Flash Flooding and Hail in North Carolina, May 16, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
254 PM EDT SAT MAY 16 2009

.SYNOPSIS...
A COLD FRONT WILL MOVE EAST FROM THE MISSISSIPPI VALLEY TOWARDS THE
CAROLINAS TONIGHT. THIS FRONT WILL MOVE ACROSS THE AREA EARLY
SUNDAY. HIGH PRESSURE WILL BUILD IN FROM THE NORTH SUNDAY NIGHT AND
REMAIN OVER THE AREA INTO MID WEEK.

&&

.NEAR TERM /THROUGH SUNDAY/...
SHOWERS HAVE BECOME NUMEROUS ACROSS THE PIEDMONT THIS AFTERNOON...
BUT COVERAGE REMAINS RATHER SPARSE OVER THE MTNS/FHILLS. THE
INTERESTING FALLOUT FROM THIS IS THAT THE AIRMASS HAS BECOME QUITE
UNSTABLE ACROSS THE MTNS...WITH SPC MESOANALYSIS INDICATING CAPE IN
EXCESS OF 2000 J/KG AS OF 18Z. WITH THIS DEGREE OF DESTABILIZATION
AND PWATS IN EXCESS OF 150 PERCENT OF NORMAL...EXPECT COVERAGE TO
INCREASE SUBSTANTIALLY ACROSS THE MTNS THIS AFTERNOON. AS A COLD
FRONT DROPS INTO THE REGION FROM THE TENN VALLEY THIS EVENING...
COVERAGE OF CONVECTION SHOULD EXPAND TO CATEGORICAL ACROSS MUCH OF
THE AREA. WE STILL HAVE LINGERING CONCERNS ABOUT THE POTENTIAL FOR
FLASH FLOODING TONIGHT...ESPECIALLY ACROSS THE MTNS. HOWEVER...
CONSIDERING THE ABSENCE OF GOOD COVERAGE ATTM...AND THE FACT THAT
RAINFALL TONIGHT WILL BE AN ALMOST EXCLUSIVELY CONVECTIVE PHENOMENA
(DIFFICULT TO PINPOINT WHERE THE HEAVIEST RAIN WILL OCCUR)...WE
STILL BELIEVE THAT ANY FLOODING WILL BE LOCALIZED IN NATURE...AND DO
NOT PLAN TO ISSUE A FLOOD WATCH ATTM.

