Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 311802
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
202 PM EDT SUN MAY 31 2015

.SYNOPSIS...
BERMUDA HIGH PRESSURE WILL PERSIST ACROSS THE REGION INTO THE EARLY
HALF OF THE WEEK.  A SERIES OF LOW PRESSURES WILL MOVE NORTHEAST
ALONG A STALLED OUT FRONT FROM LOUISIANA TO THE VIRGINIAS EARLY IN
THE WEEK.  AN UPPER LOW IS EXPECTED TO FORM OVER THE MID SOUTHEAST
EITHER MONDAY OR TUESDAY AND REMAIN FOR MUCH OF THE WEEK.  THIS WILL
MAKE IT A WETTER THAN NORMAL WEEK FOR OUR REGION.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 155 PM...ISOLATED TO WIDELY SCT CONVECTION IS DEVELOPING
ACROSS THE AREA THIS AFTERNOON...BUT HAS BECOME NUMEROUS TO
WIDESPREAD ACROSS THE TENN VALLEY/NORTH GA/TENN MTNS. LIKELY POPS
STILL LOOK VERY GOOD ACROSS OUR ZONES BORDERING TENN...BUT HAVE ALSO
BEEN EXPANDED ACROSS THE NORTHEAST GA MTNS. CELLS HAVE BEEN WELL-
BEHAVED THUS FAR...BUT INSTABILITY SHOULD BE SUFFICIENT TO SUPPORT A
COUPLE OF BRIEF/PULSE SEVERE STORMS...ALTHOUGH THE MAIN CONCERN
SHOULD CONTINUE TO BE LOCALLY HEAVY/POSSIBLY EXCESSIVE RAINFALL WITH
TRAINING/BACK-BUILDING CELLS.

AS OF 1045 AM...ALTHOUGH WIDELY SCATTERED SHOWERS PERSIST NEAR THE
SOUTHERN ESCARPMENT LATE THIS MORNING...COVERAGE AND RAIN RATES HAVE
DIMINISHED CONSIDERABLY FROM WHAT WAS SEEN ABOUT 2 HOURS AGO. THIS
APPEARS TO BE TIED TO INCREASED BL MIXING RESULTING IN WEAKENING OF
THE SW LOW LEVEL JET (SUCH AS IT WAS)...REVEALED NICELY BY THE VAD
WIND PROFILE FROM KGSP. WIDESPREAD LOW CLOUD COVER PERSISTS ACROSS
MUCH OF THE FORECAST AREA THIS MORNING...ALTHOUGH PLENTY OF BREAKS
ARE NOTED...ESPECIALLY ALONG THE EASTERN BORDER AND TENN BORDER
AREAS OF THE CWA. THESE TWO AREAS ARE GENERALLY WHERE THE BEST
INSTABILITY CAN BE FOUND...WHICH IS QUITE A BIT HIGHER THAN
YESTERDAY...THANKS TO HIGHER SURFACE DEWPOINTS AND COOLING TEMPS
ALOFT RESULTING FROM FALLING UPPER HEIGHTS. IN FACT...SBCAPE IS
ALREADY AS HIGH OR HIGHER THAN IT WAS AT ANY POINT ON SATURDAY.
PWATS FROM UPSTREAM 12Z RAOBS ARE ALSO HIGHER THAN YESTERDAY. ALL
THIS POINTS TO MUCH HIGHER PROBABILITIES OF CONVECTION THIS
AFTERNOON. IN FACT...SCATTERED SHOWERS ARE ALREADY PUSHING ACROSS
THE GREAT TENN VALLEY AHEAD OF A COLD FRONT THIS MORNING. THESE ARE
STILL A FEW HOURS AWAY FROM OUR CWA...WHICH SHOULD GIVE THE WESTERN
MTNS PLENTY OF TIME TO DESTABILIZE A BIT MORE. THIS LENDS SUPPORT TO
THE ADVERTISED LIKELY TO EVEN CAT POPS ALONG THE TENN BORDER.
FARTHER EAST...THE CONVECTIVE FORECAST GETS A LITTLE TRICKIER...
PRIMARILY OWING TO UNCERTAINTY REGARDING THE DEGREE OF INSTABILITY
DUE TO ONGOING LOW CLOUDS BUT ALSO DUE TO LESS MOISTURE CONTENT.
POPS THEREFORE TAPER FROM 40-50 PERCENT FROM THE UPPER SAVANNAH
RIVER VALLEY...NORTHEAST ALONG THE BLUE RIDGE...TO 20-30 PERCENT
ACROSS THE EASTERN THIRD OF THE FORECAST AREA. ALTHOUGH SHEAR
REMAINS WEAK...ENOUGH MID-LEVEL DRY AIR EXISTS FORECAST SOUNDINGS TO
POSE A RISK OF A WET MICROBURST OR TWO...WHILE THE POTENTIAL FOR
TRAINING/BACK-BUILDING CELLS COULD LEAD TO A LOCALIZED HEAVY...IF
NOT EXCESSIVE RAINFALL THREAT.

