Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 051108
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
708 AM EDT SUN JUL 5 2015

.SYNOPSIS...
A BROAD UPPER LEVEL TROUGH WILL REMAIN OVER THE SOUTHEAST THROUGH
MONDAY...PROVIDING LIFT AND MAINTAINING ELEVATED RAIN AND
THUNDERSTORM CHANCES EACH DAY. SLIGHTLY DRIER CONDITIONS RETURN
TUESDAY AND WEDNESDAY...BEFORE A FRONT BECOMES NEARLY STATIONARY
JUST NORTH OF OUR REGION LATE IN THE WEEK.  HIGH TEMPERATURES WILL
REMAIN BELOW AVERAGE INTO MONDAY...THEN WARM TO AROUND SEASONAL
NORMALS FOR THE REST OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 630 AM EDT SUNDAY...OTHER THAN A FEW LIGHT SHOWERS ALONG THE
I85 CORRIDOR THIS MORNING...CONDITIONS REMAIN RATHER QUIET/DRY.
BACKED OFF ON POPS THROUGH THE MORNING AS CAMS HAVE COME TO A
CONSENSUS ON LESS CONVECTION...WHILE THE 06Z NAM CONTINUES TO
INDICATE BETTER COVERAGE.  THUS PLACED A LITTLE LESS FAITH IN THE
NAM WITH THIS UPDATE.  THAT SAID...DO THINK THE CURRENT SHRA
COVERAGE WILL SUSTAIN AND SLOWLY ADVECT NORTHEAST BUT SHOULD REMAIN
SCATTERED AT BEST.  OTHERWISE...TWEAKED SKY/TEMPS/DEWS TO BETTER
REFLECT MOST RECENT OBS AND LEFT THE REMAINDER OF THE FCST AS IS.

PREVIOUS DISCUSSION...

AS OF 315 AM EDT SUNDAY...CLOSED H5 LOW CONTINUES TO ROTATE ATOP THE
TN VALLEY THIS MORNING LEADING TO DEEP SW FLOW THROUGH THE PROFILE
OVER NORTHEAST GA AND THE WESTERN CAROLINAS.  WEAK UPPER DIVERGENCE
BENEATH REAR ENTRANCE REGION OF H250 JETMAX ALONG WITH A SERIES OF
VORT IMPULSES WRAPPING AROUND THE H5 LOW CONTINUE TO SUPPORT WEAK
CONVECTION ACROSS THE WESTERN TIER OF THE FCST AREA THIS MORNING.  A
STRONGER IMPULSE IS PROGGED BY GUIDANCE TO ROUND THE BASE OF THE
LONGWAVE TROF AROUND DAYBREAK LEADING TO ADDITIONAL CONVECTIVE
INITIATION ACROSS EASTCENTRAL GA.  ALTHOUGH WEAK...INSTABILITY WILL
INCREASE THROUGH MID MORNING AHEAD OF SAID ACTIVITY YIELDING A
FAVORABLE ENVIRONMENT FOR CONVECTION ALONG THE I85 CORRIDOR.

