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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 210156
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
956 PM EDT MON MAY 20 2013

.SYNOPSIS...
AN UPPER LEVEL DISTURBANCE OVER THE AREA WILL DISSIPATE THROUGH
MID WEEK WHILE ATLANTIC HIGH PRESSURE PREVAILS UNTIL LATE WEEK. A
COLD FRONT WILL DROP THROUGH THE AREA FRIDAY...FOLLOWED BY HIGH
PRESSURE THROUGH NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
-- Changed Discussion --
ANY LINGERING CONVECTION WEST OF KSAV EARLY TONIGHT WILL DISSIPATE
BEFORE MIDNIGHT WITH THE NOCTURNAL ENVIRONMENT IN PLACE. A NARROW
BUT ELONGATED MID LEVEL IMPULSE WILL LIE OVERHEAD THROUGH THE
NIGHT WITH ITS ASSOCIATED PVA. THAT ALONG WITH LOW LEVEL
CONVERGENCE INCREASING OVER THE ATLANTIC AND NEAR THE SHORELINE
LATE WILL ALLOW FOR A BAND OF SCATTERED CONVECTION TO FORM CLOSE
TO DAYBREAK. WE HAVE LIMITED COVERAGE TO NO MORE THAN 20-30
PERCENT OVER CHARLESTON COUNTY AFTER 4 AM...WITH LITTLE TO NO RISK
ELSEWHERE. PWATS UP NEAR 1.75 INCHES SUGGESTS THAT LOCALLY HEAVY
RAINS CAN OCCUR...ALTHOUGH THE BEST CHANCES REMAINS OUT OVER THE
OCEAN.

CONVECTIVE DEBRIS CLOUDINESS WILL STEADILY DIMINISH IN OPAQUENESS
AND AREAL COVERAGE...BUT WHERE ANY CLEARING SETTLES IN WE LOOK FOR
LOWER STRATUS TO FILL THE VOID. THUS WE HAVE MAINTAINED A MOSTLY
CLOUDY SKY COVER AREA WIDE. GIVEN THE SOUPY AIR MASS...WET GROUNDS
FROM EARLIER RAINS...THE LACK OF WINDS AND FOG STABILITY INDICES
LESS THAN 15 IN MANY LOCALES...FOG WILL BECOME A WEATHER
PHENOMENON. WE/LL CARRY PATCHY COVERAGE AFTER 2 AM INLAND FROM
US-17.

IT/LL BE ANOTHER WARM AND VERY HUMID NIGHT...AND THUS RESTRICTING
LOWEST TEMPS ONLY IN THE MID AND UPPER 60S AWAY FROM THE BEACHES.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
ATLANTIC HIGH PRESSURE WILL BE THE DOMINANT FEATURE AT THE SURFACE
TUESDAY AND WEDNESDAY. THE PERSISTENT UPPER SHORTWAVE MEANDERING
OVER THE SOUTHEAST STATES WILL GRADUALLY BECOME ABSORBED BY A TROUGH
AXIS TO THE WEST MID WEEK. THE UPPER TROUGH WILL THEN CONTINUE TO
SWING TOWARD THE AREA ON THURSDAY...WITH A COLD FRONT APPROACHING
THE WESTERN ZONES BY THE EVENING HOURS.

DEEP MOISTURE AND PRECIPITABLE WATER VALUES WILL BE HIGHEST
TUESDAY UNDER THE INFLUENCE OF THE LINGERING SHORTWAVE
ENERGY...BEFORE SYNOPTIC SCALE FORCING DIMINISHES A BIT BY
WEDNESDAY. EXPECT SCATTERED COVERAGE OF MAINLY DIURNAL SHOWERS
AND THUNDERSTORMS BOTH TUESDAY AND WEDNESDAY...HIGHEST DURING THE
FAVORED AFTERNOON AND EVENING PERIODS. CONVECTION WILL MAINLY BE
DRIVEN BY A COMBINATION OF DAYTIME HEATING/INSTABILITY...SEABREEZE
CONVERGENCE...AND ANY BOUNDARY INTERACTIONS. WILL THUS ADVERTISE
BEST THUNDERSTORM POTENTIAL ALONG AND INLAND OF THE
SEABREEZE...HOWEVER THERE ARE STILL SOME INDICATIONS THAT
ISOLATED SHOWERS/WEAK THUNDERSTORMS COULD PUSH FROM THE MARINE
ZONES LOCALLY ONSHORE EACH NIGHT AND EARLY MORNING. THE
APPROACHING FRONT COULD SUPPORT BETTER CONVECTIVE COVERAGE ON
THURSDAY...YET PREFER TO MAINTAIN PERSISTENCE BY KEEPING RAIN
CHANCES IN THE 30 PERCENT RANGE TO ACCOUNT FOR SOME TIMING
DIFFERENCES SEEN IN FORECAST MODEL SOLUTIONS.