AS OF 645 AM...SHOWERS ACROSS THE EAST FACING SLOPES CONTINUE TO
DEVELOP AND DRIFT NE. I WILL UPDATE THE FORECAST TO TREND POPS
HIGHER OVER THE FAVORED AREAS. OTHERWISE...I WILL MAKE SLIGHT
CHANGES TO SKY...TEMP...AND WIND.

AS OF 530 AM...RECENT RADAR IMAGES INDICATED SEVERAL CLUSTERS OF
SHOWERS ACROSS THE EAST FACING SLOPES ALONG THE NC/SC BORDER. I WILL
INCREASE POPS FROM SCHC TO CHC THROUGH THIS MORNING. IN
ADDITION...THE FORECAST UPDATE WILL FEATURE INCREASE SKY COVER ALONG
THE UPSLOPE AREAS.

AS OF 245 AM...RADAR AND SATELLITE IMAGES INDICATE THAT AN OLD SEA
BREEZE BOUNDARY LIFT NW ACROSS THE PIEDMONT AND FOOTHILLS...BECOMING
NEARLY STATIONARY ALONG THE EAST FACING SLOPES OF THE MTNS. BKN TO
OVC STRATUS IS FORECAST TO DEVELOP ACROSS THE FORECAST AREA AROUND
DAYBREAK...REMAINING UNTIL MID MORNING. BY MID DAY...DIURNAL MIXING
SHOULD DISSIPATE THE STRATUS AND SCT TO BKN CU SHOULD DEVELOP. USING
A BLEND OF PREFERRED MOS...HIGH TEMPERATURES ARE FORECAST TO RANGE
WITHIN A DEGREE OR TWO OF VALUES OBSERVED ON SATURDAY.
HOWEVER...PERSISTENT RETURN FLOW IS EXPECTED TO YIELD AFTERNOON
DEWPOINTS 2 TO 4 DEGREES WARMER THAN SATURDAY. AT THE MID
LEVELS...HEIGHTS WILL GRADUALLY FALL ACROSS THE WESTERN ZONES AS A
CLOSED LOW DEVELOPS OVER ARKANSAS. FORECAST SOUNDINGS INDICATE THAT
WEAK TO MODERATE VALUES OF CAPE WILL EXIST ACROSS THE FORECAST AREA
THIS AFTERNOON. HOWEVER...FORECAST SOUNDINGS ALSO SHOW A SIGNIFICANT
LAYER OF CIN CENTERED AROUND H85. CAMS AND NEAR TERM MODELS INDICATE
THAT THE GREATEST COVERAGE OF SHOWERS AND THUNDERSTORMS SHOULD OCCUR
WITHIN A MOISTURE CONVERGENCE AREA ALONG THE TN/NC STATE LINE DURING
THE LATE AFTERNOON. TO THE EAST...GUIDANCE DOES NOT SHOW MUCH
COVERAGE...LIKELY THE HIGHEST OVER THE UPPER SAVANNAH RIVER VALLEY
AROUND SUNSET. I WILL CONTINUE TO INDICATE CHC POPS EAST WITH LIKELY
POPS ACROSS THE TN BORDER.

