Special Weather Statement, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
148 AM EDT MON AUG 19 2013

.SYNOPSIS...
COOL HIGH PRESSURE WILL GRADUALLY WEAKEN OVER THE NEXT SEVERAL DAYS.
A SERIES OF LOW PRESSURE AREAS WILL RIDE UP ALONG A STATIONARY
FRONTAL BOUNDARY LOCATED ALONG THE COAST BRINGING MOIST TROPICAL AIR
INTO THE REGION. THIS WILL GENERATE WIDESPREAD SHOWERS ACROSS THE
AREA THROUGH THE FIRST PART OF THE WEEK. DRIER AND WARMER WEATHER IS
EXPECTED TO RETURN BY THE MIDDLE OF THE WORK WEEK.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF THE EARLY MORNING HOURS...A LARGE SHIELD OF LIGHT TO MODERATE
RAIN CONTINUES TO MOVE ACROSS THE WESTERN CAROLINAS AIDED BY UPPER
DIVERGENCE IN THE RIGHT ENTRANCE REGION OF THE UPPER JET. HAVE
ADJUSTED NEAR TERM POP TO CATEGORICAL IN MOST PLACES. ACTUAL PRECIP
AMTS ARE PROBABLY HIGHER THAN WHAT THE RADAR INDICATES...BUT STILL
NOT ENOUGH TO RESULT IN FLOODING. TEMPS SHOULD REMAIN NEARLY STEADY.

PREVIOUS DISCUSSION...
AS OF 1035 PM EDT...SHOWER COVERAGE HAS INDEED BLOSSOMED ACROSS THE
REGION LATE THIS EVENING AS THE RIGHT ENTRANCE REGION OF A STRONG
UPPER JETLET IS SOLIDLY OVERHEAD. THIS FORCING WILL MOVE GRADUALLY
NORTHWARD ACROSS THE SRN APPALACHIANS AND ADJACENT FOOTHILLS THROUGH
THE EARLY MORNING HOURLY...WHILE A RICH TROPICAL MOISTURE PLUME
CONTINUES TO STREAM NWD FROM THE GULF OF MEXICO. POPS WILL BE
CATEGORICAL FOR MOST OF THE AREA TONIGHT. FORTUNATELY...RAINFALL
RATES IN THE BEST CELLS HAS DIMINISHED WITH THE LOSS OF
INSTABILITY...BUT THE GREATER COVERAGE WILL KEEP THE ISOLD HYDRO
THREAT GOING THROUGH THE OVERNIGHT HOURS. WILL MAINTAIN THE CURRENT
HWO WORDING...BUT THERE ARE NO PLANS TO POST ANY FLASH FLOOD WATCHES
AT THIS POINT SINCE ANY FLOODING EPISODES WOULD BE VERY
ISOLATED...BUT COULD HAPPEN JUST ABOUT ANYWHERE.

THE REMNANT UPPER LOW W OF THE MTNS WILL DAMPEN AND MOVE N OF OUR
AREA ON MONDAY AS THE OFFSHORE HIGH SLOWLY RETROGRADES W. THE
MOVEMENT OF THE RIDGE IS SLOW ENOUGH THAT SWLY FLOW REMAINS OVER THE
AREA FOR AT LEAST ANOTHER DAY. LOW LEVEL FLOW BECOMES S TO SW BUT
COPIOUS LOW LEVEL MOISTURE REMAINS IN PLACE. EXPECT ANOTHER DAY OF
LOW TO MODERATE INSTABILITY ACROSS THE AREA EVEN WITH THE ABUNDANT
LOW CLOUDS THROUGHOUT THE MORNING HOURS. EXPECT SCT SHRA/TSRA TO
REDEVELOP DURING THE AFTERNOON AFTER A LATE MORNING LULL IN PRECIP.
IN FACT...COVERAGE COULD END UP AT LIKELY LEVELS ACROSS THE MTNS
AND/OR SOUTHEAST OF INTERSTATE 85. HIGHS CONTINUE THEIR TRIP UPWARD
BACK INTO THE 80S OUTSIDE OF THE MTNS AND UPPER 70S MTN VALLEYS.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
AS OF 230 PM EDT SUNDAY...THE LATEST MODELS HAVE TRENDED WETTER
DURING THE SHORT TERM PERIOD. A PERSISTENT UPPER TROUGH OVER THE
WEST WILL SLOWLY LIFT NE MON NIGHT INTO TUE. HOWEVER...BY TUE NIGHT
THE UPPER TROUGH THEN RE-CLOSES OFF AGAIN IN THE VICINITY OF THE
OHIO VALLEY AND REMAINS THROUGH WED. MEANWHILE...AN UPPER RIDGE OF
H5 HIGH WILL REMAIN OFF THE SE COAST THRU THE PERIOD. THIS SYNOPTIC
PATTERN WILL ALLOW DEEP GULF MOISTURE TO CONTINUE TO STREAM
NORTHEASTWARD ACROSS THE CWA. IN ADDITION...A SERIES OF UPPER
DISTURBANCES WILL RIDGE ALONG THE WESTERN EDGE OF THE UPPER RIDGE
PROVIDING BETTER UPPER FORCING OVER THE REGION DURING THIS PERIOD.

