« Back
NWS Peachtree City, Ga » Text Product » GSP Area Forecast Discussion


Printer-friendly Version
Current Version              Previous Versions:   1  2  3  4  5  6  7  8  9  

Area Forecast Discussion

505
FXUS62 KGSP 020241
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1041 PM EDT WED JUL 1 2015

.SYNOPSIS...
AN UPPER LEVEL TROUGH WILL REMAIN OVER THE SOUTHEAST THROUGH THE
WEEKEND...STEERING A SERIES OF WEAK SYSTEMS OVER THE SOUTHEAST AND
TRIGGERING RAIN AND THUNDERSTORM CHANCES EACH AFTERNOON. HIGH
TEMPERATURES WILL BE NEAR NORMAL THROUGH NEXT WEEK...WITH LOWS JUST
ABOVE NORMAL.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 1030 EDT...ONLY LIGHT PRECIPITATION ACTIVITY PREVAILS AROUND
THE AREA WITH NO LIGHTNING.  DIURNAL COLLAPSE OF CAPE HAS LED TO A
MARKED REDUCTION IN THE PROSPECT FOR LIGHTNING...AND HAVE REDUCED
THUNDER COVERAGE THROUGH THE MORNING WITH THIS UPDATE.  SOME AREAS
OF LIGHT RAIN WILL CONTINUE THROUGH THE EARLY MORNING HOURS.
WEATHER ON THURSDAY WILL BE VERY SIMILAR TO WEDNESDAY.

AS OF 800 EDT...SHOWERS HAVE DECLINED IN MOST AREAS WITH THE ONLY
ACTIVITY STILL PRODUCING LIGHTNING CURRENTLY NEAR ELBERT AND ABBEVILLE
COUNTIES.  SHOWERS ARE MOVING FROM WEST TO EAST AND FURTHER LIGHT TO
MODERATE SHOWERS WITH SOME ISOLATED THUNDER ARE EXPECTED THROUGH 2AM
EARLY THURSDAY MORNING...ESPECIALLY IN SOUTHERN PARTS OF THE CWA
WHERE SHOWERS SEEN ON RADAR ARE FORECAST BY HRRR TO CONTINUE AS THEY
MOVE INTO THE AREA.  TWEAKS TO THE FORECAST TO ACCOUNT FOR THE
LATEST SKY AND TEMPERATURE OBSERVATIONS...AND TO REPRESENT THE
CURRENT CONVECTIVE TRENDS.

AS OF 515 PM EDT...A FEW SHOWERS AND THUNDERSTORMS HAVE DEVELOPED
OVER THE BLUE RIDGE MOUNTAINS.  THIS ACTIVITY IS EXPECTED TO
GRADUALLY SPREAD SOUTHEASTWARD ACROSS THE PIEDMONT.  SEVERE EXTENT
MAY BE LIMITED AS TEMPERATURES DECLINE DIURNALLY AS PRECIP. MOVES
INTO HIGHER DEWPOINT AIR. HRRR GUIDANCE IS A MIXED BAG AS IT HAS
MUCH MORE WIDESPREAD SHOWERS THAN NOW OBSERVED...BUT THE BASIC TREND
OF ESE MOVEMENT AND DECREASING ACTIVITY AFTER 10PM SEEMS
REASONABLE...AND IS IN AGREEMENT WITH OTHER CAMS.  LATEST NEAR TERM
POPS REFLECT CURRENT RADAR COVERAGE AND EXPECTED TREND THROUGH 6Z.

AT 215 PM...FOR THE LATE AFTERNOON THE MAIN CONCERN IS THE
CONVECTIVE COMPLEX OVER TN AT MID AFTERNOON. THIS IS ASSOCIATED WITH
THE MCS AT THAT DEVELOPED OVER THE LOWER MIDWEST LAST NIGHT. CAPES
OVER EASTERN TN ARE IN EXCESS OF 2000J SO IT IS MOVING INTO A
FAVORABLE ENVIRONMENT TO MAINTAIN ITSELF THROUGH THE AFTERNOON. SPC
CURRENTLY HAS A WATCH IN PLACE ABUTTING OUR WESTERN NC MOUNTAIN
COUNTIES. WOULD NOT BE SURPRISED IF THE WATCH IS EXTENDED EASTWARD
INTO OUR NE GA...WESTERN UPSTATE AND SOME OF OUR NC MOUNTAIN
COUNTIES. CAPES ARE CURRENTLY <1000J OVER THE MOUNTAINS AS DEWPOINTS
ARE AROUND 60...SO WOULD EXPECT CONVECTION TO TEND TO WEAKEN AS IT
ENCOUNTERS THE MORE STABLE AIR THERE. I HAVE ALREADY FACTORED IN THE
CONVECTION REACHING THE MOUNTAINS BY 23Z AND MOVING EASTWARD
AFTERWARDS. HAVE CATEGORICAL POPS NC BORDER COUNTIES AND THEN LIKELY
AS FAR EAST AS I-26. HAVE FOLLOWED THE HRRR TRENDS AND EXPECT
CONVECTION TO DISSIPATE AFTER MIDNIGHT OVER EASTERN AREAS.

