-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 222339
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
734 PM EDT WED MAY 22 2013

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL PREVAIL THROUGH THURSDAY. A COLD
FRONT WILL MOVE ACROSS THE AREA THURSDAY NIGHT...WITH HIGH
PRESSURE BUILDING OVER THE REGION THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH THURSDAY/...
-- Changed Discussion --
QUITE A CHANGE IN THE PATTERN SINCE YESTERDAY...WITH MUCH OF THE
AREA VOID OF ANY CONVECTION EARLIER TODAY. WE/RE FINISHED FOR THE
EVENING FOR ANY SHOWERS OR T-STORMS IN THE LOCAL ZONES...WITH THE
SEA BREEZE HAVING CLEARED OUR NW TIER. IN ITS WAKE A STABILIZED
ENVIRONMENT HAS ENSUED AND WILL PERSIST.

FOR TONIGHT... THERE IS SOME CHANGES THAT WILL TAKE PLACE IN THE
LARGER SCALE...AS THE FIRST SHORT WAVE OFF THE EASTERN FLORIDA COAST
TO GET LIFTED NE AS THE NEXT LONG WAVE TROUGH IN THE MISSISSIPPI
VALLEY SHIFTS EAST. AS THIS TRANSPIRES...IT FORCES THE LAST GRIPS OF
THE ATLANTIC RIDGE TO PULL OFFSHORE AFTER MIDNIGHT...AS A
PRE-FRONTAL TROUGH IN EASTERN ALABAMA AND WESTERN GEORGIA APPROACHES
LATE. THE FORECAST AREA WILL THEN LIE SANDWICHED BETWEEN THE FIRST
SHORT WAVE IN THE NEARBY ATLANTIC AND THE SECOND IMPULSE AND ITS
REFLECTION AT THAT SURFACE. WHILE THERE IS SOME INCREASE IN LOW
LEVEL CONVERGENCE TO THE EAST...THE SYNOPTIC FLOW MAY VEER TOO FAR
TO THE SW TO ALLOW FOR ANYTHING MORE THAN LOW END POPS OVER
CHARLESTON COUNTY CLOSE TO DAYBREAK. UPSTREAM IT APPEARS THAT THE
BEST FORCING WILL STAY TO THE WEST...SO LESS THAN 14 POPS HAVE BEEN
FORECAST ELSEWHERE.

WHILE CONDITIONS ARE NOT AS FAVORABLE FOR FOG DEVELOPMENT AS LAST
NIGHT /IE. TOO MUCH WIND IN THE BOUNDARY LAYER UNTIL LATE AND
MUCH LESS RAINFALL/...WE HAVE OPTED TO ADD PATCHY FOG TO OUR NW
TIER WHERE THEY HAVE A BETTER CHANCE OF ACHIEVING THEIR CROSS-OVER
TEMPS AND FOG STABILITY INDICES ARE IN THE LOWER 20S.

THE MIXING IN THE BOUNDARY LAYER AND AN INCREASE IN CLOUD COVER
WILL LIMIT TEMPS TO ONLY THE MID AND UPPER 60S INLAND FROM THE
SLIGHTLY WARMER BEACHES.
-- End Changed Discussion --

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
A SURFACE PRESSURE TROF WILL MOVE INTO THE CWA ON THURSDAY...WITH
MOIST SOUTHERLY WINDS AHEAD OF IT AND SOMEWHAT DRIER WESTERLY WINDS
BEHIND IT. THE TROF SHOULD BE ROUGHLY ALONG INTERSTATE 95 BY EARLY
AFTERNOON...AND AREAS ALONG AND EAST OF THE BOUNDARY WILL HAVE A
CHANCE OF SHOWERS AND THUNDERSTORMS AS DAYTIME HEATING CREATES SOME
SURFACE INSTABILITY AND CONVERGENCE. FURTHER WEST...ESPECIALLY OVER
OUR INTERIOR GEORGIA COUNTIES...THE ATMOSPHERE WILL BE DRIER AND
MORE STABLE...SO THERE WILL ONLY BE A SLIGHT CHANCE OF SHOWERS.
SKIES SHOULD AVERAGE OUT PARTLY CLOUDY...ALTHOUGH THERE WILL BE A
PERIOD OF MOSTLY CLOUDY SKIES TO THE EAST OF THE BOUNDARY DURING A
PORTION OF THE AFTERNOON.

THURSDAY NIGHT...THE INITIAL COOL FRONT PUSHES THROUGH THE
AREA...MOVING THE CHANCES FOR RAIN MOSTLY OFFSHORE...ALTHOUGH I
CANNOT RULE OUT A SLIGHT CHANCE OVER THE TRI COUNTY AREA AS THERE
MAY BE ENOUGH REMNANT MOISTURE WITH THE FRONT TO PROMOTE SOME
SHOWERS.

