Flash Flooding and Flooding in North Carolina, July 3 to 4, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1028 AM EDT WED JUL 3 2013

.SYNOPSIS...
A DEEP UPPER LEVEL TROUGH WILL REMAIN IN PLACE OVER THE OHIO AND
TENNESSEE RIVER VALLEYS THROUGH THE END OF THE WORK WEEK. THE TROUGH
WILL DISSIPATE OVER THE WEEKEND AS A BERMUDA HIGH BUILDS IN FROM THE
EAST.

&&

.NEAR TERM /THROUGH TONIGHT/...
1000 AM UPDATE...UPDATED POPS TODAY WITH PRACTICALLY EVERYWHERE
CATEGORICAL AT SOME POINT. WATCHING CONVECTION MOVE THRU NRN GA AND
NOW INTO THE WRN TIP OF THE CWFA. 850MB MOISTURE PLUME SEEMS TO BE
THE MAIN DRIVING FORCE FOR THIS ACTIVITY BUT STRENGTHENING 250MB JET
AND ASSOC UPPER DIVERGENCE IN THAT REGION AIDING IT AS WELL. WITH
DEEP SSW FLOW MOST OF THE STORMS ARE EXPECTED TO PASS JUST TO OUR
WEST BUT THE SAME FLOW WILL PROMOTE CONVECTION IN THE
MTNS/FOOTHILLS. A CLUSTER OF STORMS IS ALSO MOVING INTO THE SC
MIDLANDS NOW AND WILL LIKELY MOVE INTO THE NC PIEDMONT BY MIDDAY.
11Z HRRR REFLECTS THIS LATTER BATCH OF STORMS AND THE MOVEMENT
SUGGESTED BY RADAR TRENDS...BUT SHOWS LITTLE DEVELOPMENT IN THE
UPSLOPE AREAS WHICH IS A BIT SURPRISING. RAP AND NEW NAM ARE MORE
BELIEVABLE AND MAINTAIN SHOWERS/STMS THERE. TEMPS/DEWPTS ARE ON
TRACK FROM LAST UPDATE.

AT 230 AM EDT WEDNESDAY...AN UPPER LOW WILL MEANDER JUST WEST WEST
OF THE MID MS RIVER VALLEY TODAY AND TONIGHT...WHILE AN ATLANTIC
UPPER HIGH SLOWLY BUILDS WEST OVER THE EAST COAST. CHANNELED
VORTICITY BETWEEN THE LOW AND THE HIGH WILL MOVE NORTH ACROSS OUR
AREA TODAY...WHILE DEEP MOISTURE REMAINS OVER OUR AREA. POPS WILL
BE GREATEST NEAR THE BLUE RIDGE TODAY...WHERE LOW LEVEL UPSLOPE FLOW
IS EXPECTED TO IMPROVE. ALTHOUGH CAPE WILL BE LIMITED BY CLOUD COVER
TODAY...LOW LEVEL SHEAR WILL BE PRESENT. HIGH TEMPERATURES WILL RUN
AROUND 10 DEGREE BELOW NORMAL UNDER CLOUD COVER AND LOW HEIGHTS
ALOFT.

