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000
FXUS62 KCHS 120854
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
354 AM EST THU DEC 12 2013

.SYNOPSIS...
HIGH PRESSURE WILL BUILD TODAY THEN PERSIST THROUGH FRIDAY. A FRONTAL
SYSTEM WILL THEN IMPACT THE REGION DURING THE WEEKEND. ANOTHER AREA
OF HIGH PRESSURE WILL BUILD IN BEHIND THE DEPARTING SYSTEM EARLY
NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
PRE-DAWN...STRATOCUMULUS HAVE HUNG ON OVERNIGHT RIGHT ALONG THE
COAST OF SE GEORGIA AND SOUTH CAROLINA BUT MODELS SHOWING THAT
THEY SHOULD NOT BE AROUND BY DAWN AS MUCH DRIER 1000-500 MB AIR
MASS ARCS IN FROM THE W AS THE WEAK LOW OFFSHORE PULLS AWAY. HIGH
CLOUDS ASSOCIATED WITH THE RIGHT FRONT ENTRANCE ZONE OF A POWERFUL
175 KT UPPER JET OVER THE DELMARVA SHOULD BE MAINLY THIN EARLY
THIS MORNING. TEMPS FALLING TOWARD FREEZING WELL INLAND AND INTO
THE 30S MOST OTHER AREAS.

COLD AIR ADVECTION PATTERN TODAY AS THE UPPER WAVE RACES OFFSHORE
AFTER MID MORNING. H925 TEMPS FORECAST TO FALL FROM 7-8C AROUND
DAYBREAK TO 1-3C NORTH AND 3-6C SOUTH. DESPITE FULL SUNSHINE...WE
LOWERED A FEW HIGH TEMPS OVER NORTHERN SOUTH CAROLINA ZONES BY A
COUPLE DEGREES TO ACCOUNT FOR THE LATEST THICKNESS PROGS. A GOOD
AVERAGE FOR HIGHS TODAY MID 50S NORTH TO AROUND 60 SOUTH OF I-16.
WITH 1000 MB GEOSTROPHIC FLOW RAMPING UP TO 25-30 KT BY MID
MORNING...SOME AREAS WILL SEE NORTHERLY WIND GUSTS IN THE 15-20
MPH RANGE FOR WHILE MID MORNING INTO MID AFTERNOON AS THE DRIER
AIR PUNCHES IN.

NO CHANGES TO THE FORECAST TONIGHT...CLEAR SKIES...PERHAPS A FEW
THIN HIGH CLOUDS NEARING DAWN. FREEZING TEMPS TO AROUND THE U.S.
17 CORRIDOR SOUTH CAROLINA AND WEST OF THE I-95 CORRIDOR IN SE
GEORGIA.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
FRIDAY...AFTER STARTING WITH THE COLDEST TEMPERATURES OF THE MONTH
SO FAR...TEMPS WILL BEGIN TO REBOUND AS THE SURFACE HIGH MOVES INTO
THE ATLANTIC AND WINDS TURN AROUND TO THE EAST. TEMPS WILL COOLEST
ON FRIDAY ALONG THE IMMEDIATE COAST WHERE THE WIND WILL COME OFF THE
COOL SHELF WATERS...WHILE THE REST OF THE CWA WILL GET TO A COUPLE
OF DEGREES EITHER SIDE OF 60. CLOUDS WILL INCREASE SIGNIFICANTLY
DURING THE DAY AS THE CIRRUS SHIELD FROM THE DEVELOPING LOW PRESSURE
AREA IN THE SOUTHERN PLAINS STARTS ROCKETING EASTWARD ON THE BACK OF
A STRONG SOUTHERN STREAM JET MAX. WE WILL ALSO SEE A SLOW INCREASE
IN LOWER CLOUDS DUE TO THE LOW LEVEL ONSHORE FLOW.

BY FRIDAY NIGHT...A COASTAL TROF IS EXPECTED TO DEVELOP JUST
OFFSHORE. THE ENHANCED LOW LEVEL CONVERGENCE SHOULD CAUSE SOME
SHOWERS TO FORM OVER THE COASTAL WATERS...BUT A FEW SHOWERS MIGHT
SNEAK ON TO THE COAST TOWARD MORNING. OVERALL CHANCES WILL BE LOW
FOR MEASURABLE RAIN...HOWEVER.

