Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 021154 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 654 AM EST MON MAR 2 2015 .SYNOPSIS... TODAY WILL BRING A COLD FRONT FOLLOWED BY CHILLY HIGH PRESSURE ON TUESDAY. WEDNESDAY WILL FEATURE A DRAMATIC WARM UP ONLY TO BE FOLLOWED BY ANOTHER EVEN COLDER AIR MASS THURSDAY AND FRIDAY. THE WEEKEND WILL BRING A VERY GRADUAL WARM UP AS WELL AS AN INCREASE IN CLOUDS AND RAIN CHANCES. && .NEAR TERM /THROUGH TONIGHT/... AS OF 645 AM MONDAY...VSBYS ARE OSCILLATING BETWEEN 1/4 AND ABOUT 1 MILE...LIKELY DUE TO INCREASING WINDS AT THE TOP OF THE SHALLOW BOUNDARY LAYER DISTURBING THE "SETTLED" CONDITIONS NEEDED FOR DENSE FOG. I`LL KEEP THE ADVISORY IN EFFECT WITH THE REQUISITE 1/4 MILE VSBY STILL WITHIN REACH FOR SOME INLAND SITES OVER THE NEXT 2 HOURS. 06Z MODELS SHOWED LITTLE CHANGE FROM THEIR 00Z COUNTERPARTS. DISCUSSION FROM 330 AM FOLLOWS... CONSIDERABLE LOW-LEVEL MOISTURE AND COLD GROUND TEMPERATURES HAVE SET THE STAGE FOR DENSE FOG THIS MORNING. WHILE THE LOWEST VISIBILITIES ARE INLAND CURRENTLY...I SEE NO REASON 1/4 MILE VSBY WON`T SPREAD DOWN TO THE COAST IN THE NEXT FEW HOURS. THE ADVISORY RUNS THROUGH 10 AM...AT WHICH POINT THE LIMITED VERTICAL DEPTH OF MOISTURE SHOULD ALLOW ENOUGH INSOLATION IN TO BREAK UP THE DENSE FOG. WEAK HIGH PRESSURE ACROSS THE SOUTHEAST IS DISSIPATING WITH THE APPROACH OF A COLD FRONT FROM THE NORTH. THE WIND SHIFT ASSOCIATED WITH THIS FRONT WILL ARRIVE EARLY IN THE AFTERNOON...BUT COLD ADVECTION WILL HOLD BACK UNTIL PROBABLY 4-5 PM AS HIGH PRESSURE OVER THE MIDWEST BEGINS TO PUSH SOUTHEASTWARD INTO THE CAROLINAS. THE HIGH WILL ASSUME A WEDGE-LIKE CONFIGURATION ACROSS THE AREA TONIGHT. PRIOR FORECASTS HAD RAIN CHANCES TODAY AS A POCKET OF MID-LEVEL MOISTURE SCOOTS ACROSS THE AREA FROM THE WEST. ISENTROPIC ANALYSIS FROM ALL MODELS SHOW DOWNWARD SLOPING ISENTROPES...MEANING RAIN CHANCES SHOULD REMAIN RATHER LOW. IN FACT IF FOG BURNS OFF ON SCHEDULE THE AIR MASS ITSELF IS COMPARATIVELY MILD AND SHOULD SUPPORT HIGHS AROUND 60 ACROSS SE NORTH CAROLINA...WITH MID 60S ACROSS NE SOUTH CAROLINA. TEMPERATURES AT THE BEACHES COULD BE QUITE A BIT LOWER AS THIS MORNING`S COLD AND FOGGY AIR MASS WILL SHIFT OFFSHORE AND STAGNATE AHEAD OF THE FRONT. TONIGHT THE APPROACH OF A SHORTWAVE TROUGH FROM THE SOUTHWEST WILL CREATE VEERING WIND PROFILES...ADVECTING MOISTURE UP AND OVER THE SHALLOW COOL AIR STREAMING IN BEHIND THE COLD FRONT. THE 00Z GFS IS BY FAR THE WETTEST MODEL...AND MY FORECAST POPS CONSTITUTE OF A BLEND OF DRIER GUIDANCE WHICH HOLDS RAIN CHANCES MAINLY SOUTH OF A LINE FROM FLORENCE AND MARION TO MYRTLE BEACH AFTER MIDNIGHT. LOWS SHOULD RANGE FROM THE UPPER 30S ACROSS SE NORTH CAROLINA TO THE LOWER 40S ACROSS NE SOUTH CAROLINA. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... AS OF 3 AM MONDAY...ALL TOO FAMILIAR COOL AIR WEDGE FIRMLY IN PLACE ON TUESDAY. BETWEEN STRONGER OVERRUNNING ON THE WESTERN SIDE OF THE RIDGE AND A FAIRLY WELL DEFINED COASTAL TROUGH THERE SHOULD BE AMPLE LIFT AREA-WIDE FOR PRECIPITATION DURING AN OTHERWISE CLOUDY AND CHILLY AFTERNOON. THIS MAY CHANGE AS THE DAY WEARS ON AS THE WEDGE BREAKS DOWN RATHER QUICKLY LATER ON...PROBABLY NOT AS QUICKLY AS PROGGED THOUGH ESPECIALLY IN LIGHT OF THE POSSIBLY RE-ENFORCING RAINFALL. THIS TIMING WILL HAVE SOME BEARING ON TUESDAY NIGHT LOWS. A SLIGHT PERSISTENCE INTO TUESDAY NIGHT MAY ALLOW FOR A SMALL TEMP DROP BUT AN EARLIER BREAKDOWN WILL MEAN TUESDAY NIGHT `LOWS` WILL NEARLY MATCH TUESDAY HIGHS AS TEMPS WILL FLATLINE EARLY AND THEN SLOWLY RISE. THIS IS BEST REPRESENTED BY THE GFS OVER THE WRF AND MATCHES PREVIOUS FORECAST THINKING QUITE WELL. SINCE THE RAIN LIKELY SHUTS OFF BY EVENING AND A HEALTHY LLJ FORMS SEE NO REASON TO CHANGE THIS. WEDNESDAY PROBABLY REMAINS QUITE CLOUDY BUT WILL BE OUR ONE WELCOME DAY OF WARMTH NOT ONLY FOLLOWING A LONG STRETCH OF COOL WEATHER BUT IT WILL ALSO BE FOLLOWED BY A RETURN OF COLD CONDITIONS. WEDNESDAY WILL ALSO BE QUITE BREEZY. A SLIGHT DECREASE IN STRENGTH OF THE LLJ WILL BE OFFSET BY A TIGHTENING SURFACE PRESSURE GRADIENT BETWEEN WEST ATLANTIC HIGH PRESSURE AND AN APPROACHING COLD FRONT CONTAINING A FLAT WAVE OF LOW PRESSURE. IN THIS SSWRLY FLOW THERE WILL BE QUITE A TEMP GRADIENT ACROSS BRUNSWICK CTY DUE TO THE COLD SSTS. THIS MARINE AIR WILL ALSO TEMPER THE HIGHS ACROSS CAPE FEAR COUNTIES WHERE UPPER 60S TO LOW 70S WILL BE COMMON (MUCH COOLER BEACHES) WHILE INLAND LOCALES SOAR WELL INTO THE 70S. JUST AHEAD OF THIS BOUNDARY WEDNESDAY NIGHT WILL REMAIN VERY MILD AND AT THE VERY TAIL END MAY FEATURE SOME RAIN CHANCES ASSOC WITH THE BOUNDARY ESP OVER WESTERN ZONES. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 3 AM MONDAY...AND JUST LIKE THAT OUR TASTE OF SPRING IS GONE ON THURSDAY. VERY BROAD NEUTRALLY TILTED EASTERN U.S. UPPER TROUGH TO GRAB AIR FROM LOCATIONS WELL UP INTO CANADA AND DRIVE IT INTO THE CAROLINAS. THURSDAY HIGHS COULD VERY WELL END UP SOME 20 DEGREES BELOW CLIMO ESPECIALLY IF LOW CLOUDS BORN OF UNDERCUTTING HIGH ARE PREVALENT ENOUGH. FROM THERE THE CAA MAY CONTINUE EVEN AS THE MID LEVEL FLOW FLATTENS OUT. SOME GUIDANCE HINTING AT NEAR RECORD LOW HIGHS FOR MARCH 6 (ILM: 38, 1901). NOT QUITE CONVINCED OF THAT MAGNITUDE OF COLD ESPECIALLY GIVEN THAT THE EARLY MARCH SUN WILL BE HAVING A SAY IN THE MATTER. HOWEVER ANOTHER DAY OF 20 DEGREE TEMPERATURE SHORTAGES FROM CLIMO SEEM ON TAP FOR A SECOND DAY. BITTER CHILL EXTENDS INTO FRIDAY NIGHT ESPECIALLY HINGING UPON CLEARING/DECOUPLING POTENTIAL...WE MAY BE LOOKING AT SOME LOWS IN THE TEENS. SATURDAY WILL BRING RECOVERY IN TEMPERATURES BUT ONLY IN A RELATIVE SENSE AS HIGHS LIKELY STILL END UP 10 DEGREES BELOW CLIMO AS THE SURFACE HIGH WEAKENS AND MID LEVEL FLOW REMAINS QUITE FLAT. AN APPROACHING CLIPPER ON OVER THE WEEKEND SHOULD LEAD TO ENOUGH WARM AND MOIST ADVECTION FOR NEAR SEASONABLE TEMPS WHILE CLOUDS AND RAIN CHANCES BOTH INCREASE SLIGHTLY. MODELS DIFFER WITH RESPECT TO THE TIMING OF THIS SYSTEM. THE GFS LOOKS A LITTLE FAST IN SHOWING THIS AS SOON AS SATURDAY. WILL INCREASE CLOUD COVER A BIT FOR FOR NOW HOLD RAIN CHANCES OFF TIL SUNDAY. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... AS OF 12Z...LIFR/IFR CONDITIONS EXPECTED THROUGH LATE MORNING WITH DENSE FOG AND LOW CEILINGS. IFR CONDITIONS WILL IMPROVE TO MVFR OR BETTER BY LATE MORNING OR NOON. COLD FRONT DROPS SOUTH THIS AFTERNOON...WITH WINDS SHIFTING TO THE NORTHEAST TOWARD EVENING. THE MODELS ARE TRYING TO INTRODUCE PRECIP LATE TONIGHT SO HAVE ADDED SHOWER IN THE VICINITY. . EXTENDED OUTLOOK...BECOMING VFR TUE MORNING...WITH PERIODS OF MVFR/SHOWERS TUE AFTN AND EVENING. SHOWERS LATE WED. RAIN/IFR THUR. VFR DEVELOPING FRI. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 645 AM MONDAY...NO SIGNIFICANT CHANGES NEEDED TO THE MARINE FORECAST. FOG IS DENSE ENOUGH FOR THE FORT FISHER-SOUTHPORT FERRY TO BE CANCELED EARLY THIS MORNING. DISCUSSION FROM 330 AM FOLLOWS... WEAK HIGH PRESSURE ACROSS THE SOUTHEAST WILL DISSIPATE LATER TODAY AS A COLD FRONT APPROACHES FROM THE NORTH. THE INITIAL WIND SHIFT WITH THIS FRONT SHOULD PUSH OFFSHORE DURING THE EARLY AFTERNOON HOURS...WITH COLDER AIR BUILDING IN ON A SECONDARY SURGE THIS EVENING. MODELS SHOW QUITE A BIT OF SPREAD WITH REGARDS TO HOW STRONG WIND SPEEDS BECOME OVERNIGHT (THE 00Z GFS IS THE STRONGEST MODEL) BUT IT IS POSSIBLE WE MAY REACH SMALL CRAFT ADVISORY THRESHOLDS BY MIDNIGHT...ESPECIALLY ACROSS THE OUTER PORTION OF THE COASTAL WATERS AS NE WINDS REACH 20 KNOTS AND SEAS GRADUALLY BUILD. FOR WINDS I HAVE USED A BLEND OF ALL AVAILABLE GUIDANCE EXCEPT THE WRF-ARW. FOR SEAS I USED OUR LOCAL SWAN WAVE MODEL WITH THE TYPICAL CORRECTIONS MADE FOR ITS BIAS IN BUILDING SEA HEIGHTS TOO QUICKLY IN THE EARLY PORTIONS OF A NE SURGE EVENT. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 3 AM MONDAY...TUESDAY BRINGS AN OVERLAND WEDGE OF HIGH PRESSURE AND SURFACE TROUGHINESS IMPINGING UPON THE WATERS FROM THE EAST. THE RESULTING PINCHED GRADIENT MAY NECESSITATE A SMALL CRAFT ADVISORY THOUGH CONDITIONS WILL BE RATHER MARGINAL. BOTH FEATURES WASH OUT TUESDAY NIGHT ALLOWING FOR A WARM SEASON-LIKE SOUTHWESTERLY FLOW. WARMTH AND MOISTURE WILL FLOOD ACROSS THE COASTAL WATERS AND A SEA FOG THREAT WILL DEVELOP. ENHANCING THE HAZARD TO MARINERS LATE IN THE PERIOD WILL BE A RETURN OF SMALL CRAFT ADVISORY CONDITIONS AS THE APPROACH OF A COLD FRONT AND SURFACE WAVE FROM THE NORTHWEST TIGHTENS THE GRADIENT. LONG TERM /THURSDAY THROUGH FRIDAY/... AS OF 3 AM MONDAY...NOT A GOOD STRETCH OF WEATHER FOR MARINERS. STRONG COLD FRONT RIGHT AT THE START OF THE PERIOD WILL BLOW OUT THE SEA FOG AS COLD AIR POURS IN ON A NORTHWEST WIND. THIS SURGE WILL BE STRONG ENOUGH THOUGH TO BRING SMALL CRAFT ADVISORY WINDS AND/OR SEAS. AS THE HIGH MAKES SLOW PROGRESS EASTWARD INTO FRIDAY WINDS TURN TO THE NORTHEAST AND MAY DROP OFF A BIT LATE IN THE PERIOD. SCA FLAGS STILL FLYING FOR MOST OF FRIDAY AND POSSIBLY INTO FRIDAY NIGHT THOUGH DEPENDING ON HOW QUICKLY SEAS SETTLE FOLLOWING THE ABATING TREND OF THE WINDS. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR SCZ017-023- 024-032-033-039-053>056. NC...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR NCZ087-096- 099-105>110. MARINE...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR AMZ250-252- 254-256. && $$ SYNOPSIS...MBB NEAR TERM...TRA SHORT TERM...MBB LONG TERM...MBB AVIATION...TRA/DRH MARINE...

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