AS THE UPPER RIDGE PUSHES WEST...DRIER AIR ALOFT WILL MOVE INTO THE
PIEDMONT...WHILE DEEP MOISTURE LINGERS IN THE MOUNTAINS. THE TRAIN
OF UPPER VORT MAXES MOVING NORTH BETWEEN THE RIDGE AND THE TROUGH
WILL SHIFT WEST TO THE TN VALLEY. THIS WILL LEAD TO A GREATER RANGE
OF POPS BETWEEN THE EASTERN AND WESTERN ZONES. WARMING MID LEVELS
MAY CAP PROFILES TONIGHT...ESPECIALLY IN THE WEST...EVEN AS CAPE
INCREASES AND SHEAR PERSISTS. MINIMUM TEMPERATURES WILL RUN NEAR
NORMAL AS LOW LEVEL MOISTURE REMAINS ELEVATED.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 255 AM EDT WEDNESDAY...THERE IS SOME MODEL DISAGREEMENT IN HOW
FAR WEST THE BEST FORCING FOR PCPN MOVES THURSDAY INTO THURSDAY
NIGHT...BUT THE OVERALL CONSENSUS IS THAT IT SHIFTS A LITTLE TO THE
WEST OF THE APPALACHIANS. ONE FEATURE OF NOTE IS A SHORT WAVE AND
ATTENDANT SFC LOW THAT LIFTS OUT OF THE GOM THURSDAY AND ACROSS
MIDDLE TN THU NIGHT. H8 WINDS ON THE EAST SIDE OF THIS FEATURE
INCREASE TO 40 TO 50 KTS ON THE GFS. THE CANADIAN HAS SIMILAR TIMING
THOUGH IT/S LOW IS A LITTLE FARTHER EAST. EVEN THE NAM IS LARGELY ON
BOARD WITH THIS FEATURE. THERE SHOULD BE WIDESPREAD HEAVY RAIN IN
THE HEART OF THE STRONG LLVL JET. HOWEVER...THE FLOW EVEN INCREASES
TO BETWEEN 30-40 KTS ACROSS THE CENTRAL AND SW NC MTNS AS WELL AS
NE GA. CONSIDERING HOW MOIST THE AIRMASS IS...THIS CERTAINLY COULD
RESULT IN HEAVY RAINFALL ACROSS THESE AREAS. FARTHER TO THE EAST I
WOULDN/T EXPECT AS MUCH OF A RESPONSE OVER THE FOOTHILLS AND
PARTICULARLY THE PIEDMONT. SO I HAVE LOWER POPS TO THE EAST...VERY
MUCH IN LINE WITH THE POPS THAT THE DAY SHIFT HAD. WPC ALSO ORIENTS
THE HEAVIEST QPF WEST OF THE MTNS...THOUGH THEY STILL HAVE A SOLID
INCH OF PCPN OVER THE WRN ZONES 12 UTC THU TO 12 UTC FRI.

THERE ARE NOT ANY MODEL FEATURES FRIDAY AND FRIDAY NIGHT COMPARABLE
TO THE ONE THURSDAY...AT LEAST NOT RIGHT NOW. HOWEVER...ANOMALOUSLY
STRONG...MOIST UPSLOPE FLOW WILL CONTINUE OVER THE MOUNTAINS. THE
BEST CHANCES FOR HEAVY PCPN STAY WEST OF THE FA...AND IN FACT MAY
SHIFT FARTHER WEST WITH TIME. HOWEVER...THERE IS STILL A GOOD CHANCE
OF LOCALIZED VERY HEAVY RAIN ACROSS THE MTNS AND ADJACENT FOOTHILL
LOCATIONS...ESPECIALLY FRIDAY AFTERNOON AND EVENING. ALSO...I DON/T
SEE ANY CAPPING ON THE MODEL SOUNDINGS...EVEN OVER THE PIEDMONT. SO
EVEN AS THE BERMUDA HIGH TRIES TO BUILD IN FROM THE EAST...THERE
SHOULD STILL BE AMPLE CONVECTIVE COVERAGE AS DIURNAL TEMPERATURE
RANGES INCREASE. IN FACT...THE HIGH DOESN/T LOOK TO MAKE NEARLY THE
WESTWARD MOVE THAT WE WERE SEEING IN THE MODELS A COUPLE DAYS AGO. I
HOPE THIS DOESN/T MEAN THE WRN ZONES WILL BE UNDER A BAND OF BETTER
FORCING AND ATTENDANT HEAVY PCPN COVERAGE THAN WE CURRENTLY
THINK...BUT IT WELL MAY.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 200 AM TUESDAY...THE MEDIUM RANGE PICKS UP AT 12Z SATURDAY
WITH A BLOCKING PATTERN ALOFT OVER THE CONUS...WITH A BERMUDA HIGH
WITH TROUGH OVER MISSISSIPPI VALLEY AND HIGH OVER ARIZONA...NEW
MEXICO.  THIS PATTERN WILL CONTINUE TO CHANNEL UPSLOPE LOW LEVEL
FLOW FOR OUR AREA SAT AND SAT NIGHT. LOW LEVEL WIND FLOW GRADUALLY
BECOMES MORE PARALLEL TO THE MOUNTAINS FROM THE SW DURING SUNDAY AND
THAT WILL CONTINUE ON THE GFS AT THE 925MB LEVEL THROUGH TUES. MAIN
FOCUS FOR HEAVIER RAINFALL WILL BE ACROSS THE MTNS DURING THE
WEEKEND. ALTHOUGH THERE IS A ECLIPSE IN THE GFS DATA FROM 06Z MONDAY
TO 12Z TUESDAY...THE OBVIOUS SHIFT IS FROM THE BLOCKING PATTERN TO A
MORE ZONAL WEST TO EAST FLOW BY DAY 7 OF THE CURRENT FORECAST. THE
OLD ECMWF HOLDS ONTO THE BLOCKING PATTERN INTO THE FIRST HALF OF
NEXT WEEK. THE GENERAL TREND WILL CERTAINLY BE FOR MUCH LOWER POPS
PEAKING AT HIGH SLIGHT OR LOW CHANCE POP IN THE MAX HEATING TIME
FRAME OF THE AFTERNOON AND FAVORING THE MTNS FOR MON AND TUES.

