Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 021431
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1031 AM EDT TUE JUN 2 2015

.SYNOPSIS...
UPPER LEVEL LOW PRESSURE WILL GRADUALLY DRIFT ACROSS THE
SOUTHEASTERN STATES THROUGH THE REMAINDER OF THE WORK WEEK...WHILE
SURFACE HIGH PRESSURE WILL BUILD DOWN FROM THE NORTH WEDNESDAY. THIS
PATTERN WILL HELP ENHANCE LIFT AND MOISTURE RETURN INTO THE
AREA...CREATING ELEVATED CHANCES FOR SHOWERS AND THUNDERSTORMS...AND
KEEPING TEMPERATURES A FEW DEGREES BELOW NORMAL.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1020 AM...THE MORNING CONVECTION HAS LARGELY WANED ACRS THE
AREA...SO POPS HAVE BEEN UPDATED. LATER TODAY...AS THE COMPACT
CLOSED UPPER LOW DRIFTS TOWARD THE AREA...ANOTHER ROUND OF NUMEROUS
SHWRS AND TSTMS IS EXPECTED. LITTLE CHANGE IN THINKING...ONLY MINOR
TWEAKS TO THE POP GRIDS FOR THIS AFTN/EVE. SOME DRY AIR WRAPPING
AROUND THE MID-UPR LVL CIRCULATION WILL HELP FURTHER DESTABILIZE THE
ATMOS AND INCREASE DCAPE. SO EXPECT A FEW SEVERE STORMS THIS AFTN
INTO THIS EVENING...WITH WIND AND HAIL BEING THE MAIN THREATS. TEMPS
LOOK ON TRACK...BUT WERE NUDGED UP A DEG OR TWO GIVEN THE LARGE
BREAKS IN CLOUD COVER SEEN ON VIS SAT IMAGERY.

AS OF 650 AM...I WILL ISSUE A QUICK UPDATE TO INCREASE
POPS...ALIGNING WITH THE LATEST RADAR IMAGES. OVERALL...THE CURRENT
FORECAST APPEARS IN GOOD SHAPE.

AS OF 350 AM...RECENT WATER VAPOR IMAGES INDICATED A WELL DEFINED
CLOSED LOW OVER THE MIDDLE KY/TN LINE...WITH THE AXIS OF THE MID
LEVEL TROF ENTERING NRN GA. AT 7Z...A WEAK COLD FRONT WAS ANALYZED
OVER THE NC MTNS. RECENT SPC MESOSCALE ANALYSIS INDICATED CAPES
RANGED FROM 100-200 J/KG ACROSS THE FOOTHILLS UP TO 250 J/KG ACROSS
THE UPPER SAVANNAH RIVER VALLEY. CLUSTERS OF CONVECTION WILL LIKELY
CONTINUE TO DEVELOP ALONG AND EAST OF THE TROF AXIS AND COLD FRONT
EARLY THIS MORNING.

THIS AFTERNOON...AN INTERESTING COMBINATION OF WEATHER FEATURES
INTERSECT ACROSS THE FORECAST AREA. THE 0Z GFS INDICATES THAT THE
CENTERED OF THE CLOSED LOW WILL SLOW DRIFT EASTWARD DURING THE
DAYLIGHT HOURS. A BAND OF H5 Q-VECTOR CONVERGENCE DEVELOP ON THE
SOUTHEAST QUADRANT OF THE LOW...SWEEPING OVER THE SOUTHERN
APPALACHIANS THIS AFTERNOON. IN THE MEANTIME...A WEAK COLD FRONT IS
EXPECTED TO REMAIN NEARLY STATIONARY ACROSS THE MTNS AND FOOTHILLS
TODAY...AS A WEDGE OF COOL AIR SURGES SW ACROSS THE VIRGINIAS.
MESOSCALE MODELS INDICATE THAT A SFC WAVE WILL DEVELOP ALONG THE
FRONT OVER NRN GA BY MID DAY...REACHING THE SOUTHERN APPALACHIANS
DURING THE AFTERNOON. THE SFC PATTERN SHOULD ALLOW DEWPOINTS TO
SLOWLY RISE DURING THE DAY...RESULTING IN CAPES FROM 1000-2000 J/KG.
BASED ON THE INTERACTION OF THE MENTIONED FEATURES...I WILL USE THE
0Z NAM FOR DETAILS. I WILL FORECAST A BAND OF EARLY AFTERNOON
SHOWERS AND THUNDERSTORMS TO DEVELOP ACROSS THE EAST FACING SLOPES
WITHIN UPSLOPE FLOW. THE CONVECTION IS FORECAST TO SLIDE ENE DURING
THE MID TO LATE AFTERNOON...SLOW DRIFTING OVER THE PIEDMONT THIS
EVENING. THESE THUNDERSTORMS WILL DEVELOP WITHIN AN ENVIRONMENT OF
LFC BELOW 4 KFT...WBZ AROUND 9 KFT...AND DECENT CAPE WITHIN THE HAIL
GROWTH ZONE. BASED ON THE ENVIRONMENT...WE WILL HIGHLIGHT THE
POTENTIAL FOR SEVERAL SEVERE WIND AND HAIL EVENTS ACROSS THE
FOOTHILLS AND PIEDMONT THIS AFTERNOON AND EVENING. HIGH TEMPERATURES
ARE FORECAST TO REMAIN AROUND 5 DEGREES BELOW NORMAL.

