Flash Flood Warning 75, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
736 AM EDT TUE AUG 6 2013

.SYNOPSIS...
WEAK HIGH PRESSURE WILL REMAIN OVER THE AREA THROUGH FRIDAY. A COLD
FRONT WILL WEAKEN AS IT CROSSES THE AREA ON SATURDAY. ANOTHER COLD
FRONT WILL CROSS THE AREA ON SUNDAY...STALLING IN THE VICINITY ON
MONDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 638 AM EDT TUESDAY...A BAND OF MODERATE TO HEAVY RAIN HAS
ESTABLISHED ITSELF ALONG THE I85 URBAN CORRIDOR. AUTOMATED GAUGES
ARE SHOWING 1 INCH PER HOUR TOTALS AND THE RADAR IS ESTIMATING UP TO
TWO INCHES IN SPOTS. THIS WILL MAKE FOR A MESSY COMMUTE. POPS HAVE
BEEN UPPED UNDER THE BAND OF HEAVY RAIN AND TRIMMED A BIT OVER THE
SRN UPSTATE AND THE NRN NC ZONES WHERE IT/S CURRENTLY QUIET. AS THE
LLVL JET VEERS THE AREA OF RAIN WILL DRIFT SLOWLY TO THE SOUTH...BUT
IT SHOULD START TO WEAKEN AFTER SUNRISE AS THE 25-30 KT LLVL JET
FORCING THE PCPN BEGINS TO MIX OUT.

AS OF 410 AM EDT TUESDAY...THE KGSP WSR88D WIND PROFILER IS SHOWING
A 30 KT SSW ORIENTED LLVL JET UP AROUND 2 TO 3 KFT THIS MORNING.
THIS IS HELPING TO SUPPORT AN EXPANDING AREA OF MODERATE TO HEAVY
SHOWERS EXTENDING ALL THE WAY FROM OCONEE COUNTY TO JUST SOUTH OF
LINCOLNTON. SO LONG AS THE FORCING REMAINS...AND IT SHOULD THROUGH
SUNRISE...THE AREA OF PCPN SHOULD REMAIN. IT WILL ALSO GRADUALLY
SPREAD TO THE EAST AS THE LLVL FLOW VEERS. IT WILL ENCOUNTER MORE
STABLE AIR AS IT MOVES INTO THE WRN NC PIEDMONT...BUT THAT SHOULD BE
MORE THAN OVERCOME BY THE LLVL WARM ADVECTION AND MUCH OF THE
CHARLOTTE METRO AREA SHOULD SEE LIGHT TO MODERATE RAIN DEVELOP OVER
THE NEXT COUPLE HOURS. HEAVIER SHOWERS WILL CONTINUE OVER THE
UPSTATE. IT/S NOT OUT OF THE QUESTION THAT AN ISOLATED FLASH FLOOD
EVENT WILL OCCUR...THOUGH SO FAR THIS MORNING WE HAVE NOT SEEN ANY
CELLS REALLY ANCHOR IN ONE SPOT.

AS OF 200 AM EDT TUESDAY...KIND OF A STRANGE MORNING AS WE HAVE A
20-25KT LLVL JET THAT HELPED TO INITIATE CONVECTION ALONG THE BLUE
RIDGE A FEW HOURS BACK. HOWEVER...THE LLVL FLOW IS ACTUALLY BRINGING
DRIER AIR INTO THE REGION FROM THE MIDLANDS. THE DEWPOINT AT
GREENWOOD...FOR EXAMPLE...HAS FALLEN FROM 70 AT 2 UTC TO 64 AT 5
UTC. THE DRIER AIR HAS CAUSED TO SHOWERS TO WEAKEN AND EXPAND MORE
INTO A STRATIFORM AREA OF PCPN. THIS STILL WARRANTS HIGH POPS NORTH
OF I-85 FOR A FEW MORE HOURS. ALSO...SOME OF THE MESO-SCALE MODELS
REGENERATE CONVECTION OVER THE SRN APPS AN INTO THE UPSTATE AND NE
GA IN A FEW HOURS. I/M NOT SURGE HOW WIDESPREAD THAT CONVECTION WILL
BE...BUT IT/S REASONABLE TO EXPECT A LITTLE MORE DEVELOPMENT AND I
HAVE INCREASING POPS ACROSS THIS AREA THROUGH SUNRISE.