ON SATURDAY...CHANCES OF RAIN WILL INCREASE AS A DISORGANIZED AREA
OF LOW PRESSURE MOVES INTO THE SOUTHEAST. THE GFS AND ECMWF ARE IN
BETTER AGREEMENT TONIGHT...KEEPING THE BULK OF THE HEAVIER RAIN TO
THE WEST OF THE AREA DURING THE DAY...BUT SCATTERED SHOWERS ARE
STILL POSSIBLE AS BROAD...BUT WEAK...SYNOPTIC SCALE LIFT SPREADS
OVERHEAD. THERE MIGHT ALSO BE AN ISOLATED THUNDERSTORM OVER THE
COASTAL WATERS THAT MAY BRUSH THE COAST AS THE MODELS BRING SOME
MODEST INSTABILITY INTO THE REGION FROM THE SOUTH.

SOUTHERLY WINDS WILL BECOME ESTABLISHED DURING THE DAY AS THE
COASTAL TROF PUSHES NORTH OF THE CWA BY EARLY AFTERNOON. 925 MB
TEMPS ARE FORECAST TO SURGE TO 13-16C...SO AFTERNOON TEMPS WILL RISE
ABOVE NORMAL...POTENTIALLY REACHING 70 AGAIN SOUTH OF INTERSTATE 16.

DURING SATURDAY NIGHT...THE FRONT ASSOCIATED WITH THE COMPLEX LOW
PRESSURE SYSTEM MOVES THROUGH THE AREA. MOST IF NOT ALL AREAS SHOULD
SEE RAIN...WITH SOME LOCALLY HEAVY SPOTS IN EXCESS OF ONE INCH
POSSIBLE. INSTABILITY GUIDANCE IN THE MODELS AGAIN INDICATE THE MAIN
AREA FOR THE THREAT OF THUNDER WOULD BE OVER THE COASTAL
WATERS...BUT THERE MAY BE JUST ENOUGH OVER LAND TO ALLOW FOR AN
ISOLATED CRACK OF THUNDER.

THE FRONT WILL BE OFFSHORE BY SUNDAY MORNING...BUT THE AREA WILL BE
SLOW TO CLEAR AS WE REMAIN IN THE FAVORABLE RIGHT ENTRANCE REGION OF
THE UPPER JET FOR SYNOPTIC SCALE LIFT. THERE WILL STILL BE A GOOD
CHANCE OF SHOWERS IN EARLY IN THE DAY...WITH CHANCES GRADUALLY
TAPERING OFF FROM WEST TO EAST DURING THE AFTERNOON. THE COLD
ADVECTION BEHIND THE FRONT IS NOT EXPECTED TO BE PARTICULARLY
STRONG...SO AFTER A MILD SATURDAY...TEMPS SHOULD BACK UP A LITTLE TO
AROUND NORMAL ON SUNDAY...IN THE LOWER TO MID 60S.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
ON SUNDAY NIGHT...THE FRONT SHOULD PUSH FURTHER INTO THE
ATLANTIC...AND CLOUD COVER WILL GRADUALLY DIMINISH. TEMPS WILL FALL
BACK TO THE MID 30S INLAND AND LOWER 40S AT THE COAST. ANY REMAINING
CHANCE OF RAIN SHOULD BE CONFINED TO THE OFFSHORE COASTAL WATERS.

ON MONDAY AND TUESDAY...THE GFS IS MORE AGGRESSIVE THAN THE ECMWF IN
DEVELOPING A WEAK LOW PRESSURE TROF TO THE EAST OF THE AREA. RIGHT
NOW...MY INCLINATION IS TO KEEP THE WEATHER DRY AND COOL MONDAY AND
TUESDAY...MORE IN LINE WITH THE ECMWF...AS THE UPPER FLOW IN THE GFS
LOOKS TOO FLAT TO SUPPORT AS MUCH OF A SURFACE WAVE AS IT IS DEPICTING.

HIGH PRESSURE SHOULD CONTINUE TO RULE THROUGH MID WEEK. TEMPERATURES
WILL BE WITHIN A FEW DEGREES OF CLIMO...AND CHANCES FOR RAIN WILL BE
LOW.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS WILL PREVAIL AT BOTH KCHS AND KSAV THROUGH 06Z FRIDAY.

EXTENDED AVIATION OUTLOOK...MAINLY VFR CONDITIONS FRIDAY AND FRIDAY
NIGHT...ALTHOUGH I CANT TOTALLY RULE OUT SOME BRIEF MVFR DUE TO SOME
MARINE CLOUDS.

SATURDAY THERE COULD BE SOME PERIODS OF MVFR CIGS...ESPECIALLY IN
SCATTERED SHOWERS.

