Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 051800
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
200 PM 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 MONDAY/...
AS OF 145 PM EDT...SATELLITE IMAGERY AND THE LATEST RAP ANALYSIS
SHOW THE CLOSED 500 MB LOW CENTER OVER ERN KY THIS AFTERNOON.
VORTICITY MAXIMA ROUNDING THIS SYSTEM ARE MOVING ACROSS THE SRN
APPALACHIANS AND PROVIDING SOME TRIGGERING FOR SHRA/TSRA THIS
AFTERNOON. THE UPPER LOW WILL SLOWLY FILL AND LIFT NE TONIGHT...WITH
THE ASSOCIATED TROUGH AXIS MOVING EASTWARD INTO THE CENTRAL
APPALACHIANS. DESPITE THE APPROACHING UPPER TROUGH...850 TO 500 MB
LAPSE RATES ARE A RATHER MODEST 5 TO 5.5 DEG C/KM. HOWEVER...SBCAPE
VALUES HAVE BUBBLED UP TO 1500 TO 2000 J/KG ALONG THE NRN TIER AND
OVER THE PIEDMONT...SO AT LEAST SCT THUNDERSTORMS SHOULD FORM WITH
THE IMPROVING UPPER SUPPORT. RESIDUAL SHOWERS MAY LINGER ALONG THE
WESTERN MTNS IN LOW LEVEL WESTERLY UPSLOPE FLOW OVERNIGHT EVEN AFTER
ANY DPVA ALOFT HAS PASSED. THE CURRENT FFA WILL REMAIN IN PLACE
THROUGH 00Z. THE NORTHERN MOUNTAINS AND FOOTHILLS COULD SEE PERIODS
OF HEAVY RAIN THIS AFTN/EVENING...BUT NOT ENOUGH TO WARRANT
EXPANSION/EXTENSION OF THE WATCH.

THE UPPER TROUGH WILL MOVE SLOWLY EAST ON MONDAY...WITH MOST OF THE
FORECAST AREA GETTING MORE INTO AN NVA REGION THROUGH THE DAY. WITH
LESS CLOUDS AND MORE HEATING...CONVECTION MAY DEVELOP EASTWARD OFF
THE BLUE RIDGE MONDAY AFTN...ESPECIALLY WITH LOW LEVEL CONVERGENCE
FORMING ALONG THE ERN SLOPES AND IN A LEE TROUGH. LAPSE RATES
STEEPEN A BIT MONDAY AFTERNOON...BUT WARM AIR ALOFT IN PROFILES
SHOULD LIMIT CAPE SOMEWHAT. 850 TO 500 MB LAPSE RATES SHOULD STILL
MANAGE TO REACH 6.5 DEG C/KM...AND WITH MID LEVEL DRY AIR WRAPPING
IN...A GENERAL TSTM THREAT WITH LOCALLY GUSTY WINDS SHOULD ARISE.
TEMPS WILL WARM BACK CLOSE TO CLIMO.

&&

.SHORT TERM /MONDAY NIGHT 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 /18Z SUNDAY THROUGH FRIDAY/...
AT KCLT...INSTABILITY CONTINUES TO STEADILY BUILD OVER THE PIEDMONT
THIS AFTERNOON AHEAD OF APPROACHING UPPER VORT LOBE ENERGY FROM THE
TROUGH W OF THE MTNS. THE HRRR HAS CONVECTION CROSSING THE AIRFIELD
CIRCA 19Z TO 20Z...BUT IT INITIALIZED POORLY IN UPSTREAM AREAS...SO
WILL CONFINE PRECIP MENTION TO SHRA AT PRESENT. SHOWERS WILL
DIMINISH THIS EVENING. THERE WILL BE A CHANCE OF LOW STRATUS AGAIN
MONDAY MORNING EVEN THOUGH THIS IS NOT DEPICTED ON THE MODELS/MOS.
EXPECT SW FLOW THROUGH THE PERIOD...MAINLY 10 TO 15 KT WITH A FEW
LOW END GUSTS THIS AFTN...THEN LIGHTER THE REST OF THE PERIOD.

ELSEWHERE...SHOWER COVERAGE WILL FILL IN ACROSS THE MTN AND FOOTHILL
SITES THROUGH THE LATE AFTERNOON HOURS AS THE BETTER UPPER VORT LOBE
SUPPORT ARRIVES. TSRA CHANCES WILL BE BEST FROM KAVL TO KHKY...BUT
CANNOT RULE OUT A VCTS AT THE UPSTATE SITES SINCE INSTABILITY HAS
SLOWLY REBOUNDED AFTER THE MORNING CLOUDS SCATTERED. ANTICIPATE SW
FLOW WITH LOW END GUSTS THIS AFTN...BECOMING LIGHT TONIGHT...AND
TURNING MORE NW AT KAVL BEHIND THE PASSING TROUGH. LOW CLOUDS WILL
CERTAINLY BE POSSIBLE AGAIN MON MORNING...BUT WITH THE BEST CHANCE
IN THE FRENCH BROAD VALLEY AT KAVL.

OUTLOOK...THE WEATHER REGIME WILL RETURN TO A MORE TYPICAL DIURNAL
SUMMERTIME PATTERN THROUGH THE WEEK. THIS WILL MEAN SCATTERED
AFTN/EVENING THUNDERSTORMS OVER THE AREA...MAINLY IN THE MTNS...WITH
ASSOCIATED RESTRICTIONS UNDER THE HEAVIEST SHOWERS...AND SPOTTY LOW
CLOUDS AND FOG THE FOLLOWING MORNING.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   79%     HIGH  81%     MED   63%     MED   79%
KHKY       HIGH 100%     HIGH 100%     MED   72%     HIGH  86%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH  81%     HIGH  81%

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 UNTIL 8 PM EDT THIS EVENING FOR GAZ010-017.
NC...FLASH FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR NCZ048-051-
     052-058-059-062-063.
SC...NONE.

&&

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



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