STRATO-CU IS LIABLE TO HOLD ON FOR SEVERAL HOURS TODAY ACROSS THE
FOOTHILLS AND PIEDMONT PER THE NAM. WE WILL EVENTUALLY GET SOME
HEATING THIS AFTERNOON...THOUGH THE MID-LEVEL FLOW IS WEAKER THAN
YESTERDAY EVENING. STILL...SOME KIND OF WEAKNESS IN THE UPPER RIDGE
DEVELOPS TO OUR WEST LATE TODAY AND TONIGHT. THIS SHOULD SUPPORT
SCT SHRA/TSTMS OVER MUCH OF THE REGION LATER TODAY AND THIS EVENING.
THE 4KM SPC WRF...A CONVECTIVE ALLOWING MODEL I FIND TO BE QUITE
RELIABLE...DEVELOPS WIDESPREAD CONVECTION BY 20 UTC...FOCUSED MAINLY
ACROSS THE FOOTHILLS AND PIEDMONT. I/M NOT SURE HOW LONG INTO THE
NIGHT CONVECTION WILL GO. THE LLVL WINDS ARE PROGGED TO BE A GOOD 10
KTS WEAKER THAN THEY ARE NOW. HOWEVER...LAYER RH/S LOOK TO BE HIGH
AND THERE WILL BE THAT WEAK TROUGH JUST TO OUR WEST. OVERALL I LIKE
THE LOW CHANCE POPS THROUGH THE NIGHT THAT WE CURRENTLY HAVE IN THE
GRIDS AND I MADE ONLY SLIGHT TWEAKS TO THAT.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AT 230 AM EDT TUESDAY...AN UPPER TROUGH WILL WEAKEN ALONG THE EAST
COAST ON WEDNESDAY...WHILE A SHORTWAVE MOVES ACROSS THE CAROLINAS
AND GA. ON THURSDAY AN UPPER RIDGE OVER THE GULF STATES BRIDGES WITH
AN UPPER RIDGE OVER THE WESTERN ATLANTIC....WHILE ANOTHER SHORTWAVE
WEAKENS AS CROSSES THE CENTRAL APPALACHIANS.

AN ATLANTIC SURFACE RIDGE WILL EXTEND ALONG THE EAST COAST ON
WEDNESDAY AND THURSDAY. GULF MOISTURE WILL STREAM NORTH AND LIFT
ISOTROPICALLY OVER THE WEST SIDE OF THE RIDGE ACROSS THE SOUTHERN
APPALACHIANS AND ADJACENT FOOTHILLS. WITH ONLY A LIGHT SSW FLOW
ALOFT...UPSLOPE FLOW INTO THE BLUE RIDGE WILL BE SOMEWHAT LIMITED.

TEMPERATURES WILL WARM AS THE UPPER TROUGH WEAKENS AND HEIGHTS RISE
ALOFT...BUT THE DIURNAL RANGE WILL STILL BE LESS THAN NORMAL AS
CLOUDS LIMIT HEATING AND COOLING.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AT 230 AM EDT TUESDAY...A FLAT UPPER RIDGE WILL EXTEND FROM TX TO
THE NC COAST ON FRIDAY...WHILE A CLOSED UPPER LOW WILL RESIDE OVER
ONTARIO. THIS RIDGE WILL REMAIN IN PLACE THROUGH SATURDAY...WHILE
THE UPPER LOW PROGRESSES SLOWLY INTO QUEBEC. ON SUNDAY AND MONDAY AN
UPPER TROUGH WILL AMPLIFY ALONG THE EAST COAST...WHILE THE REMAINING
PORTION OF THE RIDGE AMPLIFIES OVER THE WEST.

AN ATLANTIC SURFACE RIDGE WILL EXTEND OVER THE CAROLINAS AND GA ON
FRIDAY...AND TYPICAL SUMMERTIME DIURNAL CONVECTION IS EXPECTED THEN.
A COLD FRONT WILL UNDERGO FRONTOLYSIS AS IT CROSSES OUR AREA FROM
THE NW ON SATURDAY...BUT THE BOUNDARY SHOULD STILL PROVIDE A FOCUS
OR GREATER CONVECTIVE COVERAGE. A SECOND COLD FRONT WILL MOVE INTO
OUR AREA ON SUNDAY...STALLING OVER SC ON MONDAY...PROVIDING A
PROLONGED FOCUS FOR ACTIVITY. TEMPERATURES WILL EXHIBIT A SLIGHTLY
LOWER THAN NORMAL DIURNAL RANG DUE TO CLOUDS AND MOISTURE...WITH
MAXIMUMS ABOUT THREE DEGREES BELOW NORMAL...AND MINIMUMS A DEGREE OR
TWO ABOVE NORMAL.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
AT KCLT...SHOWERS HAVE MOVED SOUTHEAST OF THE AIRFIELD. THE NAM
GUIDANCE BRINGS IFR CIGS INTO THE AIRFIELD  AFTER 12 UTC ALONG WITH
RAIN. THE RAIN APPEARS TO BE OVERDONE. IFR CIGS ALSO LOOK TOO
LOW...THOUGH SEVERAL HOUR OF MVFR IS LIKELY WITH THE MOIST SOUTH
SOUTHWEST FLOW OVER THE REGION. SHOWERS AND THUNDERSTORMS ARE
EXPECTED TO DEVELOP AGAIN THIS AFTERNOON. THE FLOW IS SOUTHERLY AND
THE LLVL MOIST AGAIN TONIGHT. HOWEVER...THE FLOW IS CONSIDERABLY
WEAKER. LOW CIGS MAY NOT DEVELOP OUT ACROSS THE WRN NC PIEDMONT.
THIS IS CERTAINLY THE CASE ON THE MODEL GUIDANCE. THEREFORE I/VE
KEPT A BKN040 CIG THROUGH THE NIGHT.

