Flash Flooding in North Carolina, August 5, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1136 AM EDT FRI AUG 5 2011

.SYNOPSIS...
A WEAK SURFACE FRONT WILL REMAIN STATIONARY ACROSS NORTH GEORGIA AND
THE CAROLINAS INTO THE WEEKEND.  EXPECT THE WEATHER TO BE UNSETTLED
THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1130 AM...AN AREA OF LLVL CONVERGENCE ALONG A LINE FROM THE
SRN NC FOOTHILLS...THRU MECKLENBURG COUNTY...SE INTO NE SC IS VERY
SLOW MOVING. MODERATE TO HEAVY RAIN/TSTMS CONTINUE TO FILL OUT IN
THIS ZONE...AND AT THIS POINT MINOR FLOODING OF
LOW-LYING/FLOOD-PRONE AREAS IS EXPECTED. THE MODEL WITH THE BEST
HANDLE IS THE 12Z NAM12...AND IT SHOWS QPF CONTINUING IN THESE AREAS
WELL INTO THE AFTN AS CONVERGENCE SLOWLY WEAKENS. GIVEN THE 1 TO
1.5"/HR RAIN RATES (UNDER 1-HR FFG) AND EXPECTED DISSIPATING OF LLVL
FORCING THIS AFTN...I WILL NOT BE ISSUING A FLOOD WATCH ATTM...BUT A
FEW FLOOD ADVISORIES AND POSSIBLY ISOLD FLASH FLOODING IS POSSIBLE
ACRS THE SRN NC PIEDMONT. ADJUSTED POP/QPF GRIDS TO REFLECT THE
TRENDS. TWEAKS TO TEMPS AND SKY WERE MADE AS WELL.

AS OF 930 AM...EASTERLY LLVL FLOW SEEN ON THE GSP VWP IS HELPING
STRATUS AND SHWRS DEVELOP ACRS MUCH OF THE NC FOOTHILLS AND
PIEDMONT. ACRS THE WESTERN PORTION OF THE CWFA...MID LVL CLOUDINESS
IS ALSO INCREASING IN RESPONSE TO WEAK FORCING. OVERALL...THE
CONSENSUS IS FOR THERE TO BE PLENTY OF CLOUD COVER...INCREASING
COVERAGE OF SHWRS AND TSTMS AND HIGH HUMIDITY. SO GRIDS WERE
ADJUSTED PER RADAR AND SATELLITE TRENDS. TEMPS ARE STARTING OUT
QUITE WARM...SO THINK THE FCST MAX TEMPS IS FINE. ACRS THE SRN
UPSTATE AND ELBERT GA...HEAT INDEX VALUES WILL APPROACH 105. BUT
GIVEN THE CLOUD COVER...I LEANED TOWARD NOT PUTTING A HEAT ADVISORY
ATTM.

PREVIOUS DISCUSSION...
WEAK LLVL UPGLIDE FLOW SHOULD BE PRIMARY FORCING MECHANISM FOR
STORMS TODAY AS WELL AS INITIATION ALONG SMALLER SCALE BNDRYS.
WITH THE NOSING IN OF WEAK SFC RIDGING AND THE LOWERING OF 100-85H
THICKNESS VALUES...MAX TEMPS THIS AFTERNOON WILL RANGE FROM ABOUT A
CATEGORY BELOW PERSISTENCE ACRS THE SW THIRD OF CWFA TO PERHAPS AS
MUCH AS 8 DEG F NORTH OF I-40 WHERE THE POTENTIAL FOR DEVELOPING LOW
CLDS LINGERING INTO MIDDAY EXISTS. WITH JUICY LOWER 70S DWPTS
LINGERING TODAY...THERE EXISTS THE POSSIBILITY OF A FEW LOCALES IN
THE LOWER SC AND GA PIEDMONT TO REACH HEAT INDEX VALUES NEAR 105F.

