Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 201845
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
245 PM EDT SUN APR 20 2014

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN ACROSS THE AREA BEFORE A COLD FRONT
CROSSES EAST ON TUESDAY. DRY HIGH PRESSURE BUILDS BACK IN WEDNESDAY
AND THURSDAY WITH ANOTHER COLD FRONT AFFECTING THE REGION ON FRIDAY.

&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 150 PM EDT SUNDAY...WITH THE UPPER LOW SLOWLY MOVING OUT TO
SEA...ONLY THE FAR EASTERN ZONES SHOULD SEE ANY CLOUD COVER THIS
EVENING. THE NAM IS QUITE AGGRESSIVE IN BRINGING CLOUDS INTO THE WRN
NC PIEDMONT...BUT AS THE GFS AND RUC DO NOT DO THIS...I/VE GONE WITH
A SKY FORECAST CLOSER TO THE DRIER MODELS. THERE SHOULD BE MORE
LOCALLY DENSE FOG IN THE SOUTHWEST IN MTN VALLEYS OVERNIGHT. DRY AIR
AND WEAK MIXING SHOULD KEEP MOST OTHER LOCATIONS ACROSS THE FA FROM
SEEING ANY FOG OVERNIGHT. MIN TEMPS WILL BE COOL...BUT THEY SHOULD
BE WARM ENOUGH TO PREVENT FROST OVER ALL BUT SOME OF THE INTERIOR
NORTHERN MOUNTAIN VALLEYS. MONDAY WILL BE SEASONABLY MILD WITH
INCREASING HIGH CLOUDS DURING THE AFTERNOON HOURS.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF MIDDAY SUNDAY...UPPER PATTERN BEGINS TO AMPLIFY ACRS THE ERN
CONUS MON NIGHT AS DEEP RIDGE PUSHES INTO THE GREAT PLAINS. CORE OF
TROUGH BEGINS TO DIG ACRS THE GREAT LAKES...AND SFC LOW SUBSEQUENTLY
DEVELOPS AND MOVES INTO NEW ENGLAND DURING THE DAY TUE. THE TRAILING
COLD FRONT IS STILL PROGGED TO ENTER OUR CWFA AT THAT TIME...MOVING
OUT TUE EVENING. WE WILL BE WELL SOUTH OF THE BETTER FORCING THOUGH
SOME DPVA IS PROGGED AS THE AXIS OF THE BROAD TROUGH PASSES.
FRONTOGENESIS AND LLVL CONVERGENCE FIELDS ARE MURKY...SO PRECIP
CHANCES MOSTLY RESULT FROM DECENT PREFRONTAL INSTABILITY. CAPE
PROFILES ARE SKINNY ON PROG SOUNDINGS AND DEEP SATURATION IS
INITIALLY EVIDENT. SHEAR PARAMETERS CONTINUE TO PROMPT LITTLE
CONCERN...BUT IN THE WAKE OF THE UPPER TROUGH DRYING RAPIDLY OCCURS
ABV 700 MB. THIS OCCURS IN THE MID TO LATE AFTN WHEN SOME SFC BASED
INSTABILITY IS STILL PRESENT. THUS SOME OF THE LATER STORM ACTIVITY
COULD POSE A MICROBURST AND DAMAGING WIND THREAT...MAINLY OVER THE
PIEDMONT. TEMPS MON NIGHT AND TUE WILL BE A CATEGORY OR TWO ABOVE
NORMAL.

DEEP LAYER DRYING CONTINUES TUE NIGHT AS PLAINS RIDGE MOVES INTO THE
ERN US...AND SKIES WILL CLEAR OVERNIGHT...PERHAPS MORE SLOWLY IN THE
MTNS WHERE A VERY SHALLOW SFC BASED MOIST LAYER REMAINS IN NW FLOW.
BRISK WINDS ARE LIKELY IN THE HIGH ELEVATIONS AT THAT TIME BUT THESE
SUBSIDE TOWARD DAWN WED. DRY AND MOSTLY CLEAR CONDITIONS PERSIST THRU
WED WITH SUBSIDENCE INVERSION ACRS THE FA BUT LACKING MOISTURE
ANYWAY. THICKNESSES DO DROP A BIT FOR WED...RETURNING TEMPS TO AROUND
NORMAL DESPITE PRIME INSOLATION.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 230 PM EDT SUNDAY...THE EXTENDED RANGE PERIOD INITIALIZES ON
WEDNESDAY EVENING AS DEEP LAYER RIDGING PREVAILS ACROSS THE
SOUTHEAST.  A SURFACE HIGH DIVING OUT OF ONTARIO WILL QUICKLY
TRANSITION TO A BERMUDA TYPE HIGH BY THURSDAY AFTERNOON SETTING UP
RETURN FLOW.  MEANWHILE...A NORTHERN STREAM LOW AMPLITUDE UPPER TROF
WILL PUSH THROUGH THE NORTHERN PLAINS WITH SURFACE CYCLOGENESIS
OCCURRING OVER THE CENTRAL PLAINS.  A COLD FRONT WILL PUSH
THROUGH THE MISSISSIPPI RIVER VALLEY ON THURSDAY EVENING AS THE
PARENT SURFACE CYCLONE EJECTS NORTHEAST INTO THE GREAT LAKES REGION.

