AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
158 PM EDT FRI JUL 8 2011

.SYNOPSIS...
DEEPER MOISTURE WILL GRADUALLY INCREASE OVER THE REGION THROUGH
TONIGHT AS WEAK LOW PRES ALONG THE GULF COAST PERSISTS. A WEAK COLD
FRONT WILL MOVE INTO THE AREA OVER THE WEEKEND...THEN MOVE THROUGH
AND DISSIPATE BY MON. ANOTHER FRONT WILL APPROACH FROM THE N BY
THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
DEEPER CONVECTION IS STARTING TO DEVELOP INLAND...ACROSS AREAS
WHERE MID CLOUD HAS NOT BEEN AS PREVALENT. AT THE COAST ACTIVITY
HAS SHIFTED NORTH WITH SHORTWAVE LIFTING NORTHEAST. SUBSIDENCE
BEHIND THE WAVE WILL HELP LIMIT ACTIVITY NEAR THE COAST INTO THE
EVENING HOURS. MOST OF THE ACTION THIS AFTERNOON AND EVENING WILL
BE INLAND WHERE DIURNAL HEATING HAS GENERATED SOME INSTABILITY.
FORECAST SOUNDINGS SHOW A LESS TROPICAL AIR MASS THAN WHAT IS
BEING SEEN AT THE COAST...THOUGH PRECIPITABLE WATER VALUES REMAIN
ABOVE 2 INCHES. STEEP LOW LEVEL LAPSE RATES SUGGEST ANY SEVERE
THREAT...THOUGH UNLIKELY...WOULD BE IN THE FORM OF DAMAGING WINDS
FROM WET MICROBURSTS.

TROPICAL PLUME IN PLACE OVERNIGHT WITH ANOTHER SHORT WAVE MOVING
ACROSS THE AREA. FORECAST SOUNDINGS DO SHOW SOME MID LEVEL
INSTABILITY WHICH THE SHORTWAVE MAY BE ABLE TO TAP INTO. NOT GOING
WITH LIKELY BUT DO CARRY HIGH CHANCE AT TIMES. TEMPERATURES
OVERNIGHT WILL BE SLIGHTLY ABOVE CLIMO.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
I HAVE DISCOUNTED THE 00Z NAM THIS MORNING AS SURFACE LOW SEEMS WAY
OVERDONE. I PREFER THE GLOBAL MODEL SOLUTIONS OF A SLOW MOVING FRONT
INTO THE AREA LATER IN THE WEEKEND...THEN GRADUALLY DISSIPATING
EARLY NEXT WEEK.

SATURDAY...THE ATMOSPHERE SHOULD BE STOKED WITH DEEP MOISTURE.
PWATS WILL BE 2 TO 3 SDS ABOVE NORMAL WITH ABSOLUTE VALUES IN EXCESS
OF 2 INCHES. THERE WILL BE MORE CLOUDS AROUND ON SATURDAY AS
SOUTHERN END OF MID LATITUDE TROF MEETS UP WITH REMNANTS OF THE
UPPER LOW OVER THE GULF OF MEXICO TO GIVE A SLIGHTLY ENHANCED
SOUTHWESTERLY JET OVERHEAD...TRANSPORTING A FAIR AMOUNT OF CIRRUS
INTO THE AREA. THIS WILL KEEP TEMPS A DEGREE OR TWO BELOW
AVERAGE...BUT HIGH DEW POINTS WILL KEEP THE APPARENT TEMPERATURE
ELEVATED. I WENT WITH JUST SLIGHTLY ABOVE NORMAL POPS...WITH
ACTIVITY EXTENDING INTO THE EVENING HOURS AWAY FROM THE COAST AS
PRE-FRONTAL TROF DROPS INTO THE AREA FROM THE NORTHWEST.

SUNDAY WE WILL SEE SOME SUBTLE DIFFERENCES AS WEAKENING FRONT MOVES
INTO THE NORTHERN FA. THERE WILL STILL BE PLENTY OF DEEP
MOISTURE...BUT UPPER LEVEL WINDS WILL SLACKEN BACK OFF AS HEIGHTS
BEGIN TO REBUILD...MEANING LESS CLOUD COVER. TEMPS WILL BE BACK TO
A TOUCH ABOVE NORMAL BY SUNDAY AFTERNOON...BUT DYING FRONT IN THE
AREA WILL SUPPORT ANOTHER ROUND OF AFTERNOON AND EVENING CONVECTION.
BEST CHANCES FOR THUNDERSTORMS WILL BE ALONG THE SEA BREEZE AS WELL
AS THE WEAKENING BOUNDARY.

