Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 010018 CCA AFDILM AREA FORECAST DISCUSSION...CORRECTED NATIONAL WEATHER SERVICE WILMINGTON NC 713 PM EST SAT JAN 31 2015 .SYNOPSIS... SEASONABLE TEMPERATURES WILL ARRIVE SUNDAY ALONG WITH A GRADUAL INCREASE IN MOISTURE. RAINFALL WILL SPREAD ACROSS THE REGION SUNDAY NIGHT INTO MONDAY AHEAD OF A COLD FRONT. UNSETTLED WEATHER IS EXPECTED AGAIN LATE IN THE WEEK WITH LOW PRESSURE POSSIBLY FORMING OFF THE COAST ALONG A COLD FRONT THAT MOVES THROUGH ON THURSDAY. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... AS OF 630 PM SATURDAY...TYPICALLY ONE OF THE EASIEST TIMES TO BEAT THE MODELS IS THE FIRST EVENING HIGH PRESSURE MOVES OFF THE COAST. THE MODELS TYPICALLY UNDERESTIMATE THE INTENSITY OF RADIATIONAL COOLING AFTER SUNSET WITH THE REMNANT COLD AIRMASS STILL CLINGING TO THE COASTAL PLAIN. IN THIS CASE HOWEVER...CLOUDS ARE INCREASING RATHER QUICKLY FROM THE WEST AND I AM HESITANT TO EVEN FORECAST LOWS QUITE AS COLD AS THE GFS MOS WHICH HAS MID 20S ACROSS MOST OF THE AREA. I HAVE LOWERED OUR FORECAST LOWS BY A COUPLE DEGREES... ESPECIALLY FOR THE COASTAL COUNTIES JUST INLAND FROM THE BEACHES AS THE PREVIOUS FORECAST WAS ONLY 5-8 DEGREES COLDER THAN 630 PM READINGS. THE REMNANT SEABREEZE CIRCULATION FROM THIS AFTERNOON IS STILL BLOWING AT THE BEACHES BUT SHOULD DIE AWAY IN THE NEXT HOUR WITH LIGHT/VARIABLE WINDS EXPECTED OVERNIGHT. PREVIOUS DISCUSSION FROM 300 PM FOLLOWS... FAIR AND COOL EVENING WEATHER IN STORE FOR NE SC AND SE NC AS THE HEART OF A MODIFIED ARCTIC AIR MASS SETTLES OVER THE AREA THEN SLIPS OFFSHORE INTO EARLY SUNDAY. INFILTRATION OF CIRRUS LATE TONIGHT AND WEAK RETURN WIND FLOW WILL LIKELY SERVE TO LEVEL OFF OR SIGNIFICANTLY DECELERATE TEMPERATURE FALLS INTO THE PRE-DAWN HOURS. MAINLY CLEAR SKIES THIS EVENING AND LIGHT WIND ON THE OTHER HAND WILL PROMPT RAPID DROPS IN TEMPERATURES...WITH SUB-FREEZING READINGS LIKELY BEFORE MIDNIGHT IN MANY LOCATIONS AWAY FROM BEACHES AND THE ICWW CORRIDOR. THUS LOOK FOR MINIMUMS IN MANY SPOTS POTENTIALLY TO OCCUR AROUND OR JUST AFTER MIDNIGHT BEFORE LEVELING OFF INTO THE WEE HOURS OF SUNDAY...AS H5-H6 CLOUDS THICKEN AND LIGHT S-SW WINDS PREVAIL. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 3 PM SATURDAY...RETURN FLOW GETS UNDERWAY ON SUNDAY ALBEIT PERHAPS SLOWER THAN PREVIOUSLY THOUGHT AS IT MAY BE LATER IN THE DAY. MOST OF THE RETURN FLOW WILL GO TO INCREASING CLOUDS RATHER THAN ACTUAL RAIN CHANCES WHICH SHOULD HOLD OFF UNTIL NIGHTTIME. WARMER AIR MOVING INTO THE REGION WILL ALSO BRING ABOUT SOME WELCOME SEASONABLE HIGH TEMPERATURES. AS THE RAINFALL CHANCES RAMP UP IN THE STRENGTHENING WE MAY SEE TEMPERATURES