Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 060534 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1234 AM EST FRI MAR 6 2015 .SYNOPSIS...
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ARCTIC HIGH PRESSURE WILL SETTLE ACROSS THE AREA IN THE WAKE OF A STRONG COLD FRONT AND PERSIST THROUGH THE WEEKEND. THERE IS A SMALL RISK FOR SOME VERY LIGHT WINTRY PRECIPITATION ACROSS PORTIONS OF COASTAL NORTH CAROLINA BEFORE THE RAIN AND DRIZZLE COMPLETELY SHUTOFF FRIDAY MORNING. WINTER-LIKE TEMPERATURES WILL BEGIN TO MODERATE DURING THE WEEKEND. THE SLOW WARMUP WILL CONTINUE NEXT WEEK WITH SHOWERS POSSIBLE.
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&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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AS OF 1230 AM FRIDAY...THE MAIN PRECIP SHIELD HAS CLEARED THE COAST WITH ASOS/AWOS OBS INDICATING ONLY PATCHY DRIZZLE REMAINING. WHILE THIS WOULD NORMALLY MEAN THE EVENT IS OVER...THE 00Z WAS MOST EMPHATIC THAT A SECOND WAVE OF ISENTROPIC LIFT WILL DEVELOP ALONG THE 300K SURFACE OVERHEAD JUST BEFORE DAYBREAK...ACCOMPANIED BY A SUBTLE BACKING OF THE 700-800 MB FLOW. THE GFS IS FLATTER WITH THIS DEVELOPING WAVE WITH LITTLE IF ANY IMPACT ON LAND. I HAVE MADE NO CHANGES TO THE LATE-NIGHT/FRIDAY MORNING FORECAST...HOWEVER I BELIEVE GIVEN THE PRESENCE OF AN INCREASINGLY DEEP COLD LAYER WITH SUB-FREEZING TEMPERATURES THICKENING TO 3500-4000 FEET DEPTH BENEATH THE WARM CLOUD ALOFT...SLEET WOULD BE THE PREFERRED PRECIP TYPE RATHER THAN FREEZING RAIN. DISCUSSION FROM 900 PM FOLLOWS... ISENTROPIC LIFT IS THE MAIN DRIVER IN ONGOING PRECIPITATION. THE BACK EDGE OF THE ACCUMULATING RAIN WAS ALONG A CKI TO LBT LINE AND THIS WAS IN LINE WITH THE HRRR. RADAR SHOWED THE BACK EDGE OF THE RAIN SHIELD CREEPING SLOWLY EASTWARD. TEMPERATURES WERE IN THE LOWER 40S FOR THE MOST PART...BUT A FEW SPOTS HAVE DIPPED INTO THE UPPER 30S. FACTOR IN A N WIND OF 15 TO 20 MPH WITH HIGHER GUSTS...AND IT FEELS AS IF IT WERE IN THE 20S LATE THIS EVE. THE HIGH RESOLUTION HRRR MODEL IS SHOWING A SLOW...BUT STEADY EASTWARD PROGRESSION OF THE PRECIPITATION SHIELD THROUGH MIDNIGHT WITH THE RAIN MAINLY OFFSHORE BY AROUND MIDNIGHT...LASTLY ALONG THE CAPE FEAR COAST. HOWEVER...THE COLD AIR IS SHALLOW WITH N TO NE WINDS THROUGH 4 KFT BEING TOPPED BY A DEEP AND STILL STRONG SW TO WSW FLOW. THIS DOES SUGGEST THE PRECIPITATION MAY LINGER LONGER INTO THE NIGHT. WILL HANG ONTO THE PRECIPITATION IN THE FORM OF LIGHT RAIN AND DRIZZLE FOR MOST INLAND LOCATIONS THROUGH ABOUT MIDNIGHT. WILL THEN SHOW THE PRECIPITATION ENDING ACROSS THE REMAINDER OF THE AREA OVERNIGHT AS THE COLUMN CONTINUES TO SLOWLY DRY FROM ALOFT TO THE SURFACE. SINCE THE PRECIPITATION ENDS BEFORE AIR TEMPS DROP TO 32 DEGREES OR LOWER...WILL NOT INCLUDE MENTION OF WINTRY PRECIPITATION. THE EXCEPTION WILL BE ACROSS PORTIONS OF THE CAPE FEAR AREA WHERE VERY LIGHT PRECIPITATION MAY LINGER INTO EARLY FRI MORNING AS THE CONVEYOR BELT OF DEEPER MOISTURE WILL BE RELUCTANT TO PUSH WELL OFFSHORE. AS COLDER AIR CONTINUES TO FILTER INTO THIS AREA IN THE LOW LEVELS...TEMPERATURES WILL CREEP DOWN TO AROUND 30 DEGREES. ACROSS THE CAPE