AS ABOVE NORMAL PWAT VALUES SPREAD NORTH ACRS THE REGION...FCST
SNDGS ARE EXHIBITING WEAK LAPSE RATES AND GENERALLY MOIST CONDITIONS
UP THRU THE BALANCE OF THE VERTICAL. THIS TYPE OF ENVIRONMENT SHOULD
SUPPORT ONLY ISOLATED STORMS CAPABLE OF PRODUCING GUSTY WIND...BUT
MORE LIKELY A HEAVY AND/OR LOCALLY EXCESSIVE RAIN THREAT. THE
GENERAL FLOW REGIME FEATURING WEAK LLVL WAA...ENCROACHMENT OF
WEAK VORT ENERGY AND LINGERING HIGH PWAT VALUES...REMAINS SUPPORTIVE
OF AT LEAST ISOLATED DEEP CONVECTION INTO THE NIGHT.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 220 AM FRIDAY...A WEAK UPPER TROUGH WILL AMPLIFY OVER THE FA
ON SATURDAY. THE NAM AND GFS BRING A COUPLE EMBEDDED SHORT WAVES
ACROSS THE FA...ONE IN THE MORNING AND ONE IN THE AFTN. LAYER RH/S
AND PW/S BECOME QUITE HIGH UNDER THE TROUGH. THE GFS HAS STRONG LLVL
MOISTURE FLUX DIVERGENCE OVER THE FOOTHILLS AND PIEDMONT IN THE
AFTN. AS THE PREVIOUS SHIFT SAID...THIS SHOULD RESULT IN QUITE A BIT
OF SHOWER AND THUNDERSTORM ACTIVITY ACROSS THE FA. THE SREF 3 HOUR
PROB OF A HUNDREDTH OF AN INCH OR MORE OF PCPN IS CATEGORICAL ACROSS
THE FA. WHILE THIS SHOULDN/T BE TAKEN AN EXPLICIT POP...THAT/S STILL
HIGH. SO THE PCPN SHOULD BE MOST WIDESPREAD IN THE AFTN AS THE WEAK
SHEAR SHOULD PRECLUDE MUCH IN THE WAY OF OVERNIGHT OR MORNING
CONVECTION. HOWEVER...THERE WILL BE UPSLOPE FLOW SAT MORNING AND
THIS COULD HELP MAINTAIN OR LEND A HAND IN THE EARLY INITIATION OF
CONVECTION IN THE MORNING. MAX TEMPS ARE A BLEND OF THE COOLER MET
AND WARMER MEX. CONSIDERABLE HIGH CLOUDS OR MORNING CONVECTION WOULD
OF COURSE KEEP US COOLER THAN THE L-M90S IN THE FORECAST NOW.

CONVECTIVE COVERAGE SHOULD BE CONSIDERABLY LESS ON SUNDAY AS MOST OF
THE SHORT WAVE ENERGY...LLVL CONVERGENCE AND DEEP LAYER MOISTURE
DROP SOUTH OF THE REGION. HOWEVER...THE WESTERLIES STRENGTHEN A
LITTLE OVER THE REGION...AND THE NAM AND GFS IMPLY THAT CONVECTION
MAY DEVELOP OVER MIDDLE OR ERN TN AND THEN AFFECT THE MOUNTAINS
DURING THE LATE AFTN OR EVENING. POPS HAVE BEEN RAISED A BIT...UP TO
AROUND 40 PERCENT...OVER THE MTNS TO ACCOUNT FOR THIS. GREATER SHEAR
AND A MARGINALLY DRIER MID-LEVEL AIRMASS MAY SUPPORT A LITTLE MORE
IN THE WAY OF SEVERE WEATHER. IT/S UNCERTAIN HOW FAR EAST THE
CONVECTION WILL MAKE IT IN THE EVENING...BUT IT/S CERTAINLY POSSIBLE
THAT STORMS WILL MOVE A WAYS OUT INTO THE FOOHTILLS AND PIEDMONT.
MAX TEMPS WILL JUMP BACK UP INTO THE M-U90S MOST AREAS OUTSIDE THE
MTNS.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 1230 AM FRIDAY...NOT MUCH CHANGE TO THE EXTENDED PART OF THE
FORECAST TONIGHT. A BROAD BUT FAIRLY SHALLOW LONG WAVE TROUGH WILL
REMAIN OVER THE EASTERN STATES THROUGH THE EXTENDED RANGE. HPC/S SFC
FRONTS AND PRESSURES FORECAST HAS A WEAK BNDRY OVER THE FA TUE AND
WED...WITH A STRONGER FRONT MOVING THROUGH THE REGION ON THU. MCS
ACTIVITY IS POSSIBLE JUST ABOUT ANY DAY WITH WEAK TO MODERATE /FOR
THIS TIME OF YEAR/ WESTERLY FLOW MON-THU. THE CURRENT FORECAST HAS
LOW END CHANCE POPS THROUGH WED AND I SEE NO REASON TO CHANCE THIS.
TEMPERATURES WILL GRADUALLY FALL DURING THE WEEK...BUT EVEN WITH A
STRONGER FRONT MOVING THROUGH THE REGION ON THU...READINGS ARE ONLY
PROGGED TO RETURN TO NORMAL BY THAT TIME. THE FORECAST FOR THU IS
DRY. THE LATEST OPERATIONAL GFS AND ECMWF IMPLY THAT DAY 7 WOULD SEE
AS GOOD OR A GREATER CHANCE OF PCPN THAN THE REST OF THE
EXTENDED...BUT THERE IS PLENTY TO TIME TO WAIT AND SEE IF THIS TREND
PERSISTS.

&&

.AVIATION /16Z FRIDAY THROUGH TUESDAY/...
AT KCLT...WITH E TO NE WINDS ABT 6-8 KTS THIS MORNING...THERE REMAINS
THE POSSIBILITY OF SEEING OCNL MVFR CIGS DEVELOP. THE LATEST
MESOSCALE MODELS DEPICT DEEP CONVECTION INITIATING AROUND MIDDAY AND
BLOSSOMING INTO THE AFTERNOON. BASED ON THIS...WILL CONTINUE
ADVERTISE CB STARTING AT 18 UTC. LATEST MOS GUIDANCE 6 HR TSTM
PROBABILITY DROPS TO BELOW 30 PERCENT BY 06 UTC...SO WILL LINGER CB
MENTION UNTIL ABOUT MID-EVENING. ALSO...MOS CONSENSUS IS PROGGING A
PERIOD OF MVFR BR DURING THE LATE NIGHT HOURS.

