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000
FXUS62 KCHS 160805
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
405 AM EDT THU MAY 16 2013

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL EXTEND ACROSS THE REGION THROUGH LATE
WEEK. RAIN CHANCES WILL INCREASE OVER THE WEEKEND AS UPPER LEVEL
ENERGY MOVES OVER THE AREA...WITH A COLD FRONT APPROACHING FROM
THE WEST BY LATE NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
PRE-DAWN...PATCHES OF THIN HIGH CLOUDS OVERNIGHT...OTHERWISE SKIES
GENERALLY CLEAR. TEMPS HAVE REMAINED ELEVATED AS LIGHT BREEZES HAVE
BEEN CONTINUOUS TO THE N OF I-16 AND MOST NOTICEABLE ALONG COASTAL
SOUTH CAROLINA. COOLEST TEMPS HAVE BEEN OVER FAR S GEORGIA WHERE
WINDS DECOUPLED SOONER IN THE LAP OF THE LOW LEVEL RIDGE AXIS.

TODAY...THE UPPER LEVEL RIDGE AXIS WILL SLIDE OFF THE COAST WHILE
MODELS INDICATE A WEAK 500 MB SHORT WAVE EJECTING THROUGH THE
REGION AFTER MIDDAY. REALLY NO CONCERN FOR DIURNAL CONVECTIVE
INITIATION THIS AFTERNOON AS FORECAST SOUNDINGS PAINT A 2C-4C CAP
ON PROXIMITY SOUNDINGS ACROSS THE AREA WITH WEAK INSTABILITY/MOISTURE
PROFILES. THERE SHOULD BE AN OVERALL INCREASE IN UPPER LEVEL MOISTURE
THAT COULD COME INTO PLAY AS A FACTOR FOR HIGH TEMPS THIS AFTERNOON.
LOW LEVEL THICKNESS VALUES ARE WARMER THAN YESTERDAY AND IF HIGH
CLOUDS GO EVEN LESSER/THINNER THAN MODEL EXPECTATIONS...WE COULD SEE
QUITE A FEW INLAND SPOTS TOUCH 90. WITH THIS UNCERTAINTY WE PRETTY
MUCH RETAINED OUR PREVIOUS MAX TEMP SCHEME WITH A COUPLE OF NUDGES
UPWARD ALONG THE I-95 CORRIDOR OF SOUTH CAROLINA. SW SYNOPTIC FLOW
WILL RULE ONCE AGAIN...A BIT WEAKER THAN WED...BUT STILL A DECENT
RESULTANT SEA BREEZE ALONG UPPER COASTAL SOUTH CAROLINA.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
DRY WEATHER EXPECTED TO PERSIST TONIGHT WITH MILD MIN TEMPS IN
THE 60S AND PERIODS OF MID/UPPER CLOUDINESS AT TIMES.

FRIDAY...THE UPPER LEVEL TROUGH THAT SUPPORTED SIGNIFICANT
WEATHER OVER TEXAS WEDNESDAY NIGHT WILL GRADUALLY WEAKEN AS IT
APPROACHES THE EAST COAST LATE IN THE WEEK. ONLY REMNANT SHORTWAVE
ENERGY WILL PASS OVER THE FORECAST AREA BY FRIDAY. ALTHOUGH THE
MID AND UPPER LEVEL PROFILE WILL SEE AN INCREASE IN MOISTURE...THE
LOW LEVELS WILL STILL REMAIN RELATIVELY DRY UNDER THE REACH OF
ATLANTIC SURFACE HIGH PRESSURE. THUS EXPECT ONLY AN ISOLATED
SHOWER OR THUNDERSTORM TO DEVELOP ALONG AND INLAND OF THE
SEABREEZE DURING THE AFTERNOON HOURS...WITH ANY ACTIVITY
DIMINISHING AFTER SUNSET AS HEATING AND INSTABILITY WANE. MOST
AREAS WILL REMAIN DRY...WITH JUST AN INCREASE IN SKY COVER AS THE
DAY PROGRESSES. TEMPERATURES WILL RISE WELL ABOVE SEASONAL
NORMALS...PEAKING IN THE UPPER 80S AWAY FROM THE LOCALLY COOLER
COASTLINE.