THE FRONT WILL PUSH SOUTH OF THE AREA EARLY SUNDAY...WITH PLENTY OF
MOISTURE LINGERING JUST NORTH OF THE BOUNDARY. THEREFORE...HIGH POPS
WILL BE MAINTAINED ACROSS ROUGHLY THE SOUTHERN HALF OF THE AREA.
WITH CANADIAN HIGH PRESSURE BUILDING INTO THE REGION...AND LINGERING
LOW CLOUDS AND PRECIP...MAX TEMPS SUNDAY AFTERNOON ARE EXPECTED TO
BE MUCH BELOW NORMAL.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AS OF 230 PM SATURDAY...MODELS IN GOOD AGREEMENT ON MOISTURE AND
PRECIP RAPIDLY MOVING SOUTHEAST OF THE AREA SUN NITE. KEEP FAIRLY
HIGH POP ACROSS THE SRN CWFA UNTIL MIDNIGHT...THEN QUICKLY DROP
PRECIP. EXPECT CLOUDS TO TAKE A SIMILAR TREND WITH STRONG DRYING
MOVING IN. LOWS WILL BE QUITE COOL SUN NITE AS MUCH COLDER AIR MASS
MOVES IN...AROUND 15 DEGREES COOLER THAN THE PREV NITE AND 10 TO 15
DEGREES BELOW NORMAL. WINDS DO BECOME LIGHT ACROSS THE MTNS WITH
FALLING DEW POINTS. WILL HAVE TO WATCH FOR THE POSSIBILITY OF FROST.
HIGH PRESSURE BUILDS IN TO THE NORTH WITH DRY COOL AIR MASS
REMAINING. EXPECT A BREEZY DAY MONDAY WITH A DECENT PRESSURE
GRADIENT ACROSS THE AREA. HIGHS 10 TO 15 DEGREES BELOW NORMAL.
EXPECT A BETTER RADIATIONAL NIGHT MON NITE WITH LITTLE WIND. HOWEVER
AIR MASS WILL HAVE MODERATED. LOOKS LIKE A GOOD CASE FOR NEGATIVE
LAPSE RATE OVER THE MTNS...MAKING RIDGES WARMER THAN VALLEYS.
THEREFORE...WILL HAVE TO WATCH FOR FROST IN THE VALLEYS THEN. LOWS
NEARLY STEADY TO SLIGHTLY WARMER IN THE THERMAL BELT AREAS AND
RIDGES. DRY AND MODERATING HIGH PRESSURE REMAINS RIDGED INTO THE
AREA TUESDAY. HIGHS 5 TO 10 DEGREES WARMER...BUT STILL BELOW NORMAL.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 210 PM SATURDAY...MODELS REMAIN INCONSISTENT WITH THEIR
PLACEMENT OF FEATURES DURING THE MEDIUM RANGE. THEY AGREE TO SOME
AMOUNT OF RIDGING BOUNDED BY A NRN STREAM SYSTEM AND SRN CLOSED LOW.
THE GFS CONTINUES TO KEEP THE RIDGING CENTERED NEAR THE OH VALLEY
AND CENTRAL APLCNS...WHILE THE ECMWF HAS THE RIDGING OVER THE TN
VALLEY AND SRN APLCNS. THIS MEANS THE GFS BEGINS WITH THE CLOSED
UPPER LOW AND SFC DEVELOPMENT MUCH FARTHER NORTH IN THE GULF OF
MEXICO...WHILE THE ECMWF STARTS OFF FARTHER SOUTH. BOTH MODELS MOVE
THE LOW...AND ITS ASSOCIATED MOISTURE...NORTH TO THE COAST.
HOWEVER..THE GFS IS AS MUCH AS 36 HRS FASTER. NATURALLY THERE IS
QUITE A BIT OF SPREAD IN THE ENSEMBLES. THE GFS HAS SOME SUPPORT
FROM THE UKMET AND CANADIAN GLOBAL MODELS. HOWEVER...THE ECMWF HAS
BEEN THE BETTER PERFORMER WITH TROPICAL TYPE LOWS THE PAST TWO
YEARS. THEREFORE...WILL TREND TOWARD THE ECMWF SOLN FOR NOW. THIS
MEANS A DRY FCST WITH A WARMING TREND UNTIL FRI. INTRODUCED SLIGHT
CHC POP FOR NOW FOR FRI AND SAT...WITH NEARLY STEADY TEMPS.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
SOMEWHAT COMPLEX AVIATION FORECAST THIS PERIOD...AS COMBINATION OF
SEMI-TROPICAL AIRMASS AND APPROACHING COLD FRONT WILL RESULT IN
NUMEROUS TO WIDESPREAD SHOWERS AND STORMS THROUGH MUCH OF THE
PERIOD. TEMPOS FOR CONVECTION WILL BE CARRIED AT MOST TERMINALS THIS
AFTERNOON. IN FACT...AS OF 1730Z...ALL TERMINALS EXCEPT KHKY HAVE A
SHOWER OR TS IN THE VCNY. ALTHOUGH COVERAGE OF TS IS QUITE LIMITED
ATTM...EXPECT THUNDER TO BECOME MORE COMMON LATER THIS AFTERNOON...
AS THE LOWER ATM CONTINUES TO WARM/DESTABILIZE. MVFR CIGS/VISBY WILL
ACCOMPANY MOST SHOWER ACTIVITY...WHILE IFR VISBY WILL BE LIKELY WITH
HEAVIER BURSTS OF RAINFALL. WE EXPECT COVERAGE OF SHOWERS AND STORMS
TO INCREASE OVERNIGHT...AS THE COLD FRONT MOVES IN FROM THE TENN
VALLEY. THEREFORE...CATEGORICAL SHRA WILL BE CARRIED AT ALL
TERMINALS BEGINNING LATE IN THE EVENING. OTHERWISE...IFR/LOW MVFR
CIGS SHOULD BECOME WIDESPREAD ACROSS THE AREA BY MIDNIGHT OR SO.

THE COLD FRONT SAGS SOUTH OF THE AREA ON SUNDAY...TURNING THE WINDS
AROUND TO THE NORTH/NORTHEAST. HOWEVER...LINGERING MOISTURE NORTH OF
THE FRONT WILL ALLOW SHOWER CHANCES TO CONTINUE THROUGH THE END OF
THE PERIOD...ESPECIALLY ALONG THE I-85 CORRIDOR.

OUTLOOK...VFR CONDITIONS ARE EXPECTED TO RETURN SUNDAY NIGHT AND FOR
SEVERAL DAYS THEREAFTER...THOUGH MOISTURE MAY NOT BE TOO FAR OFF TO
OUR SOUTHEAST ALONG THE STALLING FRONT.

