Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 201909 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 309 PM EDT SAT SEP 20 2014 .SYNOPSIS... DEVELOPING LOW PRESSURE OFF FLORIDA WILL LIFT NORTH THROUGH THE WEEKEND...PASSING JUST OFF THE CAROLINA COASTS. THIS LOW PRESSURE WILL REMAIN JUST FAR ENOUGH OFFSHORE SUCH THAT IMPACTS WILL BE LIMITED...BUT SHOWERS AND SOME INCREASED WIND IS LIKELY...ESPECIALLY ALONG THE COAST. A COLD FRONT WILL CROSS THE AREA MONDAY...WITH COOL HIGH PRESSURE FOLLOWING BEHIND IT THROUGH THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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AS OF 3 PM SATURDAY...THE SFC LOW PROGGED TO MOVE NE ALONG THE OFFSHORE COASTAL TROF...PARALLELING THE CAROLINA COASTLINES. AM NOT EXPECTING THE SFC COASTAL TROF TO PUSH ONSHORE DUE TO PROGRESSIVE FLOW ALOFT EVENTUALLY PUSHING THE UPPER CLOSED LOW THAT OPENS UP...TO THE ENE. HAVE CONTINUED WITH A RATHER SHARP GRADIENT OF BOTH SKY AND PCPN TRENDS ACROSS THE FA THRU TONIGHT. THIS ALSO TRANSLATES TO A GRADIENT OF MAX AND MIN TEMPS...WITH AFTERNOON HIEST MAXES OCCURRING ALONG AND WEST OF THE I-95 CORRIDOR...WITH TONIGHTS MINS LOWEST ALONG AND WEST OF I-95. AS FOR PCPN...STRATIFORM LIGHT RAINS WILL DOMINATE THE FA WITH ISOLATED CHANCE THAT ANY TSTORMS THAT DEVELOP ALONG THE COASTAL TROF PUSH ONSHORE. SEEMS LIKE MODELS ARE OVERDONE WITH THE MOISTURE CONTENT ESPECIALLY ALONG THE IMMEDIATE COAST AT THE MOMENT...WITH NAM AND GFS HAVING PROGGED PWS TO BE OVER 2 INCHES BY 200 PM EARLIER THIS AFTERNOON. THIS HOWEVER IS NOT THE CASE...ESPECIALLY WITH PCPN CONTINUING TO DRY UP/DISSIPATE AS IT MOVES ACROSS THE ILM COASTAL WATERS B4 TRYING TO PUSH ONSHORE. MODEL SOUNDINGS DO SHOW A RATHER DEEP LAYER OF ONSHORE WINDS SFC THRU 20+ KFT. THINK THIS EVENTUALLY TO OCCUR ALONG THE IMMEDIATE COAST LATE THIS AFTERNOON AND TONIGHT AND SHOULD MOISTEN THESE LOW/MID LEVELS. WITH ALL THIS SAID...SKIES...POPS AND QPF FIELDS TO MIMIC THE SHARP GRADIENT OF MOISTURE ACROSS THE ILM CWA. STAYED WITH A GOOD CHANCE TO LIKELY CATEGORIES FOR PCPN...AND MAINLY ACROSS THE COASTAL COUNTIES...ESPECIALLY FROM CAPE FEAR NORTHWARD. THE LOW TO BE POSITIONED E-ESE OFFSHORE FROM CAPE FEAR BY DAYBREAK SUN. LOOK FOR IMPROVING CONDITIONS ACROSS THE ILM CWA FROM SW-NE...MAINLY ACROSS THE ILM SC COUNTIES LATE TONIGHT.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
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AS OF 3 PM SATURDAY...THE MID LEVEL COMPONENT OF THE SYSTEM CURRENTLY MOVING UP THE COAST WILL BE SHEARING OUT AND MOVING OUT QUICKLY AS WILL THE SURFACE LOW AT THE BEGINNING OF THE PERIOD. I HAVE MAINTAINED RESIDUAL MINIMAL POPS FOR THE COASTAL AREAS FOR A FEW HOURS SUNDAY TO ADDRESS. LATE SUNDAY MORNING AND AFTERNOON SHOULD SEE A RAPID CLEARING WITH HIGHS IN THE MIDDLE 80S WITH HIGHER VALUES INLAND WHERE THERE WILL BE A LONGER PERIOD OF INSOLATION. THE FORECAST THEN SHIFTS TO THE SYSTEM CURRENTLY SEEN IN WATER VAPOR IMAGERY MOVING ACROSS NORTH DAKOTA. THIS SYSTEM WILL MOVE ACROSS LATE MONDAY WITH AN ATTENDANT COLD FRONT. GUIDANCE REMAINS UNIMPRESSED WITH CONVECTION REGARDING THIS SYSTEM AND HAVE CONTINUED TO ADVERTISE SLIGHT CHANCE POPS. THE COOLER AIR MASS IN THE WAKE OF THE FRONT WILL BE THE BIGGER STORY...AND GUIDANCE IS ADVERTISING 55 IN THE MAV AND MET IN LBT FOR TUESDAY MORNING. THE MIXED BOUNDARY LAYER WILL LIKELY PRECLUDE THESE MINIMAL VALUES BUT WE COULD SEE A LOT OF UPPER 50S INLAND AT THIS TIME.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/...