SATURDAY...WEAK TROUGHING WILL LINGER OVER THE EAST COAST...AS A
SERIES OF TRANSIENT SHORTWAVES SHIFT INTO THE SOUTHEAST STATES.
ATLANTIC HIGH PRESSURE WILL CONTINUE TO BE THE MAIN SURFACE
FEATURE...ALLOWING WARM SOUTHERLY FLOW TO SUPPORT ABOVE NORMAL
HIGHS IN THE UPPER 80S INLAND TO THE LOWER 80S ALONG THE IMMEDIATE
COAST. EXPECT BETTER COVERAGE OF SHOWERS/THUNDERSTORMS ALONG AND
WEST OF THE SEABREEZE SATURDAY AFTERNOON WITHIN IMPROVED MOISTURE
PROFILES...AND HAVE THUS INCREASED POPS INTO THE CHANCE CATEGORY
FOR MUCH OF THE FORECAST AREA. BOTH GFS AND ECMWF SOLUTIONS SHOW
THE STRONGEST IMPULSE IN THE SERIES AMPLIFYING AS IT DESCENDS INTO
THE SOUTHERN APPALACHIANS SATURDAY NIGHT. THIS EXTRA ENERGY COULD
ALLOW INLAND CONVECTION TO PERSIST AFTER SUNSET...WITH MODEL
SOLUTIONS INDICATING VARYING DEGREES OF COVERAGE. PREFER TO
MAINTAIN MENTION OF SLIGHT CHANCE POPS OVERNIGHT...HIGHLIGHTING
MAINLY THE INLAND AREAS WITH THE BEST POTENTIAL FOR AN ISOLATED
NOCTURNAL SHOWER/THUNDERSTORM.

SUNDAY...SHORTWAVE ENERGY AND WEAK TROUGHING WILL STILL BE
MEANDERING OVER THE MID ATLANTIC AND SOUTHEAST STATES...ASSISTING
IN THE DEVELOPMENT OF A WEAK SURFACE WAVE ACROSS THE UPSTATE
REGION AND AN INCREASE IN DEEP MOISTURE. EXPECT ISOLATED TO
SCATTERED CONVECTION TO ONCE AGAIN DEVELOP ACROSS THE FAVORED
LOCATIONS INLAND OF THE SEABREEZE DURING THE AFTERNOON/EARLY
EVENING HOURS. LATEST ECMWF SOLUTION HAS BACKED OFF A BIT IN
COVERAGE FROM PREVIOUS RUNS...CONFINING THE BEST CHANCES FOR RAIN
ACROSS NORTHERN AREAS CLOSEST TO THE SHORTWAVE ENERGY. AT THIS
POINT...PREFER TO KEEP POPS IN THE 30 PERCENT RANGE AWAY FROM THE
IMMEDIATE COASTLINE. TEMPERATURES COULD BE A DEGREE OR TWO COOLER
THAN PREVIOUS DAYS CONSIDERING THICK SKY COVER AND A DECREASE IN
HEIGHTS ALOFT. EXPECT DAYTIME HIGHS TO RANGE MORE IN THE MID
80S...WITH A FEW LOCATIONS NEAR THE ALTAMAHA RIVER TOUCHING THE
UPPER 80S.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
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 /07Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS WILL PREVAIL AT KCHS AND KSAV THROUGH 06Z FRIDAY.

EXTENDED AVIATION OUTLOOK...VFR. ISOLATED DIURNAL CONVECTION IS
POSSIBLE OVER THE WEEKEND INTO MON.

&&

.MARINE...
OVERNIGHT...MODERATE SW FLOW HAS BEEN ONGOING AND SEAS AT 06Z/07Z
HAVE BEEN RUNNING ABOUT 1 FT ABOVE WAVEWATCH FROM GRAYS REEF UP
TO THE EDISTO BUOY. THE TIGHTEST LOW LEVEL PRES GRADIENT WILL
CONTINUE ACROSS SOUTH CAROLINA TODAY BUT ENHANCEMENTS DO NOT APPEAR
TO BE AS EMPHATIC AS ON WED WHEN THE GRADIENT PINCHED STRONGER.
ON AVERAGE THROUGH TONIGHT...SSW TO SW FLOW 15 KT OR LESS WITH
SEAS 2 TO 4 FT. SOMEWHAT STRONGER FLOW AT TIMES...IN THE 15 TO 20
KT RANGE WILL BE FOUND AT FAVORED DIURNAL TIMES ALONG THE USUAL
STRETCHES OF CHARLESTON COUNTY OUT TOWARD BUOY 6 AND BEYOND.

FRIDAY THROUGH MONDAY...SURFACE HIGH PRESSURE WILL REMAIN CENTERED
EAST OF THE MARINE ZONES THROUGH THE PERIOD. THIS PATTERN WILL
SUPPORT SOUTHERLY WINDS INTO EARLY NEXT WEEK...WITH WIND SPEEDS
GENERALLY RANGING FROM 10 TO 15 KT. 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...
SHORT TERM...WMS
LONG TERM...WMS
AVIATION...
MARINE...WMS