Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KGSP 050736
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
336 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 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 /08Z SUNDAY THROUGH THURSDAY/...
AT KCLT...VFR CONDITIONS WILL PREVAIL THROUGH THE TAF CYCLE WITH THE
POSSIBLE EXCEPTION OF MVFR RESTRICTIONS ASSOCIATED WITH MID MORNING
SHRA...AND POSSIBLE AFTERNOON TSRA.  INITIALIZED TAF WITH LIGHT SW
WINDS UNDER SCT MID TO BKN HIGH CLOUDS.  A 3HR TEMPO WAS ADDED FROM
11Z-14Z AS LATEST HRRR INDICATES BAND OF SHRA RIDING UP THE I85
CORRIDOR AROUND OR JUST AFTER DAYBREAK.  OTHERWISE...GUSTY SW WINDS
TODAY WITH SCT LOW VFR CLOUDS UNDER BKN HIGH LEVEL CIRROSTRATUS.
PROB30 CARRIES OVER FROM PREVIOUS TAF CYCLE TO ACCOUNT FOR ANY
ADDITIONAL CONVECTIVE DEVELOPMENT THIS AFTERNOON.  WINDS WILL
SUBSIDE AFTER SUNSET AS THE MIXED LAYER ERODES ALONG WITH RISING
MID/HIGH LEVEL CIGS.

ELSEWHERE...HIGHER PRECIP CHANCES THAN THAT OF KCLT ABOVE...HOWEVER
TRENDS ARE FAIRLY SIMILAR WITH SLIGHT TIMING ADJUSTMENTS.
INITIALIZED ALL TAFS VFR WITH SOME DETERIORATION FCST AT KAVL AS
CURRENT PRECIP SLIDES NORTHEAST OVER THE AIRFIELD WITHIN AN HOUR OR
SO.  OTHERWISE...TRIED TO TIME PRECIP THROUGH THE MORNING PER LATEST
CAMS AT ALL AIRFIELDS...HOWEVER WITH LOW CONFIDENCE.  FOR THE
AFTERNOON/EVENING POPS ARE HIGHEST OVER WESTERN NC ADJACENT TO
APPROACHING UPPER LOW...THUS KAVL/KHKY HAVE PREVAILING SHRA WITH
VCTS WHILE THE REMAINING SITES FEATURE VCSH WITH PROB30S FOR TSRA.

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...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       HIGH  95%     HIGH  97%     HIGH 100%     HIGH 100%
KGSP       HIGH  95%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   70%     HIGH  88%     HIGH  97%     HIGH  93%
KHKY       HIGH  86%     HIGH  97%     HIGH 100%     HIGH 100%
KGMU       HIGH  96%     HIGH  94%     HIGH 100%     HIGH 100%
KAND       HIGH  97%     HIGH  97%     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


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