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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KGSP 171409
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1009 AM EDT FRI MAY 17 2013

.SYNOPSIS...
A WARM AND INCREASINGLY MOIST AIR MASS WILL REMAIN OVER THE REGION
THROUGH THE REST OF THIS WEEK. A MID LEVEL DISTURBANCE WILL MOVE
ACROSS THE CAROLINAS THIS WEEKEND. WARM MOIST AIR WILL REMAIN OVER
THE AREA NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 1005 AM...TEMPERATURES ACROSS THE REGION CONTINUE TO RISE AS A
THIN LAYER OF MID LEVEL CLOUDS ALLOWS FOR MODERATE RADIATIVE
HEATING.  MOST SITES WERE REPORTING TEMPS IN THE UPPER 60S WITH A
FEW SITES BEING SLIGHTLY WARMER IN THE LOWER 70S.  AFTER LOOKING AT
LATEST NEAR TERM MODEL GUIDANCE...LOOKS AS IF GREATEST THREAT FOR
ANY CONVECTIVE ACTIVITY TODAY CONTINUES TO BE ACROSS THE HIGH
TERRAIN OF THE CAROLINAS WERE UPSLOPE FLOW WILL PROVIDE ENOUGH LOW
LEVEL FORCING TO OVERCOME ANY CAPPING INVERSIONS.  FURTHER SOUTH
ACROSS THE PIEDMONT OF SOUTH CAROLINA...FORECAST SOUNDINGS AND HIGH
RES MODEL GUIDANCE TEND TO KEEP CAP INTACT. THUS...DECIDED TO
LOWER TO SLIGHT CHANCE POPS NEAR AND ALONG THE I85 CORRIDOR.
OTHERWISE... FORECAST LOOKS TO BE ON TRACK AND NO OTHER CHANGES
WERE MADE.

REMAINDER OF PREVIOUS DISCUSSION...

PREVIOUS DISCUSSION...A CLOSED LOW OVER THE MID-SOUTH OPENS UP AND
MOVES ALONG THE LOWER OH VALLEY TODAY. LOW LEVEL MOISTURE WILL BE ON
THE INCREASE ACROSS NC THRU THE DAY. THIS LEADS TO MODERATE
INSTABILITY ACROSS THE AREA BY AFTERNOON. HOWEVER...OVER NE GA AND
THE UPSTATE SOUTH OF I-85 A SIGNIFICANT AMOUNT OF CIN REMAINS IN
PLACE. THEREFORE...HAVE BEST PRECIP CHC OVER THE NC MTNS THEN
DECREASES SOUTH AND EAST. HIGHS SHUD BE 5 TO 10 DEGREES ABOVE
NORMAL.

THE NAM CONTINUES TO BE FARTHER SOUTH WITH THE UPPER LOW TONIGHT AS
IT MOVES SLOWLY EASTWARD. THE OTHER GUIDANCE KEEPS THE LOW CLOSER TO
THE OH VALLEY. EVEN WITH THE LOW POSITION...LOW LEVEL SLY FLOW
INCREASES AGAIN OVERNIGHT BRINGING AN INCREASE IN LOW LEVEL MOISTURE
AFTER MIDNIGHT. EXPECT CONVECTION TO EXHIBIT A SOMEWHAT NORMAL
DIURNAL TREND DURING THE EVENING. HOWEVER...PRECIP CHC INCREASES
FROM WEST TO EAST AFTER MIDNIGHT AS THE LOW LEVEL MOISTURE AND
FORCING INCREASE. TSRA WILL BE POSSIBLE AS WELL WITH THE FORCING AND
CONTINUED ELEVATED INSTABILITY. LOWS WILL BE AROUND 5 DEGREES ABOVE
NORMAL.
-- End Changed Discussion --

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AT 300 AM EST FRIDAY...ON SATURDAY THE REMAINS OF AN UPPER LOW
TRACKS EAST OVER THE OH RIVER VALLEY IN THE GFS...AND OVER THE TN
RIVER VALLEY IN THE NAM. BOTH MODELS THEN MOVE THE SYSTEM SOUTHEAST
SATURDAY NIGHT...WITH THE GFS DISTURBANCE CROSSING THE CENTRAL
APPALACHIANS...AND THE NAM DISTURBANCE CROSSING NORTH GA. ON SUNDAY
THE GFS SYSTEM MOVES SLOWLY ACROSS THE CAROLINAS...WHILE THE NAM
SYSTEM MOVES EVEN SLOWER INTO THE UPPER SAVANNAH RIVER VALLEY. THE
GFS SYSTEM REACHES THE COAST ON SUNDAY NIGHT.

