Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 300216
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1016 PM EDT FRI MAY 29 2015

.SYNOPSIS...
BERMUDA HIGH PRESSURE WILL PERSIST ACROSS THE REGION THROUGH THE
WEEKEND AND INTO EARLY NEXT WEEK...WITH MOIST SOUTHERLY FLOW FUELING
SCATTERED AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS.SATURDAY
WILL BE THE DRIEST DAY OF THE WEEKEND...BEFORE A COLD FRONT
APPROACHES THE AREA BY TUESDAY AND STALLS OUT THROUGH THE MIDDLE OF
NEXT WEEK...KEEPING RAIN CHANCES ABOVE AVERAGE. A SLOW DRYING
OUT/WARMING TREND IS EXPECTED BY THE END OF NEXT WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 10 PM...ONE PATCH OF SHOWERS/STORMS REMAINS OVER CALDWELL AND
ALEXANDER COUNTIES...MOVING SLOWLY OFF TO THE N/NW. WILL KEEP AN
AREA OF CHANCE POP INTO THE LATE EVENING TO ACCT FOR THIS AND
DECREASE IT BY MIDNIGHT OR SO. STILL POSSIBLE THAT THE LIGHT SE
UPSLOPE FLOW COULD TRIGGER A FEW SHOWERS TOWARD DAYBREAK NEAR THE
BLUE RIDGE. EXPECT SOME LOW CLOUD REDEVELOPMENT IN THE UPSLOPE AREAS
ALONG/E OF THE BLUE RIDGE IN THE PRE-DAWN HOURS. TEMPS LOOK OK.

REMAINDER OF PREVIOUS DISCUSSION...

MODEST BUOYANCY SHOULD KEEP THE SEVERE STORM THREAT RATHER LOW.
CONVECTION SHOULD DIMINISH QUICKLY THIS EVENING. WITH SE LOW LEVEL
FLOW PERSISTING...ANOTHER SURGE OF ATLANTIC MOISTURE IS EXPECTED TO
PUSH INTO THE AREA TOWARD DAYBREAK...AND THIS COULD RESULT IN SOME
ISOLATED SHOWERS NEAR THE ESCARPMENT...BUT WILL LIKELY BE MANIFEST
MORE AS EXPANDING LOW CLOUD COVER. MIN TEMPS WILL BE NEAR TO
SLIGHTLY ABOVE NORMAL.

SATURDAY...OTHER THAN PERSISTENT WEAK UPSLOPE FLOW AND SCANT LOW
LEVEL MOISTURE...NOT MUCH TO HANG ONE/S HAT ON IN TERMS OF THE
CONVECTIVE POTENTIAL. INSTABILITY PARAMETERS FROM FORECAST SOUNDINGS
ARE RATHER PITIFUL FOR LATE MAY...OWING TO WEAK LAPSE RATES/FAIRLY
WARM TEMPS ALOFT RESULTING FROM RISING HEIGHTS. NEVERTHELESS...
THERE WILL BE SOME DEGREE OF BUOYANCY...AND COMBINATION OF UPSLOPE
FLOW/DIFF HEATING SHOULD ALLOW FOR A FEW CELLS...MAINLY IN THE FORM
OF SHOWERS TO FORM NEAR THE HIGH TERRAIN DURING THE AFTERNOON...AND
NEAR-CLIMO POPS WILL BE ADVERTISED.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AT 2 PM EDT FRIDAY...ON SATURDAY EVENING AN UPPER RIDGE WILL BE NEAR
BERMUDA...WHILE AND UPPER TROUGH WILL BE MOVING FROM THE PLAINS TO
THE MS RIVER VALLEY. THE TROUGH CROSSES THE MS RIVER VALLEY ON
SUNDAY NIGHT...REACHING THE OH AND TN RIVER VALLEYS ON MONDAY.
SHORTWAVE ENERGY MOVING THROUGH THIS TROUGH REMAINS TO OUR WEST UNTIL
MONDAY...WHEN A SHORTWAVE CROSSES THE SOUTHERN APPALACHIANS LATE IN
THE DAY.

AT THE SURFACE...A COLD FRONT WILL SLOW WHILE CROSSING THE OH AND
LOWER MS RIVER VALLEY ON SATURDAY NIGHT. THIS FRONT REACHES THE
SOUTHERN APPALACHIANS BY EARLY MONDAY...THEN MOVES VERY LITTLE
DURING THE DAY. INSTABILITY IS EXPECTED TO INCREASE ALONG AND AHEAD
OF THIS BOUNDARY ON SUNDAY...AND SHEAR IS EXPECTED TO FOLLOW SUIT ON
MONDAY...SUPPORTING AN INCREASING CHANCE OF CONVECTION. LOW LEVEL
FLOW WILL BE VEER FROM LIGHT SW ON SUNDAY...TO SLIGHTLY GREATER BUT
NEARLY PARALLEL TO THE BLUE RIDGE ON MONDAY...LIMITING THE UPSLOPE
FLOW COMPONENT. ISENTROPIC UPGLIDE WILL BE LARGELY LACKING.
PRECIPITATION AMOUNTS WILL BE GREATEST WHERE THUNDERSTORMS MOVE
SLOWLY IN WEAK SOUTHERLY STEERING FLOW ON SUNDAY...MAINLY AGAINST
THE BLUE RIDGE...AND WHERE THEY TRAIN IN BETTER SW FLOW ON SUNDAY.
TEMPERATURES WILL RUN SLIGHTLY ABOVE NORMAL.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 230 PM FRIDAY...MODEL CONSISTENCY AT THE BEGINNING OF THE
MEDIUM RANGE IS RELATIVELY GOOD. THE PERIOD STARTS MONDAY NIGHT WITH
AN UPPER TROUGH AND ASSOCIATED SURFACE FRONT JUST TO THE WEST OF THE
SOUTHERN APALACHIANS...WITH A RATHER BROAD UPPER LOW OVER THE MS/LA
GULF COAST. THE FRONTAL BOUNDARY MEANDERS SLIGHTLY TO THE EAST...AND
REMAINS STALLED OVER OUR AREA THROUGH TUESDAY NIGHT. A MOIST AIRMASS
WILL REMAIN IN PLACE OVER THE CWA AHEAD OF THE FRONT...RESULTING IN
LIKELY POPS FOCUSED AROUND THE FRONTAL BOUNDARY WITH SLIGHTLY
DIURNAL TREND. A SURFACE HIGH WILL BUILD INTO THE NORTHEAST ON
WEDNESDAY...CREATING A WEDGE/CAD SETUP BY THURSDAY THAT SHOULD
REMAIN AT LEAST THROUGH FRIDAY.

