Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 250812 CCA
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
327 AM EDT FRI APR 25 2014

.SYNOPSIS...
A COLD FRONT WILL CROSS THE AREA TODAY...WITH DRY HIGH PRESSURE
RETURNING THROUGH THE WEEKEND. A WET AND POSSIBLY STORMY PATTERN
WILL SET UP MONDAY THROUGH WEDNESDAY...FOLLOWED BY COOLER WEATHER.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 325 AM EDT FRIDAY...A COLD FRONTAL PASSAGE WILL HIGHLIGHT THE
WEATHER ACROSS NORTHEAST GA AND THE WESTERN CAROLINAS FRIDAY. A
NEUTRAL ORIENTED UPPER TROF AXIS AND CLOSED LOW WILL OCCLUDE AND
EJECT TO THE NORTHEAST THROUGH THE DAY WHILE AN ASSOCIATED SURFACE
CYCLONE DRIVES THE PATTERN IN THE BOUNDARY LAYER.  THE ABOVE
MENTIONED COLD FRONT WILL SPREAD ACROSS THE REGION THROUGH MORNING
INTO THE AFTERNOON HOURS BEFORE PASSING WELL TO THE EAST AROUND
SUNSET.

A WARM FRONT WILL SURGE NORTHWARD ACROSS PORTIONS OF THE NC/SC
PIEDMONT REGIONS WITH SURFACE DEWPOINTS REACHING INTO THE UPPER 50S
BY MIDDAY.  LIKEWISE...TEMPERATURES WILL WARM INTO THE MID TO UPPER
70S ALONG THE I85 CORRIDOR WITH SLIGHTLY WARMER TEMPERATURES FURTHER
SOUTH DESPITE INCREASING SKY COVER.  MODEL GUIDANCE INDICATES SBCAPE
IN EXCESS OF 1000J/KG ACROSS THE PIEDMONT...TO INCLUDE CHARLOTTE
METRO.  THIS BUOYANCY COMBINED WITH WEAK SHEAR PROFILES WILL WARRANT
MENTION OF THUNDERSTORMS IN THE HWO ACROSS THESE ZONES WITH SMALL
HAIL...CLOUD TO GROUND LIGHTNING...AND GUSTY WINDS BEING THE PRIMARY
THREATS.  PWAT VALUES OF AROUND AN INCH COMBINED WITH DECENT
STEERING FLOW ALOFT YIELDING MBE VECTORS IN EXCESS OF 12-15KTS WILL
LIMIT FLOODING CONCERNS...ALTHOUGH ISOLATED INCIDENTS CANT BE RULED
OUT IN TRAINING OCCURS.  SOUTHERLY WINDS WILL INCREASE AS THE ABOVE
MENTIONED WARM FRONT SURGES AHEAD OF THE APPROACHING COLD FRONT.
EXPECTING SUSTAINED FLOW IN THE 10-15KTS RANGE WITH GUSTS NEARING
25KTS POSSIBLE...ALONG WITH HIGHER GUSTS ADJACENT TO ANY CONVECTIVE
ELEMENTS.

AS FOR THE FORECAST...WILL HIGHLIGHT CATEGORICAL POPS THIS MORNING
ACROSS THE HIGH TERRAIN FOR WIDESPREAD SHOWERS WITH ISOLATED
THUNDERSTORMS POSSIBLE.  POPS WILL RAMP UP THROUGH MID/LATE MORNING
ACROSS THE REMAINDER OF THE CWFA WITH SOLID CHANCE LEVELS ALONG THE
I85 CORRIDOR DUE TO SCATTERED THUNDERSTORMS AMIDST THE ABOVE
DESCRIBED FAVORABLE AIRMASS.  LIKELY POPS WILL RESIDE ALONG THE I40
CORRIDOR AS DEEPER MOISTURE LEADS TO MORE WIDESPREAD SHOWERS AND A
FEW ISOLATED THUNDERSTORMS.  BEYOND THAT...POPS WILL TAPER OFF
QUICKLY FROM THE WEST WITH THE EXCEPTION OF PORTIONS OF THE
NORTHWEST NC MOUNTAINS AS UPSLOPE FLOW COULD ALLOW FOR SOME
LINGERING SHOWER ACTIVITY INTO THE EARLY EVENING.  ALL POPS ARE
REMOVED FROM THE FORECAST BY AROUND MIDNIGHT WITH SKIES CLEARING OUT
FOR THE OVERNIGHT.  LOW TEMPERATURES ON SATURDAY MORNING WILL FALL
TO NEAR NORMAL LEVELS AS WEAK COLD ADVECTION PREVAILS.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 2 AM EDT FRIDAY...H5 HEIGHTS WILL GRADUALLY RISE OVER THE
FORECAST AREA SATURDAY AS AN UPPER TROUGH AXIS MOVES OFFSHORE AND AN
UPPER RIDGE AXIS APPROACHES FROM THE WEST. THE UPPER RIDGE WILL
AMPLIFY AND ITS AXIS WILL SLOWLY CROSS THE REGION SUN INTO SUN NIGHT
AS A DEEPENING UPPER LOW PRESSURE TROUGH APPROACHES FROM THE ROCKIES.