WITH MORE SUNSHINE AND GREATER ATMOSPHERIC THICKNESSES...EXPECT
TEMPERATURES TO BE NEAR SEASON NORMALS.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...PATCHY IFR DECK SHOULD ERODE OVER THE NEXT COUPLE OF HOURS
AS SOLAR HEATING EATS AWAY AT NUMEROUS THIN AREAS IN CLOUD LAYER
SEEN ON SATELLITE. IMPROVEMENT TO LOW VFR EXPECTED BY
AFTERNOON...FOLLOWED BY RETURN TO MVFR THIS EVENING. MODEL GUIDANCE
IS NOT VERY SUPPORTIVE OF VSBY RESTRICTION...AND NONE WILL BE
CARRIED OUTSIDE OF AFTERNOON AND EVENING THUNDERSTORMS ACCOMPANYING
A MID LEVEL SYSTEM. A CLUSTER OF STORMS MOVING THRU SC IS LIKELY TO
AFFECT AT LEAST THE VICINITY OF THE FIELD 16-17Z...WITH ADDITIONAL
DEVELOPMENT REMAINING POSSIBLE THRU THE AFTN. WINDS WILL FAVOR THE
SE AT UNDER 10 KNOTS.

ELSEWHERE...IFR BEGINNING TO LIFT ATTM AND CIGS SHOULD RISE TO LOW
VFR TODAY...BEFORE DROPPING BACK TO MVFR OR EVEN IFR TONIGHT. MODEL
GUIDANCE IS MOST SUPPORTIVE OF VSBY RESTRICTIONS IN THE MOUNTAINS
VALLEYS EARLY THIS MORNING AND AGAIN THURSDAY MORNING...INCLUDING AT
KAVL. WITH CONFIDENCE LIMITED DUE TO THE PRESSURE GRADIENT BETWEEN A
BERMUDA HIGH AND LOW PRESSURE TO THE WEST...GUIDANCE VSBY VALUES
HAVE BEEN RAISED SUBSTANTIALLY. OBSERVATIONS SHOW THAT ANY SITE THE
RECEIVES A SHOWER OR THUNDERSTORM HAS POTENTIAL FOR IFR VSBY OR
WORSE. WINDS WILL BE FROM THE SE AT LESS THAN 10 KNOTS.

