Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 030606 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 206 AM EDT MON AUG 3 2015 .SYNOPSIS... LOW PRESSURE WILL MOVE NORTHEASTWARD ACROSS THE FLORIDA PANHANDLE TONIGHT AND ALONG AN OLD STATIONARY FRONT ON MONDAY AND TUESDAY...BRINGING INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS TO THE COASTAL CAROLINAS. THE LOW WILL MOVE AWAY FROM THE AREA TUESDAY NIGHT...WITH TYPICAL SUMMER WEATHER EXPECTED WEDNESDAY THROUGH NEXT WEEKEND. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... AS OF 1030 PM SUNDAY...LINE OF SHOWERS HEADING TOWARDS THE COAST IS NOW FROM 15 TO 20 NM OFFSHORE AND SHOULD BE SKIRTING BALD HEAD ISLAND SHORTLY. STILL EXPECTING A GRADUAL RAMPING UP OF POPS THROUGH THE EARLY MORNING HOURS AS THE LOW PRESSURE SYSTEM CURRENTLY OVER NORTHERN FLORIDA MOVES NE ALONG A STALLED FRONTAL BOUNDARY. BOTH THE GFS AND NAM SHOW LOW LEVEL WIND FIELDS BACKING WITH HEIGHT THUS INCREASING CONVERGENCE BASICALLY ALONG THE COAST...THIS OCCURS AFTER 0600 UTC. THE GFS HAS BACKED OFF SLIGHTLY WITH THE 1200 RUN WHILE THE NAM REMAINS THE MOST AGGRESSIVE. I AM CONTINUING TO ADVERTISE GOOD CHANCE POPS ALONG THE IMMEDIATE COAST WITH MUCH HIGHER AMOUNTS OFFSHORE. FOLKS WEST OF I-95 WILL PROBABLY MISS OUT ENTIRELY. THE NAM IS ADVERTISING 0.25 TO 0.50 FOR THE SIX HOUR PERIOD WHILE THE GFS JUST UNDER A TENTH. MY EXPERIENCE SHOWS THAT ALTHOUGH MOST AREAS...ALONG THE COAST RECEIVE RAINFALL...THE QPF IS LIGHT AS THE HEAVIER ACTIVITY RESIDES JUST OFFSHORE. THIS IS PROBABLY WHAT WE WILL SEE THROUGH 1200 UTC. I LIKE THE SLIGHTLY WARMER GFS/MAV NUMBERS FOR LOWS WITH ALL OF THE CLOUD COVER MOVING IN. && .SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY NIGHT/... AS OF 300 PM SUNDAY...THE BIG PLAYER IN THE MONDAY-TUESDAY TIMEFRAME IS THE LOW CENTERED NEAR THE GULF COAST ABOUT 50 MILES SOUTHEAST OF TALLAHASSEE FLORIDA. WHILE MODEL SOLUTIONS ARE ALL OVER THE PLACE WITH REGARD TO TIMING...THE 12Z GFS APPEARS TO HAVE TO HAVE A SUPERIOR FORECAST WITH ITS SLOWER NORTHEASTWARD MOVEMENT ALONG THE OLD STATIONARY FRONT. THE 12Z NAM AND 12Z CANADIAN MODELS IN PARTICULAR ARE FAR TOO FAST AND HAVE BEEN ENTIRELY DISCOUNTED FOR THIS FORECAST. A SURGE OF DEEP TROPICAL MOISTURE AHEAD OF THE LOW WILL REACH THE CAROLINA BEACHES MONDAY MORNING. PRECIPITABLE WATER VALUES WILL EXCEED TWO INCHES ALONG THE COAST...WHILE SOUTHERLY/ONSHORE FLOW SHOULD INCREASE LOW-LEVEL CONVERGENCE ALONG