AT THE SURFACE...DRY AND WARM HIGH PRESSURE WILL SETTLE OVER THE
REGION ON SATURDAY AS A COLD FRONT PUSHES OFF THE SE COAST. WITH
INCREASING THICKNESS AND MOSTLY SUNNY SKIES...TEMPERATURES WILL RUN
AROUND 3-5 DEGREES ABOVE NORMAL ON SAT. BY SAT NIGHT...THE HIGH WILL
WEAKEN AND BEGIN TO SHIFT EAST AS A STRONG COLD FRONT APPROACHES
FROM THE FAR WEST. ALTHOUGH WE WILL SEE INCREASING MOISTURE
ADVECTION IN SOUTHERLY FLOW AHEAD OF THE APPROACHING FRONT...MODEL
SOUNDING SUGGESTS CAPPING MID-LEVEL INVERSION WILL KEEP THE AREA DRY
FOR MOST LOCATIONS DURING THE DAY ON SUNDAY. HENCE...HAVE INHERITED
DRY FORECAST BEFORE POPS RAMPING UP FROM THE WEST BY LATE SUN NIGHT.
TEMPERATURES WILL CONTINUE TO RUN AROUND 3-5 DEGREES ABOVE NORMAL ON
SUN.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 330 AM EDT FRIDAY...THE GLOBAL MODELS CONTINUE TO SUGGEST THAT
AN ACTIVE WEATHER PATTERN WILL PERSIST THROUGHOUT THE MEDIUM RANGE
PERIOD.

AN UPPER RIDGE WILL AMPLIFY OVER THE REGION MON INTO EARLY TUE AS A
DEEP UPPER LOW PRESSURE TROUGH SLOWLY APPROACHES FROM THE CENTRAL
CONUS WHILE ANOTHER UPPER LOW PRESSURE TROUGH SPINS OFF THE NEW
ENGLAND COAST. THE RIDGE AXIS WILL SLOWLY SHIFT EAST OF THE AREA BY
LATE TUE...WITH MOIST SOUTHWESTERLY FLOW ALOFT SETTING UP AHEAD OF
THE APPROACHING UPPER LOW PRESSURE TROUGH. LATEST MODELS HAVE
TRENDED SLOWER WITH THE PROGRESSION OF THIS UPPER TROUGH...LEAVING
OUR AREA UNDER THE PERSISTENT MOIST SWLY FLOW ALOFT AT LEAST INTO
THURSDAY.

AT THE SURFACE...UNSEASONABLY STRONG CANADIAN HIGH PRESSURE
(+1040MB) CENTERED OVER THE HUDSON BAY WILL NOSE DOWN INTO THE
EASTERN STATES MON INTO WED WHILE A DEEPENING SURFACE LOW SLOWLY
LIFTS NE ACROSS THE UPPER MIDWEST. BOTH THE GFS AND ECMWF AGREE THAT
A COOL AIR DAMMING WEDGE WILL SET UP...MAINLY ACROSS THE NC
PIEDMONT/FOOTHILL ZONES IN THE WAKE OF THE HIGH PRESSURE EXPANDING
FROM THE NE. HOWEVER...AREAS SOUTHERN HALF OF THE CWA INCLUDING THE
WESTERN NC MTNS...NE GEORGIA AND THE UPSTATE SC WILL BE UNDER THE
WARM SECTOR...SW OF THE WEDGE BOUNDARY MON/TUE. WITH DIURNAL
INSTABILITY...UNCAPPED ALOFT...AND INCREASING MOISTURE ADVECTION IN
DEEP S/SW FLOW AHEAD OF THE APPROACHING COLD FRONT...WE WILL SEE
ONGOING SHOWERS AND THUNDERSTORMS FAVORING THE WARM SECTOR ZONES
MON/TUE. MODELS AGREE THAT THE FRONT WILL REACH THE WESTERN MTNS BY
18Z WED AND CROSSES THE CWA THROUGH 12Z THU. VARIOUS MODEL SOUNDINGS
CONTINUE TO SUGGEST THAT AREAS OF CAPE VALUES AROUND 300-1000J/KG
WILL BE PRESENT ALONG AND AHEAD OF THE FRONT WITH 0-3KM BULK SHEAR
UP TO 40KTS. ALTHOUGH STRONGER UPPER FORCING WILL PASS NORTH OF THE
AREA...THE PRESENCE OF DECENT LLVL SHEAR AND BUOYANCY MAY SUPPORT
SEVERE WEATHER ON WED. THE FRONT IS EXPECTED TO EXIT EAST BY THU
MORNING WITH POPS RAMPING DOWN THEREAFTER.

