Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 271725 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1225 PM EST SAT DEC 27 2014 .SYNOPSIS... THE CENTER OF DRY HIGH PRESSURE WILL MOVE OFF THE COAST AND OFFSHORE THIS AFTERNOON AND TONIGHT. RETURN WINDS BEHIND THE HIGH WILL BRING INCREASING ATLANTIC MOISTURE FOR THE SECOND PART OF THE WEEKEND. RAIN CHANCES WILL CONTINUE THROUGH EARLY NEXT WEEK. A COLD FRONT WILL CROSS THE COAST TUESDAY...FOLLOWED BY DRY HIGH PRESSURE FOR THE MID-WEEK PERIOD AND CONTINUING INTO THE BEGINNING OF THE NEW YEAR. && .NEAR TERM /THROUGH TONIGHT/... AS OF 930 AM SATURDAY...LATEST VSBY SATELLITE IMAGE TRENDS INDICATE A MAINLY SUNNY MORNING THAT SHOULD CONTINUE THRU THE AFTERNOON. SOME UPSTREAM CI AND/OR AC COMING DOWN THE LEE SIDE OF THE APPALACHIANS WILL AT TIMES PUSH ACROSS THE ILM CWA BEGINNING THIS AFTERNOON AND CONTINUING TONIGHT. THE INITIAL DOWNSLOPE TRAJECTORY OFF THE MOUNTAINS WILL HELP SCOUR OUT MUCH OF THIS MOISTURE INITIALLY BEFORE REACHING THE ILM CWA. HOWEVER LATER THIS AFTN AND TONIGHT...THE FLOW ALOFT BECOMES MORE ORIENTED FROM THE SW AFTER THE UPPER RIDGE AXIS MOVES OFF THE SE U.S. COAST THIS AFTN. THEREFORE...LOOK FOR AN INCREASE IN THE TAPPING OF GULF OF MEXICO MOISTURE AS FLOW ALOFT PICKS UP FROM THE SW. OVERALL... LOOKING AT AN INCREASE AND THICKENING MID AND UPPER LEVEL LAYER OF CLOUDINESS TONIGHT. LOW LEVEL ATLANTIC MOISTURE COULD FUEL SC/ST DURING TONIGHT ESPECIALLY IN THE VICINITY OF CAPE FEAR. WILL REMAIN ON THE HIGHER SIDE OF GUIDANCE FOR THIS AFTN HIGHS...WHICH IN THIS CASE IS THE GFS MOS GUIDANCE. LOW TO MID 60S SHOULD COVER IT. WITH ADJACENT ATLANTIC SSTS IN THE 50S...THE IMMEDIATE COAST AND/OR BEACHES MAY HAVE A TOUGH TIME BREAKING ABOVE 60. PREVIOUS DISCUSSION................................. AS OF 621 AM SATURDAY...SFC HIGH PRESSURE COATED THE CAROLINAS AND COASTAL WATERS AT DAYBREAK WITH CALM TO VERY LIGHT NW WIND OVER LAND AND N 10 KT OR LESS OVER THE ADJACENT WATERS. WET GROUND AND NEAR FREEZING AIR TEMPERATURES WILL PRODUCE A BIT ON ICE ON WINDSHIELDS AND CARS SURFACES...BUT NO ROAD HAZARDS SINCE GROUND SURFACES REMAIN MUCH MILDER. THE VERY LIGHT DOWNSLOPE FLOW HAS MANAGED TO INHIBIT WIDESPREAD FOG FORMATION...AND WILL REMOVE FROM FORECAST WITH DAYBREAK UPDATE. NO OTHER CHANGES AND EXPECT TEMPERATURES TO CLIMB 25 TO 30 DEGREES INTO THE LOW AND MID 60S BY MIDDLE AFTERNOON...A LITTLE COOLER AT THE COAST. THE PREVIOUS EARLY MORNING