Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 031448
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1048 AM EDT SUN MAY 3 2015

.SYNOPSIS...
HIGH PRESSURE WILL GENERALLY DOMINATE THE REGION THROUGH MUCH OF
NEXT WEEK. ISOLATED SHOWERS AND OR THUNDERSTORMS WILL BE POSSIBLE
EACH AFTERNOON DURING PEAK HEATING OVER THE MOUNTAINS...WITH CHANCES
IMPROVING SLIGHT OUT OVER THE PIEDMONT BY THURSDAY AS A WEAK FRONT
SLIDES INTO THE REGION. TEMPERATURES WILL RISE TO ABOVE NORMAL
LEVELS...WITH HIGHS TOPPING OUT IN THE LOWER TO MID 80S THE LATTER
HALF OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1045 AM EDT...TEMPERATURES ARE OFF TO A WARM START IN MOST
PLACES AS THE EXPECTED HIGH LEVEL STRATOCUMULUS FIELD HAS NOT FILLED
IN APPRECIABLY YET. STILL ANTICIPATE SOME INCREASING CLOUD COVER
BELOW A MID LEVEL CAP...BUT WARM MORNING THICKNESSES WILL REQUIRE A
ONE DEGREE BOOST IN TEMPS IN MOST PLACES. THE LATEST HRRR RUNS
CONTINUE TO FEATURE LITTLE MORE THAN ISOLD AIRMASS TYPE
SHOWERS...BUT WITH A GENERAL FOCUS ALONG THE ERN SIDE OF THE MTNS IN
DEVELOPING LIGHT UPSLOPE. VERY LITTLE CHANGE TO THE POP FORECAST IS
EXPECTED...WITH A RELATIVE FORCING MAXIMUM TOWARD 21Z WITH THE
PASSING OF AN UPPER SHORTWAVE TO THE N.

ANY AFTN/EARLY EVENING SHOWER ACTIVITY WILL WANE QUICKLY WITH SUNSET
TONIGHT. ANOTHER ROUND OF HIGH STRATOCUMULUS/LOW ALTOCU TRAPPED
UNDER THE INVERSION WILL KEEP SOME MEASURE OF CLOUDS GOING ALL
NIGHT. IN ADDITION...THE AIRMASS WILL CONTINUE TO MODIFY WITH RISING
MIN TEMPS.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...
AS OF 230 AM EDT SUNDAY...THE SHORT TERM FCST PERIOD INITIALIZES
MONDAY MORNING AMIDST BROAD FLAT H5 SUBTROPICAL RIDGE...WITH A WEAK
DISTURBANCE SLIDING THROUGH THE MEAN FLOW ATOP THE SOUTHERN APPS.
AT THE SURFACE...HIGH PRESSURE OFF THE CAROLINA COAST WILL CONTINUE
TO ALLOW FOR SOUTHERLY WAA ACROSS NORTHEAST GA AND THE WESTERN
CAROLINAS.  STEEPENING LOW LEVEL LAPSE RATES DUE TO DIURNAL HEATING
ALONG WITH ABOVE MENTIONED UPPER IMPULSE WARRANT CHANCE LEVELS POPS
ACROSS THE HIGH TERRAIN ON MONDAY WHERE REGION OF BEST INSTABILITY
AND LEAST CIN WILL RESIDE.  POPS TAPER SHARPLY TO NON MENTIONABLE
LEVEL THROUGH THE FOOTHILLS...LEADING TO A DRY FCST FOR THE PIEDMONT
AREAS DUE TO PROXIMITY OF THE PARENT SURFACE HIGH.

THE PRIMARY UPPER RIDGE AXIS WILL SHIFT OVERHEAD ON TUESDAY WHICH IS
EXPECTED TO LIMIT CONVECTION SOMEWHAT...ESPECIALLY OUTSIDE OF THE
MTNS.  INSTABILITY WILL BE MAXIMIZED OVER THE HIGH TERRAIN...WHICH
COMBINED WITH WEAKER LOW LEVEL CIN DUE TO RETREATING PARENT SURFACE
HIGH...CONTINUE TO WARRANT CHANCE POPS.  AS STATED ABOVE...EXPECTING
ANY CAPPING TO HOLD OUTSIDE OF THE HIGH TERRAIN THUS THE FCST
REMAINS DRY FOR TUESDAY ACROSS THESE ZONES.  ANY HEAVIER
SHOWERS/THUNDERSTORMS THAT DO DEVELOP COULD PRODUCE LOCALLY HEAVY
RAINFALL AMOUNTS AS STORM MOTIONS WILL LIKELY BE LESS THAN
5-8KTS...ESPECIALLY ON TUESDAY WHEN MID LEVEL FLOW WEAKENS.
OTHERWISE...PARTLY CLOUDY SKIES WILL PREVAIL AMIDST LIGHT SOUTHERLY
FLOW.  TEMPERATURES THROUGH THE PERIOD WILL EXCEED NORMAL LEVELS
WITH HIGHS TOPPING OUT IN THE LOWER 80S ON TUESDAY.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 245 AM EDT SUNDAY...THE MEDIUM RANGE FCST PERIOD INITIALIZES
WEDNESDAY MORNING WITH LITTLE TO NO CHANGES MADE TO THE PREVIOUS
FCST.  HIGHLIGHTS OF THE PERIOD CONTINUE TO BE PREVAILING
SUBTROPICAL H5 RIDGE OVER EAST/CENTRAL CONUS WHILE SURFACE HIGH
PRESSURE REMAINS CENTERED OVER NEW ENGLAND.  FURTHER SOUTH OVER THE
NORTHERN CARRIBEAN...A MIDLEVEL DISTURBANCE AND ASSOCIATED HYBRID
LOW WILL HAVE FORMED AND MIGRATED NORTHWARD OF THE EAST COAST OF
FLORIDA.  CLOSER TO HOME...BROAD MID/UPPER LEVEL SUBSIDENCE PATTERN
IS EXPECTED TO PREVAIL INITIALLY LEADING TO A CAPPED ENVIRONMENT WITH
LITTLE IN THE WAY OF TRIGGERING AVAILABLE FOR CONVECTION ACROSS THE
PIEDMONT REGIONS.  HOWEVER...OVER THE MOUNTAINS MODELS FAVOR
INCREASING INSTABILITY WITH ESE UPSLOPING FLOW PRESENT TO AID CAP
EROSION ON WEDNESDAY.  THUS...SLIGHT/CHANCE LEVEL POPS ARE
FEATURED.

