AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
128 AM EDT SAT JUL 9 2011

.SYNOPSIS...
DEEPER MOISTURE WILL GRADUALLY INCREASE OVER THE REGION THROUGH
TONIGHT AS WEAK LOW PRESSURE ALONG THE GULF COAST PERSISTS. A WEAK
FRONT WILL MOVE INTO THE AREA LATE IN THE WEEKEND BEFORE DISSIPATING.
BERMUDA RIDGE WILL DOMINATE THE WEATHER ACROSS THE AREA EARLY NEXT
WEEK. ANOTHER FRONT WILL APPROACH FROM THE NORTH BY THE MIDDLE OF
NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
MOST OF THE SHOWER/TSTM ACTIVITY HAS DISSIPATED BUT ANOTHER SLUG OF
TROPICAL MOISTURE IS FORECAST TO MOVE UP THE COAST TONIGHT AS A
925-850MB LOW-LEVEL JET INTENSIFIES. THE MOST INTENSE MOISTURE
TRANSPORT LOOKS TO BECOME FOCUSED ALONG THE MIDDLE AND UPPER SOUTH
CAROLINA COASTS AFTER MIDNIGHT...WHICH INCLUDES MUCH OF THE
CHARLESTON TRI-COUNTY AREA. GIVEN THE TROPICAL AIRMASS THAT IS IN
PLACE...A SHOWER COULD POP JUST ABOUT ANYWHERE OVERNIGHT. WILL
MAINTAIN 20 PERCENT POPS OVERNIGHT WITH 30-40 PERCENT POPS ALONG
THE CENTRAL SOUTH CAROLINA COAST.

IT WILL REMAIN WARM AND MUGGY TONIGHT WITH LOWS RANGING FROM THE
MID 70S INLAND TO THE UPPER 70S AT THE COAST.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY/...
UPPER TROUGH ALONG THE EAST COAST AT START OF THE PERIOD WILL LIFT
NORTHEAST AT START OF THE PERIOD. BERMUDA RIDGE AND LARGE RIDGE
ACROSS THE SOUTHERN PLAINS WILL COMBINE...WITH A LARGE RIDGE OF HIGH
PRESSURE COVERING THE SOUTHERN TWO-THIRDS OF THE NATION DURING THE
LATER HALF OF THE WEEKEND AND THROUGH EARLY NEXT WEEK. A WEAK
FRONTAL BOUNDARY AT THE SURFACE WILL STRUGGLE TO PUSH SOUTHWARD AS
UPPER TROUGH LIFTS OUT. AT THIS TIME...WILL BRING DIFFUSE FRONT INTO
FORECAST AREA SUN MORNING AND THEN DISSIPATE IT THROUGH THE DAY.

PRECIPITABLE WATER VALUES ON SAT WILL STILL BE VERY HIGH AND ON THE
ORDER OF TWO AND A THIRD INCHES. ALTHOUGH SIGNIFICANT CLOUD COVER IS
EXPECTED...THERE WILL BE ENOUGH HEATING TO INCREASE CAPE VALUES
ABOVE 2000 J/KG. DEEP MOISTURE WILL REMAIN IN PLACE...ESPECIALLY
ALONG THE COAST. WILL CARRY LIKELY POPS DURING SAT. DUE TO THE HIGH
MOISTURE CONTENT...ANY CONVECTION WILL HAVE THE CAPABILITY FOR HEAVY
DOWNPOURS. DEWPOINTS IN THE MID TO PERHAPS UPPER 70S WILL COMBINE
WITH TEMPS IN THE LOWER 90S TO PRODUCE HEAT INDICES ABOVE 100
DEG...BUT MOST LOCATIONS SHOULD REMAIN JUST BELOW HEAT ADVISORY
CRITERIA.

SUNDAY SHOULD BE A TRANSITION DAY AS COLUMN BEGINS TO DRY OUT FROM
THE TOP DOWN. WEAK FRONT WILL BE IN THE PROCESS OF DISSOLVING AND
SINCE SUBSIDENCE WILL NOT HAVE A FIRM GRIP ON THE AREA...WILL DROP
POPS AS CONVECTION SHOULD BE MORE SCATTERED WITH THE HIGHEST POPS ON
SUN EXPECTED ALONG AND INLAND FROM THE SEABREEZE. BUILDING RIDGE AND
INFLUX OF DRIER AIR WILL YIELD MORE HEAT THAN ON SAT. MAXIMUMS
MAINLY IN THE MID 90S WILL COMBINE WITH HIGH DEWPOINTS TO PUSH THE
HEAT INDEX TO NEAR ADVISORY CRITERIA...ESPECIALLY AWAY FROM THE
IMMEDIATE COAST.