&&

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

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
355 PM EDT SAT MAY 16 2009

GAZ010-017-NCZ033-048>053-058-059-062>065-501-503-505-507-509-
SCZ001>003-172000-
RABUN-HABERSHAM-AVERY-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-BUNCOMBE-
GRAHAM-NORTHERN JACKSON-MACON-SOUTHERN JACKSON-TRANSYLVANIA-
HENDERSON-CALDWELL MOUNTAINS-BURKE MOUNTAINS-MCDOWELL MOUNTAINS-
RUTHERFORD MOUNTAINS-POLK MOUNTAINS-OCONEE MOUNTAINS-
PICKENS MOUNTAINS-GREENVILLE MOUNTAINS-
355 PM EDT SAT MAY 16 2009

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

SCATTERED SHOWERS AND THUNDERSTORMS WILL BECOME MORE NUMEROUS OVER
THE MOUNTAINS OF THE WESTERN CAROLINAS AND NORTHEAST GEORGIA
THROUGH THE EVENING. ISOLATED AREAS OF LOCALLY HEAVY RAIN WILL
BECOME MORE WIDESPREAD THROUGH THE EVENING AS WELL. STORMS WILL
BE SLOW MOVING AND A FEW INSTANCES OF FLASH FLOODING ARE
POSSIBLE...MAINLY THIS EVENING. AN ISOLATED MICROBURST OR LARGE HAIL
REPORT IS ALSO POSSIBLE.

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

TEMPERATURES SUNDAY NIGHT WILL BECOME COLD ENOUGH FOR FROST
OVER THE HIGHER ELEVATIONS...WHILE TEMPERATURES COLD ENOUGH FOR
FROST WILL OCCUR IN THE VALLEYS ON MONDAY NIGHT. RIGHT NOW IT IS
STILL TO EARLY TO TELL IF WINDS WILL BECOME LIGHT ENOUGH FOR
SIGNIFICANT FROST DEVELOPMENT.

.SPOTTER INFORMATION STATEMENT...

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

GAZ018-026-028-029-NCZ035>037-056-057-068>072-082-502-504-506-508-
510-SCZ004>014-019-172000-
STEPHENS-FRANKLIN-HART-ELBERT-ALEXANDER-IREDELL-DAVIE-CATAWBA-ROWAN-
CLEVELAND-LINCOLN-GASTON-MECKLENBURG-CABARRUS-UNION NC-
GREATER CALDWELL-GREATER BURKE-EASTERN MCDOWELL-GREATER RUTHERFORD-
EASTERN POLK-GREATER OCONEE-GREATER PICKENS-GREATER GREENVILLE-
SPARTANBURG-CHEROKEE-YORK-ANDERSON-ABBEVILLE-LAURENS-UNION SC-
CHESTER-GREENWOOD-
355 PM EDT SAT MAY 16 2009

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 SHOWERS AND THUNDERSTORMS WILL CONTINUE OVER THE
FOOTHILLS AND PIEDMONT OF THE WESTERN CAROLINAS AND NORTHEAST
GEORGIA THROUGH THE EVENING. AREAS OF LOCALLY HEAVY RAIN WILL
OCCUR. STORMS WILL BE SLOW MOVING AND A FEW INSTANCES OF FLASH
FLOODING ARE POSSIBLE. THE FLASH FLOOD THREAT MAY ACTUALLY
INCREASE THIS EVENING. AN ISOLATED MICROBURST OR LARGE HAIL
REPORT IS ALSO POSSIBLE.

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

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.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
413 PM EDT SAT MAY 16 2009

NCZ033-501-502-162115-
AVERY-CALDWELL MOUNTAINS-GREATER CALDWELL-
413 PM EDT SAT MAY 16 2009

...STRONG THUNDERSTORMS WITH VERY HEAVY RAINFALL TO AFFECT EASTERN
AVERY AND NORTHWESTERN CALDWELL COUNTIES THROUGH 515 PM EDT...

AT 409 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
ANOTHER IN A SERIES OF STRONG THUNDERSTORMS MOVING EASTWARD TOWARD
THE BORDER BETWEEN AVERY AND CALDWELL COUNTIES. THIS THUNDERSTORM
WAS LOCATED 5 MILES EAST OF NEWLAND...MOVING EAST AT 10 MPH.

THE THUNDERSTORM IS FOLLOWING THE TRACK OF SEVERAL PREVIOUS STORMS
THAT PRODUCED RAINFALL TOTALS IN EXCESS OF TWO INCHES ACROSS THE
AREA IN THE PAST HOUR. VERY HEAVY RAINFALL IS EXPECTED FROM SUGAR
MOUNTAIN TO UPTON THROUGH 5 PM. RAPID RISES ON AREA STREAMS AND
CREEKS CAN BE EXPECTED...AS WELL AS DEEP STANDING WATER DEVELOPING
IN LOW SPOTS IN ROADWAYS.

HG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
432 PM EDT SAT MAY 16 2009

SCZ012-019-162100-
GREENWOOD-LAURENS-
432 PM EDT SAT MAY 16 2009

...STRONG THUNDERSTORMS WILL AFFECT GREENWOOD AND SOUTHWESTERN
LAURENS COUNTIES THROUGH 500 PM EDT...

