Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 202358 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 758 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/...
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AS OF 750 PM SUNDAY...OTHER THAN PATCHY STRATOCU ACROSS THE EXTREME SE TIER OF ZONES...SKIES ARE CLEAR ACROSS THE AREA AT MID-EVENING. MODEL SOLUTIONS ARE QUITE DISPARATE REGARDING THE EVOLUTION OF THIS STRATOCU LAYER OVERNIGHT...WITH THE NAM BEING SOMEWHAT OF AN OUTLIER IN DRAGGING IT WEST TO ENCOMPASS MUCH OF THE NC PIEDMONT/EASTERN SC PIEDMONT LATER THIS EVENING. IN LIGHT OF THIS...HAVE OPTED TO INTRODUCE SKY COVER AT THE MOSTLY CLEAR/PARTLY CLOUDY END OF THE SPECTRUM ACROSS THE EASTERN THIRD OF THE AREA. 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.
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&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
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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 PRE-FRONTAL 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.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
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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 MID-SOUTH AND INTO THE TENNESSEE VALLEY. TEMPERATURES THROUGH THE EXTENDED RANGE PERIOD WILL REMAIN AT OR JUST ABOVE NORMAL LEVELS DESPITE THE FROPA FRIDAY EVENING.
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&& .AVIATION /00Z MONDAY THROUGH FRIDAY/...
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AT KCLT...VFR STRATOCU AT AROUND 060 WILL LINGER NEAR THE AIRFIELD THIS EVENING...GENERALLY REMAINING FEW/SCT...ALTHOUGH AN OCCL PERIOD OF BKN IS POSSIBLE. OTHERWISE...NE WINDS WILL GRADUALLY DIMINISH OVERNIGHT...BUT ARE EXPECTED TO REMAIN AT AROUND 5 KTS THROUGH AT LEAST THE MORNING HOURS...BEFORE POSSIBLY VEERING TOWARD THE SE BY THE END OF MONDAY. ELSEWHERE...VFR CONDITIONS THROUGH THE PERIOD...WITH GRADUALLY DIMINISHING NE WINDS EXPECTED. LIGHT/VARIABLE WINDS ARE EXPECTED IN MANY AREAS MONDAY MORNING...BUT MAY BECOME LIGHT SE BY THE END OF THE PERIOD. OUTLOOK...A FAIRLY WET FRONTAL SYSTEM...WITH PIEDMONT THUNDERSTORMS...IS EXPECTED ON TUE...WITH DRYING RETURNING MID WEEK. CONFIDENCE TABLE... 00-06Z 06-12Z 12-18Z 18-24Z 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
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&& .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...SBK NEAR TERM...JDL/MCAVOY SHORT TERM...WIMBERLEY LONG TERM...CDG AVIATION...JDL

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