OUTLOOK...VERY MOIST AND UNSETTLED CONDITIONS WILL REMAIN OVER THE
REGION THROUGH INDEPENDENCE DAY. PERIODS OF SHRA/TSRA WILL OCCUR
BOTH DURING THE DAY AND OVERNIGHT. MORNING STRATUS AND FOG IS
POSSIBLE EACH DAY ACROSS THE REGION. OVER THE WEEKEND...A BERMUDA
HIGH WILL PUSH WEST ACROSS THE SOUTHEAST...YIELDING MAINLY DIURNAL
SHRA/TSRA. MORNING FOG WILL FAVOR THE MTN VALLEYS.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-14Z
KCLT       MED   78%     LOW   58%     HIGH  87%     HIGH  92%
KGSP       MED   77%     LOW   59%     HIGH  90%     HIGH  94%
KAVL       HIGH  84%     LOW   53%     MED   64%     HIGH  98%
KHKY       HIGH  82%     LOW   52%     MED   68%     HIGH  93%
KGMU       MED   76%     MED   61%     HIGH  91%     HIGH 100%
KAND       MED   68%     LOW   52%     HIGH  80%     HIGH  93%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE
HOURLY EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE
FORECASTS ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...FLASH FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR GAZ010-017-
     018-026-028-029.
NC...FLASH FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR NCZ033-
     035>037-048>053-056>059-062>065-068>072-082-501>510.
SC...FLASH FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR SCZ001>014-
     019.

&&

SYNOPSIS...JAT
NEAR TERM...JAT/WIMBERLEY
SHORT TERM...MCAVOY
LONG TERM...DEO
AVIATION...JAT/WIMBERLEY

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
446 AM EDT WED JUL 3 2013

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-040900-
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-
446 AM EDT WED JUL 3 2013

...FLASH FLOOD WATCH IN EFFECT THROUGH THIS EVENING...

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

.DAY ONE...TODAY AND TONIGHT.

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

   FLASH FLOOD WATCH.

THE COMBINATION OF UNUSUALLY STRONG WIND SHEAR FOR JULY AND
CONSIDERABLE INSTABILITY WILL LEAD TO THE THREAT OF ISOLATED
TORNADOES TODAY AND TONIGHT. THIS WILL BE ESPECIALLY TRUE OVER
THE SOUTHERN FOOTHILLS AND PIEDMONT OF NORTH CAROLINA...UPSTATE
SOUTH CAROLINA AND NORTHEAST GEORGIA.

FREQUENT CLOUD TO GROUND LIGHTNING AND GUSTY WINDS WILL ALSO BE
POSSIBLE WITH THE STRONGER STORMS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

HEAVY RAIN WILL STILL BE POSSIBLE THURSDAY AND THURSDAY
NIGHT...THOUGH THE THREAT SHOULD SHIFT MORE INTO THE MOUNTAINS AND
ADJACENT FOOTHILL LOCATIONS. FLOOD OR FLASH WATCHES WILL LIKELY
NEED TO BE EXTENDED FOR PARTS OF THE WESTERN CAROLINAS AND
NORTHEAST GEORGIA DURING 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.

MCAVOY

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
633 AM EDT WED JUL 3 2013

NCZ049-053-031115-
BUNCOMBE-YANCEY-
633 AM EDT WED JUL 3 2013

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN BUNCOMBE AND YANCEY
COUNTIES THROUGH 715 AM EDT...

AT 631 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 5 MILES NORTH OF SWANNANOA...OR 11 MILES
NORTHEAST OF DOWNTOWN ASHEVILLE...MOVING NORTH AT 25 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  BARNARDSVILLE...
  BURNSVILLE...
  MICAVILLE...

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

HEAVY RAINS MAY FLOOD AREAS WITH POOR DRAINAGE...SUCH AS DITCHES AND
UNDERPASSES. AVOID THESE AREAS AND DO NOT CROSS FLOODED ROADS. WATER
LEVELS OF SMALL STREAMS AND RIVERS MAY ALSO RISE RAPIDLY. SEEK HIGHER
GROUND IF THREATENED BY FLOOD WATERS.

LAT...LON 3595 8219 3593 8216 3571 8227 3569 8230
      3568 8228 3561 8232 3567 8250 3580 8248
      3581 8241 3586 8242 3590 8245 3590 8247
      3603 8245

MCAVOY