AT 430 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM 3 MILES SOUTHEAST OF
WARE SHOALS TO 7 MILES SOUTH OF ABBEVILLE...MOVING EAST AT 10 MPH.

THESE STORMS WILL AFFECT THE COKESBURY AND GREENWOOD AREAS THROUGH 5
PM. PEA SIZE HAIL...WIND GUSTS OF 30 TO 40 MPH...AND TORRENTIAL
RAINFALL ARE EXPECTED WITH THESE STORMS.

HG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
511 PM EDT SAT MAY 16 2009

NCZ065-162145-
HENDERSON-
511 PM EDT SAT MAY 16 2009

...A STRONG THUNDERSTORM WILL AFFECT HENDERSON COUNTY THROUGH 545 PM
EDT...

AT 510 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 4 MILES EAST OF ETOWAH...OR 4 MILES WEST OF
HENDERSONVILLE...MOVING EAST AT 10 MPH.

THIS THUNDERSTORM WILL AFFECT LOCATIONS FROM HENDERSONVILLE TO DANA
THROUGH 545 PM. PEA SIZE HAIL...WIND GUSTS OF 30 TO 40 MPH...AND
TORRENTIAL RAINFALL ARE EXPECTED WITH THIS STORM.

HG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
555 PM EDT SAT MAY 16 2009

NCZ051-052-162245-
HAYWOOD-SWAIN-
555 PM EDT SAT MAY 16 2009

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN SWAIN AND
NORTHWESTERN HAYWOOD COUNTIES THROUGH 645 PM EDT...

AT 554 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 9 MILES EAST OF GATLINBURG...MOVING EAST AT 5
MPH.

THIS THUNDERSTORM WILL AFFECT TENNESSEE BORDER LOCATIONS FROM
NEWFOUND GAP TO WATERVILLE THROUGH 645 PM.  PEA SIZE HAIL...WIND
GUSTS OF 30 TO 40 MPH...TORRENTIAL RAINFALL AND FREQUENT LIGHTNING
ARE EXPECTED WITH THIS STORM.

MOVE INDOORS BEFORE THIS THUNDERSTORM REACHES YOUR LOCATION.

HG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
606 PM EDT SAT MAY 16 2009

NCZ065-162300-
HENDERSON-
606 PM EDT SAT MAY 16 2009

...STRONG THUNDERSTORMS WILL PRODUCE HEAVY RAINFALL IN HENDERSON
COUNTY THROUGH 700 PM EDT...

AT 603 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 3 MILES SOUTH OF MOUNTAIN HOME...OR 4 MILES WEST
OF HENDERSONVILLE...MOVING EAST AT 10 MPH. THIS THUNDERSTORM WILL
AFFECT THE AREA FROM MOUNTAIN HOME TO HENDERSONVILLE TO DANA THROUGH
630 PM. ADDITIONAL THUNDERSTORMS ARE DEVELOPING TO THE WEST NEAR
ETOWAH...AND THESE WILL LIKELY TRACK OVER THIS SAME AREA THROUGH 5
PM.

RADAR ESTIMATES RAINFALL TOTALS OF 1 TO 2 INCHES IN THE PAST
HOUR...AND ADDITIONAL HEAVY RAINFALL IS EXPECTED THROUGH 7 PM. DEEP
PONDING OF WATER WILL LIKELY DEVELOP IN LOW AREAS...AND MANY STREAMS
AND CREEKS WILL RISE RAPIDLY IN THE AREA.

HG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
637 PM EDT SAT MAY 16 2009

NCZ035-502-162300-
ALEXANDER-GREATER CALDWELL-
637 PM EDT SAT MAY 16 2009

...A STRONG THUNDERSTORM WILL AFFECT EASTERN CALDWELL AND
NORTHWESTERN ALEXANDER COUNTIES THROUGH 700 PM EDT...

AT 635 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR KINGS CREEK...OR 8 MILES NORTHEAST OF
LENOIR...MOVING NORTHEAST AT 10 MPH.

THIS THUNDERSTORM WILL AFFECT MAINLY THE KINGS CREEK AREA AND
LOCATIONS NORTHWEST OF ELLENDALE THROUGH 7 PM. PEA SIZE HAIL...WIND
GUSTS OF 30 TO 40 MPH...TORRENTIAL RAINFALL...AND FREQUENT LIGHTNING
ARE EXPECTED WITH THIS STORM.

MOVE INDOORS NOW. STAY AWAY FROM WINDOWS AND DOORS AND AVOID USING
TELEPHONES UNLESS IT IS AN EMERGENCY.

HG