Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 271851
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
251 PM EDT SAT SEP 27 2014

.SYNOPSIS...
HIGH PRESSURE BUILDING FROM THE NORTH WILL BRING A DRYING TREND
THROUGH THE WEEKEND AS A COASTAL TROUGH WEAKENS OFFSHORE. A WET
FORECAST IS SHAPING UP FOR EARLY NEXT WEEK AS LOW PRESSURE MOVES
ACROSS THE SOUTHEAST. HIGH PRESSURE WILL RE-BUILD FROM THE NORTH
THROUGH MID WEEK...WITH A COLD FRONT MOVING IN AT THE END OF THE
WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 3 PM SATURDAY...HIGH PRESSURE CONTINUES TO WEDGE DOWN THE
COAST THIS AFTN...INTERACTING WITH A COASTAL TROUGH THAT SEEMS TO
BE EVER-PRESENT JUST OFFSHORE. WEAK LOW PRESSURE OFF THE
CHARLESTON, SC COAST WILL CONTINUE TO DROP WEAKLY TO THE SOUTH
TONIGHT AS HIGH PRESSURE BECOMES MORE DOMINANT.

AREAS OF SHOWERS ALONG THE COASTAL TROUGH HAVE BEEN TRYING TO PUSH
ONSHORE TODAY...DRIVEN BY THE E/NE FLOW BETWEEN THE SURFACE WEDGE
AND COASTAL TROUGH. THE MID-LEVELS OF THE COLUMN...THOSE ABOVE
750MB...ARE VERY DRY...AND THE CONTINENTAL AIR MASS IS DRIER THAN
THAT OFFSHORE. THIS IS PRECLUDING MOST OF THE SHOWER ACTIVITY FROM
MAKING IT ONSHORE...BUT CANNOT RULE OUT SOME ISOLATED LIGHT
SHOWERS THROUGH TONIGHT...FOCUSED ALONG THE COAST...WITH BEST
CHANCE ALONG THE GRAND STRAND AND DOWN TOWARDS THE SOUTH SANTEE
RIVER. THE NAM FORECAST PROFILES ARE HANDLING THE CLOUD COVER BEST
TODAY...SO USING THIS AS A GUIDE EXPECT LOW LEVEL CLOUDINESS TO
PERSIST INTO TONIGHT. AS THE HIGH BECOMES MORE STRONGLY ENTRENCHED
LOCALLY CLOUD COVER WILL WANE...BUT EXPECT ONCE AGAIN QUITE A BIT
OF STRATUS AROUND TONIGHT. THIS WILL LIMIT OVERALL COOLING AND
HAVE AGAIN SIDED WITH THE LAV NUMBERS...AND AM FORECASTING LOWS
AROUND 60 IN THE FAR WESTERN ZONES...TO NEAR 70 ALONG THE GRAND
STRAND.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 3 PM SATURDAY...UPPER RIDGE OVER EASTERN CONUS BREAKS DOWN
THROUGH THE SHORT TERM AS A SERIES OF STRONG SHORT WAVES DROP
ACROSS NEW ENGLAND AND THE GREAT LAKES REGION. THE SURFACE PICTURE
IS A LITTLE MUDDLED DUE TO A WEAK PRESSURE PATTERN AND A
DIVERGENCE OF MODEL SOLUTIONS. HOWEVER...A CONSENSUS OF GUIDANCE
HAS A FRONTAL SYSTEM DRAPED ACROSS THE DEEP SOUTH ON SUNDAY
LIFTING NORTH ON MONDAY INTO COASTAL GEORGIA AND SOUTH CAROLINA.
INCREASING MOISTURE ADVECTION WILL MAKE FOR A CLOUDY MONDAY WITH
POPS STEADILY INCREASING FROM SLIGHT CHANCE IN THE MORNING TO
LIKELY OVERNIGHT. SUNDAY HOWEVER LOOKS TO BE A DECENT DAY WITH
MINIMAL CHANCES OF PRECIP AND A GOOD BIT OF SUN...ESPECIALLY EARLY
ON. DAYTIME HEATING WILL LIKELY POP A CU FIELD IN THE
AFTERNOON...AND THE CIRRUS SHIELD WILL STEADILY INCREASE IN
ADVANCE OF MONDAYS FRONTAL SYSTEM. TEMPERATURES WILL BE QUITE
SEASONAL THROUGH THE PERIOD.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 3 PM SATURDAY...FORECAST MODELS FOR THE MEDIUM RANGE ARE IN
DECENT AGREEMENT ON THE SYSTEM MOVING ACROSS THE SOUTHEAST DURING
THE FIRST COUPLE OF DAYS. BOTH THE GFS AND ECMWF OPERATIONAL
MODELS SHOW A RATHER LETHARGIC SHORTWAVE THAT WAVERS BETWEEN AN
OPEN WAVE AND CLOSED LOW. I HAVE MAINTAINED THE GOOD CHANCE OF
SHOWERS FOR THE FIRST PART OF TUESDAY TRENDING DOWN THEREAFTER.

