964 FXUS62 KCHS 261759 AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 159 PM EDT WED JUN 26 2013 .SYNOPSIS... BERMUDA HIGH PRESSURE WILL PREVAIL THIS WEEK...WHILE A WEAK TROUGH OF LOW PRESSURE LINGERS INLAND. A COLD FRONT WILL APPROACH AND POSSIBLY STALL NEAR THE AREA EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... WATER VAPOR IMAGERY SHOWS DISTINCT SHORTWAVES SLIPPING TOWARD THE SOUTHEAST COASTLINE WITHIN A WEAK UPPER TROUGH. PWAT VALUES NEAR ONE INCH REFLECT THE ABUNDANT DEEP MOISTURE...AND WHEN COMBINED WITH DECENT DIURNAL INSTABILITY...HAS SUPPORTED ISOLATED TO SCATTERED SHOWER INITIATION BY EARLY AFTERNOON. CONVECTIVE COVERAGE CURRENTLY FAVORS THE SOUTHEAST GEORGIA REGION...AS THESE LOCATIONS ARE WITHIN THE MOST UNSTABLE AIR AND ARE CLOSEST TO APPROACHING SHORTWAVE ENERGY FROM THE WEST/SOUTHWEST. CONVECTION HAS BEEN SLOWER TO DEVELOP EAST OF INTERSTATE 95 AND ACROSS THE CHARLESTON TRI COUNTY AREA...LIKELY A RESULT OF THE SEABREEZE PINNED WITHIN WESTERLY MID LEVEL FLOW AND POSSIBLY SOME DISRUPTION IN THE ENVIRONMENT FROM EARLIER CONVECTION UPSTREAM. NUMERICAL MODEL SOLUTIONS ARE IN FAIRLY GOOD AGREEMENT THAT COVERAGE WILL EVENTUALLY SPREAD EAST/NORTHEAST DURING THE NEXT SEVERAL HOURS. HAVE TRENDED RAIN CHANCES INTO THE 30 TO 40 PERCENT RANGE BY MID AFTERNOON...HIGHEST INLAND LOCATIONS. ALTHOUGH THERE WILL BE SOME SYNOPTIC SCALE SUPPORT FROM THE VARIOUS SHORTWAVES...THE WIND PROFILE IS RATHER UNIMPRESSIVE AND LAPSE RATES ARE AVERAGE. THUS...ANY ISOLATED STRONG TO SEVERE THUNDERSTORM DEVELOPMENT WILL BE DEPENDENT ON MESOSCALE BOUNDARY INTERACTIONS. THE MAIN HAZARDS FROM ORGANIZED CONVECTION WILL BE STRONG WINDS AND PERHAPS EVEN SOME HAIL. HOURLY FORECAST TEMPERATURES ARE ON TRACK WITH LATEST OBSERVATIONS...AND WILL THUS MAINTAIN FORECAST HIGH TEMPERATURES IN THE LOWER 90S INLAND TO THE UPPER 80S CLOSER TO THE COAST. CONVECTIVE ACTIVITY SHOULD BE DIMINISHING THIS EVENING...WITH ONLY ISOLATED SHOWERS AND THUNDERSTORMS OVERNIGHT AS WEAK SHORTWAVE ENERGY CONTINUES TO SLIP THROUGH THE REGION. LOWS WILL BE IN THE LOWER TO MIDDLE 70S. && .SHORT TERM /THURSDAY THROUGH SATURDAY/... THURSDAY AND THURSDAY NIGHT...EXPECT A RATHER ACTIVE PERIOD AS A MID AND UPPER LEVEL TROUGH SHIFTS EAST OF THE SOUTHERN APPALACHIANS ON THURSDAY...THEN DIGS SOUTHWARD ALONG THE SOUTHEAST COAST THURSDAY NIGHT. THE SYNOPTIC SOUTHWEST FLOW BETWEEN ATLANTIC HIGH PRESSURE AND A LEE-SIDE TROUGH INLAND WILL ALLOW FOR CONSIDERABLE ADVECTION OF MOISTURE...WITH PRECIPITABLE WATER VALUES APPROACHING 2 INCHES IN MANY AREAS. SHOWERS AND THUNDERSTORMS WILL BECOME SCATTERED IN COVERAGE DURING THE LATE MORNING AND AFTERNOON...AND COULD EVEN INCREASE IN COVERAGE THROUGH THE EVENING AS A POTENT SHORT WAVE CROSSES THE AREA. MODEL SOUNDINGS... ESPECIALLY FROM THE GFS...ARE RATHER IMPRESSIVE IN TERMS OF SEVERE WEATHER POTENTIAL. SURFACE BASED CAPE VALUES REACH 2500-3000 J/KG AND LI/S ARE DOWN TO -8C. THE PRIMARY THREAT WITH ANY SEVERE THUNDERSTORMS WILL BE DAMAGING WINDS GIVEN A WINDEX OF 61 KT AND DOWNDRAFT CAPE VALUES OVER 700 J/KG...HAIL WILL BE LESS LIKELY WITH WET BULB ZERO HEIGHTS AROUND 13K FT. TEMPERATURES WILL REACH HIGHS IN THE LOWER 90S AWAY FROM THE IMMEDIATE COAST...WITH NIGHTTIME LOWS IN THE LOWER TO MID 70S. FRIDAY AND FRIDAY NIGHT...THE REGION WILL BE BENEATH