EXPECT A STEADY WARMING TREND TUESDAY THROUGH THURSDAY. HIGH
TEMPERATURES WILL RANGE FROM THE LOW TO MID 80S FOR THE MAJORITY
OF THE FORECAST AREA ON TUESDAY...WITH THE EXCEPTION OF THE FAR
SOUTHWEST COUNTIES WHERE TEMPERATURES COULD CLIMB INTO THE UPPER
80S. HIGH TEMPERATURES WILL THEN PEAK IN THE UPPER 80S MOST INLAND
LOCATIONS FOR THURSDAY...WHILE BEING SUPPRESSED IN THE LOW TO MID
80S CLOSER TO THE COASTLINE.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
FAIRLY GOOD MODEL CONSISTENCY REGARDING AN UPPER TROUGH SHIFTING
SOUTHEAST AND A COLD FRONTAL PASSAGE FRIDAY OR FRIDAY NIGHT. DRY AND
SLIGHTLY COOLER CANADIAN HIGH PRESSURE LOOKS TO BUILD IN FOR THE
WEEKEND BEFORE SHIFTING OFFSHORE EARLY NEXT WEEK.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
KCHS...VFR WEATHER TONIGHT INTO TUESDAY MORNING...UNLESS CLOUDS
THIN OUT ENOUGH THEN THERE WOULD BE A RISK OF LIGHT FOG DEVELOPING.
A RICH TROPICAL-LIKE FEED OF MOISTURE AND COASTAL CONVERGENCE WILL
INTERACT WITH THE SEA BREEZE DURING THE LATE MORNING AND AFTERNOON
HOURS ON TUESDAY...PRODUCING SCATTERED SHRA AND POSSIBLE TSRA. FOR
NOW WE HAVE INCLUDED A PROB30 GROUP FOR SHRA AND MVFR CONDITIONS
FROM 15-21Z UNTIL TRENDS CAN BE BETTER DEFINED.

KSAV...PROVIDED THAT CLOUD COVER DECREASES ENOUGH LATE TONIGHT/TUESDAY
MORNING...WE ANTICIPATE A FEW HOURS OF MVFR CONDITIONS IN LIGHT
FOG/LOW STRATUS. OTHERWISE VFR CONDITIONS TO PREVAIL TONIGHT. ISOLATED
TO SCATTERED CONVECTION WILL FORM ALONG THE SEA BREEZE BOUNDARY
DURING TUESDAY AFTERNOON...THUS A PROB30 GROUP FROM 16-21Z.

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 WED AND THU...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
ATLANTIC WILL EXTEND W ACROSS THE COASTAL WATERS...GENERATING SE
AND S WINDS AT OR BELOW 10 OR 12 KTS AND SEAS IN THE 2-4 FOOT
RANGE. COULD SEE SOME STRONGER STORMS MOVING IN FROM THE SOUTH
OVERNIGHT.

HIGH PRESSURE WILL REMAIN OVER THE WESTERN ATLANTIC THROUGH
THURSDAY NIGHT...MAINTAINING A GENERAL SOUTHERLY FLOW AND
ALLOWING SEABREEZE CIRCULATIONS TO DEVELOP EACH AFTERNOON. A COLD
FRONT WILL DROP THROUGH THE REGION EARLY FRIDAY...WITH A NORTHEAST
FLOW DEVELOPING AS CANADIAN HIGH PRESSURE BUILDS IN ITS WAKE.
WINDS AND SEAS WILL LIKELY INCREASE OVER THE WEEKEND AS A RESULT.
-- End Changed Discussion --

&&

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

&&

$$

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