000
FXUS62 KCHS 162340
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
740 PM EDT THU MAY 16 2013

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL EXTEND INTO THE REGION THROUGH MUCH OF
THE WEEKEND...AS UPPER LEVEL ENERGY MOVES THROUGH. UPPER RIDGING
WILL THEN RETURN THROUGH MID WEEK...WITH A COLD FRONT POSSIBLY
APPROACHING LATE IN THE WEEK.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
A SHORT WAVE DISTURBANCE WILL CONTINUE TO PUSH OFFSHORE THIS
EVENING...WITH WEAK RIDGING BUILDING ALOFT IN ITS WAKE FOR THE
OVERNIGHT HOURS. MEANWHILE AT THE SURFACE...ATLANTIC HIGH PRESSURE
WILL CONTINUE TO EXTEND INTO THE SOUTHEAST STATES. THE THICK HIGH
LEVEL CLOUD COVER ASSOCIATED WITH THE SHORT WAVE WILL CONTINUE TO
MOVE OUT OF THE AREA THIS EVENING...WITH ONLY SOME THIN JET CIRRUS
EXPECTED FOR THE REMAINDER OF THE NIGHT. LOW TEMPERATURES WILL BE
RELATIVELY CLOSE TO NORMAL IN THE LOWER TO MIDDLE 60S.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
FRIDAY AND FRIDAY NIGHT...THE PATTERN ALOFT WILL FEATURE A SHORTWAVE
TROUGH TO THE WEST CAUGHT WITHIN THE LARGER SCALE UPPER RIDGE. THIS
LOW AMPLITUDE SHORTWAVE WILL RESULT IN A BAGGY AREA IN THE UPPER
HEIGHTS THAT EXTENDS FROM THE UPPER MIDWEST TO THE DEEP SOUTH. THE
SURFACE WILL PRIMARILY BE DETERMINED BY SUBTROPICAL HIGH PRESSURE
OVER THE ATLANTIC THAT WILL CONTINUE TO EXTEND WESTWARD INTO THE
SOUTHEAST. THIS WILL RESULT IN A WARM SOUTHWEST FLOW IN THE LOW
LEVELS AND THICKNESS VALUES SUPPORT HIGHS IN THE UPPER 80S TO NEAR
90. THE MAIN FORECAST PROBLEM IS THE POTENTIAL FOR SHOWER AND
THUNDERSTORM DEVELOPMENT. THE CAP NOTED IN PREVIOUS DAYS WILL BE
NOTICEABLY WEAKER...DIMINISHING ALTOGETHER BY THE EARLY AFTERNOON.
THE MODELS ARE GENERATING 500-1000 J/KG OF CAPE AND SHOW A
PROGRESSIVE SEABREEZE IN THE AFTERNOON. THE MAIN LIMITING FACTOR
MAY BE THE DRY LOW LEVELS AND THE OVERALL MODEL RESPONSE SUPPORTS
ISOLATED CONVECTION AT BEST AND I HAVE KEPT THE SLIGHT CHANCE GOING.
OVERNIGHT...ANY LINGERING CONVECTION WILL QUICKLY DIMINISH AND A
MILD NIGHT IS ON TAP. LOWS WILL ONLY FALL INTO THE MID 60S IN MOST
AREAS.