ABOVE MENTIONED HIGH PRESSURE WILL PREVAIL ACROSS THE SOUTHERN
APPALACHIANS...AHEAD OF THE APPROACHING FRONT ON FRIDAY
MORNING/AFTERNOON. A WARM FRONT WILL SURGE NORTHWARD FROM THE GULF
AND WESTERN ATLANTIC SOURCE REGIONS ALLOWING FOR INCREASING
DEWPOINTS AND STEEPENING LAPSE RATES DURING THE AFTERNOON HOURS.
THIS WILL LEAD TO MODEST INSTABILITY ACROSS THE CWFA WITH GFS/ECMWF
SOLUTIONS INDICATIVE OF SBCAPE IN EXCESS OF 1000J/KG WITH ENOUGH
SHEAR TO SUPPORT SOME ORGANIZED CONVECTION.  STILL TOO MUCH
UNCERTAINTY TO DIAL IN ON STORM MODES AND SPECIFIC TIMING/INTENSITY.
HOWEVER...CURRENT FCST SOUNDINGS DO INDICATE PW VALUES APPROACHING
1.5 INCHES LEADING TO MODERATELY HEAVY RAIN RATES WITH CAPE PROFILES
SUPPORTIVE OF LARGE HAIL.  DUE TO UNCERTAINTY...CAPPED POPS AT HIGH
END CHANCE LEVELS ACROSS THE REGION FOR FRIDAY.  THE FRONT WILL PASS
INTO THE COASTAL PLAINS/MIDLANDS BY EARLY MORNING SATURDAY LEADING
TO A DRY FCST UNTIL SUNDAY AFTERNOON.  AT THAT TIME POPS SLOWLY RAMP
UP ACROSS THE WESTERNMOST ZONES AS ANOTHER SYSTEM MOVES THROUGH THE
MIDSOUTH AND INTO THE TENNESSEE VALLEY.  TEMPERATURES THROUGH THE
EXTENDED RANGE PERIOD WILL REMAIN AT OR JUST ABOVE NORMAL LEVELS
DESPITE THE FROPA FRIDAY EVENING.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
AT KCLT AND ELSEWHERE...A BAND OF STRATO-CU WITH BASES OF 5-6KFT HAS
BEEN SLOWLY APPROACHING THE KCLT AIRFIELD FROM THE EAST DURING THE
DAY. THE NAM BRINGS THE CLOUDS ACROSS THE THE AIRFIELD BY 21 UTC AND
KEEPS THEM IN MUCH OF THE NIGHT. THE GFS AND RUC ARE MUCH DRIER AND
NEVER BRING THE CLOUDS THAT FAR WEST. THE NAM LLVL RH FIELDS ALREADY
LOOK OVERDONE...AND I/VE ADDED A FEW HOURS OF FEW060 TO ACCOUNT FOR
CLOUDS ALONG THE EASTERN HORIZON. WINDS ACROSS THE REGION WILL BE
OUT OF THE NE THROUGH THE NIGHT. WINDS WILL DECREASE FAIRLY QUICKLY
THIS EVENING...THOUGH SOME WEAK MIXING SHOULD PERSIST THROUGH THE
NIGHT. WITH LARGE TEMP/DEWPOINT SPREADS INDICATED ON MODEL
SOUNDINGS...I DON/T ANTICIPATE ANY FOG AT ANY OF THE AIRFIELDS
OVERNIGHT.

OUTLOOK...DRY HIGH PRES WILL DEVELOP THROUGH MONDAY. A FAIRLY WET
FRONTAL SYSTEM...WITH PIEDMONT THUNDERSTORMS...IS EXPECTED ON
TUE...WITH DRYING RETURNING MID WEEK.

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...MCAVOY
SHORT TERM...WIMBERLEY
LONG TERM...CDG
AVIATION...MCAVOY





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