FEAR AREA...THIS WILL COMPLICATE THINGS AS ANY LIGHT PRECIPITATION WITH TEMPS BELOW FREEZING DOES HAVE THE POTENTIAL TO FREEZE. HOWEVER...GIVEN THE VERY WARM TEMPS OF THE LAST TWO DAYS...GROUND TEMPS TO INCLUDE ROADWAYS...AND EXPOSED SURFACES TO INCLUDE BRIDGES...TREES...POWER LINES AND CARS ARE NOT EXPECTED TO HAVE SUFFICIENT TIME TO REACH FREEZING BEFORE THE LIGHT PRECIPITATION ENDS. THUS...ALTHOUGH INSTRUMENTS MAY REPORT SOME LIGHT FREEZING RAIN OR FREEZING DRIZZLE...NO ICE ACCRUAL IS EXPECTED.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... AS OF 300 PM THURSDAY...WINTER WILL MAKE AN APPEARANCE THROUGH THE SHORT TERM AS ARCTIC HIGH PRESSURE BUILDS INTO THE CAROLINAS. WHILE WELL BELOW NORMAL TEMPERATURES ARE A CERTAINTY FOR FRIDAY AND SATURDAY...WHAT IS UNCERTAIN IS WHETHER ANY PRECIP WILL LINGER FRIDAY MORNING...POTENTIALLY AS A WINTRY TYPE. COLD FRONT WILL BE WELL OFFSHORE FRIDAY MORNING...BUT SOME RESIDUAL LOW-LEVEL MOISTURE WILL PERSIST IN THE COLUMN FOR THE FIRST FEW HOURS OF FRIDAY. GUIDANCE HAS BACKED OFF CONSIDERABLY ON AMOUNT OF MOISTURE LEFT IN THE COLUMN...AND SREF PROBABILITIES ARE LESS THAN MENTIONABLE. FOR THIS REASON HAVE CUT BACK POP TO SILENT FOR ALL BUT THE IMMEDIATE BEACHES...AND EVEN THERE ONLY A SCHC IS WARRANTED FOR A COUPLE OF HOURS FRIDAY MORNING. THIS PRECIP MAY BE A BIT OF IP/ZR BUT NO IMPACTS ARE ANTICIPATED FROM ANY WINTRY PRECIP. THEREAFTER...RAPID DRYING OCCURS AND AMPLE SUNSHINE WILL ENVELOP THE AREA FRIDAY AFTN. EVEN WITH FULL MARCH SUN...TEMPS ON FRIDAY WILL RISE ONLY INTO THE MID/UPR 30S - A FULL 25-30 DEGREES BELOW NORMAL! HIGH PRESSURE BUILDS TOWARDS THE AREA FRIDAY CAUSING CAA TO WEAKEN...AND A VERY COLD NIGHT IS EXPECTED AS THE DRY COLUMN AND WEEK WINDS SUPPORT STRONG LONGWAVE COOLING. GUIDANCE HAS COOLED A BIT...AND WE MAY APPROACH RECORD LOWS FRIDAY NIGHT (20 AT WILMINGTON AND 20 AT FLORENCE). CURRENT FORECASTS ARE JUST ABOVE THESE NUMBERS...BUT AN EXCEEDINGLY COLD NIGHT IS EXPECTED. A WARMER DAY EXPECTED SATURDAY AS THE AIRMASS BEGINS TO MODIFY...BUT TEMPS WILL STAY ABOUT 10 DEGREES BELOW NORMAL EVEN BENEATH THE INCREASING MARCH SUN ANGLE. HIGH PRESSURE SHIFTS OFFSHORE LATE SATURDAY ALLOWING FOR WARM RETURN FLOW TO DEVELOP. THIS WILL KEEP MINS MUCH WARMER SATURDAY NIGHT THAN FRIDAY NIGHT...SO WHILE STILL EXPECTING BELOW NORMAL VALUES FOR LOWS...MOST OF THE AREA WILL REMAIN JUST ABOVE FREEZING. && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 330 PM THURSDAY...MEDIUM RANGE GUIDANCE IS SHOWING A SPLIT FLOW DEVELOPING AS THE MAIN BELT OF WESTERLIES JOGS TO THE NORTH WITH A WEAKER SOUTHWEST FLOW OVER THE SOUTHERN U.S. SURFACE FEATURES INCLUDE A WEAK AND DRY BACKDOOR FRONT SUNDAY WITH A BROAD BAROCLINIC ZONE ALIGNED OFFSHORE. THIS IS WHAT REMAINS OF OF THE ARCTIC FRONT THAT MOVES ACROSS LATER TODAY. BEYOND THIS WEAK HIGH PRESSURE WILL PREVAIL AT THE SURFACE BUT POPS WILL REMAIN IN THE FORECAST DUE TO MID AND UPPER LEVEL INFLUENCES. WITH THE WEAK FORCING...CONFIDENCE IS LOWER THAN USUAL BUT FOR NOW WE HAVE THE HIGHEST POPS...CHANCE VALUES FOR TUESDAY AND THURSDAY WHEN THE FORCING IS SLIGHTLY BETTER. TEMPERATURE TRENDS SHOW A LITTLE BELOW NORMAL FOR DAYTIME HIGHS BUT OVERNIGHT LOWS...MODERATED QUITE A BIT BY THE MOISTURE...WELL ABOVE NORMAL WITH 45-50 DEGREES. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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AS OF 06Z...AT THE INLAND TERMINALS MVFR CIGS WILL IMPROVE TO VFR AROUND 09Z...BUT THERE WILL STILL BE SOME POTENTIAL FOR A TEMPO MVFR CIG UNTIL SHORTLY AFTER SUNRISE. WINDS WILL BE N GUSTING TO AROUND 25 KT DECREASING TO NE AROUND 12 KT BY LATE MORNING. AT THE COASTAL TERMINALS THE SAME TREND IN CIGS IS EXPECTED EXCEPT IMPROVEMENT WILL BE SEVERAL HOURS LATER. PRECIPITATION WILL MOVE OFFSHORE EARLY THIS MORNING BUT LINGER JUST ALONG THE COAST THROUGH POTENTIALLY 12-14Z. THERE COULD BE A FEW ICE PELLETS AT KILM AROUND SUNRISE. WINDS WILL BE N GUSTING TO 25-30KT DECEASING TO NE AROUND 12 KT BY EARLY AFTERNOON. VFR EXPECTED BY LATE MORNING WITH CLOUDS BECOMING SCT BY AFTERNOON. N WINDS WILL CONTINUE. EXTENDED OUTLOOK...VFR. EXTENDED OUTLOOK...VFR.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 1230 AM FRIDAY...NO SIGNIFICANT CHANGES NEEDED TO THE FORECAST. DISCUSSION FROM 900 PM FOLLOWS... A GALE WARNING REMAINS IN EFFECT. THE STRONGEST NORTHERLY SURGE AND THE TIGHTEST PRESSURE GRADIENT WILL BE IN PLACE OVERNIGHT AND FRI MORNING. WIND SPEEDS WILL BE UP TO 30 TO 35 KT. SEAS WILL PEAK IN THE RANGE OF 5 TO 9 FT. SEAS WILL BE LOWER ACROSS THE VERY NEAR SHORE WATERS TO INCLUDE LONG BAY. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 300 PM THURSDAY...ARCTIC COLD FRONT WILL BE WELL OFFSHORE FRIDAY MORNING...BUT A TIGHT GRADIENT WILL REMAIN OVER THE WATERS AND THE GALE WARNING CURRENTLY IN PLACE WILL PERSIST THROUGH 10AM FOR NORTH WINDS GUSTING ABOVE 34 KTS. WINDS BEGIN TO EASE THEREAFTER...BUT WILL ONLY SLOWLY FALL THROUGH FRIDAY...REMAINING 15-20 KTS INTO SATURDAY MORNING. THESE CONTINUED STRONG NORTH WINDS WILL KEEP WAVE HEIGHTS ABOVE 6 FT ALL OF FRIDAY...AND AN SCA WILL BE NEEDED ONCE THE GALE WARNING DROPS. HIGH PRESSURE WILL MOVE TOWARDS...AND THEN OVER...THE WATERS ON SATURDAY BEFORE DRIFTING OFFSHORE SATURDAY NIGHT. THIS WILL DRIVE PRIMARILY LIGHT AND VARIABLE WINDS SATURDAY AND SATURDAY NIGHT...EVENTUALLY TAKING ON A PREDOMINANT SW DIRECTION LATE. WAVE HEIGHTS WILL FALL STEADILY ON SATURDAY...LEVELING OFF AT 1-2 FT TOWARDS THE END OF THE PERIOD. LONG TERM /SUNDAY THROUGH TUESDAY/... AS OF 330 PM THURSDAY...A RATHER WEAK PRESSURE PATTERN WILL CONTINUE THROUGH THE PERIOD. THIS LEADS TO MODEST WIND FIELDS AND SIGNIFICANT SEAS. WITH WEAK HIGH PRESSURE TO THE WEST...NORTHWEST AND AN OLD BOUNDARY LINGERING OFFSHORE WIND DIRECTIONS WILL BE MOSTLY NORTHEAST. SPEEDS WILL DISPLAY SOME VARIATION BUT OVERALL A RANGE OF 10-15 KNOTS SHOULD BE GOOD. SIGNIFICANT SEAS WILL START OFF VERY LOW...1-2 FEET SUNDAY AND INCREASE MONDAY AND TUESDAY AS WINDS HOVER AROUND THE HIGHER END OF THE RANGE FOR SEVERAL PERIODS. COULD EVEN SEE SMALL CRAFT CONDITIONS TUESDAY.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...GALE WARNING UNTIL 10 AM EST FRIDAY FOR AMZ250-252-254-256. && $$ NEAR TERM...RJD/TRA SHORT TERM...JDW LONG TERM...SHK AVIATION...MRR

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