Damaging Winds in North Carolina, April 11 to 12, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1032 PM EDT MON APR 11 2011

.SYNOPSIS...
A COLD FRONT WILL APPROACH THE AREA TONIGHT AND CROSS TO THE EAST
THROUGH TUESDAY. HIGH PRESSURE WILL THEN BUILD IN TUESDAY NIGHT AND
PERSIST INTO THURSDAY. ANOTHER COLD FRONT WILL APPROACH FROM THE
WEST TOWARD THE END OF THE WEEK.

&&

.NEAR TERM /THROUGH TUESDAY/...
AT 1030 PM...LATEST RADAR COMPOSITE INDICATED A LINE OF SHOWERS AND
THUNDERSTORMS ACROSS NRN GA. THE CONVECTION WILL MOVE EAST THIS
EVENING...REACHING EXTREME WESTERN NC AND NE GA BETWEEN 11 PM AND
MIDNIGHT...TRACKING ACROSS THE NC MTNS AND THE UPSTATE OF SC BETWEEN
MIDNIGHT AND 3 AM.

IT APPEARS THAT THE STRONGEST LINE SEGMENTS WILL PUSH ACROSS THE
UPPER SAVANNAH RIVER VALLEY AND THE SC UPSTATE. LLVL WIND FIELDS AND
SHEAR WILL REMAIN MODERATE TO STRONG ALONG AND AHEAD OF THE
CONVECTION...KEEPING THE LINEAR STRUCTURE INTACT.
HOWEVER...INSTABILITY WILL REMAIN LOW ACROSS THE CWA...WITH LIMITED
CAPE EXPECTED ACROSS THE SAVANNAH RIVER VALLEY THROUGH 3 AM. WIND WILL
BE THE PRIMARY SEVERE THREAT...ONLY SMALL HAIL APPEARS POSSIBLE AT
THIS TIME.

IN ADDITION...I WILL INCREASE POPS AND TSRA CHC FOR TUESDAY
AFTERNOON ACROSS THE PIEDMONT AND LOWER HIGH A DEGREE. STEEPER LAPSE
RATES AND PASSING SFC FRONT SHOULD TRIGGER A FEW STORMS.
OTHERWISE...QG FORCING AND DEEPER MOISTURE WILL SUPPORT CLUSTERS OF
SHRA AND WIDESPREAD CLOUD COVER THROUGH THE AFTERNOON
HOURS...ESPECIALLY ACROSS THE WESTERN CAROLINAS.

PREVIOUS DISCUSSION...

TUESDAY...GUIDANCE HAS TRENDED SLOWER AND A LTL SOUTH WITH THE UPPER
LOW AND EVEN KEEPS ENUF MOISTURE AND LIFT FOR SCATTERED SHWRS ACRS
THE I-77 CORRIDOR INTO EARLY AFTN. HOWEVER...THE MAIN CHC OF PRECIP
WILL BE CONFINED TO THE TN BORDER AS NW FLOW MOISTURE WILL BE FAIRLY
DEEP AND UPSLOPE FORCING IS DECENT. TEMPS WILL BE TOO WARM FOR
ANYTHING BUT RAIN IN THE MTNS THRU TUESDAY AFTN. TEMPS OUTSIDE THE
MTNS WILL BE MAINLY IN THE LWR-MID 70S...BUT POSSIBLY A TAD COOLER
IF THERE IS MORE CLOUDINESS WITH THE UPR LOW.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
AS OF 230 PM MONDAY...THE UPPER LOW IS EXPECTED TO PULL AWAY SLOWLY
TUESDAY NIGHT. NW FLOW SHOWER PRODUCTION WILL GRADUALLY DIMINISH
AFTER SUNSET AND MOISTURE WILL PULL OUT BY AROUND SUNRISE ON
WEDNESDAY. FEW CHANGES WERE MADE TO THE PRECIP CHANCES...WHICH ARE
MAINLY OVER THE NORTHERN MTNS. TEMPS WILL COOL OFF INTO THE LOW TO
MIDDLE 30S. ONLY ELEVATIONS ABOVE ABOUT 4500 FEET SHOULD DROP BELOW
FREEZING. ALTHO THE VALLEYS WILL BE COOL ENOUGH FOR FROST...THE WIND
SHOULD STAY UP FROM THE NW AROUND 10 KT ENOUGH TO KEEP FROST FROM
BECOMING WIDESPREAD.

