Special Weather Statement, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
453 PM EDT SAT JUL 21 2012

.SYNOPSIS...
A STATIONARY FRONT WILL REMAIN WEST TO EAST OVER THE REGION BEFORE
DISSIPATING EARLY IN THE WEEK. AS A WEAK RIDGE TRIES TO BUILD INTO
THE REGION FROM THE SOUTHEAST...A LEE TROF WILL DEVELOP AND REMAIN
ACROSS THE PIEDMONT THROUGH MUCH OF THE UPCOMING WEEK.

&&

.NEAR TERM /THROUGH SUNDAY/...
SO FAR THIS AFTERNOON...COVERAGE OF CONVECTION HAS BEEN LIMITED TO
WIDELY SCATTERED...EXCEPT FOR A SMALL AREA ACROSS THE SMOKIES AND
THE BALSAMS. WATER VAPOR SUGGESTS...AND THE LATEST SHORT RANGE MODEL
GUIDANCE CONFIRMS THAT A MID-LEVEL VORT MAX IS PUSHING INTO THE
CENTRAL CAROLINAS ATTM. THIS WOULD CERTAINLY EXPLAIN THE PALTRY
COVERAGE IN OUR AREA...AND THE NUMEROUS-WIDESPREAD COVERAGE TO OUR
EAST. NEVERTHELESS...COVERAGE IN OUR CWA IS GRADUALLY INCREASING.
WITH CAPE VALUES OF 2000-3000+ OVER THE AREA...I AM VERY HESITANT TO
BACK OFF POPS TOO MUCH FROM THE CURRENT 50-60 PERCENT FORECAST...
ESPECIALLY SINCE THERE MAY BE JUST ENOUGH LOW LEVEL SHEAR (AROUND 15
KT IN THE 0-3 KM LAYER) TO ALLOW FOR SOME CLUSTERING OF CELLS ALONG
OUTFLOW BOUNDARIES. THE BEST CHANCE FOR SEVERE WEATHER MAY BE ACROSS
OUR WESTERN ZONES...WHERE DRIER MID/UPPER LEVEL AIR IS BEGINNING TO
MAKE A PUSH. HOWEVER...AN ISOLATED SEVERE WEATHER EVENT WILL BE
POSSIBLE ANYWHERE...ESPECIALLY IF CELLS ARE ABLE TO ORGANIZE.

THE CONVECTION SHUD DIMINISH THRU THE EVENING AND END OVERNIGHT.
HOWEVER...A LINGERING SHOWER IS POSSIBLE AT ALMOST ANY TIME. SHUD BE
ANOTHER NIGHT OF DEVELOPING LOW CLOUDS AND PATCHY DENSE FOG. LOWS
SHUD BE NEAR TO SLIGHTLY ABOVE NORMAL.