ELSEWHERE...CONSIDERABLE DEBRIS CLOUDS HAS REALLY LIMITED FOG CVRG
EARLY THIS MORNING...AND IT SEEMS THAT THE BEST CHANCE FOR ANY
FLIGHT RESTRICTIONS WILL BE FROM A BRIEF MVFR CIG THIS MORNING.
DESPITE POPS IN THE CHANCE RANGE...WILL CONTINUE TO MENTION CB
AT ALL TERMINALS UNTIL MID-EVENING. WILL ALSO INTRODUCE RESTRICTIONS
DUE TO FOG DURING THE LATE NIGHT HOURS.

OUTLOOK...MOISTURE ON EASTERLY FLOW WILL INCREASE THRU THE WEEKEND.
RESTRICTIONS COULD LINGER INTO THE WEEKEND IN THE MOIST UPSLOPE
FLOW. EXPECT SCATTERED TO NUMEROUS SHWRS/TSTMS SATURDAY AFTN. MORE
TYPICAL DIURNAL TSTMS EXPECTED FROM SUNDAY INTO NEXT 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...DEO
NEAR TERM...ARK/CSH
SHORT TERM...MCAVOY
LONG TERM...MCAVOY
AVIATION...CSH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
503 AM EDT FRI AUG 5 2011

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-060915-
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-
503 AM EDT FRI AUG 5 2011

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

.DAY ONE...TODAY AND TONIGHT.

SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS THE REGION
TODAY. WITH WEAK WINDS AND A VERY MOIST AIRMASS IN PLACE OVER THE
WESTERN CAROLINAS AND NORTHEAST GEORGIA...SOME OF THE STORMS WILL
PRODUCE LOCALLY VERY HEAVY RAINFALL. ISOLATED FLASH FLOODING IS
POSSIBLE...ESPECIALLY WHERE STORMS AFFECT URBAN LOCATIONS. ONE OR
TWO OF THE STORMS THIS AFTERNOON MAY ALSO PRODUCED SMALL AREAS OF
DAMAGING WIND.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

NONE.

14

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
936 AM EDT FRI AUG 05 2011

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

0645 PM     TSTM WND DMG     1 SW BELTON             34.51N 82.51W
08/04/2011                   ANDERSON           SC   FIRE DEPT/RESCUE

            A FEW TREES DOWN AROUND BELTON...TWO ON FOREST LANE ON
            THE SOUTHWEST SIDE...A GOOD SIZE TREE AT THE FIRE
            DEPARTMENT DOWN...AND HE KNEW OF A FEW MORE THAT NOBODY
            CALLED IN FOR HELP.

&&

OUTLAW

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1041 AM EDT FRI AUG 5 2011

NCZ068>071-082-508-051630-
CLEVELAND-GASTON-GREATER RUTHERFORD-LINCOLN-MECKLENBURG-UNION-
1041 AM EDT FRI AUG 5 2011

...VERY HEAVY RAINFALL EXPECTED ACROSS THE SOUTHERN FOOTHILLS AND
PIEDMONT OF WESTERN NORTH CAROLINA THROUGH EARLY AFTERNOON...

AT 1038 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED AN
AREA OF NEARLY STATIONARY SHOWERS AND THUNDERSTORMS STRETCHING FROM
EASTERN RUTHERFORD COUNTY THROUGH THE CHARLOTTE METRO AREA. THESE
THUNDERSTORMS WERE PRODUCING RAINFALL AT RATES OF ONE HALF TO ONE
INCH PER HOUR. THIS HEAVY RAINFALL WILL LIKELY CONTINUE UNTIL AT
LEAST THE EARLY AFTERNOON HOURS.

THE HEAVY RAINFALL WILL CREATE RAPID RISES ON AREA STREAMS AND
CREEKS...AND MAY FLOOD LOW LYING AREAS SUCH AS DITCHES AND
UNDERPASSES. DO NOT ATTEMPT TO DRIVE THROUGH ANY FLOODED ROADWAYS.

LAT...LON 3482 8031 3481 8079 3494 8079 3511 8094
      3505 8104 3515 8106 3519 8197 3525 8196
      3535 8208 3548 8213 3553 8208 3554 8185
      3561 8175 3556 8165 3555 8099 3549 8095
      3550 8079 3527 8066 3517 8046 3518 8028

HG

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1124 AM EDT FRI AUG 05 2011

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

0642 PM     TSTM WND DMG     3 NE HARTWELL           34.38N 82.89W
08/04/2011                   HART               GA   PARK/FOREST SRVC

            A SMALL TREE FELL IN THE STORM WITHIN THE MILLTOWN
            CAMPGROUND PARK AREA. THIS IS A LITTLE SOUTH OF THE
            PREVIOUSLY REPORTED POWER POLE DOWN OFF REED CREEK SCHOOL
            ROAD BY COUNTY DISPATCH.

&&

OUTLAW