A BROAD UPPER LEVEL TROUGH WHILE ATLANTIC HIGH PRESSURE AND A LEE SIDE TROUGH PREVAIL AT THE SURFACE. EXPECT SCATTERED SHOWERS AND THUNDERSTORMS MAINLY DURING THE AFTERNOON AND EVENING ALTHOUGH COVERAGE SHOULD BE A BIT LESS THAN THURSDAY GIVEN LOWER PRECIPITABLE WATER VALUES AND WEAK NEGATIVE VORTICITY ADVECTION ALOFT. HIGHS REMAIN IN THE LOWER 90S WITH LOWS IN THE LOWER TO MID 70S. SATURDAY...UNDER A SIMILAR SYNOPTIC PATTERN...THIS COULD BE A RATHER WET DAY AS AN AXIS OF DEEP MOISTURE SHIFTS OVER THE AREA AND A SHORT WAVE DISTURBANCE CROSSES. WITH PRECIPITABLE WATER VALUES OF 2.00-2.25 INCHES THERE IS THE POTENTIAL FOR HEAVY RAINFALL...BUT FORTUNATELY STORM MOTIONS APPEAR RATHER PROGRESSIVE WHICH SHOULD LIMIT THE POTENTIAL FOR SIGNIFICANT FLOODING UNLESS TRAINING OF CELLS OCCUR. THE FORECAST INDICATES A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS...BUT PROBABILITIES MAY NEED TO BE INCREASED WITH FUTURE FORECASTS. TEMPERATURES COULD BE KEPT A DEGREE OR TWO COOLER THAN PREVIOUS DAYS GIVEN CLOUD COVER AND GREATER COVERAGE OF PRECIPITATION. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... MEDIUM RANGE GUIDANCE IS IN FAIRLY GOOD AGREEMENT INDICATING THE POTENTIAL FOR UNSETTLED CONDITIONS THROUGH MUCH OF THE LONG TERM PERIOD. THE SYNOPTIC PATTERN IN THE MID AND UPPER LEVELS OF THE ATMOSPHERE WILL FEATURE AN UNSEASONABLY DEEP TROUGH OVER THE CENTRAL UNITED STATES WITH A RIDGE OVER THE WESTERN ATLANTIC ALLOWING FOR ADVECTION OF DEEP MOISTURE OVER THE REGION. AT THE SURFACE... ATLANTIC HIGH PRESSURE WILL PREVAIL AS A LEE SIDE TROUGH LINGERS INLAND. THE FORECAST WILL INDICATE A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS EACH DAY...WITH A SLIGHT CHANCE OR LOW CHANCE OF SHOWERS AND THUNDERSTORMS AT NIGHT. OVERALL...PARTS OF THE REGION COULD EXPERIENCE SEVERAL INCHES OF RAINFALL DURING THE COURSE OF THE LONG TERM PERIOD. NEAR NORMAL TEMPERATURES ARE EXPECTED EACH DAY WITH NEAR TO SLIGHTLY ABOVE NORMAL TEMPERATURES AT NIGHT. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... ISOLATED TO SCATTERED CONVECTION WILL EVENTUALLY APPROACH AND/OR DEVELOP NEAR THE TERMINALS AS THE AFTERNOON PROGRESSES. WILL MAINTAIN VCTS AT KCHS AND KSAV THROUGH ABOUT 21Z. EXPECT THUNDERSTORM ACTIVITY TO DIMINISH IN COVERAGE AFTER SUNSET WITH THE LOSS OF DIURNAL HEATING AND INSTABILITY. ALTHOUGH BRIEF REDUCTIONS IN CEILINGS/VISIBILITIES COULD OCCUR IN THUNDERSTORMS...VFR CONDITIONS ARE OTHERWISE EXPECTED TO PREVAIL THROUGH 18Z THURSDAY. EXTENDED AVIATION...SCATTERED SHOWERS AND TSTMS EXPECTED EACH AFTERNOON/EVENING WITH BRIEF REDUCTIONS IN VSBY/CIG POSSIBLE. && .MARINE... ATLANTIC HIGH PRESSURE WILL PREVAIL...AS A TROUGH OF LOW PRESSURE LINGERS INLAND. THIS PATTERN WILL MAINTAIN SOUTH/SOUTHWEST FLOW ACROSS THE WATERS THROUGH THE PERIOD. THE GRADIENT IS EXPECTED TO TIGHTEN A BIT LATE IN THE WEEK INTO THE WEEKEND AND COULD RESULT IN SMALL CRAFT ADVISORY CONDITIONS OVER PARTS OF THE WATERS...ESPECIALLY THE OUTER GEORGIA WATERS...ANYTIME FROM THURSDAY NIGHT THROUGH SUNDAY NIGHT. WINDS SHOULD BE STRONGEST DURING THE DAY ALONG THE LAND/SEA INTERFACE AND AT NIGHT OVER THE COASTAL WATERS WITH NOCTURNAL SURGING. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...NONE. && $$ NEAR TERM...WMS SHORT TERM...JAQ LONG TERM...JAQ AVIATION...WMS MARINE...JAQ/JRL