TONIGHT...THE CONVECTIVE BAND MAY REMAIN INTO THE EARLY MORNING
HOURS...RESULTING IN A WELL WORKED OVER AIR MASS LATE TONIGHT. AT
THE SFC...HIGH PRESSURE WILL BE SLIDING SOUTHWARD ACROSS THE MID
ATLANTIC...REACHING THE NC LINE BY DAY BREAK. LOW PRESSURE WILL
REMAIN ACROSS THE DEEP SOUTH. THIS ENVIRONMENT WILL BE RIPE FOR FOG
DEVELOPMENT...POSSIBLY DENSE BY THE PRE DAWN HOURS.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 300 AM TUE...CLOSED UPPER LOW WILL SLOWLY BEGIN TO FILL AS IT
CROSSES THE CWFA WED AND THU. HIGH PRESSURE OVER NEW ENGLAND WILL
BRIEFLY TAKE ON A CAD-LIKE CONFIGURATION...THE WEDGE STRENGTHENING
THRU WED AND SEEMINGLY PEAKING WED NIGHT. HOWEVER THE MAIN DRIVER FOR
PRECIP WED AND EVEN WED EVENING IS STILL EXPECTED TO BE DIURNAL
INSTABILITY. LOW LEVEL FLOW IS EASTERLY BUT NOT VERY STRONG...AND IT
IS NOT UNTIL WED NIGHT THAT PROFILES REFLECT ENOUGH LOW LEVEL
SATURATION IN THE WEDGE TO EXPECT STRATIFORM RAIN. HOWEVER THE UPPER
LOW AFFORDS GOOD LAPSE RATES...AND IT IS MAINLY FOR THIS REASON POPS
ARE IN LIKELY RANGE ACRS MOST OF THE AREA WED. WITH THE PATTERN
BEGINNING TO BREAK DOWN THU...POPS ARE SOMEWHAT LOWER WITH THE WEAKER
UPSLOPE COMPONENT. A NOTABLE MOISTURE PLUME IS SEEN TO OUR EAST ON
NAM/GFS PROGS...WITH PWAT VALUES ABOVE NORMAL IN THE CWFA BUT NOT
EXCEPTIONAL. DESPITE THIS ABUNDANT MOISTURE WILL STILL BE AVAILABLE
AND HEAVY RAIN MAY BE A CONCERN AT TIMES. ON WED 0-6KM BULK SHEAR
WILL BE SOMEWHAT ATYPICAL FOR OUR AREA IN JUNE...20 TO 30 KT. THIS
AND THE ABOVE AVERAGE BUOYANCY HAS PROMPTED THE INCLUSION OF MAINLY
OUR SC/GA ZONES IN THE MARGINAL RISK AREA ON THE SPC DAY 2 OUTLOOK.

MAX TEMPS WILL BE BELOW CLIMO BOTH WED AND THU...ESPECIALLY OVER WRN
NC WHERE MANY AREAS WILL ONLY SEE HIGHS IN THE MID 70S. MINS WILL BE
NEAR NORMAL.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 230 AM TUE...THE UPPER LOW OVER THE CWFA DRIFTS EASTWARD
FRIDAY...AND AN AMPLIFYING NRN STREAM TROUGH QUICKLY PHASES WITH IT.
AS THE SAME TROUGH MOVES INTO NEW ENGLAND IT SHOULD HELP ERODE WHAT/S
LEFT OF THE WEDGE...WHICH WILL BE LOSING STRENGTH ANYWAY GIVEN THE
DEPARTURE OF THE PARENT HIGH. THOUGH FLOW WILL BE NWLY AND
DOWNSLOPING...SUFFICIENT SBCAPE VALUES ARE PROGGED FOR MODEST POPS.

CONFIDENCE BECOMES A BIT LOWER GOING INTO SATURDAY AS MODEL SOLUTIONS
BEGIN TO DIVERGE. A SHORTWAVE EXITING THE OHIO VALLEY WILL APPROACH
OUR AREA. THE EC IS FASTER THAN THE GFS WITH THIS FEATURE AND BRINGS
IT IN FAST ENOUGH TO ACTUALLY REINFORCE THE SHORTWAVE REMAINING OVER
THE CAROLINAS FROM EARLIER IN THE WEEK...TURNING IT INTO ANOTHER
NEARLY STATIONARY UPPER LOW OVERHEAD. BOTH MODELS DO FEATURE A BROAD
SFC HIGH BUILDING IN BEHIND THAT NORTHERN STREAM TROUGH. THIS PUSHES
A COLD FRONT AT LEAST AS FAR SOUTH AS KY/VA BY SUNDAY. EASTERLY FLOW
ACCORDINGLY RESUMES INTO OUR AREA. EC DEPICTS MORE MOISTURE ALONG THE
BOUNDARY...AND LOWER HEIGHTS OVER OUR CWFA ON ACCOUNT OF THE MERGED
UPPER LOW SITTING ATOP IT. THE GFS PATTERN FOR SUNDAY IS MUCH MORE
LIKE CAD THOUGH THE EC/S INTERACTING BOUNDARY AND UPPER LOW WOULD
PRODUCE SIMILAR EFFECTS FOR US. BOTH MODELS BREAK DOWN THESE PATTERNS
LATE SUNDAY AND EARLY MONDAY AS HEIGHTS FALL TO OUR NORTH AND
WEST...AND A COLD FRONT SUBSEQUENTLY MOVES IN.