SATURDAY NIGHT INTO SUNDAY MORNING LOOKS LIKE THERE WILL BE A HIGH
CHANCE OF MVFR/IFR CIGS AT TIMES DUE TO RAIN AND LOW CLOUDS WITH THE
FRONTAL PASSAGE. CONDITIONS SHOULD BE IMPROVING AGAIN LATE SUNDAY
INTO THE FIRST HALF OF NEXT WEEK.

&&

.MARINE...
WE HAVE ISSUED A SMALL CRAFT ADVISORY FOR NEAR SHORE WATERS TODAY
MAINLY FOR CONDITIONS IN THE OUTER 10 NM OF OUR MARINE LEGS. AN
INCREASING NORTHERLY FLOW IS EXPECTED TO FREQUENTLY GUST TO NEAR
25 KT FROM THE CHARLESTON PILOT BUOY SOUTHWARD TO GRAYS REEF NMS.
WITHIN IN 10 NM OF THE COAST AND IN THE HARBOR/SOUNDS...CONDITIONS
LIKELY TO REMAIN JUST BELOW CRITERIA WITH OCCASIONAL GUSTS
EXCEEDING 20 KT. ADVISORY CONDITIONS OVER OUTER GEORGIA WATERS
WILL CONTINUE TODAY WITH SEAS 5 TO 7 FT WITH THE NORTH FLOW.

AS HIGH PRES SETTLES OVER GEORGIA AND THE CAROLINAS TONIGHT...
MODEST PRES GRADIENT CONTINUES OVER THE WATERS TONIGHT ALONG WITH
SOME SHARP THERMAL GRADIENTS. THIS SHOULD KEEP NE FLOW IN THE 15
OR 15-20 KT RANGE WITH SEAS 3-4 FT NEAR SHORE AND 4-6 FT OFFSHORE.
SEAS SHOULD SUBSIDE TO BELOW 6 FT OVER OUTER GEORGIA WATERS BY
DAYBREAK ON FRIDAY...BUT PROGRESS OVERNIGHT WILL BE SLOW WITH THE
MORE FAVORABLE FETCH.

NORTHEAST WINDS OF 10 TO 15 KNOTS WILL VEER TO THE EAST DURING
FRIDAY AS HIGH PRESSURE GRADUALLY MOVES INTO THE WESTERN ATLANTIC.
WINDS WILL TURN MORE SOUTHEAST ON FRIDAY NIGHT AS A COASTAL TROF
DEVELOPS...THEN SOUTHERLY AND INCREASE ON SATURDAY AS THE TROF MOVES
QUICKLY NORTHWARD AHEAD OF AN ADVANCING COLD FRONT.

BY LATE SATURDAY AND DURING SATURDAY NIGHT...SOUTH AND SOUTHWESTERLY
WINDS LOOK TO BE JUST BELOW SCA CRITERIA IN THE NEIGHBORHOOD OF 20
KNOTS IN THE OFFSHORE WATERS...BUT SEAS WILL GET UP TO 6 FEET IN AT
LEAST AMZ374...AND POSSIBLY ALSO AMZ350...SO SCAS MAY HAVE TO BE
LIFTED WITH A LATER FORECAST CYCLE.

ON SUNDAY...BEHIND THE FRONT...THE WINDS WILL TURN
NORTHWESTERLY...BUT SINCE THE PRESSURE GRADIENT IS NOT EXPECTED TO
BE PARTICULARLY TIGHT AND THE COLD ADVECTION ONLY MODEST...WINDS AND
SEAS SHOULD DROP BELOW SCA CRITERIA ONCE AGAIN.

MONDAY AND TUESDAY WINDS SHOULD BE NORTH TO NORTHEASTERLY AS WEAK
HIGH PRESSURE BUILDS IN TO THE SOUTHEASTERN STATES. THE GFS IS
ADVERTISING STRONGER WINDS MONDAY AFTERNOON AND EVENING IN THE
OFFSHORE GEORGIA WATERS THAN I AM CURRENTLY ADVERTISING BECAUSE I
THINK IT OVERLY DEVELOPS A WEAK SURFACE WAVE IN THE WESTERN
ATLANTIC.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR AMZ350-
     352-354.
     SMALL CRAFT ADVISORY UNTIL 5 AM EST FRIDAY FOR AMZ374.

&&

$$

SYNOPSIS...
NEAR TERM...
SHORT TERM...FWA
LONG TERM...FWA
AVIATION...
MARINE...FWA