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000
FXUS62 KCHS 212344
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
744 PM EDT TUE MAY 21 2013

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL PREVAIL THROUGH THURSDAY. A
COLD FRONT WILL MOVE THROUGH THE AREA ON FRIDAY WITH DRY HIGH
PRESSURE BUILDING IN NEXT WEEKEND INTO EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
GIVEN THE LOSS OF DAYTIME HEATING AND DECREASING
INSTABILITY...LINGERING CONVECTION WEST OF I-95 IN SE GA WILL COME
TO AN END BY 10 PM. AN ISOLATED STRONG STORM CAN STILL OCCUR WEST
AND NW OF KSAV BEFORE ENDING.

THE FORECAST AREA LIES UNDERNEATH A WELL-DEFINED MID LEVEL IMPULSE
ACROSS FLORIDA WITH STRUNG OUT VORTICITY STRETCHING NORTH AND NE
OVERHEAD TO OFF THE COAST OF NC AND SE VA. THIS FEATURE WILL MOVE
LITTLE THROUGH THE NIGHT. MEANWHILE...THE BERMUDA HIGH WILL LIE
ATOP THE REGION AS A SUBTLE TROUGH DEVELOPS OVER THE NEARBY
ATLANTIC LATE.

MUCH OF THE REST OF THE NIGHT WILL BE RAINFREE...ALTHOUGH WITH THE
SHORT WAVE ALOFT AND SOME CONVERGENCE DOWNSTAIRS...GIVEN THAT
PWATS ARE NEAR 2 STANDARD DEVIATIONS ABOVE NORMAL FOR LATE
MAY...WE LOOK FOR SOME CONVECTION TO BREAK OUT AGAIN OVER THE
ATLANTIC OVERNIGHT. WE/RE ALREADY SEEING SIGNS OF THAT OUT NEAR
THE GULF STREAM. SOME OF THIS ACTIVITY WILL MOVE INTO CHARLESTON
AND FAR SE BERKELEY COUNTY BY SUNRISE.

GIVEN THE COPIOUS AMOUNT OF RAINS FROM EARLIER TODAY...FOG WILL
BECOME PROBLEMATIC AGAIN OVERNIGHT WHERE CLOUD COVER DIMINISHES.
WE HAVE ADDED PATCHY FOG TO THE GRIDDED FORECAST OVER THE WESTERN
HALF OF THE CWFA...GIVEN THE ONSHORE SYNOPTIC FLOW. LOCALLY DENSE
FOG IS CERTAINLY A CONCERN AND WE WILL RE-EVALUATE AGAIN WITH
FUTURE UPDATES.

CONDITIONS WILL BE STICKY AND BALMY TONIGHT...WITH MINIMUM TEMPS
NO LOWER THAN THE MID-UPPER 60S INLAND AND AROUND 70 NEAR THE SHORE.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
A FAIRLY SIMILAR PATTERN WILL PERSIST WEDNESDAY AND THURSDAY WITH
BROAD UPPER TROUGHING INLAND AND HIGH PRESSURE OVER THE ATLANTIC.
THIS PATTERN WILL MAINTAIN DEEP MOISTURE OVER THE AREA WITH DECENT
RAIN CHANCES THROUGH THE PERIOD...MOSTLY CONFINED INLAND DURING THE
DAY AND OVER THE ATLANTIC AT NIGHT. THE RISK FOR SEVERE WEATHER
APPEARS LOW GIVEN THE LACK OF ORGANIZATION POTENTIAL...ALTHOUGH
HEAVY RAINFALL COULD RESULT IN LOCALIZED FLOODING. HIGH/LOW
TEMPERATURES WILL ULTIMATELY DEPEND ON CLOUD COVER/RAINFALL BUT
GENERALLY SHOULD BE CLOSE TO SLIGHTLY ABOVE NORMAL.