SATURDAY THROUGH SUNDAY...FOR THE WEEKEND THE FORECAST AREA WILL SEE
PASSING SHORTWAVE ENERGY ALOFT WITHIN THE BAGGY TROUGH CAUGHT UNDER
THE LARGER SCALE RIDGE. THOUGH THE BULK OF THE ENERGY WILL REMAIN
NORTH OF THE REGION...IT WILL PROVIDE SOME SLIGHTLY LOWER HEIGHTS
EACH DAY. THE ENVIRONMENT WILL BECOME MODESTLY MORE CONDUCIVE TO
CONVECTION EACH DAY AS THE AMOUNT OF MOISTURE INCREASES AND THE MID
LEVELS COOL JUST A BIT. PWATS WILL INCREASE TO 1.3-1.4 ON SATURDAY
AND AROUND 1.5 BY SUNDAY. SATURDAY SOUNDINGS SHOW MODERATE
INSTABILITY DEVELOPING...WHICH MAY SUPPORT A FEW STRONG STORMS. BUT
WITH DCAPE VALUES ON THE LOW END DUE TO THE MOISTENING PROFILE...THE
THREAT OF SEVERE STORMS IS LOW. THE COVERAGE ON SUNDAY MAY BE A BIT
HIGHER WITH EVEN MORE MOISTURE TO WORK WITH...BUT POPS HAVE BEEN
KEPT IN THE CHANCE RANGE. TEMPS FEATURE A BIT OF A COOLING TREND
THANKS TO LOWERING THICKNESSES AND LINGERING CLOUD COVER...THOUGH
STILL SLIGHTLY ABOVE NORMAL EVEN BY SUNDAY.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
A WEAK UPPER LEVEL PATTERN WILL ALLOW SHORTWAVE ENERGY TO PERSIST
OVER THE REGION THROUGH AT LEAST MONDAY...WITH A LESS DEFINED
SURFACE PATTERN INLAND OF THE ATLANTIC SURFACE HIGH. EXPECT
SHOWER/THUNDERSTORM ACTIVITY TO STILL BE DRIVEN BY DIURNAL
HEATING/INSTABILITY AND SEABREEZE FORCING...WITH JUST A SLIGHTLY
IMPROVED POTENTIAL FOR ISOLATED CONVECTION TO PERSIST AFTER SUNSET
UNDER SOME SYNOPTIC LEVEL SUPPORT. THE LOSS OF SHORTWAVE ENERGY
WITHIN A MORE WEAKLY RIDGED PATTERN ALOFT SHOULD RESULT IN JUST
ISOLATED THUNDERSTORM COVERAGE LIMITED TO THE DAYTIME HOURS
TUESDAY AND WEDNESDAY. WILL THUS REDUCE POPS TO THE 20 PERCENT
RANGE DURING THE MORE CLIMATOLOGICALLY FAVORED AFTERNOON/EARLY
EVENING PERIOD BY MID WEEK. A STRONGER SHORTWAVE TROUGH WILL SWING
SOUTHEAST LATE WEDNESDAY THROUGH THURSDAY...POSSIBLY PUSHING A
COLD FRONT TOWARD THE AREA BY LATE WEEK.

HIGH TEMPERATURES EACH DAY WILL GENERALLY RANGE FROM THE UPPER 80S
INLAND TO THE LOWER 80S ALONG THE COASTLINE. WILL NEED TO MONITOR
MODEL TRENDS FOR COOLER CONDITIONS BY THURSDAY IF THE FRONT CAN
SHIFT TOWARD THE FORECAST AREA.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
VFR CONDITIONS WILL PREVAIL AT KCHS AND KSAV THROUGH 00Z SATURDAY.

EXTENDED AVIATION OUTLOOK...PRIMARILY VFR. ISOLATED TO SCATTERED
AFTERNOON SHOWERS/THUNDERSTORMS EXPECTED EACH AFTERNOON THROUGH
EARLY NEXT WEEK.

&&

.MARINE...
QUIET MARINE CONDITIONS EXPECTED THROUGH THE OVERNIGHT PERIOD AS SURFACE
HIGH PRESSURE REMAINS SITUATED EAST OF THE WATERS. GENERALLY
EXPECT S/SW WINDS 10-15 KTS WITH SEAS 2-3 FEET...HIGHEST BEYOND 20
NM.

FRIDAY THROUGH MONDAY...OVERALL THE PERIOD WILL BE MARKED BY HIGH
PRESSURE TO THE EAST EXTENDING WESTWARD ACROSS THE LOCAL WATERS.
WINDS WILL REMAIN SOUTH TO SOUTHWEST DURING THIS TIME WITH A FEW
MODEST SURGES OCCURRING AS THE GRADIENT TIGHTENS DUE TO WEAK INLAND
LOW PRESSURE. REGARDLESS...WINDS WILL REMAIN 15 KTS OR LESS AND WAVE
HEIGHTS WILL BE 2 TO 4 FT...HIGHEST OVER THE OUTER WATERS.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.

&&

$$

SYNOPSIS...
NEAR TERM...JAQ
SHORT TERM...BSH
LONG TERM...WMS
AVIATION...JAQ
MARINE...ECT/BSH