Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 031756
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
156 PM EDT SUN MAY 3 2015

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN ACROSS THE REGION THROUGH THE MIDDLE OF
THE WORK WEEK. ISOLATED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE
EACH AFTERNOON OVER THE MOUNTAINS...WITH CHANCES IMPROVING ACROSS
THE PIEDMONT THURSDAY WHEN A WEAK COLD FRONT MOVES IN FROM THE
NORTH. 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 MONDAY/...
AS OF 145 PM EDT...AN UPPER LEVEL SHORTWAVE MOVING EAST ACROSS THE
OH VALLEY THIS AFTERNOON HAS SPAWNED SCATTERED SHOWERS BACK ACROSS
KY. THIS WAVE WILL MOVE THROUGH THE CENTRAL/SRN APPALACHIANS LATE
THIS AFTN...WITH THE BEST DPVA CROSSING THE NRN HALF OF THE FORECAST
AREA THROUGH 22Z. A 500 MB COLD POCKET IN THE UPPER THERMAL TROUGH
WILL CROSS THE NRN TIER OVERNIGHT...WHICH COULD KEEP ISOLD SHOWERS
GOING ALONG THE INTERSTATE 40 CORRIDOR WHERE LAPSE RATES WILL BE
STEEPEST. WILL FEATURE MAINLY MTN ISOLD TO SCT POPS FOR LATE
AFTN...THEN PUSH ISOLD SHOWER POPS EAST INTO THE WRN NC PIEDMONT
INTO THE EARLY MORNING HOURS. INSTABILITY REMAINS WEAK...AND SOME
MEASURE OF CAPPING IS FOUND IN RAOB AND MODEL PROFILES AT 10 TO 12
KFT...SO WILL ONLY MENTION SHOWERS FOR NOW. EXPECT A SCATTERED TO
BKN MID DECK OF CLOUDS TO PERSIST OVERNIGHT UNDER THE WEAK CAPPING
LAYER...WITH WARMER MIN TEMPS MAINLY IN THE 50S/HIGH MTN UPPER 40S.

THE CENTER OF THE SE SFC HIGH PRESSURE WILL MOVE FARTHER OFFSHORE
OVERNIGHT THROUGH MONDAY...WITH BERMUDA HIGH PRESSURE DOMINATING THE
REGION. MODEL PROFILES EXHIBIT LESS CAPPING ALOFT ON MONDAY
AFTN...AND LIGHT SRLY UPSLOPE FLOW SHOULD PERSIST AROUND THE
ATLANTIC RIDGE. WILL THUS FEATURE SLIGHTLY BETTER SCATTERED MOUNTAIN
COVERAGE FOR MONDAY AFTERNOON. MAX TEMPS WILL RECOVER ANOTHER COUPLE
OF DEGREES ABOVE SUNDAY VALUES IN MOST AREAS.

&&

.SHORT TERM /MONDAY NIGHT 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 /18Z SUNDAY THROUGH FRIDAY/...
AT KCLT AND ELSEWHERE...VFR CONDITIONS WILL CONTINUE THROUGH THE
PERIOD WITH SCATTERED TO BROKEN HIGH BASED STRATOCUMULUS FROM
DAYTIME HEATING AND A MID LEVEL NOCTURNAL INVERSION. BASES SHOULD BE
MAINLY 7 TO 8 KFT THE REST OF THE AFTN THROUGH TONIGHT...LOWERING
WITH RECOVERING DEWPOINTS TO 5 TO 6 KFT ON MONDAY. SFC WINDS WILL
REMAIN SOUTHERLY AROUND THE COASTAL/OFFSHORE HIGH PRES...GENERALLY
10 KT OR LESS DURING THE DAYLIGHT...AND LIGHT OVERNIGHT. COVERAGE OF
ANY SHRA SHOULD BE TOO LOW TO MENTION...BUT MTN COVERAGE WILL LIKELY
PICK UP ON MON AFTN TO POSSIBLY APPROACH KAVL JUST BEYOND THE TAF
PERIOD.

OUTLOOK...RETURN FLOW MOISTURE WILL CONTINUE TO REDEVELOP ACROSS THE
TERMINAL FORECAST AREA THROUGH MID WEEK. ISOLD TO SCATTERED DIURNAL
CONVECTION IS EXPECTED EACH DAY...MAINLY OVER THE MTNS...WITH
SOUTHERLY FLOW CONTINUING THROUGH AT LEAST WED.

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 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...SBK
NEAR TERM...HG
SHORT TERM...CDG
LONG TERM...CDG
AVIATION...HG



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