AT THE SURFACE...MOIST LLVL S/SELY FLOW WILL PREVAIL OVER THE REGION
AS A BERMUDA HIGH PRESSURE CONTINUES TO RIDGE WESTWARD INTO THE CWA
THRU MOST OF THE PERIOD. MODELS HAVE QUITE A BIT OF QPF RESPONSE
(0.25-0.75") OVER THE REGION MON NIGHT INTO TUES MORNING AS AN UPPER
DISTURBANCE PASS OVERHEAD. WITH THE PRESENCE OF ELEVATED CAPE VALUES
AROUND 300-500J/KG MAINLY EAST OF THE MTNS...HAVE CARRIED SOLID
CHANCE POPS FOR TSRA THERE WITH SHOWERS IN THE MTNS MON NIGHT INTO
TUE MORNING. FOR TUESDAY...EXPECT WIDESPREAD CONVECTION TO DEVELOP
ACROSS MUCH OF THE CWA AS ATMOS WILL REMAIN UNCAPPED WITH AFTERNOON
SBCAPE VALUES PEAKING AROUND 15000-2000J/KG. ANOTHER UPPER
DISTURBANCE WILL MOVE OVERHEAD TUE NIGHT INTO WED MORNING.
HENCE...WE MAY SEE ONGOING CONVECTION THRU THE OVERNIGHT HOURS ON
TUES. WEDNESDAY...LLVL SE FLOW WILL PERSIST WITH PW VALUES PEAKING
NEAR 2 INCHES OVER THE PIEDMONT. IN ADDITION...SBCAPE VALUES WILL
PEAK MUCH HIGHER TO AROUND 25000-3000J/KG IN THE AFTERNOON. THE LI
VALUES WILL PLUNGE TO AROUND -3 TO -4 MEANING ATMOS WILL BE QUITE
UNSTABLE. WITH THAT SAID...POPS ONCE AGAIN HAVE BEEN RAISED TO 40-50
PERCENT RANGE FOR MOST LOCATIONS. THANKS TO CLOUD COVER AND ONGOING
PRECIP...TEMPERATURES WILL REMAIN 3-5 DEGREES BELOW NORMAL.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 1230 PM SUNDAY...ATOP THE SE CONUS FOR THE LATTER HALF OF THE
WORK WEEK...MEDIUM RANGE MODEL CONSENSUS AND GUIDANCE IS PROGGING A
BROAD BUT WEAK SSW FLOW BETWEEN BERMUDA HIPRES AND WEAK MID/UPPER
LEVEL TROUGH. DAILY DIURNAL TSTM CHANCES WILL BE NEAR CLIMO AND
MAX TEMPS WILL CONTINUE TO WORK THEIR WAY BACK TOWARD NORMAL. FOR
NEXT WEEKEND...WITH A WEAKNESS PERSISTING ATOP THE CWFA...BETWEEN
WEAK BERMUDA HIPRES AND MID-CONUS UPPER LEVEL ANTICYCLONE...DAILY
TSTM CHANCES DO NOT LOOK LIKE THEY WILL BE INHIBITED. WILL PLAN ON
KEEPING DIURNAL 20-30 POP EACH DAY...AND MAX TEMPERATURES PRETTY
CLOSE TO CLIMO.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AT KCLT...A LARGE AREA OF PRECIP WILL MOVE ACROSS THE AIR FIELD
THROUGH THE PRE-DAWN HOURS. VISIBILITY MAY DROP INTO MVFR RANGE AS
SOME OF THE HEAVIER SHOWERS MOVE ACROSS. CLOUD CEILINGS WILL VARY
FROM VFR TO MVFR FOR THE NEXT SEVERAL HOURS...BUT MOST INDICATIONS
ARE THAT AN IFR CEILING SHOULD DEVELOP BY 10Z AT THE LATEST. ONCE
ESTABLISHED...THE IFR WILL BE AROUND THROUGH THE LATE MORNING. THIS
SHOULD BE FOLLOWED BY A BRIEF MVFR CEILING AS THE BOUNDARY LAYER
HEATS UP...THEN VFR WITH AN INCREASING THREAT OF THUNDERSTORMS
MONDAY AFTERNOON. HAVE INCLUDED A PROB30 FOR THUNDERSTORMS ON MONDAY
EVENING...BUT DETAIL WILL NEED TO BE FILLED IN LATER. WINDS WILL
GRADUALLY VEER THROUGH TODAY.

