Severe Thunderstorm Warning 69, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
334 PM EDT SAT MAY 15 2010

.SYNOPSIS...
A WEAK FRONT WILL REMAIN STALLED OVER THE AREA THROUGH MONDAY.
ANOTHER COLD FRONT WILL APPROACH FROM THE WEST MONDAY AND CROSS THE
AREA MONDAY NIGHT AND TUESDAY. HIGH PRESSURE WILL SLOWLY BUILD IN
FROM THE NORTH FOR MID TO LATE WEEK.

&&

.NEAR TERM /THROUGH SUNDAY/...
CLUSTERS OF THUNDERSTORMS WILL CONTINUE TO INCREASE OVER THE MTNS
THROUGH THIS AFTERNOON AND INTO THE EVENING. AT 1845Z...AN ISOLATED
SHRA WAS DEVELOPING NEAR GAFFNEY WITHIN A BAND OF CU ALONG AND AHEAD
OF A WEAK COLD FRONT. COVERAGE AND INTENSITY OF THE STORMS WILL
INCREASE THROUGH 2Z...ESPECIALLY ACROSS THE MTNS AND ALONG THE
FRONT. I WILL INDICATE THE CATE COVERAGE OF SHRA AND TSRA ACROSS THE
MTNS AND LIKELY TO CHC ALONG A WEAK COLD FRONT ACROSS THE NC
FOOTHILLS AND PIEDMONT.

GIVEN CAPES OF 1500-2500 J/KG AND MARGINAL WIND FIELDS...STORMS MAY
ORGANIZE IN CLUSTERS OR BROKEN LINES THROUGH THIS EVENING. SLOW WNW
STORM MOTIONS SHOULD KEEP COVERAGE LIMITED UNTIL OUTFLOWS BEGIN TO
INITIATE ADDITIONAL CONVECTION.  FREEZING LEVELS ARE FORECAST TO
REMAIN 13.5 TO 15.5 KFT THIS EVENING...ALLOWING ONLY THE LARGEST
STORMS TO PRODUCE HAIL. STORM STRUCTURE AND DCAPE VALUES AROUND 800
J/KG MAY SUPPORT STRONG TO SVR WINDS. IN ADDITION...PWS AROUND 1.5
INCHES AND K INDEX INT THE MID TO U30S MAY YIELD A FEW EXCESSIVE
RAINFALL EVENTS. WE WILL CONTINUE TO HIGHLIGHT THE SVR AND FF
POTENTIAL IN THE HWO.

TONIGHT...CONVECTION SHOULD DISSIPATE AROUND MIDNIGHT.
HOWEVER...DEBRIS CLOUDS AND HIGH CLOUDS WILL KEEP SIGNIFICANT CLOUD
COVER ACROSS THE CWA OVERNIGHT. RECENT RAINFALL MAY YIELD PATCHY FOG
LATE TONIGHT...ESPECIALLY WITHIN THE MTN VALLEYS. SOUTH WINDS AND
SKY COVER WILL PROMOTE ANOTHER NIGHT OF ABOVE NORMAL TEMPERATURES.

SUNDAY...MID LEVEL RIDGE WILL WEAKEN AS A TROF DIVES SOUTHEAST
ACROSS THE PLAINS. SFC LOW PRESSURE SHOULD TRACK SW TO NE ACROSS TN
AND KY...BRINGING MOIST AND UNSTABLE AIR ACROSS THE FORECAST AREA.
THE COMBINATION OF UNSTABLE AIR AND LIFT ASSOCIATED WITH THE LOW AND
PASSING WARM FRONT WILL RESULT IN HIGH SHRA/TSRA COVERAGE TOMORROW
AFTERNOON AND EVENING. I WILL FORECAST CATE POPS IN THE MTNS WITH LIKELY
EAST. SVR THREAT IS MARGINAL WITH LOWER CAPE AND HIGH FREEZING
HEIGHTS. HOWEVER...PW GREATER THAN 1.5 INCHES AND MID 30S K INDEX
FAVOR ANOTHER DAY OF HEAVY DOWNPOURS. THE GREATER COVERAGE FOLLOWING
TWO DAY OF DEEP CONVECTION COULD PROVIDE FAVORABLE CONDITIONS FOR
FLASH FLOODING.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AS OF 325 PM SATURDAY...STALLED FRONT REMAINS OVER THE AREA SUN NITE
AND MONDAY AS A COLD FRONT APPROACHES FROM THE WEST. SFC FEATURES
TAKE ON A CAD LOOK WITH SFC HIGH NOSING IN FROM THE NORTH. RIGHT
NOW...MDLS SHOWING THAT THE MAIN AREA OF CAD WILL BE NORTH OF THE
CWFA...BUT COULD CREEP DOWN INTO THE I-40 CORRIDOR. EITHER
WAY...THERE WILL BE QUITE A BIT OF LIFT AND DEEP MOISTURE OVER THE
AREA. THIS WILL LEAD TO WIDESPREAD SHOWERS AND SCT STORMS AS WEAK
INSTABILITY CONTINUES. RIGHT NOW...QPF AMOUNTS DO NOT APPEAR TO BE
EXCESSIVE. HOWEVER...GIVEN THE WEEKEND PRECIP...THIS WILL NEED TO BE
WATCHED. LOWS WILL BE WELL ABOVE NORMAL...WHILE HIGHS WILL BE NEAR
NORMAL. THAT SAID...HIGHS COULD BE BELOW NORMAL ACROSS THE NRN TIER
DEPENDING ON WHERE THE CAD SETS UP.