NEARLY FLAT OR EVEN RISING OVER SUNDAY NIGHT WITH LOW TEMPERATURES FAIRLY CLOSE TO SEASONABLE HIGHS AND THE NIGHT WILL GROW INCREASINGLY BREEZY AS THE LOW LEVEL JET REALLY RAMPS UP IN STRENGTH. SIMILARLY MONDAY WILL BE QUITE BREEZY WITH SHOWERS THAT WILL BE OF MODERATE INTENSITY. ALL TOLD SOME AREAS COULD NET A HALF INCH OF PRECIP. MONDAY MAY FEATURE A SECOND PERIOD OF NON-DIURNAL TEMPERATURE CURVE AS THE MIDDAY FROPA LEADS TO AFTERNOON FALLING TEMPERATURES. BACK TO REALITY MONDAY NIGHT WITH TEMPERATURES NEAR OR BELOW THEIR SEASONABLE NORMS. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 3 PM SATURDAY...UNCERTAINTY REMAINS PROMINENT DURING THE PERIOD CONCERNING THE EVOLUTION OF SOUTHERN STREAM SYSTEM NEXT WEEK. WHILE CONFIDENCE IN THE SOUTHERN STREAM FEATURE DEVELOPING IS QUITE HIGH THE EXTENT OF ITS INTERACTION WITH A NORTHERN STREAM SHORTWAVE MID TO LATE WEEK REMAINS UNCLEAR. LATEST GFS/CMC CONTINUE TO SHOW INTERACTION OF THESE 2 FEATURES WITH UNSETTLED WEATHER ACROSS THE SOUTHEAST THU AS THE LOW MOVES UP THE COAST AND THEN FRI AS THE 5H TROUGH MOVES OVERHEAD. IN ADDITION THIS SOLUTION HAS SUPPORT FROM A LITTLE MORE THAN HALF OF THE GFS ENSEMBLE MEMBERS. ON THE OTHER HAND THE ECMWF PAINTS A MUCH DRIER PICTURE. IT HAS LIMITED INTERACTION BETWEEN THE NORTHERN AND SOUTHERN STREAM SYSTEMS AND MOVES THE 5H FEATURE AND THE SURFACE LOW ACROSS THE FL PENINSULA. IT IS WORTH NOTING THAT WITH THE LAST SYSTEM...THE NORTHEAST BLIZZARD EARLIER THIS WEEK...THERE WAS DISAGREEMENT BETWEEN THE GUIDANCE AND AT THE 5 DAY MARK THE CMC ENDED UP BEING PRETTY CLOSE. NOT PLANNING MUCH IN THE WAY OF CHANGES FOR NOW GIVEN THE LARGE AMOUNT OF UNCERTAINTY LATE IN THE PERIOD. UNTIL THE NORTHERN STREAM SHORTWAVE IS ASSESSED BY THE UPPER AIR NETWORK GUIDANCE WILL LIKELY CONTINUE TO STRUGGLE WITH THE TIMING...STRENGTH...AND TRACK OF THE SYSTEM. EITHER WAY TEMPERATURES ARE GOING TO BE GENERALLY AT OR BELOW CLIMO THROUGH THE PERIOD WITH HIGHS POTENTIALLY WELL BELOW CLIMO MID TO LATE WEEK. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/...
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AS OF 00Z...VFR EXPECTED THROUGH THIS TAF VALID PERIOD. EVEN THOUGH WINDS ARE CURRENTLY S 6-8 KT AT KCRE/KMYR...A STRONG INVERSION WILL CAUSE WINDS TO BE LIGHT AND VARIABLE THROUGH SUNRISE. TAFS REFLECT LOWEST POSSIBLE CEILINGS OF 13K THROUGH 18Z. ACTUAL CEILINGS MAY NOT DEVELOP UNTIL AFTER 09Z AND MAY BE HIGHER AND OF SHORTER DURATION. FROM 16-18Z WINDS BECOME S AROUND 10 KT AS CEILINGS IMPROVE TO 20K OR SO. EXTENDED AVIATION OUTLOOK...SHOWERS/MVFR LIKELY LATE SUN THROUGH MON MORNING...THEN BECOMING VFR AGAIN THROUGH WED. POSSIBLE RAIN THURS.