RIDGE AXIS BUILDS OVER THE AREA SUNDAY DIMINISHING THE EFFECT OF THE
LINGERING SHORT WAVE ENERGY. UPPER JET WILL MOVE EAST OF THE AREA AS
WELL ENDING SIGNIFICANT DIVERGENCE. THE WEAK LOW LEVEL BOUNDARY WILL
CONTINUE TO WASH OUT...BUT THE REMNANTS OF THE BOUNDARY OR A
DEVELOPING LEE TROF WILL REMAIN IN PLACE. LOW LEVEL MOISTURE WILL
REMAIN QUITE HIGH...BUT DEEP MOISTURE WILL DIMINISH. THE ATMOS WILL
REMAIN UNSTABLE...SO CONVECTION SHUD REDEVELOP. HOWEVER...COVERAGE
SHUD BE LESS THAN PREVIOUS DAYS. HAVE SCT CONVECTION GENERALLY ALONG
AND NORTH OF I-85 AND ISOLATED TO THE SOUTH. HIGHS WILL REBOUND BACK
TO NEAR TO SLIGHTLY ABOVE NORMAL.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AS OF 230 PM SATURDAY...THE FRONTAL BOUNDARY IS EXPECTED TO REMAIN
NORTH OF THE APPALACHIANS AS UPPER RIDGE OF HIGH STRAIGHTENS OVER
THE REGION MON/TUE. THE COMBINATION OF MODERATE DIURNAL
INSTABILITY...WITH CAPE VALUES IN THE 1500 TO 2000 J/KG
RANGE...LITTLE CAPPING INVERSION AND RELATIVELY HIGH PW VALUES WILL
SUPPORT AFTERNOON SCATTERED THUNDERSTORMS EACH DAY. WITH WEAK MEAN
FLOW ALOFT IN A MOIST ENVIRONMENT....STORMS WILL MOVE SLOWLY AND
PRODUCE HEAVY RAINFALL WHICH COULD RESULT IN LOCALIZED FLOODING.
HENCE...WILL FORECAST DIURNAL POPS IN THE 30S ACROSS MUCH OF OUR CWA
EACH DAY. TEMPERATURES WILL REMAIN A COUPLE DEGREES ABOVE SEASONAL
AVERAGES WITH HIGHS IN THE LOW TO MID 90S ACROSS THE PIEDMONT.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 200 PM SATURDAY...THE LATEST MEDIUM RANGE MODELS CONTINUE TO
INDICATE THAT A FRONTAL BOUNDARY OVER THE OHIO VALLEY DROPS SOUTH
ACROSS THE REGION AS AN UPPER TROUGH DEEPENS ACROSS THE MID ATLANTIC
REGION WEDNESDAY. THEN THE LATEST GFS KEEPS THE FRONT STALLED OUT
OVER THE REGION THROUGH MUCH OF THE EXTENDED FORECAST PERIOD WHILE
THE ECMWF PUSHES THE FRONT BACK TO THE NORTH ON THURSDAY AS A WEAK
UPPER RIDGE BUILDS ACROSS THE SOUTHEAST. BY NEXT WEEKEND...BOTH GFS
AND ECMWF SUGGEST THAT ANOTHER UPPER TROUGH DEVELOPS ACROSS THE
GREAT LAKES INTO THE MID ATLANTIC REGION...RESULTING IN SECONDARY
FRONT SLIDING SOUTH INTO THE REGION. WITH HIGH PW VALUES AND GOOD
DIURNAL INSTABILITY...WILL SEE SCATTERED AFTERNOON CONVECTION EACH
DAY. TEMPERATURES WILL REMAIN NEAR SEASONAL AVERAGES WITH HIGHS IN
THE LOW 90S ACROSS THE PIEDMONT THROUGH THE PERIOD.

&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
AT KCLT...MVFR SHUD BE LOW VFR BY 19Z. TSRA SHUD HOLD OFF UNTIL THEN
AS WELL. THAT SAID...ANOTHER AFTERNOON/EARLY EVENING OF NUMEROUS
TSRA EXPECTED. HAVE GONE PREVAILING VFR TSRA UNTIL 01Z THEN TEMPS
MVFR TSRA UNTIL 04Z. WILL AMD AS CELLS APPROACH THE AIRFIELD. IFR
CIGS AND MVFR VSBY EXPECTED AGAIN BY DAYBREAK. SHUD BE QUICKER TO
LIFT TO VFR SUN MORN AS FLOW WILL HAVE LESS OF AN UPSLOPE COMPONENT
WITH ONLY A MINOR LOW LEVEL INVERSION. WINDS WILL GENERALLY BE SW
THRU THE PERIOD WITH A NORMAL DIURNAL SPEED TREND.

ELSEWHERE...VFR EXPECTED THRU THE EVENING XCPT WHEN ONE OF THE
NUMEROUS TSRA MOVE ACROSS AN AIRFIELD. WILL AMD AS NEEDED FOR
CONVECTION. SWLY WIND WITH SOME LOW END GUSTS THRU THE AFTERNOON
BECOMING LIGHT SW FOR THE EVENING. CONVECTION WILL LINGER BUT
DIMINISH THRU THE EVENING AND END AROUND MIDNIGHT. IFR TO MVFR CIGS
AND VSBY EXPECTED BY DAYBREAK. SHUD BE QUICKER TO LIFT SUN MORNING
AS FLOW WILL HAVE LESS OF AN UPSLOPE COMPONENT WITH ONLY A MINOR LOW
LEVEL INVERSION. LIGHT WINDS OVERNIGHT BECOME WSW DURING THE MORNING.

