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