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&& .MARINE... NEAR TERM/THROUGH TONIGHT/... AS OF 630 PM SATURDAY...ONLY TWO CHANGES WERE MADE TO THE FORECAST AND BOTH DEAL WITH NEARSHORE EFFECTS: THE REMNANT AFTERNOON SEABREEZE CIRCULATION MAY TAKE ANOTHER HOUR OR TWO TO DIE AWAY GIVEN CURRENT OBSERVATIONS OF SOUTH WINDS NEAR 10 KNOTS AT THE BEACHES. ALSO...NEARSHORE SEAS WERE A LITTLE HIGH IN THE PREVIOUS FORECAST BASED ON 6:00 PM DATA FROM THE SUNSET BEACH NEARSHORE BUOY OF 1 FOOT SEAS IN A 9 SECOND PERIOD. OTHERWISE NO SIGNIFICANT CHANGES WERE MADE TO THE FORECAST. DISCUSSION FROM 300 PM FOLLOWS... A VASTLY IMPROVING MARINE ENVIRONMENT INDEED MATEYS...AS SURFACE HIGH PRESSURE PARKS OVER THE WATERS AND WINDS DIE OUT TO 10 KT OR LESS OVERNIGHT. THE BULK OF WAVE ENERGY HAS BEEN LINKED WITH WINDS SO AS WINDS TAIL OFF...SEA HEIGHT WILL AND PRESENTLY ARE SUBSIDING. 2-4 FOOT SEAS LATE THIS AFTERNOON WILL FALL TO 2-3 FT THIS EVENING TO 1.5-2 FT INTO FIRST LIGHT SUNDAY WITH LIGHT WIND. THIS WILL LIKELY ALLOW E WAVES OF 1-1.5 FT EVERY 9-10 SECONDS TO BECOME THE DOMINANT WAVE ACTION IN GENTLE ROLLING SWELL. NO TSTMS OR RESTRICTIONS TO VISIBILITY ARE EXPECTED THROUGH TONIGHT. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 3 PM SATURDAY...VERY UNSETTLED FOR ALL BUT THE VERY START OF THE PERIOD. THIS RELATIVE CALM COMES THROUGH MIDDAY SUNDAY AS HIGH PRESSURE INITIALLY JUST OFFSHORE MOVES A BIT FURTHER OUT TO SEA. THIS ALLOWS FOR A BROAD SWATH OF SWRLY RETURN FLOW TO SET UP ALL ALONG THE EAST COAST. SUNDAY NIGHT INTO MONDAY WARM AND MOIST AIR WILL STREAM INTO THE SOUTHEAST IN THIS RETURN FLOW REGIME. MEANWHILE AN UPPER DISTURBANCE AND SURFACE COLD FRONT APPROACH FROM THE NORTHWEST. A SMALL CRAFT ADVISORY IS EXPECTED FOR BOTH WIND AND SEAS...EASILY. THE MAIN QUESTION IS WHETHER OR NOT GALES WILL OCCUR AND BE FREQUENT ENOUGH THAT A GALE WARNING WILL BE NEEDED. AT THIS TIME A GALE WATCH COULD BE HOISTED BUT AFTER COLLAB WITH NEIGHBORING WFOS HAVE ELECTED TO HOLD OFF FOR NOW. THE TWO MAIN ISSUES THAT MAY PRECLUDE GALES ARE: 1.THE STRONGER LOW LEVEL WIND FIELDS ON THE WRF MAY BE OVERDONE AND 2. THE COOL SSTS WILL REALLY INHIBIT VERTICAL MIXING IN THIS OTHERWISE WARM AIRMASS. SOME PRETTY STRONG WINDS MAY BE LURKING JUST OFF THE DECK BUT MAY HAVE TROUBLE REACHING THE SURFACE...WITH ANY REGULARITY. REGARDLESS IT LOOKS LIKE HAZARDOUS CONDITIONS PERSIST AND A MIDDAY OR EARLY PM FROPA WILL ADD A STEEPENING ELEMENT OF CONFUSION TO WAVE FACES DUE TO ABRUPT WIND SHIFT. LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 3 PM SATURDAY...SURFACE HIGH BUILDING IN FROM THE WEST TUE WILL MOVE OVERHEAD AND OFFSHORE TUE NIGHT AND WED. PINCHED GRADIENT INITIALLY WILL HAVE NORTHEAST FLOW IN THE 15 TO 20 KT RANGE BUT GRADIENT IS QUICK TO RELAX AND BY MIDDAY NORTHEAST FLOW WILL BE 10 KT OR LESS. LIGHT AND VARIABLE WINDS TUE NIGHT BECOME SOUTHERLY ON WED. EARLY THU WINDS VEER TO NORTHERLY AS COLD FRONT MOVES ACROSS THE WATERS. STILL SOME UNCERTAINTY LATE IN THE PERIOD BUT NEARLY ALL OF THE SOLUTIONS DO SHOW MODERATE TO STRONG NORTHERLY FLOW DEVELOPING THU INTO THU NIGHT. HEADLINES MAY BE REQUIRED LATE IN THE PERIOD. LIGHT AND VARIABLE WINDS WILL KEEP SEAS 2 TO 3 FT TUE AND WED WITH AN INCREASE EXPECTED LATE IN RESPONSE TO INCREASED WIND SPEEDS. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 AM MONDAY TO 1 AM EST TUESDAY FOR AMZ250-252-254-256. && $$ NEAR TERM...MJC/TRA SHORT TERM...MBB LONG TERM...III AVIATION...MRR

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