MODEL DIVERGENCE BEGINS ON THURSDAY...WITH THE GFS NOW SUGGESTING A
WETTER END OF THE PERIOD THAN THE ECMWF. THE GFS MAINTAINS AN UPPER
LEVEL LOW SLOWLY LIFTING NORTHWARD FROM THE GULF COAST WHICH
WOULD PREVENT CLEARING OF THE FRONTAL BOUNDARY FROM OUR AREA...WHILE
THE ECMWF DIVES THE LOW INTO THE GULF AND ALLOWS THE FRONT AND
ITS ASSOCIATED MOISTURE TO CLEAR BY FRIDAY. WENT WITH POPS JUST
ABOVE CLIMO WITH A DIURNAL PEAK...WEIGHTING THE GFS MORE HEAVILY DUE
TO ITS BETTER RUN-TO-RUN CONSISTENCY. INSTABILTY REMAINS MEAGER
THROUGH THE EXTENDED PERIOD...SO ANY CONCERNS SHOULD BE MAINLY
LIMITED TO LOCALLY HEAVY RAINFALL ASSOCIATED WITH WEAK STEERING
FLOW/TRAINING.

MAX TEMPS WILL BE NEAR OR JUST BELOW CLIMO AT THE BEGINNING OF THE
MEDIUM RANGE...AND THE MOIST AIRMASS WILL KEEP LOWS A CATEGORY OR
TWO ABOVE CLIMO...LIMITING THE DIURNAL TEMPERATURE RANGE. HIGHS WILL
REBOUND SLIGHTLY TO NORMAL OR JUST ABOVE BY THE END OF THE PERIOD.

&&

.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT...SHOWER ACTIVITY IS EXPECTED TO REMAIN TO THE N/NW OF THE
AIR FIELD AS THE ONGOING RADAR ECHOES WILL BE PUSHED AWAY BY A SE
WIND. THE BALANCE OF THE NIGHT IS EXPECTED TO BE VFR WITH A LIGHT S
OR SE WIND. THE MODEL GUIDANCE SHOWS THE DEVELOPMENT OF A NEW LOW
CLOUD DECK JUST BEFORE DAYBREAK MOVING UP FROM THE SE AND FORCED DUE
TO WEAK UPGLIDE. THE MODEL TREND IS TO BRING THIS IN AS A MVFR/IFR
CEILING...SO THE TAF REFLECTS THIS MORE PESSIMISTIC THINKING...ALTHO
THE CEILING IS KEPT LOW MVFR FOR NOW...AND CONFIDENCE IS ONLY MODEST
AT BEST. THE CEILING WILL GRADUALLY LIFT AND THEN SCATTER THRU THE
MORNING. EXPECT CONDITIONS TO IMPROVE TO VFR BY 15Z OR SO...WITH A
LIGHT S/SE WIND.

ELSEWHERE...A SHOWER COULD IMPACT KHKY THRU 01Z OR SO AND WILL BE
WATCHED FOR RESTRICTIONS. AT THE MOMENT THE SHOWER IS MOVING SLOWLY
SO WILL ONLY GO VCSH FOR NOW. KHKY AND KAVL COULD SEE SOME FOG
DEVELOPMENT IN THE PRE-DAWN HOURS...SO THAT WAS INCLUDED BECAUSE OF
RECENT NEARBY RAINFALL THIS AFTERNOON. THE FOG SHOULD BURN OFF
QUICKLY AFTER SUNRISE SATURDAY. THE UPSTATE SC TERMINALS SHOULD BE
VERY SIMILAR TO KCLT WITH MINOR TIMING DIFFERENCES AND THE
POSSIBILITY OF BRIEF FOG RESTRICTIONS AT KAND. WIND SHOULD BE LIGHT
FROM THE SE TO S.

OUTLOOK...MOIST SW FLOW WILL CONTINUE TO AFFECT THE TERMINAL
FORECAST AREA THROUGH THIS WEEKEND...AS A COLD FRONT LAYS OVER TO
THE NORTH OF THE AREA. EXPECT POCKETS OF MORNING FOG AND/OR STRATUS
MOST DAYS...WITH CONTINUED CHANCES OF AFTN/EVENING SHRA/TSRA EACH
DAY.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       HIGH 100%     HIGH 100%     HIGH  84%     HIGH 100%
KGSP       HIGH 100%     HIGH  93%     HIGH  81%     HIGH 100%
KAVL       HIGH 100%     HIGH  97%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH  87%     HIGH 100%
KGMU       HIGH 100%     HIGH  90%     HIGH  85%     HIGH 100%
KAND       HIGH 100%     HIGH  91%     HIGH  82%     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...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...LEV
NEAR TERM...JDL/PM
SHORT TERM...JAT
LONG TERM...LEV
AVIATION...PM



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