AFTER THE LOW MOVES AWAY...AN UPPER RIDGE WILL BUILD SLOWLY OVER THE
WESTERN CAROLINAS ON WEDNESDAY AND THURSDAY...SUPPORTING SURFACE
HIGH PRESSURE MOVING OVER THE SOUTHEAST. THIS WILL GIVE US TWO
FAIRLY QUIET DAYS DURING THE MIDDLE OF THE WEEK. TEMPS WERE
GENERALLY NUDGED TOWARD THE MAV GUIDANCE.

WE SHOULD BEGIN TO FEEL THE AFFECTS OF THE NEXT SYSTEM ON THURSDAY
NIGHT. A STRONG SHORT WAVE WILL CLOSE OFF AN UPPER LOW OVER THE
PLAINS...WHICH IN TURN PROVIDES FOR THE DEVELOPMENT OF UPPER
DIFLUENCE OVER THE SOUTHEAST AND CAROLINAS. THE GULF SHOULD OPEN UP
WITH HIGH PRESSURE OFF THE SOUTHEAST COAST. EXPECT SOME MOISTURE
RETURN AT LOW LEVELS BY FRIDAY MORNING. HOWEVER...THINK THE GUIDANCE
IS BEING OVERZEALOUS AS USUAL...SO HAVE OPTED TO KEEP MOST OF THE
NIGHTTIME PERIOD FREE OF PRECIP. TEMPS SHOULD BE MILD WITH THE
INCREASING CLOUDS AND WARM ADVECTION...SO THE MUCH WARMER HPC
NUMBERS WERE FAVORED.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 220 PM MONDAY...DECENT AGREEMENT IS SEEN IN THE OP MODELS WRT
TO THE TIMING OF THE COLD FRONT FRI. THE CMC IS A BIT OF NRN OUTLIER
WITH THE UPPER LEVEL LOW...HOWEVER THE ECWMF AND THE GFS HAVE COME
INTO DECENT AGREEMENT WITH THE SYNOPTIC FEATURES AND THE OVERALL
CONFIDENCE IS GOOD WITH THE EXPECTED ONSET AND TIMING OF THE FROPA.

THE DIFFERENCES LIE WITH THE AMOUNT OF FORCING AVAILABLE. THE GFS
SFC LOW IS SUPPORTED MORE DYNAMICALLY WITH A NEG TILT H5 LOW AND
BETTER ULVL DIV. THIS SLOWS THE GFS DOWN A LITTLE MORE THAN THE
ECMWF AND ALLOWS AN INSITU SFC HIGH AHEAD OF THE SYSTEM TO PERSIST
LONGER AND MAINTAIN A E/LY LLVL WIND FIELD...THUS THE AMOUNT OF SFC
BASED INSTABILITY AVAILABLE. THE ECWMF IS MORE UNSTABLE WITH BL
WINDS DEVELOPING S/LY EARLY FRI AND THIS WILL BE GIVEN MORE WEIGHT.

IT/S JUST HARD TO BELIEVE THE ATMOS WILL NOT BE UNSTABLE AT ALL
AHEAD OF A DAYTIME FRONTAL PASSAGE THIS TIME OF YEAR. SO...THE GRIDS
WERE MAINTAINED WITH TS ACTIVITY BEGINNING EARLY FRI...SHIFTING EAST
THROUGHOUT THE DAY. EXPECT A QUICK MOVING DRY SLOT TO PUSH IN FRI
NIGHT AS THE UPPER LOW REMAINS CUTOFF. VERY GOOD BULK SHEAR AND 50+
KT H85 JET WILL AIDE IN A STRONG TO SEVERE POTENTIAL AS THE TRIPLE
POINT LOW MOVES INTO THE WRN ZONES AROUND 06Z SAT. SO...SOME
ORGANIZED QLCS IS THE MOST LIKELY STORM MODE AHEAD OF THIS SYSTEM.
SUPERCELL DEVELOPMENT IS NOT LIKELY DUE TO A MOIST COLUMN AND LACK
OF HIGH END SBCAPE...HOWEVER A LOW END HYDRO EVENT IS POSSIBLE WITH
PW/S APPROACHING 1.25 INCHES FOR SEVERAL HOURS. TOTAL QPF FOR THE
EVENT COULD NEAR 2 INCHES ACROSS THE NC MTNS WHERE STREAMS AND SMALL
RIVERS MAY FLOOD OR REACH BANKFULL.