COLD FRONT CROSSES THE AREA MON NITE TAKING THE FOCUS FOR PRECIP
WITH IT. HOWEVER...PRECIP DOES NOT TAPER OFF UNTIL AFTER MIDNIGHT.
CANNOT RULE OUT SCT SHOWERS AND STORMS TUESDAY...BUT PRECIP SHOULD
END FROM WEST TO EAST DURING THE DAY. LOWS AND HIGHS NEAR NORMAL
BOTH PERIODS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 230 PM SATURDAY...FCST TRICKY EARLY IN THE MEDIUM RANGE AS
UPPER LOW SLOWLY MOVES EASTWARD ACROSS THE MID-ATLANTIC. THIS KEEPS
SOME MOISTURE AND ELY FLOW OVER THE AREA. THE MAIN THREAT FOR PRECIP
WILL BE TO OUR EAST...BUT THIS MOISTURE COULD BE CLOSE ENUF FOR
DIURNAL CONVECTION TO FORM. WITH CLOUDS AND ELY FLOW...LOWS WILL BE
NEAR NORMAL AND HIGHS BELOW NORMAL WED AND THU. A STORM SYSTEM
APPROACHES FROM THE WEST FRI AND SAT. THIS WILL KEEP THE THREAT OF
DIURNAL CONVECTION OVER THE AREA. HIGHS WILL RISE TO NEAR NORMAL
WITH LOWS REMAINING STEADY NEAR NORMAL.

&&

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
AT KCLT...AT 1730Z...VIS SAT WAS INDICATING ENHANCED CU ALONG AND
AHEAD OF A WEAK BACK DOOR COLD FRONT ACROSS THE CLT METRO AREA.
SHRA/TSRA SHOULD DEVELOP WITHIN THE BAND OF ENHANCED CU LATER THIS
AFTERNOON AND REMAIN INTO THE EVENING. I WILL MENTION A CB IN THE
SKY GROUP FROM 20Z UNTIL 2Z...OTHERWISE...CONVECTION CHC WILL NEED
TO BE MONITORED ON A RADAR SCAN TO SCAN BASIS. OUTSIDE OF THE
CONVECTION THREAT...CONDITIONS SHOULD REMAIN QUIET WITH LIGHT TO
CALM WINDS AND BKN MID TO HIGH SKY COVER.

ELSEWHERE...DEEP CONVECTION WILL BLOSSOM ACROSS THE MTNS AND
EVENTUALLY EAST ALONG AND AHEAD OF A WEAK BACK DOOR COLD FRONT. KAVL
AND KHKY WILL SEE THE GREATEST CHC FOR TSRA THIS AFTERNOON AND
EVENING. THE RAINFALL WILL FAVOR THE DEVELOPMENT OF FOG LATE
TONIGHT. OTHERWISE...WESTERN CAROLINA TERMINALS TAFS WILL FEATURE CB
IN THE SKY GROUP UNTIL 01-02Z. CONVECTION CHC WILL NEED TO BE
MONITORED ON A RADAR SCAN TO SCAN BASIS. OUTSIDE OF THE CONVECTION
AND FOG THREAT...CONDITIONS SHOULD REMAIN QUIET WITH LIGHT TO CALM
WINDS AND BKN MID TO HIGH SKY COVER.

OUTLOOK...A COLD FRONT WILL STALL OVER THE REGION INTO EARLY NEXT
WEEK...WITH CONVECTION ASSOCIATED RESTRICTIONS IN THE AREA DURING
THE AFTERNOONS AND EVENINGS...AND POSSIBLE FOG BASED MORNING
RESTRICTIONS WHERE IT RAINS.

&&

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

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
247 PM EDT SAT MAY 15 2010

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-161900-
RABUN-HABERSHAM-STEPHENS-FRANKLIN-HART-ELBERT-AVERY-ALEXANDER-
IREDELL-DAVIE-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-BUNCOMBE-CATAWBA-
ROWAN-GRAHAM-NORTHERN JACKSON-MACON-SOUTHERN JACKSON-TRANSYLVANIA-
HENDERSON-CLEVELAND-LINCOLN-GASTON-MECKLENBURG-CABARRUS-UNION NC-
CALDWELL MOUNTAINS-GREATER CALDWELL-BURKE MOUNTAINS-GREATER BURKE-
MCDOWELL MOUNTAINS-EASTERN MCDOWELL-RUTHERFORD MOUNTAINS-
GREATER RUTHERFORD-POLK MOUNTAINS-EASTERN POLK-OCONEE MOUNTAINS-
PICKENS MOUNTAINS-GREENVILLE MOUNTAINS-GREATER OCONEE-
GREATER PICKENS-GREATER GREENVILLE-SPARTANBURG-CHEROKEE-YORK-
ANDERSON-ABBEVILLE-LAURENS-UNION SC-CHESTER-GREENWOOD-
247 PM EDT SAT MAY 15 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST GEORGIA...PIEDMONT
NORTH CAROLINA...WESTERN NORTH CAROLINA AND UPSTATE SOUTH CAROLINA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

THUNDERSTORMS WILL INCREASE THROUGH MID EVENING AS A COLD FRONT
MOVES IN FROM THE NORTH. SOME STORMS WILL BECOME SEVERE WITH DAMAGING
WIND AND LARGE HAIL. IN ADDITION...SLOW MOVING STORMS COULD
PRODUCE AREAS OF EXCESSIVE RAINFALL.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

THUNDERSTORMS ARE EXPECTED AGAIN SUNDAY WITH THE APPROACH OF A LOW
PRESSURE SYSTEM. A FEW OF THESE STORMS COULD ALSO BECOME SEVERE WITH
DAMAGING WIND AND LARGE HAIL. SEVERAL OF THE STORMS WILL PRODUCE
VERY HEAVY RAINFALL...POSSIBLY RESULTING IN AREAS OF FLASH FLOODING.

.SPOTTER INFORMATION STATEMENT...

NONE.

NED

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