MEANWHILE FURTHER NORTH...THE OLD STALLED BOUNDARY WILL BE ADVECTING
NORTHWARD INTO SW VA WHICH WILL SHIFT THE FOCUS FOR BEST SFC
CONVERGENCE AND THUS RESIDUAL MODEL QPF TODAY.  THAT SAID...CANNOT
RULE OUT CONTINUED HEAVY RAIN AND FLASH FLOODING THREAT OVER THE
MTNS THANKS TO PROXIMITY OF UPPER LOW AND ANY UPSLOPE ENHANCEMENT
FROM MODEST SSW LLJ.  THE FCST FEATURES NUMEROUS/WIDESPREAD SHOWERS
AND ISOLATED THUNDERSTORMS OVER THE GA/NC HIGH TERRAIN THIS
MORNING/AFTERNOON.  POPS ARE TAPERED DOWN A BIT OUTSIDE OF THE MTNS
WHERE SCATTERED/NUMEROUS LEVELS ARE FAVORED.  ALL SAID...AFTER THE
PASSAGE OF THE INITIAL IMPULSE/CONVECTION THIS MORNING THERE SHOULD
BE A LULL BEFORE ANY AFTERNOON CONVECTION GETS UNDERWAY.  EVEN
THEN...MODELS FAVOR RATHER WEAK INSTABILITY PROFILES THUS WOULD BE
SURPRISED TO SEE ANYTHING MORE THAN GARDEN VARIETY TSRA WITH THE
BEST CHANCES FOR STRONGER CELLS BEING SOUTH OF THE I85 CORRIDOR WHERE
BEST HEATING IS LIKELY.  POPS WILL TAPER THROUGH THE OVERNIGHT INTO
MONDAY MORNING AS THE UPPER LOW BEGINS EJECTING NORTHEAST.  WITH
THAT...THE CURRENT FLASH FLOOD WATCH WILL CONTINUE AS PLANNED WITH
EXPIRATION AT 00Z MONDAY.  TEMPERATURES ON SUNDAY WILL REMAIN BELOW
NORMAL AMIDST PARTLY/MOSTLY CLOUDY SKIES.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...UPPER LOW BEGINS TO FILL AND LIFT NEWD MONDAY
AS A LARGER SCALE SHORTWAVE AND SFC LOW MOVE ACRS THE NORTH CENTRAL
CONUS. AT LEAST THRU EARLY AFTN THE LOW WILL STILL BE IN POSITION TO
ENHANCE LIFT OVER THE NRN HALF OF THE CWFA. HOWEVER SOME SIGNIFICANT
DIFFERENCES ARE NOTED IN THE NAM AND GFS DEPICTIONS OF THE FEATURE.
GFS MORE QUICKLY BRINGS IN SUBSIDENCE IN ITS WAKE...SO FAR AS TO HAVE
RESOLVED A WEAK SFC HIGH MOVING OVER THE AREA DURING THE AFTN. THE
NAM FEATURES MORE FAVORABLE LAPSE RATES DUE TO LOWER HEIGHTS DURING
THE DAY...SUGGESTING BETTER CONVECTIVE COVERAGE THAN THE GFS. IT IS
DIFFICULT TO TELL HOW THE BETTER FORCING EARLY IN THE DAY WILL
BALANCE WITH THE EXPECTATION FOR MORE INSTABILITY LATE. POPS REFLECT
SOMEWHAT OF A COMPROMISE...WITH MENTIONABLE VALUES THROUGHOUT THE
MRNG...AND A PEAK EARLIER THAN THE TIME OF PEAK HEATING. PWAT VALUES
WILL TAKE A HIT AS DRYING OCCURS BEHIND THE DEPARTING LOW...BUT
OTHERWISE SOME HEAVY RAIN THREAT WILL REMAIN MAINLY DUE TO SLOW STORM
MOTION VECTORS. MAX TEMPS WILL WARM UP A CATEGORY OR SO BUT REMAIN
BELOW CLIMO.

COVERAGE SHOULD DIMINISH MON EVENING...BUT SOUTHWEST FLOW CONTINUES
INTO THE AREA MON NIGHT...WITH WEAK WARM ADVECTION OVER THE SERN
STATES AHEAD OF THE SYSTEM MOVING ACRS TO OUR NORTH. THIS WARRANTS A
LOW MTN POP OVERNIGHT. MINS WILL BE NEAR CLIMO TUE MRNG.

BY TUE THE SUBTROPICAL RIDGE WILL HAVE REGAINED FOOTING OVER THE
SOUTHEAST AND NO SIGNIFICANT UPPER FEATURES ARE EXPECTED TO AFFECT
THE CWFA...THOUGH HEIGHTS FALL SLIGHTLY TUE NIGHT AS THE NRN STREAM
LOW MOVES EAST. SO DIURNAL INSTABILITY WILL BE THE MAIN DRIVER FOR
TUE POPS...CHANCES ENDING UP CLOSE TO CLIMO FOR EARLY JULY. PROFILES
WILL BE SUBSTANTIALLY DRIER IN THE UPPER LEVELS AND THE FLOW WILL
HAVE WEAKENED ALLOWING SHEAR PARAMETERS TO RETURN TO SEASONABLY SMALL
VALUES. PULSE STORMS PRODUCING GUSTY WINDS AND HAIL WILL RETURN AS
OUR MAIN CONCERN. TEMPS WILL TOP OUT AROUND NORMAL. WED NIGHT LOW
POPS WERE MAINTAINED NEAR THE TENN BORDER WITH A COLD FRONT POSSIBLY
SINKING INTO THE OH/TN VALLEYS.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 200 AM SUNDAY...THE MEDIUM RANGE BEGINS 12Z WEDNESDAY AS A
FRONTAL BOUNDARY STEERED BY AN UPPER TROUGH OVER THE
CENTRAL PLAINS/GREAT LAKES REGION CONTINUES ITS EASTWARD PROGRESSION
TOWARDS THE FORECAST AREA. H5 HEIGHTS ON WED AND THURS WILL BE
ROUGHLY WEST TO EAST WITH A BROAD 591 HEIGHT CLOSED OFF ANTICYCLONE
OVER THE GULF COASTAL REGION. ON FRIDAY INTO SATURDAY THIS PATTERN
WILL STRENGTHEN FURTHER INTO A CLOSED 594 HEIGHT. THIS 500MB PATTERN
CENTER WILL BE OVER ROUGHLY MS AND LA ON THE GFS AND OVER NORTH TEXAS
ON THE ECMWF. MOST OF THE EXPECTED CONVECTIVE SYSTEMS ARE EXPECTED TO
MAINLY AFFECT THE NC MTNS AS THE FLOW OVER THE TOP OF THE RIDGE BRINGS
IMPULSES ACROSS KY AND VA. THE TREND IN THE LATEST MODEL RUNS ARE TO
KEEP THE SURFACE FRONT TO THE NORTH OF OUR REGION UNTIL AT LEAST THE
WEEKEND.  THIS IS EVIDENT IN BOTH THE GFS AND ECMWF. TEMPS WILL BE AROUND
NORMAL FROM WED THROUGH FRI...THEN MAY GO SLIGHTLY ABOVE NORMAL ON
SATURDAY AS THE RIDGE BUILDS. HOWEVER...IF THE RIDGE BUILDS FARTHER
WEST AS A DIP IN THE HEIGHTS OCCURS OVER THE CAROLINAS...THAT WOULD
TEND TO LOWER OUR TEMPS A BIT.

