Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 030722
AFDGSP

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

.SYNOPSIS...
THE FORECAST SYNOPSIS FOR NORTHEAST GEORGIA AND THE WESTERN CAROLINAS
CONTINUES TO PROMOTE DEEP LAYER RIDGING THROUGH MUCH OF NEXT WEEK.
ISOLATED SHOWERS AND OR THUNDERSTORMS WILL BE POSSIBLE EACH
AFTERNOON DURING PEAK HEATING OVER THE MOUNTAINS...WITH CHANCES BEING
SLIGHTLY ELEVATED OVER THE PIEDMONT REGIONS ON THURSDAY AS A WEAK
FRONTAL BOUNDARY COULD SLIDE INTO THE REGION.  TEMPERATURES WILL
MODERATE TO ABOVE NORMAL LEVELS WITH HIGHS TOPPING OUT IN THE LOWER
TO MID 80S NEAR PERIODS END.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 230 AM...A FEW PATCHES OF HIGH BASED STRATOCU RUNNING
AROUND...TRAPPED UNDER THE INVERSION. OTHERWISE...A QUIET NIGHT.
TEMPS ARE IN FAIRLY GOOD SHAPE.

FOR TODAY AND TONIGHT...THE UPPER FLOW SHOULD BECOME WEAKER AND MORE
ZONAL ACROSS THE CAROLINAS...EVEN AS ONE LAST VORT CENTER DRIFTS
DOWN INTO THE REGION AND IS LEFT BEHIND TO LINGER INTO THE EARLY
PART OF THE WEEK. THIS DEVELOPMENT WILL ALLOW THE CENTER OF HIGH
PRESSURE TO SLIP OFF THE E COAST TODAY...SETTING THE STAGE FOR
GRADUAL MOISTURE RETURN FROM THE GULF. THE OPERATIONAL MODELS ARE
SOMEWHAT INTERESTING FOR THIS AFTERNOON IN THAT MORE CONVECTIVE
DEVELOPMENT IS SHOWN OVER THE NC MTNS...EVIDENTLY AIDED BY WEAK LOW
LEVEL CONVERGENCE AND WEAK DPVA FROM THE PREVIOUSLY MENTIONED VORT
CENTER. HAVE EXPANDED THE PRECIP CHANCES OVER THE HIGHER TERRAIN PER
THE MODEL TRENDS. EXPECT THIS ACTIVITY TO WEAKEN DIURNALLY. TEMPS
WILL BE A FEW DEGREES WARMER/MILDER.

&&

.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 /08Z SUNDAY THROUGH THURSDAY/...
ZCZC GSPWRKTAF 022343
TTAA00 KGSP DDHHMM

AT KCLT AND ELSEWHERE...VFR THRU 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 A LIGHT WIND THRU DAYBREAK. ON
SUNDAY...WITH HIGH PRESSURE TO THE EAST...SOME MOISTURE RETURN WILL
TAKE PLACE FROM THE S. EXPECT WIND TO COME UP FROM THE S OR SSW
DURING THE LATE MORNING. 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...

            07-13Z        13-19Z        19-01Z        01-06Z
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
NEAR TERM...PM
SHORT TERM...CDG
LONG TERM...CDG
AVIATION...PM


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