FRIDAY...THE WINDS WILL BE NORTHWEST BEHIND THE FRONT IN THE
MORNING...PROMOTING SOME DOWNSLOPE LOW LEVEL FLOW AND HEATING.
HOWEVER...DRIER AIR MOVING IN SHOULD PREVENT ANY RAIN...OR MUCH IN
THE WAY OF CLOUDS FOR THAT MATTER. A SECONDARY COLD FRONT WILL MOVE
THROUGH LATER IN THE DAY...CAUSING THE WINDS TO VEER TO NORTH AND
INCREASE AS COLD ADVECTION PICKS UP. FRIDAY NIGHT WILL BE MUCH
COOLER THAN THE PREVIOUS FEW.

SATURDAY...TEMPS WILL BEGIN WELL BELOW NORMAL AS MODIFIED AIR POURS
IN TO THE AREA...BUT THIS TIME OF YEAR THAT MEANS TEMPS MAINLY IN
THE 50S. PLENTY OF SUNSHINE WILL ALLOW AFTERNOON MAX TEMPS TO REACH
TO 80 OR ABOVE...BUT DEWPOINTS WILL DROP INTO THE 40S AWAY FROM THE
COAST.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
MEDIUM RANGE GUIDANCE IS IN GOOD OVERALL AGREEMENT THROUGH THE LONG
TERM PERIOD. THE MID AND UPPER LEVEL PATTERN WILL FEATURE A NEARLY
ZONAL FLOW OVER THE REGION LATE IN THE WEEKEND INTO EARLY NEXT
WEEK...WITH A RIDGE THEN BUILDING TOWARD THE MIDDLE OF NEXT WEEK. AT
THE SURFACE...HIGH PRESSURE WILL PASS NORTH OF THE AREA LATE IN THE
WEEKEND...THEN SETTLE OVER THE WESTERN ATLANTIC THROUGH THE MIDDLE
OF NEXT WEEK.

RAIN-FREE CONDITIONS ARE EXPECTED TO PERSIST INTO EARLY NEXT
WEEK...THEN INCREASING MOISTURE COULD ALLOW FOR SOME MAINLY DIURNAL
ISOLATED CONVECTION ALONG AND AHEAD OF THE SEA BREEZE TUESDAY AND
WEDNESDAY. TEMPERATURES WILL BE SLIGHTLY BELOW NORMAL SUNDAY...THEN
RETURN TO NEAR OR SLIGHTLY ABOVE NORMAL NEXT WEEK.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
WHILE WE HAVE MAINTAINED PREVAILING VFR THROUGH 00Z FRIDAY...THERE
IS THE RISK OF MVFR CONDITIONS IN LIGHT FOG/STRATUS A FEW HOURS
EITHER SIDE OF DAYBREAK...AND ALSO MARGINAL MVFR CONDITIONS IN
ISOLATED TO SCATTERED SHRA/TSRA WITH A PRE-FRONTAL TROUGH IN THE
LATE MORNING THROUGH MID AFTERNOON. IF THE TROUGH IS QUICKER THAN
ANTICIPATED THERE COULD BE SOME GUSTY WINDS LATE IN THE TAF CYCLE.

EXTENDED AVIATION...VFR. WINDS COULD GET A BIT GUSTY FRIDAY AFTERNOON
BEHIND THE SECONDARY FRONT.

&&

.MARINE...
TONIGHT...THE SUB TROPICAL RIDGE IN THE ATLANTIC CENTERED OUT NEAR
32N AND 60W WILL START TO RELAX ITS GRIP ACROSS THE COASTAL WATERS
LATE...AS IT STARTS TO GIVE WAY TO AN UPSTREAM PRE-FRONTAL TROUGH.
THE PRESSURE GRADIENT WILL TEMPORARILY TIGHTEN A BIT BETWEEN THESE
TWO FEATURES...ALLOWING FOR SE AND SOUTH WINDS UP TO 15 KT THROUGH
ABOUT 06-08Z...BEFORE DROPPING OFF TO 10 OR LESS LATE. SEAS WON/T
CHANGE MUCH...AVERAGING 2-4 FT AND HIGHEST ACROSS THE OUTER GA
WATERS. WE/LL NEED TO MONITOR FOR SOME GUSTY SHOWERS/T-STORMS
OVERNIGHT AS LOW LEVEL CONVERGENCE INCREASES.

THURSDAY THROUGH MONDAY...ATLANTIC HIGH PRESSURE WILL DOMINATE
WITH SOUTHERLY FLOW UNTIL A COLD FRONT PUSHES OFFSHORE EARLY
FRIDAY. A NORTHERLY SURGE IS EXPECTED TO DEVELOP IN WAKE OF THE
FRONT FRIDAY NIGHT INTO EARLY SATURDAY AND COULD RESULT IN SMALL
CRAFT ADVISORY CONDITIONS. CONDITIONS WILL THEN IMPROVE LATER IN
THE WEEKEND INTO EARLY NEXT WEEK WITH WINDS/SEAS EXPECTED TO
REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS.

&&

.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 AND MONDAY EVENING...WINDS WILL NOT BE AS
CONDUCIVE...YET MINOR SALTWATER FLOODING WILL STILL BE POSSIBLE.

&&

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

&&

$$

SYNOPSIS...
NEAR TERM...
SHORT TERM...FWA
LONG TERM...JAQ
AVIATION...
MARINE...
TIDES/COASTAL FLOODING...