&&

.AVIATION /11Z SUNDAY THROUGH THURSDAY/...
AT KCLT...VFR CONDITIONS WILL PREVAIL THROUGH THE TAF CYCLE WITH THE
POSSIBLE EXCEPTION OF MVFR RESTRICTIONS ASSOCIATED AFTERNOON TSRA.
INITIALIZED TAF WITH LIGHT SW WINDS UNDER BKN HIGH CLOUDS WITH A 1HR
TEMPO FROM 12Z-13Z TO ACCOUNT FOR IFR/MVFR STRATUS SLIDING ALONG THE
I85 CORRIDOR.  OTHERWISE...GUSTY SW WINDS TODAY WITH SCT LOW VFR
CLOUDS UNDER BKN MID LEVEL CIRROSTRATUS.  PROB30 CARRIES OVER FROM
PREVIOUS TAF CYCLE TO ACCOUNT FOR ANY ADDITIONAL CONVECTIVE
DEVELOPMENT THIS AFTERNOON.  WOULD NOTE CONFIDENCE IN CONVECTIVE
INITIATION/TIMING IS LOW ALONG THE I77 CORRIDOR AS CAM GUID FAVORS
LOW COVERAGE YET 06Z NAM REMAINS ROBUST.  WINDS WILL SUBSIDE AFTER
SUNSET AS THE MIXED LAYER ERODES ALONG WITH RISING MID/HIGH LEVEL
CIGS.

ELSEWHERE...A MIXTURE OF VFR/MVFR AND IFR TO HEADLINE THIS TAF
CYCLE.  INITIALIZED ALL SC TAFS MVFR WITH AN IFR SCT DECK ASSOCIATED
WITH STRATUS ALONG THE I85 CORRIDOR...WHICH SHOULD ERODE WITHIN THE
FIRST TWO HOURS OF THE FCST CYCLE.  OTHERWISE...AS STATED ABOVE
CONFIDENCE IN PRECIP OCCURRENCE/TIMING IS MODEST AT BEST AS IT
PERTAINS TO ANY SITES OUTSIDE OF KAVL THIS MORNING THEREFORE ONLY
VCSH WAS MENTIONED...NO WX ELSEWHERE.  AS FOR THIS AFTERNOON PROB30S
ARE FEATURED AT THE SC SITES WHILE KAVL/KHKY HAVE PREVAILING SHRA
WITH VCTS.  WINDS WILL REMAIN GUSTY OUT OF THE SW AT THE SC SITES
AND SLIGHTLY WEAKER FURTHER NORTH OVER THE NC SITES.

OUTLOOK...THE PATTERN WILL FINALLY RETURN TO MORE OF A DIURNAL
NATURE ON MONDAY AS THE UPPER LOW EJECTS NORTHEAST.  THIS DIURNAL
PRECIPITATION TREND WILL PERSIST THROUGH MOST OF THE WORK WEEK.
RESTRICTIONS WILL REMAIN A POSSIBILITY EACH AFTERNOON DUE TO
SHRA/TSRA...AND ALSO EACH MORNING WHERE PREVIOUS RAINS HAVE OCCURRED.

CONFIDENCE TABLE...

            11-17Z        17-23Z        23-05Z        05-06Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       MED   62%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     MED   66%
KHKY       MED   75%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       MED   69%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  81%     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...FLASH FLOOD WATCH THROUGH THIS EVENING FOR GAZ010-017-018-026-
     028-029.
NC...FLASH FLOOD WATCH THROUGH THIS EVENING FOR NCZ048-051-052-058-
     059-062-063.
SC...FLASH FLOOD WATCH THROUGH THIS EVENING FOR SCZ001-004.

&&

$$
SYNOPSIS...DEO
NEAR TERM...CDG
SHORT TERM...WIMBERLEY
LONG TERM...DEO
AVIATION...CDG



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