MUCH DRIER AIR SHOULD BE IN PLACE ON MON WITH PRECIPITABLE WATER
VALUES DROPPING TO LESS THAN ONE AND A HALF INCHES. SUBSIDENCE WILL
BE STRONGER ON MON THAN OVER THE WEEKEND. AS CAPPING INVERSION
ERODES WITH STRONG HEATING THROUGH THE AFTERNOON...WILL CARRY SLIGHT
CHANCE TO LOW CHANCE FOR AFTERNOON AND EARLY EVE SHOWERS AND
THUNDERSTORMS...WITH SLIGHTLY HIGHER POPS INLAND AND ALONG THE
SEABREEZE. MONDAY WILL LIKELY BE THE MOST UNCOMFORTABLE DAY OF THE
PERIOD. HIGHS IN THE MID 90S TO UPPER 90S INLAND WILL RESULT IN HEAT
INDICES ABOVE 105 DEGREES ACROSS MOST OF THE AREA.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
TUESDAY LOOKS QUITE SIMILAR TO MONDAY AS WIDELY SCATTERED
AFTERNOON AND EVENING CONVECTION IS EXPECTED...BUT LOTS OF
SUNSHINE WILL ALLOW TEMPS TO RISE WELL INTO THE 90S AWAY FROM THE
COAST WITH HEAT INDICES INTO THE MID 100S.

THE SECOND HALF OF THE WEEK IS MORE COMPLICATED. GFS HAS SHIFTED
SIGNIFICANTLY FROM ITS SOLUTION 24 HOURS. NOW..INSTEAD OF HOLDING UP
THE NEXT COLD FRONT NORTH OF THE AREA...IT PLOWS IT THROUGH MID WEEK
AND BRINGS IN A SIGNIFICANTLY DRIER AIR MASS FOR THURSDAY AND
FRIDAY. I HAVE ONLY NUDGED THE FORECAST SLIGHTLY IN THAT DIRECTION
DUE TO THE LACK OF CONTINUITY...PLUS THE FACT THAT YESTERDAYS ECMWF
HAS BACKED OF ITS FRONTAL PASSAGE BY A DAY.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
OVERNIGHT...OCCASIONAL MVFR CIGS MAY BRUSH KCHS WITH MAINLY VFR
CONDITIONS ANTICIPATED AT KSAV. WE WILL MONITOR FOR VICINITY
OF SHOWERS OR TSTMS AT KCHS OVERNIGHT BUT MUCH OF THE ACTIVITY
MAY SKIRT JUST OFF TO THE E WHERE CONVERGENCE BOUNDARIES ARE
IN PLACE. POTENTIAL FOR TSTMS AT BOTH TERMINALS LOOKS FAIRLY
SIGNIFICANT THIS AFTERNOON. TIMING ESTIMATES MAINLY BETWEEN
17Z-23Z.

EXTENDED AVIATION OUTLOOK...AS IS USUALLY THE CASE IN MID
SUMMER...THE BEST CHANCE FOR MVFR/IFR CIGS/VSBYS IS WITH THE
CHANCES OF AFTERNOON AND EVENING CONVECTION NEAR THE TERMINALS.
ALSO...WITH WINDS EXPECTED TO GET VERY LIGHT ON MONDAY AND TUESDAY
MORNINGS...THERE COULD BE A COUPLE OF HOURS OF BR AROUND SUNRISE
EACH DAY.

&&

.MARINE...
WE CONTINUE TO TREND HIGHER ON WINDS/SEAS OVERNIGHT. SCA CONDITIONS
WILL OCCUR OCCASIONALLY ALL NEAR SHORE WATERS WITH FREQUENT SCA
CONDITIONS WHERE WE HAVE ADVISORIES OFF THE CHARLESTON COUNTY AND
OVER OUR OUTER GEORGIA WATERS. WINDS 15 TO 25 KT OVERNIGHT WITH
SEAS 4 TO 7 FT...HIGHEST BEYOND 20 NM OFFSHORE.

WINDS WILL BE FROM THE SW SAT AND SAT EVE AND STRONGEST WINDS ARE
EXPECTED THROUGH SAT MORNING. HOWEVER...AS NOCTURNAL JET
DISSIPATES...SW WINDS ACROSS THE WATERS WILL BE DIMINISHING. WILL
CONTINUE SCA FOR OUTER GEORGIA WATERS THROUGH ABOUT MIDDAY ON SAT
FOR LINGERING 6 FT SEAS AND WIND GUSTS TO 25 KT. ELSEWHERE...WILL
CAP WINDS AT 15 KT WITH GUSTS TO 20 KT AND SEAS AT 3 TO 5 FT. SW
WINDS WILL CONTINUE TO SLOWLY DIMINISH SAT NIGHT AND BY SUN MORNING
SHOULD BE LESS THAN 10 KT THROUGHOUT. THE WIND DIRECTION MAY BECOME
LIGHT AND VARIABLE FOR A TIME...ESPECIALLY ACROSS THE NORTHERN
WATERS DUE TO THE PROXIMITY OF A WEAK FRONT ON SUN.

GRADIENT WILL BE PRETTY SLACK MONDAY THROUGH WEDNESDAY WITH LIGHT
WINDS GENERALLY OUT OF THE SOUTH AND SOUTHWEST...TURNING ONSHORE
NEAR THE COAST IN THE AFTERNOON AND EVENING. WINDS MAY PICK UP
SOME AGAIN ON WEDNESDAY AHEAD OF THE NEXT FRONT.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR
     AMZ350-374.

&&

$$