DISCUSSION FOLLOWS. AN UPPER RIDGE AXIS WILL SHIFT SLOWLY EAST...PULLING THE CENTER OF SURFACE HIGH PRESSURE OFFSHORE. NEUTRAL HEIGHT RISES OVER THE AREA HOWEVER WILL ALLOW A WESTWARD EXTENSION OF THE HIGH...PROVIDING FAIR CONDITIONS AND MILD TEMPERATURES ABOVE NORMAL FOR LATE DECEMBER. THIS WILL ALSO RESULT IN VERY WEAK RETURN FLOW. THE LAND VS SEA TEMP DIFFERENTIAL IN THE AFTERNOON MAY DRIVE A WEAK ONSHORE BREEZE NEAR THE COAST WHEREAS INLAND A LIGHT SW FLOW SHOULD PREVAIL. THIS WILL PRODUCE EARLIER MAXIMUMS NEAR THE SEA. WE SHOULD RACK UP PLENTY SUNSHINE MINUTES TODAY RELATIVELY SPEAKING FOR EARLY WINTER. PRIMARILY HIGH CLOUDS WILL TRACK WSW TO ENE OVER NE SC AND SE NC TODAY. CLOUDS THICKEN TONIGHT AS AN UPPER GULF MOISTURE TAP ALIGNS OVER THE AREA AHEAD OF AN UPPER TROUGH CUTTING THROUGH TEXAS. ALSO A WEAK LOW LEVEL ATLANTIC MOISTURE TAP COULD BRING OCEAN CUMULUS AND FEW SPRINKLES ALONG THE SOUTH COAST AND CAPE FEAR TOWARD DAYBREAK SUNDAY. THE CLOUDS OVERNIGHT WILL SLOW COOLING AND MINIMUMS AT DAYBREAK SUNDAY IN THE RETURN FLOW REGIME...44-48 INLAND AND 49-52 ALONG THE COASTAL ZONES/ICW CORRIDOR. THE BLANKET OF INCREASING CLOUDS LATE TONIGHT SHOULD TRAP TOO MUCH WARMTH FOR PROBLEMATIC FOG DEVELOPMENT THROUGH VERY EARLY SUNDAY. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 330 AM SATURDAY...LOW CONFIDENCE FORECAST WITH ELONGATED AND WEAKLY FORCED COLD FRONT AFFECTING THE AREA THROUGH THE SHORT TERM PERIOD. A COUPLE OF SHORTWAVES WILL RIDE THROUGH THE BROAD SOUTHWEST FLOW ALOFT WHICH WILL ENHANCE RAINFALL THROUGH THE PERIOD. THE FIRST ONE MISSES OUR AREA TO THE NORTH SUNDAY AFTERNOON AND EVENING. AREAS TO THE WEST WILL SEE RAIN...BUT OUR AREA COULD REMAIN DRY. IN FACT...MODELS HAVE NUDGED THE SURFACE RIDGE A LITTLE FURTHER NORTH WITH THE LATEST CYCLES. CAVEAT TO THIS IS THE CAPE FEAR AREA WHERE THE NAM PAINTS A LITTLE LIGHT RAIN MOVING ACROSS SUNDAY MORNING VIA LOW LEVEL CONVERGENCE. PAST EXPERIENCE...THIS SEEMS TO HAPPEN A LOT AND I HAVE ADJUSTED POPS ACCORDINGLY. MONDAY LOOKS A LITTLE MORE STRAIGHT FORWARD AS ANOTHER WAVE MOVES ACROSS WITH LIGHT RAIN AND DRIZZLE LIKELY PRETTY MUCH ALL DAY AND WELL INTO THE EVENING HOURS. TEMPERATURE GUIDANCE IS IN FAIRLY GOOD AGREEMENT WITH THE EXCEPTION OF HIGHS IN WILMINGTON SUNDAY. THE NAM/MET IS CONSIDERABLY COOLER PROBABLY DUE TO THE AREA OF LIGHT RAIN MOVING ACROSS. STILL EXPECT A WARM COUPLE OF DAYS WITH HIGHS IN THE 60S. NOT MUCH DIURNAL VARIATION DUE TO THE MOISTURE. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 330 AM SATURDAY...THE EXTENDED PERIOD WILL BE HIGHLIGHTED BY A SPLIT FLOW PATTERN AS A BROAD MID LEVEL TROUGH SPLITS AS LOW PRESSURE CLOSES OFF AND RETROGRADES SOUTHWEST OVER CALIFORNIA. ACROSS THE EAST A CYCLONIC FLOW WILL DEVELOP AND CONTINUE UNTIL LATE IN THE PERIOD WHEN THE AFOREMENTIONED LOW GETS KICKED OUT AND BEGINS TO MOVE EAST. THIS WILL PROBABLY BE THE NEXT SIGNIFICANT WEATHER MAKER FOR OUR AREA. SURFACE FEATURES INCLUDE A COLD FRONT THAT SHOULD CROSS THE AREA TUESDAY MORNING WHICH WILL RESET TEMPERATURES BACK TO NEAR SEASONAL NORMS. HIGH PRESSURE...CENTERED OVER THE ROCKY MOUNTAIN REGION WILL SLOWLY MOVE EASTWARD TUESDAY THROUGH FRIDAY. OVERALL THE FORECAST HAS CHANGED LITTLE FROM THE PREVIOUS PACKAGE. TEMPERATURE GUIDANCE IS RELATIVELY STABLE ALTHOUGH WITH THE ZERO DEGREE 850MB ISOTHERM ALIGNED WEST TO EAST ACROSS THE AREA SOME VARIABILITY CAN BE EXPECTED WITH SUBSEQUENT MODEL CYCLES. I DID MAINTAIN THE LOW CHANCE POPS ASSOCIATED WITH THE NEXT SYSTEM VERY LATE IN THE PERIOD. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... AS OF 18Z...OTHER THAN SOME PASSING CIRRUS...VFR CONDITIONS ARE EXPECTED THROUGH THIS EVENING. MID-LEVEL RIDGE AND SFC HIGH WILL BOTH PUSH OFF THE CAROLINA COASTS THIS AFTN AND EVENG. THIS WILL ALLOW INCREASING HIGH LEVEL CLOUDS THIS AFTERNOON...THICKENING UP THIS EVENING...WITH MID-LEVEL CLOUDS BECOMING DOMINANT OVERNIGHT. A SFC FRONTAL BOUNDARY WILL BECOME ORIENTED ENE TO WSW ACROSS THE WESTERN CAROLINAS...WITHIN A GSO TO GSP LINE...BY MIDDAY SUNDAY. SHRA-/R- WILL FOR THE MOST PART REMAIN JUST OUTSIDE THE ILM CWA...AND THE LOCAL TERMINALS. CEILINGS WILL SLOWLY COME DOWN THRU THIS TIME PERIOD...DROPPING TO A MID-LEVEL AC/AS TONIGHT...AND WILL FURTHER AND PARTIALLY DROP TO A LOW LEVEL SC/CU CLOUD DECK. MOS GUIDANCE HAS BEEN ILLUSTRATING IR/LIFR CEILINGS BY DAYBREAK SUN AND THERE-AFTER. WILL HOLD OFF WITH THESE CEILINGS UNTIL THE VARIOUS MODELS MOS GUIDANCE AGREE WITH ONE ANOTHER. EXTENDED OUTLOOK...MODERATE CONFIDENCE FOR RAIN WITH MVFR/IFR CONDITIONS MONDAY...POSSIBLY LINGERING INTO TUE. VFR WED AND THU. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 945 AM SATURDAY...NICE DOCILE DAY ON TAP FOR WFO ILM COASTAL WATERS. SFC PG RATHER LOOSE AS THE CENTER OF HIGH PRESSURE LIES NEARLY OVERHEAD AT THE MOMENT. THE CENTER OF THE HIGH IS PROGGED TO SLIDE OFF THE CAROLINA COASTS TODAY AND OFFSHORE THIS AFTN THROUGH TONIGHT. A VARIABLE WIND 10 KT OR LESS INITIALLY...WILL BECOME SW-WSW 10 KT LATER TONIGHT INTO SUN DUE TO RETURN FLOW HAVING SET UP ACROSS THE LOCAL WATERS AS THE CENTER OF THE HIGH EXITS INTO THE OFFSHORE WATERS OF THE CAROLINAS. SIGNIFICANT SEAS ARE NOW A COMBINATION OF THE LOCALLY PRODUCED WIND DRIVEN WAVES...AND A NORTHEAST TO EAST 1-3 FOOT BONAFIDE GROUND SWELL WITH PERIODS AT 11-13 SECONDS. LOCAL BUOYS SUCH AS 41013 ARE PICKING UP ON THIS GROUND SWELL. AND FOR THE MOST PART...THIS GROUND SWELL IS DOMINATING THE OVERALL SIGNIFICANT SEAS ACROSS THE ILM WATERS. PREVIOUS DISCUSSION................................... AS OF 621 AM SATURDAY...A WELCOMING MARINE ENVIRONMENT ASIDE FROM CHILLY SST VALUES. DOCILE SEAS OVERALL AROUND 2 FT TODAY...MOSTLY SE WAVES 1.5-2 FT EVERY 7 SECONDS AND LIGHT INSHORE SE CHOP IN THE AFTERNOON AS A WEAK SEA BREEZE FORMS. ALSO IN THE SPECTRAL MIX LONG PERIOD E SWELL AROUND 15 SECONDS IS PROPAGATING TO SHORE OF MORE DISTANT ORIGIN BUT IN HEIGHTS A FOOT OR LESS. NO TSTMS ARE EXPECTED ON THE 0-20 NM THROUGH TONIGHT. PATCHY FOG IN THE EARLY MORNING COULD PRODUCE PATCHY LOW VSBYS NEAR INLETS OR THE ICWW. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 330 AM SATURDAY...LIGHT WINDS INITIALLY WILL INCREASE SOMEWHAT THROUGH THE DAY SUNDAY AS THE PRESSURE GRADIENT SHAPES UP WITH LOW PRESSURE SLIDING BY TO THE NORTHWEST. EXPECT A SOUTHWEST FLOW INCREASING TO 10-15 KNOTS BY EVENING. WIND DIRECTIONS QUITE VARIABLE MONDAY WITH LIGHTER SPEEDS AS A WARM FRONT TRIES TO MOVE ACROSS. WE HAVE A SOUTHERLY COMPONENT BUT CONFIDENCE IS LOW. FORTUNATELY THE WEAK NATURE OF THE SYSTEMS KEEPS SPEEDS CAPPED AT TEN KNOTS OR LESS. THE SAME WEAK WINDS KEEP SIGNIFICANT SEAS IN CHECK AT 1-3 FEET. LONG TERM /TUESDAY THROUGH WEDNESDAY/... AS OF 330 AM SATURDAY...RATHER CONSISTENT WIND FIELDS FOR THE EXTENDED MARINE FORECAST AS MASSIVE HIGH PRESSURE...WELL TO THE WEST WILL BE THE PRIMARY DRIVER OF THE WINDS AND SEAS. WITH THE SLOW MOVEMENT OF THIS SYSTEM...A NORTHERLY FLOW OF 10-15 KNOTS WILL PREVAIL TUESDAY AND WEDNESDAY. SIGNIFICANT SEAS WILL BE A LITTLE ELEVATED WITH THE HIGHER WIND SPEEDS JUST OUTSIDE OF THE LOCAL WATERS. OVERALL EXPECT 2-4 FEET WITH THE POSSIBILITY OF 3-5 FEET LATE TUESDAY INTO WEDNESDAY MORNING. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...SHK NEAR TERM...DCH/MJC SHORT TERM...SHK LONG TERM...SHK AVIATION...DCH/HDL

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