THE STATIONARY FRONT. A SUBTLE 300 MB DISTURBANCE MOVING ACROSS NORTHERN NC AND OFF THE COAST MONDAY MORNING WILL HELP ENHANCE UPPER LEVEL DIVERGENCE ACROSS OUR AREA...AND IT WOULD NOT BE SURPRISING AT ALL TO SEE GOOD COVERAGE OF STORMS ONGOING AT DAYBREAK. HEAVY RAINFALL IS EXPECTED AND THERE IS SOME POTENTIAL OF FLOODING...ESPECIALLY WITHIN 50 MILES OF THE COAST BENEATH THE DEEP MOISTURE CHANNEL. ONSHORE WINDS WILL CONTINUE MONDAY NIGHT INTO TUESDAY AS THE LOW APPROACHES THE AREA. I HAVE HELD OFF INCREASING POPS BEYOND 50 PERCENT FOR EITHER PERIOD NOT KNOWING HOW SYMMETRIC CONVECTION WILL BE DISTRIBUTED AROUND THE LOW...AND TO ACCOUNT FOR MESOSCALE SUBSIDENCE AREAS AROUND LARGE CONVECTIVE STRUCTURES POTENTIALLY DEVELOPING OUT OVER THE GULF STREAM. TUESDAY NIGHT THE LOW SHOULD BE MOVING NORTHEAST OF THE AREA. DRIER AIR WRAPPING IN BEHIND THE CIRCULATION SHOULD HELP ERODE CLOUDS AND KILL PRECIPITATION CHANCES. EXTRATROPICAL STORM SURGE GUIDANCE SHOWS SURGE VALUES REMAINING UNDER HALF A FOOT AT THE BEACHES...AND WE ARE MOVING PAST THE FULL MOON WHICH SHOULD PREVENT COASTAL FLOODING ISSUES. FARTHER INLAND ALONG AND WEST OF THE INTERSTATE 95 CORRIDOR (WHERE RAIN IS BADLY NEEDED) THE BULK OF THIS EVENT WILL REMAIN TOO FAR EAST. POPS ARE ONLY 10-30 PERCENT AND DAYTIME TEMPERATURES SHOULD RUN 5-8 DEGREES WARMER THAN AT THE COAST. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 3 PM SUNDAY...RAIN CHANCES WILL REMAIN QUITE MINIMAL FOR MOST OF WEDNESDAY BUT LATE IN THE DAY SOME WEAK CYCLONIC CURVATURE MAY IMPINGE UPON US FROM THE WEST. AS THIS CONTINUES INTO THURSDAY WITH THE AID OF DAYTIME HEATING THE RADAR SHOULD LIGHT UP PRETTY NICELY IN THE AFTERNOON EVEN THOUGH THE GFS IS NOT TOO ENAMORED WITH THE IDEA. THE LOWERED HEIGHTS AND ADDED CLOUDS SHOULD TEMPER THE HEAT EVEN IF ONLY BY A FEW DEGREES. FROM THERE RAIN CHANCES SHOULD INCREASE EVEN FURTHER ON FRIDAY AS BOTH A COLD FRONT AND STRONGER ENERGY ALOFT APPROACH FROM POINTS NORTH AND WEST. THERE MAY EVEN BE A HEALTHY WAVE ALONG THE FRONT WHICH COULD LEAD TO QUITE A BIT OF RAIN. THE FRONT WILL BE DECELERATING MAKING FIGURING OUT HOW QUICKLY WE DRY OUT DIFFICULT. WILL JUST SHOW A SLOW DECREASE IN RAIN CHANCES DURING THE LATTER PART OF THE WEEKEND. WE SHOULD ALSO SEE A RETURN OF MORE SEASONABLE DAYTIME HIGHS LATE IN THE PERIOD WHEREAS AREAS AWAY FROM THE WATER MAY FLIRT WITH HEAT ADVISORY CRITERIA WEDNESDAY AND THURSDAY. && .AVIATION /06Z MONDAY THROUGH FRIDAY/...
