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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 200210
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1010 PM EDT SUN MAY 19 2013

.SYNOPSIS...
AN UPPER LEVEL DISTURBANCE OVER THE AREA WILL DISSIPATE THROUGH
TUESDAY. ATLANTIC HIGH PRESSURE WILL THEN PREVAIL UNTIL LATE WEEK.
A COLD FRONT WILL DROP THROUGH THE AREA LATE FRIDAY INTO
SATURDAY...FOLLOWED BY HIGH PRESSURE THROUGH NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
-- Changed Discussion --
DEEP RIDGING IN THE ATLANTIC AND STRETCHING FROM THE GULF OF
MEXICO INTO CANADA IS INTERRUPTED BY A SHORT WAVE FOUND NEARBY
TONIGHT. AT THE SURFACE THE FORECAST REGION WILL LIE UNDER THE
WESTERN EXTENSION OF STRONG ATLANTIC HIGH PRESSURE...AS MESO-SCALE
BOUNDARIES FROM EARLIER CONVECTION CONTINUE TO DISSIPATE.

WHILE WE CAN/T ENTIRELY RULE OUT A STRAY SHOWER OR TWO PRIOR TO
MIDNIGHT FROM ANY LEFT OUTFLOWS...OUR ATTENTION TRANSFERS OVER
THE ATLANTIC AFTER MIDNIGHT...WITH A SOUTHERLY FLOW OF RICH
TROPICAL-LIKE MOISTURE TO PREVAIL. PWATS WILL BE NEAR 1.75
INCHES...OR JUST A TAD BELOW 2 STANDARD DEVIATIONS ABOVE NORMAL.
CONVERGENCE WILL BECOME ENHANCED WITH A SOUTH TO SW FLOW WITHIN
THE FIRST MILE OF SO OF THE TROPOSPHERE. THUS WE LOOK FOR THE
POTENTIAL OF TRAINING OF ECHOES TO OCCUR AND A LOCALIZED HEAVY
RAIN RISK LATE.

WE HAVE SHOWN LITTLE TO NO POPS THROUGH 2 AM...BEFORE POPS RAMP
UP THEREAFTER...WITH THE GREATEST COVERAGE /40-50 PERCENT/ TO
OCCUR AFTER 3 OR 4 AM AND MAINLY OVER CHARLESTON AND BERKELEY
COUNTIES WHERE THE BEST LIFT/MOISTURE WILL BE FOUND.

IT/LL BE ANOTHER UNUSUALLY WARM AND MUGGY NIGHT WITH WEAK WARM
ADVECTION...PLENTIFUL CLOUD COVER AND ELEVATED DEW POINTS. LOWEST
TEMPS WILL BE IN THE UPPER 60S AND LOWER 70S...ABOUT 4-8 DEGREES
ABOVE NORMS.

GIVEN THE RAINFALL IN MANY LOCATIONS EARLIER...AND WITH SATELLITE
IMAGES SHOWING A LITTLE CLEARING ATTEMPTING TO SET IN...WE COULD
EXPERIENCE SOME LOW STRATUS AND FOG FORMATION. BUT PROBABILITIES
STILL REMAIN TOO LOW TO INCLUDE IN THE GRIDDED WEATHER ELEMENTS.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
THE SHORTWAVE TROUGH ALOFT WILL BE SITUATED OVER THE REGION MONDAY
THEN WILL WEAKEN/UNRAVEL AND HIGHER PWATS SHOULD BE SHUNTED INLAND
TUESDAY AS HEIGHTS TEMPORARILY BUILD ALOFT AND ATLANTIC SURFACE HIGH
PRESSURE EXPANDS WESTWARD. THUS...EXPECT GREATER COVERAGE OF
SHOWERS/THUNDERSTORMS MONDAY AS COMPARED TO TUESDAY.
MONDAY...FORECASTS INDICATE HIGH CHANCE/LIKELY POPS AT MANY
LOCATIONS AWAY FROM THE BEACHES AROUND THE TIME OF MAX HEATING
MIDDAY UNTIL LATE AFTERNOON. THEN...CAPPED GREATEST POPS IN CHANCE
CATEGORY AWAY FROM THE BEACHES TUESDAY AFTERNOON. HOWEVER...IF THE
SHORTWAVE TROUGH PERSISTS INTACT LONGER THAN EXPECTED...TUESDAY
COULD BECOME SOMEWHAT MORE ACTIVE THAN INDICATED IN THIS FORECAST.

CANNOT RULE OUT BRIEF/PULSE SEVERE THUNDERSTORMS MONDAY OR TUESDAY
AFTERNOON...ESPECIALLY WHERE MESOSCALE BOUNDARY INTERACTIONS
OCCUR...BUT THE PRIMARY CONCERN WILL REMAIN LOCALLY HEAVY RAIN AS
PWATS REMAIN AROUND 1.75 INCHES ESPECIALLY MONDAY AND MULTICELL
CONVECTION EXHIBITS SLOW/SOMEWHAT ERRATIC PROPAGATION.
TUESDAY...PWATS SHOULD DECREASE TO SOME DEGREE.