ON MONDAY...THE FRONT WILL ESSENTIALLY HAVE DISSIPATED...ALTHOUGH A
VERY WEAK SURFACE TROF AND MID LEVEL SHEAR ZONE IS EXPECTED TO HANG
AROUND. PWS WILL DROP BACK BELOW 2 INCHES WITH A LITTLE MID LEVEL
DRYING FROM THE RIDGE BUILDING NORTH OF THE AREA...BUT CONVECTIVE
TEMPS WILL BE EASILY REACHED IN THE AFTERNOON DUE TO PLENTIFUL
SUNSHINE...SO AT LEAST A SLIGHT CHANCE OF THUNDERSTORMS IS EXPECTED.

ALSO...WITH HIGHER TEMPS IN THE AFTERNOON AND DEW POINTS REMAINING
REASONABLY HIGH...HEAT INDICES MAY START TO APPROACH ADVISORY
LEVELS. THIS WILL HAVE TO BE WATCHED.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
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 /18Z FRIDAY THROUGH WEDNESDAY/...
KCHS...CONVECTION CONTINUING ATTM AS TROPICAL MOISTURE STREAMS OVER
A COASTAL TROUGH. ALTHOUGH SHOWERS ARE BECOMING MORE SCATTERED IN
NATURE...STILL A GOOD CHANCE THAT CHS WILL SEE TEMPO MVFR CIGS FOR
THE FIRST FEW HOURS. AFTER THAT HAVE CARRIED JUST CB DUE TO
UNCERTAINTY IN TIMING AND LOCATION OF SHOWERS. GUIDANCE HINTING AT
SOME LOW STRATUS TONIGHT AND WITH COLUMN BECOMING LESS SATURATED WE
MAY CLEAR ENOUGH FOR THIS TO COME TO FRUITION. AT THE SAME
TIME...SIGNIFICANT ELEVATED INSTABILITY COMBINED WITH A PASSING
SHORTWAVE MAY RE-INITIATE CONVECTION BEFORE DAYBREAK WHICH WOULD
LIMIT STRATUS POTENTIAL. NO FOG THREAT DUE TO ENHANCED WINDS
OVERNIGHT. MORE CONVECTION IS EXPECTED ON SATURDAY.

KSAV...LIMITED CONVECTION ACROSS THE AREA WILL LIKELY FILL IN AS
SIGNALED BY BOTH HIGH RES GUIDANCE AND LATEST RUC FORECAST
SOUNDINGS. NOT ENOUGH CONFIDENCE TO MENTION ANYTHING BUT CB IN
TAF...BUT KSAV MAY SEE SOME CONVECTION THAT WILL REQUIRE AMD/S LATER
THIS AFTN. LOW LEVEL STRATUS IS A CONCERN HERE AS WELL
OVERNIGHT...BUT WILL BE IMPACTED CONSIDERABLY BY HOW MUCH CLOUD
COVER/CONVECTION CAN DEVELOP OVERNIGHT. ANOTHER DAY OF WIDESPREAD
SHOWERS/TSTMS EXPECTED SATURDAY.

EXTENDED AVIATION...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...
PINCHED GRADIENT BETWEEN BERMUDA HIGH AND WEAK LOW PRESSURE
DROPPING INTO THE SOUTHEAST WILL SUPPORT WINDS OF 15 TO 20 KT. IN
ADDITION STRONG LOW LEVEL JET...BETWEEN 20 AND 25 KT...WILL
RESULT IN GUSTY WINDS. CONDITIONS ACROSS NEAR SHORE ZONES WILL
REMAIN BELOW SCA THRESHOLDS...BUT OFFSHORE GEORGIA ZONES ARE
LIKELY TO SEE SLIGHTLY HIGH WINDS AND SEAS. WITHIN 20 NM MILES
SEAS WILL RUN 3 TO 5 FT...WHILE FARTHER OFFSHORE 4 TO 6 FT...WITH
OCCASIONAL 7 FT...IS LIKELY.

RIP CURRENTS...SE SWELLS WILL INCREASE TODAY AND THIS WILL
CONTRIBUTE TO AN ENHANCED RISK FOR RIP CURRENTS FOR ALL OF OUR
BEACHES.

WINDS WILL STAY UP ON SATURDAY IN THE 15 TO 20 KNOT RANGE...MAYBE A
BIT STRONGER IN THE EARLY MORNING HOURS IN THE CHARLESTON COUNTY
WATERS...BUT WILL START TO DIMINISH AS THE FRONT WEAKENS SATURDAY
NIGHT AND SUNDAY. GRADIENT WILL BE PRETTY SLACK ON MONDAY AND
TUESDAY 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 FROM 6 PM THIS EVENING TO 6 AM EDT
     SATURDAY FOR AMZ374.

&&

$$