TEMPERATURES WILL BE AROUND NORMAL RANGE MANLY OVER THE NC
PIEDMONT/FOOTHILLS MON THRU WED WITH 2-5 DEGREES ABOVE NORMAL
ELSEWHERE. BY THU...TEMPS WILL COOL OFF TO AROUND 3-5 DEGREES BELOW
NORMAL.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
AT KCLT...VFR CONDITIONS WILL PREVAIL FOR THE BEGINNING OF THE
PERIOD BEFORE LOW LEVEL MOISTURE ADVECTION REDUCES CIGS TO MVFR/IFR
LEVELS BY AROUND DAYBREAK.  COLD FRONT WILL PUSH THROUGH THE REGION
DURING THE LATE MORNING TO EARLY AFTERNOON.  CIGS WILL LIFT TO LOW
VFR LEVELS BY LATE MORNING WITH INCREASING INSTABILITY LEADING TO
TS.  THUS KEPT PREVIOUS PROB30 FOR MVFR CIGS/VISB AND TSRA FOR THE
LATE MORNING TO AFTERNOON HOURS.  CONDITIONS WILL IMPROVE BEHIND THE
FRONT INTO THE EARLY EVENING HOURS WITH ONLY HIGH LEVEL SKY COVER
PREVAILING.  WINDS WILL REMAIN SOUTHERLY GUSTING TO AROUND 20KTS
AHEAD OF THE FRONTAL PASSAGE WITH SOME LOCALLY HIGHER GUSTS POSSIBLE
ADJACENT TO ANY TS.  WINDS WILL VEER NORTHWESTERLY BEHIND THE
BOUNDARY LATE IN THE PERIOD WILL GUSTS SUBSIDING.

ELSEWHERE...MUCH THE SAME AS KCLT ABOVE WITH INITIALIZED VFR CIGS
GIVING WAY TO MVFR/IFR CIGS BY MID/LATE MORNING.  INCLUDED MENTION
OF SHRA AT KAVL AS FRONTAL MOISTURE WILL INTRUDE INTO THE MOUNTAINS
BEFORE THE AIRMASS CAN DESTABILIZE WITH HEATING.  HOWEVER...BY LATE
MORNING HAVE EITHER MENTION OF VCTS OR TSRA AT ALL SITES VIA
PREVAILING GROUPS OR PROB30S.  WINDS AT ALL SITES WILL BE GUSTY AND
OUT OF THE SOUTH BEFORE VEERING NORTHWESTERLY BEHIND THE FRONT AND
WEAKENING.

OUTLOOK...DRY HIGH PRES RETURNS SATURDAY THRU SUNDAY. INCREASED
MOISTURE RETURNS TO THE REGION EARLY NEXT WEEK...WITH A BLOCKED
PATTERN SETTING UP WHICH COULD BRING PERIODS OF SHRA/TSRA AND
ASSOCIATED RESTRICTIONS INTO MIDWEEK.

CONFIDENCE TABLE...

            07-13Z        13-19Z        19-01Z        01-07Z
KCLT       HIGH  87%     HIGH  86%     HIGH 100%     HIGH 100%
KGSP       HIGH  90%     MED   67%     HIGH 100%     HIGH 100%
KAVL       HIGH  86%     MED   67%     HIGH 100%     HIGH 100%
KHKY       HIGH  81%     MED   62%     HIGH 100%     HIGH 100%
KGMU       HIGH  91%     MED   67%     HIGH 100%     HIGH 100%
KAND       HIGH  97%     MED   76%     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...JOH
NEAR TERM...CDG
SHORT TERM...JOH
LONG TERM...JOH
AVIATION...CDG






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