DEEP MOISTURE AND INSTABILITY WILL INCREASE AS THE REMAINS OF THE
UPPER LOW APPROACH...SUPPORTING INCREASING POPS...GENERALLY GREATER
DURING THE DAYTIME HOURS...BUT WITH OVERNIGHT ACTIVITY AS WELL.
CONVECTION WOULD APPEAR TO FINALLY WANE FROM THE WEST ON SUNDAY
NIGHT... ASSUMING THE GFS TIMING IS CORRECT. WITH A DEEP MOIST
LAYER...DRY AIR WILL NOT BE AVAILABLE FOR EVAPORATIVE COOLING...
LIMITING DOWNDRAFT PATERNAL. CONVECTIVE CELLS COULD PRODUCE HEAVY
RAINFALL...BUT WIND PROFILES SUGGEST CELLS WILL MOVE OFF TO THE
NORTHEAST ON MONDAY...AND MORE SLOWLY TO THE EAST ON SUNDAY...WITH A
WEAK SOUTHERLY UPSLOPE FLOW IN HTE LOWEST LEVELS. HIGH TEMPERATURES
WILL BE NEAR NORMAL...AND LOW TEMPERATURES A COUPLE OF CATEGORIES
ABOVE NORMAL.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AT 300 AM EST FRIDAY...THE ECMWF AND GFS MOVE AN UPPER RIDGE SLOWLY
ACROSS THE SOUTHERN APPALACHIANS FROM MONDAY THROUGH WEDNESDAY...
ALTHOUGH THE GFS SHOWS A WEAKNESS IN THE RIDGE OVER THE CAROLINAS
THAT LINGERS INTO THURSDAY. AN UPPER TROUGH WILL MOVE FROM THE MS
RIVER VALLEY ON WEDNESDAY TO THE OH AND TN VALLEYS BY THURSDAY.

THE SOUTHEAST WILL REMAIN IN A WARM AND MOIST AIR MASS FROM MONDAY
THROUGH THURSDAY...WITH WEAK GULF INFLOW MAINLY TO THE WEST OF THE
APPALACHIANS. DIURNALLY MODULATED POPS WILL BE CARRIED...FAVORING
THE MOUNTAINS FOR THE HIGHEST POPS WITH OROGRAPHIC EFFECTS. MAXIMUM
TEMPERATURES WILL RUN NEAR NORMAL...WITH MINIMUMS A COUPLE OF
CATEGORIES ABOVE NORMAL.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
AT KCLT AND ELSEWHERE...GENERALLY VFR CONDITIONS WILL CONTINUE
THROUGH THE TAF PERIOD. EXPECT INCREASING MID AND UPPER LEVEL CLOUDS
THRU THE MORNING. WITH SCT LOW VFR CLOUDS DEVELOPING BY NOON WITH
LOW VFR CIGS DEVELOPING DURING THE AFTERNOON. SHOULD SEE AN INCREASE
IN CONVECTIVE CHC TODAY...MAINLY ACROSS NC. THEREFORE...HAVE
INCLUDED PROB30 THERE BUT LEFT OUT OF SC WHERE INSTABILITY AND
MOISTURE ARE LOWER. SHUD SEE A DECREASE IN CONVECTION BY LATE
EVENING...BUT LOWER VFR CIGS CONTINUE. S TO SW WINDS INCREASE THRU
THE DAY THEN DIMINISH DURING THE EVENING. MVFR FOG MOST LIKELY BY
DAYBREAK SAT AT KAVL/KAND. COULD SEE FOG ELSEWHERE IF TSRA MOVE
OVER.

OUTLOOK...SHOWER AND THUNDERSTORM COVERAGE...AND ASSOCIATED
RESTRICTIONS...WILL GRADUALLY INCREASE SATURDAY THROUGH MONDAY. FAIR
WEATHER MAY RETURN BY TUESDAY.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-14Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  98%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  96%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  98%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  98%

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
-- End Changed Discussion --

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JAT
NEAR TERM...CDG/RWH
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...RWH