HIGH PRESSURE BUILDS IN SAT AND AN AIRMASS CHANGE/MIX WILL PUSH IN
SAT NIGHT. THERE MAY BE A BRIEF PERIOD OF -SNSH ACROSS THE NC MTN
SPINE IN COLD WRAP AROUND MOISTURE...HOWEVER CONFIDENCE AND POPS ARE
LOW RIGHT NOW TO INCLUDE IN THE FCST. MAX TEMPS WILL START OUT FRI A
FEW DEGREES ABOVE NORMAL...AND BY SUN HIGHS SHOULD ONLY REACH A FEW
DEGREES BELOW NORMAL. A SRN STREAM SYSTEM IS PROJECTED TO DEVELOP
LATE SUN NIGHT ACROSS THE NRN GOM...BUT THE TIMING AND STRENGTH OF
THIS SYSTEM STILL NEED TO BE IRONED OUT...SO SILENT SLIGHT POPS WERE
INTRODUCED FOR MON.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
AT KCLT AND ELSEWHERE...GUSTY SW WNDS WILL CONTINUE UNTIL 1Z...THEN
SW WINDS WILL REMAIN IN THE LOW TEENS AHEAD OF THE APPROACHING COLD
FRONT. SATELLITE AND RADAR TRENDS INDICATE THAT BEST CONVECTIVE
STRUCTURE REMAINS GENERALLY ACROSS THE DEEP SOUTH NORTH TO THE TN
LINE. THE REMNANT PORTION OF THIS LINE SHOULD CROSS THE UPPER
SAVANNAH RIVER VALLEY LATE THIS EVENING AND ACROSS THE PIEDMONT LATE
TONIGHT. ELSEWHERE...EXPECTING CLUSTERS OF SHRA WITH EMBEDDED TSRA
LATE TONIGHT. THE ARRIVAL OF SHRA/TSRA SHOULD BRING LOWER
CEILINGS...POSSIBLY MVFR. MVFR CONDITIONS SHOULD REMAIN UNTIL
SUNRISE...THE CEILINGS MAY SCT OR LIFT TO VFR. WEST-SOUTHWEST WINDS
SHOULD BECOME GUSTY SHORTLY AFTER SUNRISE...VEERING NORTHWEST AND
INCREASING AFTER THE EARLY AFTERNOON PASSAGE OF THE COLD FRONT.
DEEPER MOISTURE AND CAA WILL SPREAD ACROSS THE CWA DURING THE LATE
AFTERNOON...POSSIBLE A THIN LINE OF TSRA ALONG THE FRONT. I WILL
INDICATE VCSH AND SHRA FOR NOW. LATE AFTERNOON CEILINGS ACROSS THE
MTNS AND FOOTHILLS MAY FALL TO LMVFR

OUTLOOK...DRIER HIGH PRES IS EXPECTED TUE AND WED. CONDITIONS BECOME
UNSETTLED AHEAD OF THE NEXT SYSTEM THU THROUGH FRI.

&&

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

&&

SYNOPSIS...SBK
NEAR TERM...NED/ARK
SHORT TERM...PM
LONG TERM...SBK
AVIATION...NED

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1018 PM EDT MON APR 11 2011

GAZ010-017-018-026-028-029-NCZ033-048>053-058-059-062>065-SCZ001>007-
010>012-019-130230-
RABUN-HABERSHAM-STEPHENS-FRANKLIN-HART-ELBERT-AVERY-MADISON-YANCEY-
MITCHELL-SWAIN-HAYWOOD-BUNCOMBE-GRAHAM-NORTHERN JACKSON-MACON-
SOUTHERN JACKSON-TRANSYLVANIA-HENDERSON-OCONEE MOUNTAINS-
PICKENS MOUNTAINS-GREENVILLE MOUNTAINS-GREATER OCONEE-
GREATER PICKENS-GREATER GREENVILLE-SPARTANBURG-ANDERSON-ABBEVILLE-
LAURENS-GREENWOOD-
1018 PM EDT MON APR 11 2011

...TORNADO WATCH 132 IN EFFECT UNTIL 3 AM EDT TUESDAY...

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

.DAY ONE...TONIGHT.

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   TORNADO WATCH.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

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.

NCZ035>037-056-057-068>072-082-501>510-SCZ008-009-013-014-130230-
ALEXANDER-IREDELL-DAVIE-CATAWBA-ROWAN-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-
CHEROKEE-YORK-UNION SC-CHESTER-
1018 PM EDT MON APR 11 2011

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

.DAY ONE...TONIGHT.

A COLD FRONT WILL CROSS THE AREA FROM THE WEST TONIGHT...
ACCOMPANIED BY THUNDERSTORMS. SOME OF THESE THUNDERSTORMS MAY BE
SEVERE...PRODUCING DAMAGING WIND...AND PERHAPS LARGE HAIL.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

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.