TONIGHT...CONVECTION COVERAGE MAY LINGER WELL INTO THE
NIGHT...SUPPORTED BY THE APPROACH OF A COLD FRONT AND SOUTH LLVL
WINDS. IN ADDITION...THE H5 TROF/CLOSED LOW CENTERED OVER THE
MISSISSIPPI RIVER DEEPENS DURING THE NIGHT. THE COMBINATION OF LOW
PRESSURE TO THE WEST AND HIGH PRESSURE OVER THE ATLANTIC...THE
ENVIRONMENT SHOULD REMAIN VERY MOIST OVERNIGHT. THE FORECAST WILL
FEATURE BKN TO OVC CLOUD COVER. LOW TEMPERATURES WILL RANGE FROM THE
LOW 60S WITHIN THE MTN VALLEYS TO MID TO UPPER 60S EAST.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 215 AM SUNDAY MORNING...THE SHORT TERM FCST PICKS UP AT 12Z ON
MONDAY WITH UPPER RIDGING LINGERING OVER THE REGION AND AN UPPER
TROF GRADUALLY MAKING ITS WAY TOWARDS THE CWFA. IT APPEARS THAT THE
MODELS HAVE SLOWED THE TROFS PROGRESSION EVEN MORE OVER THE PAST DAY
OR SO. THEY DEPICT A CLOSED H5 LOW DEVELOPING BY EARLY TUES WITH THE
LOW THEN STALLING OUT JUST TO OUR WSW ON WED. IT APPEARS THAT THE
LOW WILL REMAIN COMPLETELY SEPARATED FROM THE MEAN UPPER FLOW TO THE
NORTH WELL INTO THE MEDIUM RANGE.

AT THE SFC...MOIST SLY FLOW WILL OVERSPREAD MOST OF THE CWFA BY MON
MORNING. AS WE MOVE THRU MON...WIDESPREAD SHOWERS AND TS REMAIN
LIKELY WITH SLY FLOW TO OUR SOUTH AND NLY FLOW ASSOCIATED WITH THE
GREAT LAKES HIGH TO OUR NORTH. ITS APPEARS THAT WE WILL REMAIN
SANDWICHED IN BETWEEN THE NLY AND SLY FLOW THRU THE REMAINDER OF THE
PERIOD AS THE GREAT LAKES HIGH SLIDES FARTHER EAST. ANY DEGREE OF
WEDGING ASSOCIATED WITH THE HIGH WONT LIKELY DEVELOP UNTIL BEYOND
WED. AS FOR THE SENSIBLE FCST...NO SIG CHANGES WERE NEEDED FOR THE
PERIOD WITH WIDESPREAD LIKELY POPS FOR MON AFTERNOON/EARLY EVENING
HOURS. POPS REMAIN AT HIGH END CHANCE THRU 12Z WED WITH LINGERING
DEEP MOISTURE OVER THE AREA. MODEL PROFILES CONTINUE TO FEATURE HEALTHY
AMOUNTS OF SFC BASED CAPE EACH DAY WITH SPC INCLUDING OUR CWFA UNDER
A SLIGHT RISK AREA ON MON AND TUES. SUFFICE TO SAY...CONDITIONS
LOOK FAVORABLE FOR WIDESPREAD TS ACTIVITY WITH SOME STORMS BECOMING
SEVERE. TEMPS WILL HAVE A REDUCED DIURNAL RANGE DUE TO SIG CLOUD
COVER AND MOISTURE...WITH MAXES NEAR NORMAL AND MINS A FEW DEGREES
ABOVE NORMAL.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 135 PM SUNDAY AFTERNOON...THE MEDIUM RANGE FCST STARTS AT
00Z THURSDAY WITH A 500MB CUTOFF LOW SOMEWHERE AROUND ALABAMA.  THIS
CUTOFF LOW IS FORECAST TO DRIFT EITHER SOUTH ACROSS THE GULF OR SE
OVER FLORIDA AT THE END OF THE WEEK. WHILE THE CUTOFF LOW DOES
THIS IT IS FORECAST TO OPEN UP INTO GENERAL TROFINESS OVER THE EAST
COAST WITH AN UPPER RIDGE BUILDING OVER TEXAS.