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AS OF 3 PM SATURDAY...RIGHT ON CUE THE AREA SEEMS TO BE IN FOR SOME FALL-LIKE WEATHER. HIGH PRESSURE CENTERED OVER THE OHIO VALLEY WILL COVER MUCH OF THE EASTERN HALF OF THE NATION. THIS IS A BIT FURTHER SOUTH THAN WHAT WAS PROGGED YESTERDAY, BETTER SUPPRESSING FRONTAL MOISTURE OFF TO OUR SOUTH FOR WHAT SHOULD AMOUNT TO A FAIR AMOUNT OF SUNSHINE. DESPITE THE SUNSHINE TEMPERATURES WILL AVERAGE A FEW DEGREES BELOW CLIMATOLOGY IN A WEAKENING COOL ADVECTION REGIME. SIMILARLY A COOL TUESDAY NIGHT IS ON TAP WITH MOST PLACES GETTING DOWN INTO THE 50S. THROUGH THE MID WEEK PERIOD HIGH PRESSURE WEDGE HOLDS ITS GROUND AT THE SURFACE. HOWEVER AS THE ANTICYCLONE JUST ABOVE THE SURFACE WEAKENS THERE WILL BE AN INCREASINGLY ONSHORE FLOW OF MOISTURE. FRICTIONAL CONVERGENCE ASIDE, THERE WON`T BE MUCH FORCING FOR PRECIPITATION AND RAINFALL AMOUNTS WILL BE QUITE LIGHT, AND MAYBE HARD-PRESSED TO MAKE MUCH INLAND PROGRESS. THIS MAY CHANGE LATE THURSDAY THROUGH SATURDAY AS THE LOW LEVEL FLOW BECOMES A BIT MORE CONVERGENT AND SOME WEAK ISENTROPIC UPGLIDE DEVELOPS ATOP THE PERSISTENT WEDGE.
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&& .AVIATION /19Z SATURDAY THROUGH THURSDAY/... AS OF 18Z...THE NAM IS STARTING TO COME MORE IN LINE WITH THE GFS...NAMELY NOT PUSHING AS MUCH MOISTURE WELL INLAND. LOOK FOR ISOLATED ACTIVITY EARLY THIS AFTERNOON...MAINLY ALONG THE IMMEDIATE COAST. ONLY MINOR AVIATION IMPACTS WITH PREDOMINATELY VFR CONDITIONS EXPECTED THIS AFTERNOON...EXCEPT MVFR ALONG THE IMMEDIATE COAST FROM LOW CLOUD DECK AND REDUCED VSBY FROM PCPN. GUSTY NORTHEAST FLOW WILL CONTINUE INTO TONIGHT. A BIT MORE UNCERTAINTY WITH RESPECT TO THE EXPANSION OF PRECIPITATION AND CEILING HEIGHTS. WILL GO WITH A BLENDED MODEL INTERPRETATION WITH LOW MVFR/IFR CEILINGS OVERNIGHT DUE TO STRATIFORM LIGHT TO MODERATE RAIN. FLO AND LBT WILL LIKELY STAY OUT OF MOST IF NOT ALL OF THE PRECIP. SUNDAY...SLOW IMPROVING CONDITIONS FOR THE IMMEDIATE COAST... WITH INLAND TERMINALS MUCH QUICKER. THE LOW TO PULL OFF TO THE NORTHEAST...BRINGING A DRYING NORTHWEST WIND ON ITS BEHIND. ALL LOCATIONS WILL IMPROVE TO VFR BY LATE MORNING...ILM LIKELY BEING THE LAST TO IMPROVE. EXTENDED OUTLOOK...GUSTY NORTHEAST WINDS WILL BECOME NORTHWEST AND DECREASE SUN AS LOW PRESSURE MOVES NE FURTHER AWAY FROM THE TERMINALS. OTHERWISE VFR SUN THROUGH WED WITH A CHANCE OF A SHOWER WITH A COLD FRONT ON MONDAY. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 3 PM SATURDAY...THE NAM AND GFS KEEP THE SFC LOW OFFSHORE AS IT TRAVELS NE ALONG THE COASTAL TROF...AND MAKES ITS CLOSEST APPROACH DURING LATE IN THE PRE-DAWN SUNDAY HRS. THE CANADIAN BRINGS IT TOO CLOSE IF NOT WITHIN THE COASTAL WATERS AND SEEMS TO BE THE ODD MODEL OUT. NEVERTHELESS...LOOKING AT TIGHTENED SFC PG WITH SPEEDS IN THE 15-25 KT RANGE WITH THE WATERS REMAINING ON THE COOL SIDE OF THE LOW...IE. WINDS NE BACKING TO N LATE. THE HIEST WINDS REMAIN ON THE WARM SIDE...IE. THE EASTERN SEMI-CIRCLE OF THE LOW. THERE WINDS TO REACH GALE FORCE. THE ILM COASTAL WATERS WILL REMAIN IN A MODEST SMALL CRAFT ADVISORY. MAY NEED TO TEMPORARILY EXPAND THE SCA INTO DAYLIGHT SUNDAY...WILL MONITOR FOR NOW AND SEE WHAT 18Z MODEL OFF RUNS DISPLAY. SIGNIFICANT SEAS WILL PEAK LATE THIS AFTERNOON THRU MUCH OF TONIGHT AT 4 TO 7 FT HIEST OFF CAPE FEAR...THEN BACK DOWN AS WINDS BACK TO MORE OF AN OFFSHORE TRAJECTORY BY DAYBREAK SUN AS THE LOW PASSES BY. WIND DRIVEN WAVES WITH DOMINANT PERIODS IN THE 4 TO 5 SECOND PERIOD RANGE TO DOMINATE THE SIG. SEAS. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 3 PM SATURDAY...WINDS AND SEAS WILL BE ON THE DECREASE THROUGHOUT THE DAY SUNDAY AS LOW PRESSURE MOVES QUICKLY AWAY TO THE NORTHEAST. A NORTHWESTERLY FLOW WILL BACK TO THE SOUTHWEST BY DAYS END AS A FRONT APPROACHES FROM THE NORTHWEST. WIND SPEEDS WILL BE IN A 10-15 KNOT RANGE. MONDAY WILL FEATURE THE WIND SHIFT AS THE FRONT PUSHES ACROSS THE WATERS LATE IN THE DAY. EXPECT A NORTHERLY COMPONENT TO BE IN PLACE BY 0000 UTC TUESDAY THEN VEERING TO NORTHEAST BY TUESDAY AM. SPEEDS WILL INCREASE FROM NEAR TEN KNOTS LATE MONDAY TO 15-20 KNOTS TUESDAY. THERE WILL BE SOME RESIDUAL 3-5 FOOT SEAS EARLY SUNDAY DROPPING TO 2-3 FEET UNTIL EARLY TUESDAY WHEN THEY WILL INCREASE SLIGHTLY. LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 3 PM SATURDAY...HIGH PRESSURE WEDGE TO REMAIN IN PLACE FIRMLY THROUGH THE PERIOD IN A PATTERN MORE TYPICAL OF LATER INTO THE COOL SEASON. THE GRADIENT ITSELF WILL BE STRONG ENOUGH TO YIELD SMALL CRAFT ADVISORY WINDS, BUT SEAS WILL ALSO BE ADVISORY-WORTHY AREA WIDE (AMZ254 MAY HAVE A BIT OF TROUBLE DUE TO WAVE SHADOW OFF CAPE FEAR). NOT ONLY WILL THE ADVISORY BE IN EFFECT FOR THE DURATION OF THE PERIOD BUT ALSO LIKELY BEYOND AS THE WEDGE SHOWS LITTLE SIGN OF WEAKENING OR MOVING HEADING INTO THE WEEKEND.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR AMZ250-252-254- 256. && $$ SYNOPSIS...SHK NEAR TERM...DCH SHORT TERM...SHK LONG TERM...MBB AVIATION...DCH

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