000 FXUS62 KGSP 041743 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 143 PM EDT FRI JUL 4 2008 .SYNOPSIS... A COLD FRONT APPROACHING THE REGION FROM THE NORTHWEST WILL DISSIPATE ACROSS THE CAROLINAS ON SATURDAY...AND LINGER IN THE AREA THROUGH EARLY NEXT WEEK. THEN...THE WESTERN PERIPHERY OF SUBTROPICAL HIGH PRESSURE WILL RETURN TO THE FORECAST AREA AND REMAIN IN CONTROL THROUGH LATE NEXT WEEK. && .NEAR TERM /THROUGH SATURDAY/... DEW POINTS SLOW TO MIX OUT WITH LAPS CAPE VALUES OVER 100 J/KG MUCH OF CWA SO SCT SHWRS/TSTMS WILL CONTINUE TO DEVELOP AND MOVE E ACROSS CWA. FREEZING LEVEL OVER 13K FT TODAY SO 50-55DBZ CORES OVER 30KFT NEEDED FOR LARGE HAIL...AROUND 28KFT FOR DAMAGING WINDS. BEST COVERAGE SHOULD BE OVER THE MTNS BUT STRONG STORMS COULD OCCUR ANYWHERE. CONVECTION SHOULD TAPER OFF BY LATE EVE BUT AT LEAST ISOLD TSTMS PSBL OVERNIGHT. LOOK FOR MORNING LOWS U60S-L70S PIEDMONT... U50S-L60S MTNS. CONVECTION WILL INCREASE AGAIN BY LATE SAT MORNING AND WITH SFC BOUNDARY MOVG IN FROM THE NW EXPECT LIKELY POPS OVER MTNS...SOLID CHANCE REST OF CWA THRU THE AFTN. AFTN HIGHS M80S TO AROUND 90...M70S-AROUND 80 MTNS. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... AS OF 1 PM FRIDAY...THE UPPER PATTERN FOR DAYS TWO AND THREE CONSISTS OF A WEAKENING AND SLOWLY PROGRESSIVE TROUGH OVER THE APPALACHIANS. BY LATE MONDAY NIGHT A RATHER FLAT UPPER RIDGE REACHES THE MOUNTAINS. THE DECAYING SURFACE FRONT OVER OUR AREA SATURDAY NIGHT WILL REMAIN IN THE AREA THROUGH MONDAY NIGHT...LEAVING A PERSISTENT MOISTURE BAND ALONG AND EAST OF THE MOUNTAINS. WITH THE DEMISE OF THE FRONT...MODEL WIND FIELDS TAKE ON A CLIMATOLOGICALLY FAVORED SOUTH SOUTHWEST DIRECTION...RESULTING IN LITTLE UPSLOPE COMPONENT...BUT INSTABILITY WILL BE MAXIMIZED IN THE SLIGHTLY WARMER AIR OVER THE PIEDMONT...WHERE THE BETTER CHANCE OF AFTERNOON AND EVENING POPS WILL BE LOCATED. ALTHOUGH SHEAR WILL BE RATHER WEAK...INSTABILITY AND MOISTURE SUPPORT A THREAT OF SEVERE THUNDERSTORMS...ESPECIALLY IF FREEZING LEVELS AND WET BULB ZEROS LOWER IN THE VICINITY OF THE FRONT. MODEL GUIDANCE POPS ARE RATHER LOW ON SUNDAY GIVEN THE ABOVE MENTIONED PARAMETERS...AND THE FACT THAT UPPER LEVEL ENERGY ROUNDING THE TROUGH ALOFT WILL BE CROSSING THE AREA. CHANCE POPS ABOVE GUIDANCE VALUES WILL BE MAINTAINED IN THE FORECAST ON SUNDAY...WITH A GRADUALLY DECREASING TREND THEREAFTER AS THE UPPER TROUGH WEAKENS...DIRECTING IMPULSES TO THE NORTH OF OUR AREA. TEMPERATURES WILL BE CLOSE TO NORMAL IN A WARM AND HUMID SUMMERTIME AIR MASS...WITH THE DIURNAL RANGE A FEW DEGREES LESS THAN NORMAL UNDER CLOUD COVER. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 115 PM FRIDAY...THERE IS LITTLE CHANGE TO THE THINKING BEHIND THE MEDIUM RANGE FORECAST FROM THE PAST COUPLE OF PACKAGES. A STRONG SUBTROPICAL RIDGE IS EXPECTED TO BE IN PLACE FROM TUES THROUGH FRI...WITH THE BELT OF WESTERLIES SITUATED OFF TO THE NORTH. THE ECMWF DOES SHOW SOME WEAKENING OF THE RIDGE BY THURSDAY AS BROAD TROUGHING MOVES ACROSS THE GREAT LAKES AND THE OHIO VALLEY. HOWEVER...IF IT COMES TO PASS...THIS SHOULD HAVE LITTLE SIGNIFICANT IMPACT ON THE SENSIBLE WX WHICH IS STILL EXPECTED TO BE DOMINATED BY TYPICAL SUMMERTIME DIURNAL CONVECTION. PERSISTENT SOUTHERLY TO SOUTHWESTERLY SURFACE FLOW AROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL HIGH SHOULD PROVIDE AMPLE LLVL MOISTURE AND INSTABILITY TO SUPPORT SCATTERED CONVECTION EACH DAY. POPS REFLECT THIS TREND WITH NEARLY A CARBON COPY...30 TO 40 POP EVERYWHERE EACH AFTERNOON AND EVENING. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... SCT SHWRS/TSTMS WILL CONTINUE TO DEVELOP AND MOVE E ACROSS THE CWA THIS AFTN-EVE. TEMPO MVFR AND STRONG GUSTY WINDS PSBL IN HEAVIER SHOWERS. EXPECT PREDOMINATE SW WIND DIRECTION AROUND 10 KTS WITH OCNL GUSTS...TAPERING OFF THIS EVE. CONVECTION SHOULD ALSO TAPER OFF BY LATE EVE WITH MVFR VSBY LIKELY KAVL AFT 06Z...OTHER SITES THAT GET RAIN CAN EXPECT MVFR VSBY AS WELL...ESP AROUND DAYBREAK. SCT TO ISOLD CONVECTION MAY CONTINUE AT TIMES OVERNIGHT BUT CHANCE TOO LOW TOO MENTION ATTM. CONVECTION PICKS UP AGAIN LATE SAT MORNING WITH WINDS INCREASING FROM THE SW TO AROUND 8KTS. OUTLOOK...MOISTURE WILL CONTINUE TO INCREASE THROUGH SUN WITH SOLID CHANCE SHOWERS/TSTMS THRU WEEKEND...INCLUDING CIG/VSBY RESTRICTIONS. DIURNAL CONVECTION EXPECTED THRU MID WEEK. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...BSH NEAR TERM...RB SHORT TERM...JAT LONG TERM...BSH AVIATION...RB