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Area Forecast Discussion

289
FXUS62 KGSP 031043
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
643 AM EDT FRI JUL 3 2015

.SYNOPSIS...
A BROAD UPPER LEVEL TROUGH WILL REMAIN OVER THE SOUTHEAST THROUGH
MONDAY...STEERING A SERIES OF WEAK DISTURBANCES OVER THE REGION.
THESE FEATURES WILL INCREASE RAIN AND THUNDERSTORM CHANCES EACH
AFTERNOON AND EVENING...AND KEEP SKIES CLOUDIER THAN USUAL. SLIGHT
DRYING WILL OCCUR TUESDAY...BEFORE ANOTHER FRONT PUSHES THROUGH IN
THE MIDDLE OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 630 AM EDT FRIDAY...SCATTERED LIGHT/MODERATE SHOWERS CONTINUE
TO ADVECT EAST ACROSS THE REGION AS STATIONARY CONVERGENCE AXIS
REMAINS PREVALENT.  STARTING TO SEE INCREASING LIGHTNING INTENSITY
IN THE CELLS NOW OVER EAST/CENTRAL GA WHERE BETTER MUCAPE IS
PRESENT.  ANY CELLS THAT PUSH INTO THE UPSTATE AND NORTHEAST GA THIS
MORNING COULD PRODUCE THUNDER...BUT SHOULD NOT BE STRONG.  AS
PREVIOUSLY DISCUSSED...CONDITIONS LOOK FAVORABLE THIS AFTERNOON FOR
STRONG/SEVERE CONVECTION THANKS TO AMPLE SHEARING AND INSTABILITY.
AS SUCH...SPC HAS PLACED THE ENTIRE NORTHEAST GA AND UPSTATE SC AREA
IN THE SLIGHT RISK AS THIS IS WHERE SHEARING WILL BE BEST THANKS TO
40-50KT LLJ.  AS FOR THE FCST...TWEAKED POPS TO ACCOUNT FOR MOST
RECENT RADAR TRENDS.  MADE SLIGHT ADJUSTMENTS TO TEMPS/DEWS/SKY TO
BETTER ALIGN WITH OBS...LEFT THE REMAINDER OF THE FCST AS IS.

PREVIOUS DISCUSSION...

AS OF 315 AM EDT FRIDAY...THE UPPER PATTERN THIS MORNING IS
HIGHLIGHTED BY A BROAD/DEEP TROF OVER THE EASTERN CONUS.  A RATHER
POTENT SHORTWAVE TROF WILL CONTINUE TO EJECT THROUGH THE MEAN FLOW
ALOFT ACROSS THE MIDWEST...INTO THE OH/TN VALLEYS DURING THE NEAR
TERM FCST PERIOD.  MEANWHILE AT THE SURFACE...AN AXIS OF CONVERGENCE
EXTENDS IN AN EAST/WEST ORIENTATION IN PROXIMITY TO THE I40 CORRIDOR
OVER WEST/MIDDLE TN WESTWARD INTO AR/MO.  THIS BOUNDARY CONTINUES TO
PROVIDE ENOUGH LIFT FOR CONVECTION THIS MORNING OVER THE TN VALLEY
REGION AND WILL CONTINUE ADVECTING EAST INTO WESTERN NC AND
NORTHEAST GA...BEFORE SPREADING INTO THE FOOTHILL/PIEDMONT REGIONS
OF NC/SC AROUND OR JUST AFTER DAYBREAK.  THUS POPS ARE FAIRLY
HEALTHY FOR RUSH HOUR WITH LIKELY LEVELS FAVORED ALONG THE I85/I26
CORRIDORS...WITH HIGH LEVEL CHANCE POPS FAVORED EAST OVER CLT AND
THE I77 CORRIDOR.