OTHERWISE...THE NAM AND GFS CONTINUE TO BE SOMEWHAT AT ODDS AGAIN
LATE TONIGHT AND THU IN REGARD TO THE AMOUNT OF CONVECTION/QPF. NAM
IS MUCH MORE AGGRESSIVE IN DEVELOPING ANOTHER CONVECTIVE CLUSTER OVER
NORTH GA/SE TN LATE TONIGHT APPARENTLY USING ISENTROPIC UPGLIDE OVER
REMNANT COLD POOL FROM TODAY`S MCS AS A TRIGGER. GFS ON THE OTHER
HAND DOES NOT SHOW ANY ENHANCED QPF. WILL GIVE A NOD TO THE NAM AND
INCREASE POPS LATE TONIGHT WESTERN SECTIONS AND THEN ALLOW THIS
ACTIVITY TO SPREAD EASTWARD ON THURSDAY AS A DECENT LOOKING SHORT
WAVE MOVES INTO THE BASE OF THE UPPER TROUGH. HENCE...WILL INCREASE
POPS INTO THE LIKELY CATEGORY MOST PLACES ON THU. WITH INCREASED
CLOUDS AND PRECIP TEMPS SHOULD BE HELD A COUPLE DEGREES BELOW CLIMO.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 230 PM WEDNESDAY...UNSETTLED WEATHER EXPECTED FOR THE REGION
DURING THE HOLIDAY WEEKEND. ON FRIDAY...A SHORTWAVE EMBEDDED WITHIN
THE LONGWAVE H5 TROUGH WILL RIPPLE ACROSS THE MID MISSISSIPPI AND
OHIO RIVER VALLEYS. AT THE SFC...WEAK LOW PRESSURE IS FORECAST TO
DEVELOP ACROSS KY AND ACROSS THE SOUTHERN APPALACHIANS. WIND AND
THERMAL PROFILES ACROSS THE REGION SHOW LITTLE CHANGE FROM EARLIER
IN THE WEEKS...INVERTED-V BELOW H8...WEAK TO MODERATE CAPE...AND 0-6
KM BULK SHEAR VALUES AROUND 20 KTS. I WILL HIGHLIGHT THE CONVECTIVE
POTENTIAL WITH LIKELY POPS ACROSS THE MTNS WITH HIGH CHC POPS EAST.
GIVEN THE MOSTLY CLOUDY SKY AND EARLY ONSET OF
RAINFALL...TEMPERATURES SHOULD RANGE SLIGHTLY BELOW NORMAL.

ON SAT...4TH OF JULY...THE SFC LOW IS EXPECTED TO TRACK NE OFF THE
MID ATLANTIC COAST...LEAVING A WEST TO EAST STATIONARY FRONT NORTH
ACROSS THE VIRGINAS. BROAD CYCLONIC MID LEVEL FLOW AND LINGERING
INSTABILITY WILL LIKELY SUPPORT SCT TSRA ACROSS THE SOUTHEAST
THROUGH FRI NIGHT. IN FACT...THE GFS INDICATES THAT A NOCTURNAL MCS
WILL MOVE FROM THE ARKLATX REGION TO NORTHERN MS/AL BY SUNRISE SAT.
12Z NAM AND ECMWF ALSO INDICATE THAT THE SAME AREA WILL SEE
CONVECTION 12Z SAT. STEERING FLOW WILL TRANSPORT THE CONVECTION
EAST...REACHING THE FA BETWEEN 18Z TO 0Z. I WILL FORECAST LIKELY
POPS ACROSS THE TN BORDER WITH 30 TO 40 POPS EAST. HIGH TEMPERATURES
ARE FORECAST TO RANGE FROM THE LOW 80S ACROSS THE NC MTN VALLEYS TO
THE U80S EAST.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 215 PM WEDNESDAY...THE MEDIUM RANGE BEGINS SATURDAY NIGHT AMID
A TREND OF RISING HEIGHTS. A SURFACE BOUNDARY/DEVELOPING LOW
PRESSURE SYSTEM WILL BE HOVERING ACROSS THE SOUTHERN
APPALACHIANS...THOUGH A LACK OF DISCERNIBLE UPPER FORCING OVER THE
PIEDMONT/FOOTHILLS SHOULD KEEP MOST NOCTURNAL CONVECTION CONFINED TO
THE HIGHER TERRAIN. ANOTHER RATHER POTENT SHORTWAVE WILL PROPAGATE
AROUND THE BASE OF THE UPPER TROUGH AND ACROSS THE CWA ON
SUNDAY...WHERE DEEP MOISTURE WILL BE PLENTIFUL. POPS WILL THEREFORE
BE WELL ABOVE CLIMO...BUT WILL STILL FOLLOW A DIURNAL TREND. SURFACE
CYCLOGENESIS APPEARS TO OCCUR RIGHT OVER OR JUST TO THE SOUTH OF THE
FORECAST AREA ON MONDAY...KEEPING POPS ELEVATED ACROSS THE WHOLE CWA
IN THE AFTERNOON ONCE AGAIN. THE UPPER PATTERN FLATTENS OUT
CONSIDERABLY BY THE MIDDLE OF NEXT WEEK...WITH AN UPPER HIGH TAKING
SHAPE OVER THE SOUTHEAST/SOUTHERN PLAINS. ANOTHER POSSIBLE SURFACE
FRONTAL BOUNDARY WILL APPROACH AROUND THE SAME TIME...THOUGH THE
EXTENT OF THE SENSIBLE IMPACTS FROM IT WILL BE DETERMINED BY THE
PLACEMENT AND STRENGTH OF THE CUT-OFF UPPER HIGH OVER THE SOUTHERN
CONUS.