WEDNESDAY...TEMPERATURES IN THE UPPER 80S TO AROUND 90F WILL BECOME
MORE COMMON AS THE ATLANTIC RIDGE PREVAILS. HOWEVER...THE SYNOPTIC
SCALE UPPER TROUGH APPROACHING FROM THE WEST WILL BEGIN TO IMPACT
THE REGION...SO AT LEAST SLIGHT CHANCE/CHANCE POPS FOR DIURNAL
SHOWERS/THUNDERSTORMS ARE JUSTIFIED DUE TO THE INFLUENCE OF THE SEA
BREEZE AND THE UPPER TROUGH.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
SIGNIFICANT MODEL DIFFERENCES APPEAR IN THE LONG TERM...MAINLY
REGARDING THE NEXT UPPER TROUGH THAT SHIFTS INTO THE EASTERN UNITED
STATES LATE IN THE WEEK. WE ARE TRENDING TOWARD THE ECMWF WHICH
MOVES THE UPPER TROUGH AND A COLD FRONT THROUGH THE AREA ON SATURDAY
WITH A DRY AND COOLER CANADIAN HIGH PRESSURE SYSTEM BUILDING IN
THEREAFTER. THUS WE ARE SHOWING DIURNAL...MAINLY SEABREEZE-DRIVEN
POPS THURSDAY AND FRIDAY...THEN DRY OVER THE WEEKEND.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
KCHS...VFR WEATHER TO PREVAIL AT LEAST THROUGH THE FIRST PART OF
TONIGHT. WE THEN LOOK INTO THE ATLANTIC OVERNIGHT AS A FEED OF
ABUNDANT MOISTURE AND ITS ASSOCIATED CONVERGENCE WILL PRODUCE
SCATTERED CONVECTION OVERNIGHT INTO MONDAY MORNING. WHILE MUCH OF
THIS ACTIVITY LOOKS TO REMAIN EAST OF THE TERMINAL...CHANCES ARE
SUFFICIENT ENOUGH TO MENTION VCSH AND MIST FROM 07-15Z WITH
BORDERLINE MVFR CONDITIONS TO OCCUR. A GREATER RISK OF SHRA AND
POSSIBLE TSRA WITH PERIODIC FLIGHT RESTRICTIONS THEN EXISTS FROM
15-21Z AS THE SEA BREEZE MOVES THROUGH AND INTERACTS WITH A SHORT
WAVE ALOFT AND VARIOUS OTHER MESO-SCALE BOUNDARIES.

KSAV...VFR OVERNIGHT WEATHER COULD DROP TO THE MVFR RANGE IN
LIGHT FOG/LOW STRATUS LATE TONIGHT INTO MONDAY MORNING. THERE IS
THEN A HIGH END CHANCE OF SHRA AND POSSIBLE TSRA FROM 16-22Z
MONDAY WITH SEVERAL MESO-SCALE BOUNDARIES IN PLACE AIDED BY A
SHORT WAVE ALOFT. MVFR WEATHER CAN CERTAINLY OCCUR PERIODICALLY
DURING THIS TIME.

EXTENDED AVIATION...THE MAIN CONCERN WILL BE SPORADIC REDUCTIONS
IN CEILINGS AND VISIBILITIES...MAINLY ASSOCIATED WITH SCATTERED
SHOWERS AND THUNDERSTORMS THROUGH THE PERIOD. THE GREATEST CHANCES
WILL BE IN THE AFTERNOON HOURS SUNDAY THROUGH TUESDAY...ALTHOUGH
EARLY MORNING FLIGHT RESTRICTIONS CANNOT BE RULED OUT EACH DAY.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
TONIGHT...A STRONG RIDGE OF HIGH PRESSURE CENTERED OVER THE NW
ATLANTIC WILL EXTEND ACROSS THE COASTAL WATERS...GENERATING SE AND
SOUTH WINDS OF 10-15 KT OR LESS AND SEAS IN THE 2-4 FOOT RANGE.
MARINERS SHOULD BE ALERT FOR ISOLATED TO SCATTERED
T-STORMS...MAINLY AFTER MIDNIGHT WHICH WILL PRODUCE GUSTY
WINDS...FREQUENT LIGHTNING AND VERY HEAVY RAINS REDUCING
VISIBILITY TO NEAR ZERO AT TIMES.

OFFSHORE HIGH PRESSURE WILL PERSIST THROUGH LATE WEEK...WITH
LOCALLY/BRIEFLY STRONGER ONSHORE WINDS AS HIGH AS 20 KT DUE TO THE
DIURNAL SEA BREEZE CIRCULATION EACH DAY. SEAS WILL AVERAGE 2 TO 4
FEET MUCH OF THE TIME. AHEAD OF AN APPROACHING COLD FRONT LATE IN
THE PERIOD...A TIGHTENING SURFACE PRESSURE GRADIENT COULD CONTRIBUTE
TO STRONGER WINDS AND BUILDING SEAS...AND THE PROBABILITY FOR LOW
END SMALL CRAFT ADVISORY CONDITIONS WILL INCREASE SOMEWHAT MID TO
LATE WEEK.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...
NEAR TERM...
SHORT TERM...SPR
LONG TERM...JRL
AVIATION...
MARINE...