FOR THE AFTERNOON/EVENING...MODELS FAVOR THE NORTHERN TIER OF THE
FCST AREA AS THEY SEEM TO BE CUTTING DOWN INSTABILITY OVER THE
SOUTHERN TIER THANKS TO THE ONGOING/MORNING CONVECTION.  WOULD NOT
BE SURPRISED IF THERE IS SOME DIFFERENTIAL HEATING...HOWEVER THINK
THE CAPE FIELDS THIS AFTERNOON MIGHT BE A BIT MORE HOMOGENEOUS THAN
THE GUID LEADS ON AS SKIES WILL BE PARTLY/MOSTLY CLOUDY REGIONWIDE.
SOUNDINGS DO EXHIBIT ENOUGH INSTABILITY/SHEAR TO SUPPORT STRONG TO
PERHAPS ISOLATED SEVERE THUNDERSTORMS THAT COULD PRODUCE ISOLATED
DAMAGING GUSTS/HAIL.  MOST IMPRESSIVE HOWEVER CONTINUES TO BE PWATS
APPROACHING/EXCEEDING 2IN LEADING TO CONTINUED ISOLATED FLASH
FLOODING THREATS...ALL OF WHICH WILL BE HIGHLIGHTED IN THE HWO.  AS
FOR THE FCST...LIKELY POPS PERSIST ACROSS MUCH OF NORTHEAST GA AND
THE UPSTATE THIS AFTERNOON...WITH AN INCREASING GRADIENT NORTHWARD
TO CATEGORICAL POPS NORTH OF I40.  COVERAGE WILL DECREASE INTO THE
EVENING/OVERNIGHT HOURS AS BEST UPPER FORCING AND CONSEQUENT SURFACE
WAVE EJECT TO THE EAST...THEREFORE POPS WILL FALL OFF AS WELL.
TEMPERATURES THROUGH THE NEAR TERM WILL REMAIN BELOW NORMAL AS
CLOUDY SKIES LIMIT HEATING.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 315 AM FRI...AS UPPER TROUGH SWINGS ACRS THE SRN APPALACHIANS
SATURDAY...SFC LOW IS PUSHED OFF THE MID-ATLANTIC COAST. HOWEVER THE
BASE OF THE TROUGH CONCURRENTLY SHEARS OFF LEAVING A SLOW-MOVING
SHORTWAVE TO LINGER OVER OUR REGION INTO EARLY MONDAY. SOME SEMBLANCE
OF THE FRONT WILL REMAIN ACROSS THE CAROLINAS...AND THOUGH IT IS
INITIALLY HARD TO IDENTIFY ANY DISTINCT SOURCE OF FORCING...WEAK
CONVERGENCE SHOULD ENHANCE PRECIP CHANCES IN ADDITION TO EMBEDDED
VORTICES HIGHER ALOFT. ON SUNDAY THE BOUNDARY IS STRENGTHENED AS HIGH
PRESSURE BUILDS EWD IN THE WAKE OF THE LARGER SCALE TROUGH. DEEP
MOISTURE WILL REMAIN IN PLACE BOTH DAYS AND ROUNDS OF HEAVY RAIN WILL
CONTINUE...WITH PWAT VALUES BEING ABOVE THE 90TH PERCENTILE AT TIMES.
WINDS ALOFT WILL RELAX AS THE LOW PULLS AWAY SATURDAY...AND PROFILES
WILL REMAIN UNIDIRECTIONAL THRU THE PERIOD...SO SLOW MOVING AND/OR
TRAINING CELLS WILL BE A CONCERN. POPS AND QPF ARE EXPECTED TO BE
HIGHER SUNDAY ON ACCOUNT OF THE ENHANCED LLVL CONVERGENCE. CLOUD
COVER WILL LIMIT TEMPS TO ABOUT A CATEGORY BELOW CLIMO.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 130 AM FRIDAY...THE UPPER PATTERN BEGINS TO DEAMPLIFY OVER THE
CWFA MONDAY AS A SHORTWAVE PASSES THRU ONTARIO...GRADUALLY ABSORBING
THE STAGNANT UPPER LOW OVER THE SRN APPALACHIANS. THIS FEATURE WILL
HOWEVER STILL BE IN PLACE TO MAINTAIN ELEVATED POPS MONDAY...WITH
CLOUDY CONDITIONS KEEPING TEMPS A CATEGORY OR SO BELOW NORMAL.
HEIGHTS RISE INTO MIDWEEK...ALLOWING POPS TO FALL BACK TO A TYPICAL
CLIMATOLOGICAL RANGE. HOWEVER THE PATTERN REMAINS UNSETTLED ENOUGH TO
PRECLUDE A NORMAL NOCTURNAL MINIMUM. A COLD FRONT ASSOC WITH THE
CANADIAN LOW STALLS OVER THE TENN VALLEY WED OR WED NIGHT. GFS
DEPICTS THE FRONT HANGING UP IN THAT AREA AS THE BERMUDA HIGH
RETROGRADES SLIGHTLY. EC DIFFERS IN THAT THE FRONT ENTERS OUR AREA
JUST AS A SHORTWAVE CROSSING THE MID MISSISSIPPI VALLEY BEGINS TO
LIFT IT NWD AS A WARM FRONT. GFS IS THUS MORE UNSETTLED FOR THU
COMPARED TO THE EC. HOWEVER...THE EC SHOWS LOW PRESSURE MOVING ACRS
TO OUR NORTH THU NIGHT AND PULLING THE BOUNDARY ACRS THE SRN
APPALACHIANS AT THAT TIME. THE RETURN TO SWLY FLOW AROUND THE BERMUDA
HIGH WILL LEAD TO A GRADUAL WARMING TREND IN TEMPS...WITH AFTN MAXES
BEING SLIGHTLY ABOVE NORMAL BY THU.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
AT KCLT...A MIXTURE OF VFR/MVFR WILL HIGHLIGHT THIS TAF CYCLE.
INITIALIZED TAF AMIDST BKN MVFR CIGS AND LIGHT SW WINDS.  MODELS
CONTINUE TO PROG SCATTERED SHRA CURRENTLY SLIDING THROUGH WESTERN NC
HOLDING TOGETHER AND ARRIVING AT THE AIRFIELD AT APPROX
13Z...THEREFORE CARRIED A TEMPO TO ACCOUNT FOR SUCH ALONG WITH BKN
IFR CIGS THROUGH 16Z.   WINDS ARE EXPECTED TO INCREASE LATE MORNING
AS POTENT LLJ IMPROVES...WHICH WILL LEAD TO GUSTING AND INCREASED
CHANCES FOR STRONG/SEVERE TSRA THIS AFTERNOON.  THEREFORE OPTED TO
PREVAIL 4SM TSRA BY EARLY AFTERNOON AMIDST 17KT SW GUSTS...SOME
GUSTS COULD BE SUBSTANTIALLY STRONGER ADJACENT TO DEEPER
CONVECTION.  CONDITIONS WILL IMPROVE BEYOND 00Z AS PRIMARY
SHORTWAVE FORCING AND SURFACE WAVE EJECT NORTHEAST.