THE AFOREMENTIONED OPERATIONAL MODELS DIVERGE WITH REGARDS TO THE
MID LEVEL PATTERN FOR THE REMAINDER OF THE PERIOD. THE GFS KEEPS A
WEAKNESS AROUND THE AREA...MUCH LIKE WE HAVE SEEN THIS WEEK WHILE
THE ECMWF HAS A MORE PROGRESSIVE SOLUTION. WPC FAVORS MORE
BLENDING WITH ECMWF SOLUTIONS SO I HAVE BACKED OFF THE SLIGHT
CHANCE POPS LINGERING INTO WEDNESDAY AND THURSDAY. BEYOND THIS...A
STRONG SHORTWAVE MOVING THROUGH THE OHIO VALLEY AND ATTENDANT COLD
FRONT MOVE ACROSS LATE FRIDAY AND SATURDAY. AT THIS POINT THE
FRONT LOOKS TO BE MOISTURE STARVED AND INTRODUCED LOWER CHANCE
POPS FOR THE NEW DAY OF THE FORECAST PERIOD...SATURDAY.

REGARDING TEMPERATURES...I GENERALLY ADDED A DEGREE OR TWO ACROSS
THE BOARD TO WPC GUIDANCE AS THE WESTERLY FLOW THAT IS FORECAST TO
DEVELOP SHOULD ALLOW A DOWNSLOPE COMPONENT TO WARRANT. HOWEVER
MOST VALUES ARE WITHIN A FEW DEGREES OF CLIMATOLOGY.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AS OF 18Z...HIGH PRESSURE CONTINUES TO WORK INTO THE AREA WHILE
COASTAL TROUGH AND LOW PRESSURE LINGER OFFSHORE. WHILE THE HIGH
PRESSURE WILL KEEP MOST OF THE PRECIP CONFINED TO THE MYRTLES AND
OFFSHORE...LOW-LEVEL MOISTURE WILL CREATE PERIODS OF MVFR CIGS
TODAY...MOST WIDESPREAD AT CRE AND MYR. CEILINGS WILL BREAK FOR AT
LEAST A TIME AFTER DARK WITH LOSS OF HEATING...BUT MAY REDEVELOP
LATE AS MOISTURE BECOMES TRAPPED BENEATH THE NOCTURNAL INVERSION. NO
IFR IS CURRENTLY ANTICIPATED...ALTHOUGH THE NAM IS AGGRESSIVE SO
WILL NEED TO MONITOR. WINDS WILL BE HIGH ENOUGH TO PREVENT FOG
HOWEVER. CEILINGS WILL BE SLOW TO BREAK ON SUNDAY AND MVFR MAY
PERSIST WELL INTO THE AFTN WITH CONTINUED NE WINDS.

EXTENDED OUTLOOK...CHANCE OF SHOWERS/MVFR MON AND TUE AS LOW
PRESSURE MOVES ACROSS THE SOUTHEAST. MVFR/IFR CIGS ON WED AND
POSSIBLY THURSDAY.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 3 PM SATURDAY...HIGH PRESSURE WEDGING DOWN THE COAST AND A
COASTAL TROUGH POSITIONED ABOUT 50 MILES OFFSHORE...CONTINUE TO
KEEP THE COASTAL WATERS PINCHED IN BETWEEN. THIS IS CREATING GUSTY
NE WINDS OF 15-25 KTS...AND SEAS OF 3 TO 6 FT THIS AFTN. A SLOW
DECREASE IN WIND SPEEDS IS EXPECTED TONIGHT AS THE HIGH PRESSURE
PUSHES FURTHER SOUTH...WEAKENING THE GRADIENT...BUT SPEEDS OF
10-20 KTS WILL REMAIN INTO SUNDAY MORNING. HOWEVER...THE SLIGHTLY
LOWER SPEEDS WILL ALLOW WAVE HEIGHTS TO DROP TO BELOW 6 FT...AND
THE SCA SHOULD BE ABLE TO EXPIRE AT 8PM FOR THE NORTHERN WATERS.
THEREAFTER...A SCEC MAY BE NEEDED FOR THE MUCH OF THE REST OF THE
NEAR TERM AS SEAS ARE FORECAST TO REMAIN 3-5 FT.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 3 PM SATURDAY...NORTHEAST WINDS OF 10 TO 15 KTS ON SUNDAY
WILL DECREASE TO AROUND 10 KTS OR LESS ON MONDAY AS OVERALL
PRESSURE GRADIENT SLACKENS. SEAS OF AROUND 3 FT ON SUNDAY WILL
DECREASE TO AROUND 2 FT ON MONDAY.

LONG TERM /TUESDAY THROUGH THURSDAY/...
AS OF 3 PM SATURDAY...A MODEST NORTHEASTERLY FLOW WILL GREET
MARINERS TUESDAY MORNING ALONG WITH WIDESPREAD RAINFALL. WIND
SPEEDS WILL BE LIGHT INITIALLY...LESS THAN TEN KNOTS. AS WE
PROGRESS INTO EARLY WEDNESDAY...THE FLOW WILL BACK TO MORE OF A
DUE NORTHERLY DIRECTION AND INCREASE TO 10-15 KNOTS AS THE LOW
PRESSURE SYSTEM PULLS AWAY SLOWLY. BY THE END OF THE PERIOD WINDS
ARE BACK TO A NORTHEAST DIRECTION AS HIGH PRESSURE BUILDS DOWN
FROM THE CANADIAN MARITIMES. SIGNIFICANT SEAS SHOULD BE ON THE LOW
SIDE CITING THE LACK OF STRONG WINDS AND CHANGES IN THE
FETCH...GENERALLY 1-3 TO 2-4 FEET.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR AMZ250-
     252.

&&

$$

SYNOPSIS...REK
NEAR TERM...JDW
SHORT TERM...REK
LONG TERM...SHK
AVIATION...DL
MARINE...REK/JDW/SHK




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