OUTLOOK...AS A COLD FRONT STALLS OVER THE AREA...SCATTERED
CONVECTION EXPECTED SUNDAY AFTERNOON. LATE NIGHT/MORNING FOG AND LOW
STRATUS PROBABILITIES WILL ALSO REMAIN FAIRLY HIGH...ESPECIALLY IN
THE MTN VALLEYS. THUNDERSTORMS WILL BECOME LESS NUMEROUS AS THE
BERMUDA HIGH BUILDS INTO THE REGION DURING THE FIRST PART OF THE
WEEK.

AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE
PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE
CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)...

WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM

&&

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

&&

SYNOPSIS...PAT
NEAR TERM...JDL/RWH
SHORT TERM...JOH
LONG TERM...JOH
AVIATION...RWH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1238 PM EDT SAT JUL 21 2012

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-221645-
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-
1238 PM EDT SAT JUL 21 2012

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

NUMEROUS THUNDERSTORMS WILL CONTINUE TO DEVELOP AND MOVE SLOWLY
ACROSS THE AREA THIS AFTERNOON AND EVENING. THE STRONGEST STORMS
HAVE THE POTENTIAL TO PRODUCE SMALL AREAS OF DAMAGING DOWNBURST
WINDS. LARGE HAIL IS POSSIBLE BUT LESS LIKELY. STRONG GUSTY WINDS
AND CLOUD TO GROUND LIGHTNING ARE POSSIBLE WITH ANY STORM. LOCALLY
HEAVY RAINFALL IS LIKELY...AND COULD LEAD TO FLOODING...ESPECIALLY
LOCATIONS WHERE STORMS REPEATEDLY MOVE OVER.

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTERS ARE REQUESTED TO FORWARD ANY REPORTS OF LARGE
HAIL...DAMAGING WINDS...TORNADOES OR FLASH FLOODING TO OUR OFFICE.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
629 PM EDT SAT JUL 21 2012

NCZ036-037-057-212300-
DAVIE-IREDELL-ROWAN-
629 PM EDT SAT JUL 21 2012

...A STRONG THUNDERSTORM WILL AFFECT EASTERN IREDELL...NORTHWESTERN
ROWAN AND SOUTHWESTERN DAVIE COUNTIES THROUGH 700 PM EDT...

AT 629 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 7 MILES NORTHWEST OF CLEVELAND...OR 7 MILES EAST
OF STATESVILLE...MOVING NORTHEAST AT 10 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  CLEVELAND...

PEA SIZE HAIL...WIND GUSTS UP TO 40 MPH AND TORRENTIAL RAIN ARE
EXPECTED WITH THIS STORM.

LAT...LON 3598 8060 3577 8049 3569 8081 3585 8090

HG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
650 PM EDT SAT JUL 21 2012

NCZ035-056-502-504-212315-
ALEXANDER-CATAWBA-GREATER BURKE-GREATER CALDWELL-
650 PM EDT SAT JUL 21 2012

...A STRONG THUNDERSTORM WILL AFFECT EASTERN BURKE...NORTHERN
CATAWBA...SOUTHEASTERN CALDWELL AND WESTERN ALEXANDER COUNTIES
THROUGH 715 PM EDT...

AT 650 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR SAWMILLS...OR 8 MILES SOUTH OF LENOIR...
MOVING NORTHEAST AT 15 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  GRANITE FALLS...
  LAKE HICKORY...

PEA SIZE HAIL...TORRENTIAL RAINFALL...WIND GUSTS UP TO 40 MPH AND
FREQUENT LIGHTNIG ARE EXPECTED WITH THIS STORM.

LAT...LON 3600 8127 3579 8116 3568 8153 3585 8162

HG

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
710 PM EDT SAT JUL 21 2012

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0700 PM     FLASH FLOOD      LONGVIEW                35.73N 81.38W
07/21/2012                   CATAWBA            NC   COUNTY OFFICIAL

            FIRE DEPT REPORTS FLOODING OF AN APARTMENT COMPLEX ON
            18TH ST IN LONGVIEW.

&&

LANE

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