ON THURSDAY POPS WILL EXPAND FURTHER INTO THE NC/SC PIEDMONT AND
NORTHEAST GA AS THE ABOVE MENTIONED HYBRID LOW...AND ITS LOCATION AT
THE TIME BECOMES VITAL TO THE FCST.   MODEL DISCONTINUITY AS TO ITS
LOCATION WOULD PROVIDE VASTLY DIFFERENT OUTCOMES AS IT PERTAINS TO
SENSIBLE WX FOR THE REMAINDER OF THE PERIOD.  THE GFS HAS THE LOW
SETUP APPROX 2-3 HUNDRED MILES OFF THE SC COAST THURSDAY
AFTERNOON...WHILE THE ECMWF IS ABOUT THE SAME DISTANCE FURTHER OUT
TO SEA.  THE GFS SOLUTION WOULD RESULT IN FLOW ON THE WESTERN FLANK
OF THE WAVE YIELDING A NORTHERLY COMPONENT OF MOTION...WHICH WOULD
AID INTRUSION OF A WEAK BACK DOOR FRONT INTO THE REGION.  THE ECMWF
ON THE OTHER HAND INDICATES THE SAME BACK DOOR FRONT...ALBEIT
WEAKER.  IF THE GFS VERIFIED THE FROPA COULD PROVIDE ENOUGH OF A
FOCUS FOR CONVECTION TO OCCUR OUTSIDE OF THE MTNS...THEREFORE FOR
THE FCST SLIGHT CHANCE POPS ARE MENTIONED.  BOTH THE GFS/ECMWF
ILLUSTRATE A WESTWARD JAUNT OF THE LOW ON FRIDAY/SATURDAY
EFFECTIVELY KEEPING IT JUST OFF THE GA/SC COAST PER THE GFS...AND
THE SC/NC COAST PER THE ECMWF.  MOISTURE WRAPPING AROUND THE LOW
SHOULD STAY JUST TO THE EAST...THEREFORE THE FCST IS DRY FOR
PIEDMONT REGIONS ALL THE WHILE FEATURING SLIGHT/CHANCE LEVEL POPS
OVER MTNS WHERE DIURNAL CONVECTION IS FAVORED.  TEMPERATURES THROUGH
THE PERIOD WILL CONTINUE TO MODERATE TO 5-8 DEGREES ABOVE CLIMO.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
AT KCLT AND ELSEWHERE...VFR IS EXPECTED THROUGH THE PERIOD COURTESY
OF DRY HIGH PRESSURE. WILL CONTINUE TO SEE SOME HIGH BASED STRATOCU
TRAPPED UNDER THE SUBSIDENCE INVERSION...BUT THIS SHOULD NOT BE
OPERATIONALLY SIGNIFICANT. EXPECT WINDS TO COME UP FROM THE SSE TO
SSW THROUGH EARLY AFTN AS HIGH PRESSURE MOVES OFF THE COAST. WITH
HIGH PRESSURE TO THE EAST...SOME MOISTURE RETURN WILL TAKE PLACE
FROM THE S. A CU FIELD IS EXPECTED TO DEVELOP FROM MIDDAY
ONWARD...THAT WILL PROBABLY RESULT IN A CEILING IN MOST PLACES IN
THE AFTERNOON...BUT WITH A CLOUD BASE AT 060 OR HIGHER. THE MODELS
ARE MORE SUPPORTIVE/REACTIVE WITH PRECIP OVER THE HIGHER TERRAIN
THIS AFTERNOON...SO A VICINITY SHOWER WAS INCLUDED AT KAVL.

OUTLOOK...RETURN FLOW MOISTURE WILL SLOWLY REDEVELOP THROUGH MID
WEEK...PRODUCING ISOLD TO SCATTERED DIURNAL CONVECTION EACH DAY...
MAINLY OVER THE HIGH TERRAIN.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     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...CDG/HG
NEAR TERM...HG
SHORT TERM...CDG
LONG TERM...CDG
AVIATION...HG/PM


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