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AS OF 06Z...SURGE OF PRECIPITATION MOVING UP AND ALONG THE SE U.S. COAST. FORECAST ISSUE OF THE DAY WILL BE THE SURFACE LOW ACROSS THE NE GULF OF MEXICO MOVING/DRIFTING NE INTO NRN FLORIDA...AND THEN INTO GEORGIA WITHIN THE NEXT 24 HOURS. PWAT AMOUNTS INCREASE TO ABOUT 2.25 INCHES ACROSS MAINLY THE COASTAL AREAS AS PER THE MODEL SOUNDINGS BUT REMAINING LESS THAN 2 INCHES INLAND. MODELS SHOW SHARP DECREASE IN THE PRECIPITATION SHIELD AS YOU MOVE WESTWARD...WITH INTERSTATE 95 ACTING LIKE THE DIVIDING LINE BETWEEN PCPN OR NO PCPN. ANY SHIFT IN THE MODELS JUST 30 MILES EITHER WAY CAN HAVE A SIGNIFICANT IMPACT ON THE FORECAST. WILL MAINLY HEDGE WITH MVFR PERHAPS IFR ALONG THE COASTAL TERMINALS DURING THE DAY WITH PERIODS OF RAIN SOME OF WHICH MIGHT BE HEAVY AND VFR/MVFR INLAND WITH SOME SHWRS. MOST OF THE ACTIVITY WILL BE ALONG THE COAST. CONFIDENCE IN FORECAST CONDITIONS ARE LOW AS MODELS DIFFER WITH SPEED AND STRENGTH OF LOW COMING OUT OF THE GOM. EXTENDED OUTLOOK...PREDOMINANTLY VFR THROUGH THE PERIOD WITH A SLIGHT CHANCE AFTERNOON SHRA/TSRA.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1030 PM SUNDAY...LATEST OBS SHOW SOUTHERLY WINDS AT AROUND 15 KTS WITH 4 FT SEAS. THIS FITS IN WELL WITH THE LATEST FORECAST WHICH PROJECTS A GRADUAL TIGHTENING OF THE GRADIENT OVERNIGHT...WITH SEAS INCREASING UP TO 5 FT. PREVIOUS DISCUSSION FROM THIS AFTERNOON FOLLOWS: THE PRESSURE GRADIENT WILL INCREASE SLIGHTLY THROUGH THE LATER AFTERNOON AND OVERNIGHT HOURS. THE OVERALL PATTERN IS STILL RELATIVELY WEAK HOWEVER (41013 IS CURRENTLY REPORTING CALM WINDS) AND WINDS WILL LOSE THE SEA BREEZE INFLUENCE OF A SE DIRECTION AND GO MORE SOUTHWEST. SPEEDS SHOULD SETTLE NICELY INTO A 10-15 KNOT RANGE. SEAS WILL INCREASE FROM 2-4 FEET TO 3-5 FEET AFTER 0600 UTC VIA THE SUBTLE INCREASE IN WINDS AND A DECENT SWELL COMPONENT REMAINING IN THE MIX. SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 300 PM SUNDAY...A ROUGH COUPLE OF DAYS FOR THE MARINE COMMUNITY IS COMING UP AS LOW PRESSURE CENTERED ABOUT 50 MILES SOUTHEAST OF TALLAHASSEE FLORIDA MOVES ACROSS THE COASTAL CAROLINAS. THE GFS MODEL IS THE BASIS FOR OUR FORECAST...SHOWING A MUCH SLOWER MOVEMENT OF THE LOW THAN THE NAM OR CANADIAN MODELS. SOUTH WINDS WILL INCREASE TO 15-20 KT MONDAY INTO TUESDAY AHEAD OF THE LOW. MULTIPLE WAVES OF SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS THE AREA...ACCOMPANIED BY LOW VISIBILITY IN HEAVY RAIN AND POSSIBLE SQUALLY WIND GUSTS. THE LOW WILL MOVE NORTHEAST OF CAPE FEAR TUESDAY NIGHT...WITH LIGHTER OFFSHORE WINDS DEVELOPING OVERNIGHT. SEAS WILL BUILD TO 4-6 FEET MAINLY IN 6 SECOND SOUTH WAVES PRODUCED BY THE FETCH BEGINNING NEAR JACKSONVILLE FL AND ENDING AT OUR BEACHES. SMALL CRAFT ADVISORIES WILL LIKELY BE NEEDED. LONG TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 3 PM SUNDAY...BERMUDA HIGH PRESSURE AND WEAK PIEDMONT TROUGHINESS THE MAIN PLAYERS ON WEDNESDAY. SOUTHWESTERLY WINDS A LITTLE ON THE LIGHT SIDE POSSIBLY CAPPED AT 10 KNOTS. THE TROUGH WILL BE STRONGER ON THURSDAY OPENING THE FORECAST UP TO A MORE TYPICAL 10 TO 15 KT AND POSSIBLY DECREASING THE NEARSHORE/OFFSHORE WAVE HEIGHT GRADIENT EVER SO SLIGHTLY. A COLD FRONT WILL BE APPROACHING ON FRIDAY THOUGH ITS SPEED IS A BIT UNCERTAIN ESPECIALLY SINCE IT MAY BE DECELERATING. THERE MAY BE A SLIGHT LATE PERIOD VEERING AND INCREASE IN WIND SPEED. && .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...NONE. NC...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...TRA NEAR TERM...REK/SHK SHORT TERM...TRA LONG TERM...MBB AVIATION...DCH/MAC

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