ELSEWHERE...MUCH THE SAME AS KCLT ABOVE HOWEVER WITH SLIGHT TIMING
ADJUSTMENTS AS IT PERTAINS TO SHRA/TSRA THIS AFTERNOON.  INITIALIZED
ALL TAFS WITH LIGHT SW WINDS UNDER MIXED MVFR/IFR STRATUS ALONG WITH
WX MENTION TO ACCOUNT FOR CURRENT SHRA AROUND THE REGION.  PRECIP
CHANCES INCREASE FURTHER THIS AFTERNOON AS SHEAR/INSTABILITY RAMP UP
AHEAD OF A POTENT SURFACE WAVE AND LLJ.  THUS ALL SITES SEE
PREVAILING SHRA WITH VCTS FOR THUNDERSTORMS.  WINDS WILL BE QUITE
GUSTY ON FRIDAY AT THE SC SITES AND KAVL...LESS SO AT KHKY...ALL
THANKS TO STRONG LLJ DEVELOPMENT WHICH GUIDANCE FAVORS AT AROUND
40KTS/5KFT.

OUTLOOK...A LINGERING FRONTAL BOUNDARY WILL PERSIST THROUGH THE
WEEKEND INTO THE START OF THE NEXT WORK WEEK.  THIS WILL LEAD TO
ON/OFF CHANCES FOR SHOWERS EACH DAY...ENHANCED DIURNALLY.
AFTERWARDS...THE PATTERN BECOMES INCREASINGLY DIURNAL FOR THE
REMAINDER OF THE WEAK.  RESTRICTIONS WILL BE POSSIBLE ASSOCIATED
WITH CONVECTION...AND ALSO EACH MORNING ATOP RAIN SOAKED AREAS.

CONFIDENCE TABLE...

            10-16Z        16-22Z        22-04Z        04-06Z
KCLT       MED   75%     HIGH  89%     HIGH 100%     HIGH 100%
KGSP       MED   75%     HIGH  97%     HIGH 100%     HIGH 100%
KAVL       HIGH  86%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       MED   61%     HIGH  83%     HIGH 100%     HIGH 100%
KGMU       HIGH  80%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       MED   75%     HIGH 100%     HIGH 100%     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...WIMBERLEY
NEAR TERM...CDG
SHORT TERM...WIMBERLEY
LONG TERM...LEV/WIMBERLEY
AVIATION...CDG



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