ELSEWHERE...WIDESPREAD COVERAGE OF RAIN HAS BROUGHT VARIABLE
VISIBILITY AND SKY CONDITION ACROSS THE REGION. THINK THE
DEVELOPMENT OF IFR STRATUS IS A DECENT BET BY AROUND 09Z...BUT SOME
OF  THE DETAIL AROUND THIS DEVELOPMENT STILL NEEDS TO BE IRONED OUT.
OTHERWISE...OTHER TAF SITES SHOULD BE SIMILAR TO KCLT.

OUTLOOK...DEEP...MOIST SW FLOW WILL CONTINUE THROUGH AT LEAST MID
WEEK BEFORE THE PATTERN BEGINS TO CHANGE SLIGHTLY. THIS WILL LIKELY
MEAN MORNING RESTRICTIONS IN LOW CLOUDS AND MTN VALLEY FOG...AND
SCATTERED AFTERNOON THUNDERSTORMS WITH ASSOCIATED RESTRICTIONS EACH
DAY.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-05Z
KCLT       MED   67%     MED   74%     HIGH  88%     HIGH  93%
KGSP       HIGH  80%     HIGH  83%     HIGH  84%     MED   78%
KAVL       MED   65%     MED   75%     HIGH  83%     HIGH  85%
KHKY       HIGH  82%     MED   75%     HIGH  86%     HIGH  93%
KGMU       HIGH  83%     HIGH  82%     HIGH  80%     MED   78%
KAND       HIGH  84%     MED   72%     HIGH  87%     HIGH  82%

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...CSH
NEAR TERM...HG/PM
SHORT TERM...JOH
LONG TERM...CSH
AVIATION...PM

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1054 PM EDT SUN AUG 18 2013

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-200300-
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-
1054 PM EDT SUN AUG 18 2013

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

.DAY ONE...TONIGHT.

WIDESPREAD RAIN...WITH EMBEDDED MODERATE TO HEAVY RAIN
SHOWERS...WILL AFFECT THE REGION DURING THE OVERNIGHT HOURS. A FEW
THUNDERSTORMS WILL BE POSSIBLE AS WELL. THE MAIN THREAT WILL BE
FROM OCCASIONALLY HEAVY RAINFALL...BUT A FEW CLOUD TO GROUND
LIGHTNING STRIKES WILL BE POSSIBLE AS WELL. THE VERY MOIST AIR
MASS IN PLACE ACROSS THE REGION WILL COMBINE WITH SATURATED SOIL
CONDITIONS TO INCREASE THE POTENTIAL FOR ISOLATED FLASH FLOODING
OVERNIGHT IN ANY AREAS IMPACTED BY MULTIPLE ROUNDS OF HEAVY RAIN
SHOWERS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

A TROUGH OF LOW PRESSURE WILL PERSIST TO THE WEST THROUGH
WEDNESDAY...ALLOWING DEEP GULF MOISTURE TO CONTINUE STREAMING
NORTHWARD ACROSS THE REGION. THE COMBINATION OF UNSTABLE AIR EACH
AFTERNOON ALONG WITH CONTINUED DEEP MOISTURE WILL SUPPORT GOOD
COVERAGE OF THUNDERSTORMS ACROSS THE REGION MONDAY THROUGH
WEDNESDAY. THE MAIN THREAT WILL BE HEAVY RAIN WITH LOCALIZED
FLASH FLOODING.

.SPOTTER INFORMATION STATEMENT...

NONE.

HG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
308 AM EDT MON AUG 19 2013

NCZ071-072-190800-
CABARRUS-MECKLENBURG-
308 AM EDT MON AUG 19 2013

...A STRONG THUNDERSTORM WILL AFFECT MECKLENBURG AND WESTERN CABARRUS
COUNTIES THROUGH 400 AM EDT...

AT 306 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR CHARLOTTE MOTOR SPEEDWAY...OR 4 MILES
NORTHEAST OF UNC CHARLOTTE...MOVING NORTHEAST AT 15 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  CHARLOTTE MOTOR SPEEDWAY...
  CONCORD...

TORRENTIAL RAIN IS 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 3515 8070 3516 8098 3535 8096 3536 8092
      3537 8095 3550 8094 3551 8092 3550 8065
      3537 8045

ARK