000
FXUS62 KCHS 200527
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
127 AM EDT MON MAY 20 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 THIS MORNING/...
COMPLICATED PATTERN OVER THE REGION EARLY THIS MORNING WITH A MID
LEVEL TROUGH OVER THE INLAND CAROLINAS AND N GEORGIA. CLOUDS HAVE
DISSIPATED MANY AREAS AND WE WILL LOOK FOR SOME POTENTIAL FOR
PATCHY FOG AND LOW CLOUDS OVERNIGHT...ESPECIALLY INLAND ZONES.

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. LOW TEMPS
WILL BE IN THE UPPER 60S AND LOWER 70S.

&&

.SHORT TERM /6 AM THIS 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 /05Z MONDAY THROUGH FRIDAY/...
KCHS...VFR WEATHER TO PREVAIL OVERNIGHT UNTIL LATE. A FEED OF
ABUNDANT MOISTURE AND ASSOCIATED CONVERGENCE WILL PRODUCE
SCATTERED CONVECTION THIS MORNING. WHILE MUCH OF THIS ACTIVITY LOOKS
TO REMAIN EAST OF THE TERMINAL PRIOR TO DAYBREAK...MODELS DEVELOP
CONVECTIVE RAINS AROUND DAWN AND THEN RAIN CHANCES FOR THE REST OF
TODAY LOOK PRETTY GOOD AS DEEP MOISTURE INTERACTS WITH THE UPPER
TROUGH AND THE SEA BREEZE. SHOWERS/TSTMS SHOULD DECREASE LATE DAY
WITH MAINLY VFR CONDITIONS THIS EVENING.

KSAV...VFR OVERNIGHT WEATHER COULD DROP TO THE MVFR RANGE IN
LIGHT FOG/LOW STRATUS LATE. THERE IS THEN A DECENT 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.

&&

.MARINE...
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.
ISOLATED TO SCATTERED SHOWERS AND T-STORMS ARE EXPECTED TO DEVELOP
ALONG THE SOUTH CAROLINA COAST LATER TONIGHT.

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.

&&

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

&&

$$

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