A COLD FRONT SHOULD PUSH THROUGH FRIDAY MORNING...ALTHOUGH THE
NORTHWEST DOWNSLOPE FLOW WILL HELP TO OFFSET THE COLD ADVECTION.
THIS SHOULD LEAD TO TEMPERATURES CLOSE TO NORMAL IN THE MID 80S. THE
BIGGER CHANGE WILL BE THE DRIER AIR WHICH WILL MAKE IT FEEL A LOT
MORE COMFORTABLE.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
THERE IS GOOD MODEL AGREEMENT THAT DRY CANADIAN HIGH PRESSURE WILL
EXPAND SOUTHEAST INTO THE FORECAST AREA OVER THE WEEKEND THEN SHIFT
OFFSHORE. DEWPOINTS LOOK TO DROP INTO THE LOWER 50S SATURDAY AND
SUNDAY...WHICH COMBINED WITH HIGHS IN THE LOWER 80S WILL RESULT IN
PLEASANT SPRING WEATHER. OVERNIGHT LOWS WILL PROBABLY DROP INTO THE
UPPER 50S IN SPOTS. LOW-LEVEL MOISTURE INCREASES EARLY NEXT WEEK AS
THE SURFACE HIGH SHIFTS OFFSHORE...BUT WE DID NOT SEE ANY STRONG
SYNOPTIC SCALE FEATURES TO WARRANT ADDING PRECIP.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
DIMINISHING CONVECTION NEAR KSAV WILL END THIS EVENING...OTHERWISE
MAINLY VFR AT BOTH TERMINALS THROUGH THE NIGHT AND EARLY
WEDNESDAY. COULD SEE A FEW HOURS OF MVFR CONDITIONS AS LOW STRATUS
AND LIGHT FOG ATTEMPT TO FORM CLOSER TO DAYBREAK.

ANOTHER ROUND OF SCATTERED CONVECTION WILL OCCUR LATE WEDNESDAY
MORNING INTO THE AFTERNOON...BRINGING WITH IT THE POSSIBILITY OF
SHRA AND TSRA. FOR NOW PROB30 GROUPS WILL SUFFICE UNTIL TRENDS
PAINT A BETTER PICTURE. PERIODIC MVFR CONDITIONS WITH GUSTY WINDS
CAN OCCUR IN ANY TSRA THAT DOES IMPACT THE TERMINALS.

EXTENDED AVIATION...SPORADIC REDUCTIONS IN CEILINGS/VSBYS MAINLY IN
AFTERNOON/EVENING SHOWERS OR STORMS THROUGH THURSDAY.

&&

.MARINE...
TONIGHT...THE TYPICAL SUB-TROPICAL RIDGE OF HIGH PRESSURE WILL
CONTINUE TO STRETCH ACROSS THE COASTAL WATERS...GENERATING SE AND
SOUTH WINDS OF LESS THAN 10 OR 15 KT. SEAS WILL HOLD IN A FAIRLY
STEADY STATE...AVERAGING 2-4 FT. WHILE THE RISK IS NOT
PARTICULARLY HIGH...THERE IS NONETHELESS A CHANCE OF ISOLATED
STRONGER STORMS MOVING IN AFTER MIDNIGHT.

WEDNESDAY THROUGH SUNDAY...ATLANTIC HIGH PRESSURE WILL DOMINATE
WITH SOUTHERLY FLOW UNTIL A COLD FRONT PUSHES THROUGH FRIDAY. THE
MUCH COOLER AND DRIER AIR MASS BEHIND THE FRONT WILL MOVE IN AND
LEAD TO INCREASING WINDS AND BUILDING SEAS...POSSIBLY REACHING
ADVISORY LEVELS...AT LEAST ACROSS THE WATERS BEYOND 20 NM.

&&

.TIDES/COASTAL FLOODING...
HIGH ASTRONOMICAL TIDES AND FAVORABLE NORTH/NORTHEAST WINDS COULD
LEAD TO MINOR SALTWATER INUNDATION NEAR THE COAST DURING THE HIGH
TIDE FRIDAY AND SATURDAY EVENING. BY THE TIME OF THE HIGH TIDE
SUNDAY EVENING AS WELL AS MONDAY EVENING...WINDS WILL NOT BE AS
CONDUCIVE BUT MINOR SALTWATER FLOODING WILL STILL BE POSSIBLE.

&&

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

&&

$$

SYNOPSIS...
NEAR TERM...
SHORT TERM...RJB
LONG TERM...JRL
AVIATION...
MARINE...
TIDES/COASTAL FLOODING...