ELSEWHERE...WIDESPREAD SHOWER ACTIVITY HAS DEVELOPED ACROSS THE
SOUTH CAROLINA UPSTATE THIS MORNING. THIS IS IN RESPONSE TO A LOW
LEVEL WIND MAX OF 25 TO 30 KTS ABOUT 2000 OFF THE GROUND. THE SHOWER
SHOULD LAST FOR ANOTHER HOUR OR TWO...BUT THEY SHOULD END AS THE LOW
LEVEL JET WEAKENS. IN ITS WAKE MVFR CIGS ARE EXPECTED TO LAST WELL
INTO THE AFTN HOURS OVER THE UPSTATE. WITH ALL THE RAIN A PERIOD OF
IFR CIGS IS ALSO POSSIBLE. FEW008 WAS ADDED TO THE UPSTATE SITES TO
ACCOUNT FOR THIS. KAVL MAY SEE IFR CIGS INGER IN THE FRENCH BROAD
VALLEY FOR A COUPLE HOURS BEFORE SLOWLY MIXING OUT. ONCE THE SHOWERS
END THIS MORNING...MORE SHOWERS AND THUNDERSTORMS SHOULD DEVELOP
ACROSS THE REGION THIS AFTERNOON AND TEMPO THUNDER HAS BEEN ADDED TO
EVERY SITE. EXPECTING MORE LOW CIGS TONIGHT WITH A VERY MOIST
AIRMASS AND SOUTHERLY FLOW.

OUTLOOK...MOISTURE AND INSTABILITY CONTINUE THROUGH THE REST OF THE
WEEK...LEADING TO CONTINUED CHANCES FOR MAINLY DIURNAL CONVECTION.
EARLY MORNING PATCHY FOG AND LOW CLOUDS MAY OCCUR OVER AREAS OF
RECENT RAINFALL AND MTN VALLEYS.

CONFIDENCE TABLE...

            11-17Z        17-23Z        23-05Z        05-11Z
KCLT       MED   70%     MED   63%     HIGH 100%     HIGH  95%
KGSP       HIGH  96%     HIGH  87%     HIGH  98%     HIGH  91%
KAVL       HIGH  81%     HIGH  98%     HIGH  83%     HIGH  94%
KHKY       MED   79%     HIGH  93%     HIGH  95%     HIGH  88%
KGMU       MED   77%     HIGH  88%     HIGH  98%     HIGH  90%
KAND       HIGH  89%     HIGH  98%     HIGH 100%     HIGH  83%

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...NONE.
NC...NONE.
SC...NONE.

&&

SYNOPSIS...JAT
NEAR TERM...MCAVOY
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...MCAVOY

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
516 AM EDT TUE AUG 6 2013

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-070930-
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-
516 AM EDT TUE AUG 6 2013

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

.DAY ONE...TODAY AND TONIGHT.

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED ACROSS MUCH OF
THE WESTERN CAROLINAS AND NORTHEAST GEORGIA TODAY. THE STORMS WILL
BE SLOW MOVING AND SOME OF THEM WILL DROP LOCALLY EXCESSIVE
RAINFALL...RESULTING IN AN ISOLATED FLASH FLOOD THREAT.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

NONE.

14

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
811 AM EDT TUE AUG 6 2013

SCZ006-010>012-061300-
ABBEVILLE-ANDERSON-GREATER GREENVILLE-LAURENS-
811 AM EDT TUE AUG 6 2013

...A STRONG THUNDERSTORM WILL AFFECT EASTERN ANDERSON...NORTHEASTERN
ABBEVILLE...SOUTHERN GREENVILLE AND WESTERN LAURENS COUNTIES THROUGH
900 AM EDT...

AT 806 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 3 MILES SOUTH OF WILLIAMSTON...OR 10 MILES
NORTHEAST OF ANDERSON...MOVING SOUTHEAST AT 25 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  HONEA PATH...
  DUE WEST...
  BOYD MILL POND...

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

THE COMBINATION OF GUSTY WINDS AND WET SOIL CONDITIONS WILL CAUSE
SCATTERED TREES AND POWER LINES TO FALL. SEEK SHELTER INSIDER AN
INTERIOR ROOM.

LAT...LON 3427 8243 3456 8262 3469 8246 3450 8209
      3440 8223 3440 8226 3434 8233

KRENTZ

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
934 AM EDT TUE AUG 6 2013

SCZ012-061415-
LAURENS-
934 AM EDT TUE AUG 6 2013

...A STRONG THUNDERSTORM WILL AFFECT LAURENS COUNTY THROUGH 1015 AM
EDT...

AT 932 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR ORA...OR 4 MILES NORTH OF LAURENS...MOVING
SOUTHEAST AT 30 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  CLINTON...
  JOANNA...

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

THE COMBINATION OF GUSTY WINDS AND WET SOIL CONDITIONS COULD CAUSE
SCATTERED TREES AND POWER LINES TO FALL. SEEK SHELTER INSIDER AN
INTERIOR ROOM.

LAT...LON 3451 8216 3467 8206 3462 8193 3458 8187
      3459 8186 3460 8185 3452 8165 3446 8169
      3444 8173 3436 8178 3434 8182

KRENTZ