AT THE SFC...A LARGE PLUME OF PERSISTENT DEEP LYR MOISTURE
ASSOCIATED WITH A DISSIPATING FRONTAL ZONE WILL KEEP THE FCST AREA
UNDER FAVORABLE CONDITIONS FOR WIDESPREAD SHOWERS AND MAINLY PM
THUNDER FOR THE SECOND HALF OF THE WEEK.  THIS PATTERN WEAKENS
SOME BY SUNDAY WITH THE RIDGE TO OUR WEST NOSING IN A BIT PRIOR TO
ANOTHER 500MB REINFORCING TROUGH DIPPING DOWN FROM MID CANADA.
ALSO NEXT WEEKEND...SURFACE HIGH PRESSURE IS EXPECTED TO DROP SE
FROM CANADA TO BE OVER NEW ENGLAND CREATING A TRANSIENT WEDGE OF
COOL AIR OVER OUR REGION.  THE LATEST GFS HAS A 500MB CUTOFF LOW
FORM DIRECTLY OVER OUR AREA SUNDAY THEN DRIFTING A BIT EAST GOING
INTO NEXT MONDAY. THIS WOULD ENHANCE THE COOLING EFFECT OF COMBINED
NE FLOW FROM SURFACE HIGH PRESSURE NEAR NEW ENGLAND WITH THE
DEEPER COOLING AND LOWER FREEZING LEVEL WITH THE H5 LOW. CAPE
VALUES FOR THE FOOTHILLS AND PIEDMONT EACH DAY SHOULD BE GREATER
THAN 1500 ACCORDING TO ALL MODELS WHICH WILL SUPPORT PM THUNDER.
HIGH TEMPERATURES WILL BE COOLER THAN NORMAL AND MAY TREND COOLER
IF THE INFLUENCE OF THE CUTOFF LOWS AND WEDGE BECOME GREATER.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
AT KCLT...SCATTERED CONVECTION HAS DEVELOPED ACROSS THE FOOTHILLS
THIS AFTERNOON...BUT IT NOT MAKING MUCH EASTWARD PROGRESS.
NEVERTHELESS...OUTFLOW BOUNDARIES FROM THIS ACTIVITY COULD PUSH INTO
THE PIEDMONT BY LATE AFTERNOON. VCSH IS BEING CARRIED AFTER 20Z...
ALONG WITH A TEMPO FOR SHRA. THUNDER CAN CERTAINLY NOT BE RULED
OUT...BUT DIDN/T HAVE CONFIDENCE TO INCLUDE TS IN THE TEMPO ATTM.
OTHERWISE...SW WINDS AT 5-10 KTS WILL CONTINUE THROUGH THE
AFTERNOON...ALONG WITH SCT/BKN CU IN THE 035-045 RANGE. LOW LEVEL
MOISTURE WILL PERSIST THROUGH THE PERIOD...BUT THE POTENTIAL FOR
THIS TO DEVELOP AS LOW CLOUDS APPEARS LOWER FOR MONDAY MORNING THAN
IN RECENT DAYS. THEREFORE...KEPT CONDITIONS AT THE VFR LEVEL THROUGH
THE PERIOD...EXCEPT FOR THE TEMPO SHRA THIS PM.

ELSEWHERE...ISOLATED CONVECTION IS DEVELOPING OVER THE WESTERN
CAROLINAS EARLY THIS AFTERNOON. HOWEVER...NUMEROUS TO WIDESPREAD
CELLS ARE AMASSING ACROSS THE MTNS AND GREAT VALLEY OF EAST TENN...
AND INTO NORTH GEORGIA. THIS ACTIVITY IS NOT MAKING A GREAT DEAL OF
EASTWARD PROGRESS...BUT WILL GRADUALLY SPREAD INTO THE AREA FROM
MID-AFTERNOON THROUGH EARLY EVENING. SCATTERED ACTIVITY WILL LIKELY
DEVELOP OUT AHEAD OF THIS ACTIVITY...SO VCTS WILL BE CARRIED BY NO
LATER THAN 21Z. MEANWHILE...TEMPOS ARE BEING CARRIED AT KHKY/KAVL IN
LIGHT OF CURRENT ACTIVITY NEAR THOSE TERMINALS. LOW LEVEL MOISTURE
WILL PERSIST THROUGH THE PERIOD...BUT THE POTENTIAL FOR THIS TO
DEVELOP AS LOW CLOUDS APPEARS LOWER FOR MONDAY MORNING THAN IN
RECENT DAYS. THEREFORE...GENERALLY KEPT CONDITIONS AT THE VFR LEVEL
THROUGH THE PERIOD...EXCEPT AT KAVL...WHICH WILL SEE BETTER CHANCES
FOR RESTRICTIONS TOWARD DAYBREAK.

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...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH  92%     HIGH  87%
KAVL       HIGH 100%     HIGH  99%     HIGH  81%     HIGH  83%
KHKY       HIGH 100%     HIGH 100%     HIGH  88%     MED   76%
KGMU       HIGH 100%     HIGH 100%     HIGH  96%     HIGH  87%
KAND       HIGH 100%     HIGH 100%     HIGH  97%     HIGH  83%

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...DEO
NEAR TERM...JDL/NED
SHORT TERM...JPT
LONG TERM...DEO
AVIATION...JDL



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