POPS WILL CONTINUE TO REFLECT SOME DIURNAL VARIATION BUT THE PATTERN
WILL SUPPORT SOME DEGREE OF NOCTURNAL CONVECTION. ABOVE CLIMO POPS
ARE EXPECTED EACH DAY WITH THE BEST CHANCE EXPECTED SATURDAY. TEMPS
WARM SLIGHTLY FRIDAY TO SATURDAY...REACHING NEAR CLIMO
VALUES...BEFORE DIPPING AGAIN SUNDAY ON THE COOL SIDE OF THE BOUNDARY
/OR WITHIN THE WEDGE/. SLIGHTLY WARMER TEMPS RETURN MONDAY.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
AT KCLT...RECENT WATER VAPOR IMAGES INDICATED A WELL DEFINED CLOSED
LOW OVER THE MIDDLE KY/TN LINE...WITH THE AXIS OF THE MID LEVEL TROF
ENTERING NRN GA. AT 9Z...A WEAK COLD FRONT WAS ANALYZED OVER THE
NC/SC MTNS BORDER. CLUSTERS OF CONVECTION WILL LIKELY CONTINUE TO DEVELOP
ALONG AND EAST OF THE TROF AXIS AND COLD FRONT EARLY THIS MORNING.
BASED ON MOS...I WILL INDICATE THE CEILINGS WILL GRADUALLY LOWER
THROUGH SUNRISE...ESPECIALLY WITHIN GAPS OF SHRA. UNTIL FROPA THIS
EVENING...WINDS WILL REMAIN FROM THE SOUTHWEST LESS THAN 10 KTS. CAMS AND
NAM12 GENERALLY AGREE THAT A LINE TO BROKEN LINE OF TSRA WILL
DEVELOP ACROSS THE EAST FACING SLOPES THIS AFTERNOON. ONCE THE LINE
DEVELOPS...IT WILL TRACK EASTWARD...CROSSING THE TERMINAL BETWEEN
22Z THROUGH 6Z...INDICATED WITH A FM GROUP. WIDESPREAD LOW CLOUDS
ARE FORECAST TO DEVELOP ACROSS THE REGION TONIGHT...PRIMED BY
ADVANCING WEDGE FRONT AND WET GROUND.

ELSEWHERE...CONVECTION WILL REMAIN THE PRIMARY CHALLENGE AS COVERAGE
WILL INCREASE WITH THE PASSAGE OF COLD FRONT AND A DEEP H5 TROF. FOR
THE FIRST ONE TO TWO HOURS OF THE 12Z TAFS...I WILL INDICATE
RESTRICTIVE CEILINGS AT KAVL...KGSP... AND KGMU. I WILL HIGHLIGHT
THE LATE AFTERNOON AND EVENING FOR A BAND OF MTN TSRA TO ORGANIZE
AND SLIDE EAST. CONVECTION WILL BEGIN TO SHIFT EAST OF THE REGION
AROUND MIDNIGHT. IT APPEARS THAT ALL TAF SITES WILL SEE SOME
RAINFALL BY MID EVENING. WIDESPREAD LOW CLOUDS
ARE FORECAST TO DEVELOP ACROSS THE REGION TONIGHT...PRIMED BY
ADVANCING WEDGE FRONT AND WET GROUND.

OUTLOOK...A MID LEVEL LOW IS FORECAST TO REMAIN ACROSS THE DEEP
SOUTH THROUGH THE WORK WEEK. DEEP MOISTURE WILL LINGER ACROSS
THE SOUTHEAST CONUS THROUGH THE WEEK. SHOWERS AND THUNDERSTORMS MAY
DEVELOP EACH AFTERNOON AND EVENING. MORNING STRATUS AND FOG WILL
REMAIN A POSSIBILITY...ESPECIALLY OVER WET GROUND.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       HIGH  98%     HIGH 100%     MED   75%     MED   70%
KGSP       HIGH 100%     MED   77%     MED   71%     LOW   57%
KAVL       HIGH  95%     HIGH  95%     HIGH  83%     HIGH  87%
KHKY       HIGH  93%     MED   70%     HIGH  80%     HIGH  84%
KGMU       HIGH 100%     MED   66%     MED   74%     MED   67%
KAND       HIGH 100%     HIGH 100%     LOW   41%     LOW   49%

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...ARK/NED
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...NED



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