSIBLY REACHING THE SOUTHERN
APPALACHIANS REGION DURING THE LATE AFTERNOON. AS THE TROF
APPROACHES...THE WESTERN EDGE OF THE W/V BAND WILL PUSH FURTHER
EAST. THE COMBINATION OF THE APPROACHING MID LEVEL FEATURE AND
DIURNAL RIDGETOP CONVERGENCE SHOULD YIELD SHRA/TSRA DEVELOPMENT BY
MID DAY. BY MID AFTERNOON...EXPECT A BROKEN BAND OF CONVECTION TO
DEVELOP AHEAD OF THE W/V BAND...EXTENDING SW ACROSS GA/AL. STEERING
FLOW SHOULD BRING THE ACTIVITY NE ACROSS THE CWA DURING THE MID
AFTERNOON. GIVEN THE DEEP MOISTURE AND MODERATE INSTABILITY IT
APPEARS THAT ANOTHER DAY OF LIKELY POPS WILL HIGHLIGHT THE EXPECTED
CONVECTION. HIGH TEMPERATURES MAY PEAK A DEGREE OR TWO ABOVE TODAY/S
VALUES.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 215 PM TUESDAY...IT APPEARS THAT FOR OVERALL SENSIBLE WEATHER
THAT THE MODELS HAVE SETTLED ON A SOLUTION OF A SLIGHT RETROGRESSION
OF THE BERMUDA HIGH AXIS...WHILE THE UPPER LEVEL HIGH IN THE FOUR
CORNERS OF THE U.S. EXPANDS NORTH. THIS ALLOWS THE UPPER FLOW (H5)
IN PARTS OF THE EASTERN CONUS TO BECOME FLAT-NWLY AT OUR LATITUDE...
WHILE AND OLD WAVY SURFACE FRONTAL BOUNDARY SETTLE INTO THE REGION /
OR BECOMES DIFFUSE /. MODEL PRECIPITABLE WATER VALUES CONTINUE TO
POOL ON BOTH THURSDAY AND FRIDAY AFTERNOON TO BETWEEN 2.00 AND 2.10
INCHES GENERALLY EAST OF THE FOOTHILLS IN NC...MUCH OF THE UPSTATE
OF SC AND NORTHEAST GA. WITH UPPER LEVEL HEIGHTS EDGING DOWN WOULD
EXPECT PERHAPS SLIGHTLY STEEPER LAPSE RATES WITH CONVECTION TO
DEVELOP ALONG THE OLD BOUNDARY / OR THE HIGHER TERRAIN / AND DRIFT
SLOWLY SOUTHEASTWARD. CERTAINLY SOME GULLY WASHERS ARE NOT OUT OF
THE QUESTION...AS WELL AS A FEW WET MICRO-BURSTS. WE HAVE EDGED
DAYTIME POPS INTO THE LIKELY CATEGORY FOR A FEW HOURS BOTH THURSDAY
AND FRIDAY AFTERNOON...WHILE RUNNING TEMPERATURES A FEW DEGREES
BELOW READINGS OF THE PAST FEW DAYS.

MEANWHILE WE HAVE NOT COMPLETLEY ELIMINATED POPS AT NIGHT CONSIDERING
THE VERY MOIST ATMOSPHERE IN PLACE AND POSSIBILITY OF WEAK
PERTURBATIONS MOVING THROUGH THE MEAN FLOW. FINALLY THE NAM AND TO
SOME EXTENT CANADIAN MODEL WERE BOTH HINTING AT SOME TYPE OF LOW
PRESSURE SYSTEM LIFTING NORTH FROM THE BAHAMAS LATE IN THE WORK
WEEK. DIFFICULT TO SEE ANY EVOLUTION NOW AND WILL CONTINUE FORWARD
WITH OUR THINKING MENTIONED ABOVE.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 215 PM TUESDAY...THE CURRENT SUITE OF MODELS WERE SUGGESTING
THAT THE FIRST DIFFUSE SURFACE FRONT WHICH WILL BECOME ERRATIC AND
HARD TO FIND BY THE START OF THE UPCOMING WEEKEND...MAY BE
RE-ENFORCED BY A SECONDARY WEAK FRONT / WIND SHIFT / IN THE
AFOREMENTIONED NWLY H5 FLOW. THIS SECOND FEATURE SETTLES ACROSS PART
OF OUR FORECAST AREA (FA)...PERHAPS FROM SOUTHEAST TO
NORTHWEST...BUT THAT IS VERY PROBLEMATIC. NEVERTHELESS THERE SHOULD
BE A SMATTERING OF CONVECTION BOTH SATURDAY AND SUNDAY AFTERNOON'S
AND EVENING. HAVE KEPT POPS IN THE CHANCE CATEGORY OVER THE
WEEKEND.

AS WE MOVE INTO THE START OF THE NEW WORK WEEK...RIDGING ALOFT
SHOULD GRADUALLY BECOME ESTABLISHED. UPSHOT WOULD BE LESS CONVECTION
MONDAY AND TUESDAY...IN COMPARISON TO PREVIOUS DAY. ALSO WILL ALSO
EDGE TEMPERATURES UP ABOVE CLIMO ACROSS THE BOARD LATE IN THIS
FORECAST CYCLE.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
AT KCLT AND ELSEWHERE...SHRA AND TSRA COVERAGE WILL REMAIN MAINLY
ACROSS THE MTNS THROUGH 20Z. SHRA AND TSRA COVERAGE SHOULD INCREASE
SIGNIFICANTLY EAST THE MTNS BETWEEN 20Z TO 5Z. I WILL CARRY A CB AT
ALL TAF SITES WITH LATE AFTERNOON AND EARLY EVENING TEMPOS AT KAVL
AND KHKY DUE TO IDEAL STORM MOTIONS. THE THREAT FOR PRE DAWN FOG AND
LOW CLOUDS WILL REMAIN THE GREATEST NEAR AREAS OF TODAY/S RAINFALL.
GIVEN THE HIGH COVERAGE AND ONGOING HAZY CONDITIONS I APPEARS LIKELY
THAT ALL TAF SITES WILL SEE SOME DEGREE OF VIS RESTRICTIONS. I WILL
FAVOR MVFR FOG...BUT KAVL IS EXPECTED TO SEE IFR. FOG WILL DISSIPATE
SHORTLY AFTER SUNRISE WEDNESDAY...UNDER FEW TO SCT CU AND HIGH
DEBRIS CLOUDS.

OUTLOOK...A VERY UNSETTLED PATTERN WILL BE IN PLACE ALL WEEK AS ONE
FRONT DISSIPATES IN THE VICINITY AND ANOTHER COLD FRONT ARRIVES FROM
THE NW LATE IN THE WEEK. MORNING MVFR FOG IS LIKELY...AT LEAST IN
THE MTN VALLEYS...WITH SCATTERED TO NUMEROUS AFTN/EVENING TSTMS EACH
DAY.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

SYNOPSIS...TS
NEAR TERM...NED
SHORT TERM...TS
LONG TERM...TS
AVIATION...NED

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