OVERALL...UNCERTAINTIES STILL EXIST IN THE TIMING OF SOME OF THESE
FEATURES IN THE MEDIUM RANGE...THOUGH PLENTIFUL DEEP MOISTURE AND
SOURCES OF WEAK FORCING ABOUND FOR THE WHOLE PERIOD. THEREFORE A
TYPICAL SUMMERTIME ACTIVE PATTERN WITH GOOD DIURNAL SHOWER AND
THUNDERSTORM COVERAGE WILL PERSIST. PROFILES ARE PARTICULARLY MOIST
WITH PWATS WELL ABOVE CLIMO THOUGH THE MIDDLE OF NEXT WEEK AS
WELL...AND THOUGH NO DAY STANDS OUT AS HAVING ESPECIALLY HIGH
QPF...RAINFALL TOTALS FOR THE HIGHER TERRAIN OVER THE WHOLE MEDIUM
RANGE WILL BEAR WATCHING AS THE PERIOD COMES INTO BETTER FOCUS.

AS FOR TEMPERATURES...MAX TEMPS HAVE TRENDED COOLER IN THE GUIDANCE
FOR THE MEDIUM RANGE...POSSIBLY DUE TO INCREASED MOISTURE IN THE
VERTICAL PROFILES AND THEREFORE INCREASED CLOUD COVER. A LACK OF
PRONOUNCED HEIGHT TENDENCIES LATER IN THE MEDIUM RANGE WILL ALSO
CONTRIBUTE TO MAX TEMPS STAYING NEAR CLIMO THROUGH THE WHOLE PERIOD.
THE MOIST AIRMASS WILL LIMIT THE DIURNAL TEMPERATURE RANGE
SOMEWHAT...KEEPING MIN TEMPS JUST ABOVE AVERAGE.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...MAIN CONCERN IS CHANCES FOR THUNDER NEAR
TERM AND TOMORROW AFTERNOON.  THIS EVENING...RADAR TRENDS HAVE BEEN
FAIRLY BENIGN WITH SPORADIC LIGHTNING STAYING WELL AWAY FROM TAF
SITES.  FOLLOWING GUIDANCE FROM VARIOUS MODELS...SHOWERS ARE LIKELY
TO CONTINUE UNTIL 6Z OR SO TONIGHT WITH AN OCCASIONAL ISOLATED
THUNDERSHOWER.  SYNOPTIC PATTERN IS FAIRLY STABLE WITH A LARGE
MIDLEVEL TROUGH OVER THE EASTERN CONUS.
INSTABILITY...WINDSHEAR...AND QG FORCING WILL ALL BE SIMILAR
TOMORROW TO WHAT WAS SEEN TODAY...WITH POSSIBLY SLIGHTLY MORE
INSTABILITY.  HAVE THUS CONTINUED THE PROB30 FOR THUNDER TOMORROW
AFTERNOON.  INITIATION IS AGAIN MORE LIKELY IN THE BLUERIDGE
MOUNTAINS WITH SHOWERS MOVING EASTWARD...HOWEVER GIVEN DYNAMICAL
FORCING AND VARIOUS POSSIBLE OUTFLOW BOUNDARIES...TRW ARE POSSIBLE
THURSDAY AFTERNOON IN ALL AREAS.

OUTLOOK...A UPPER TROUGH WILL SUPPORT MAINLY AFTERNOON AND EVENING
THUNDERSTORMS THROUGH THE WEEKEND. RESTRICTIONS MAY OCCUR WITH
PASSING STORMS...AND EACH MORNING OVER RAIN SOAKED AREAS.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  83%     HIGH  83%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH  97%     HIGH 100%

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...LG
NEAR TERM...LG/WJM
SHORT TERM...NED
LONG TERM...LEV
AVIATION...LG/WJM



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.