Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 230530 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1230 AM EST TUE DEC 23 2014 .SYNOPSIS... MOISTURE WILL OVERRUN COOL AIR OVERNIGHT LEADING TO FOG AND PERIODS OF DRIZZLE. THE CHILLED AIR WILL LIFT OUT ON TUESDAY CLEARING THE PATH FOR WARMER TEMPERATURES BUT EVEN MORE MOISTURE. A COLD FRONT MAY ADD SOME THUNDER WEDNESDAY AND WEDNESDAY NIGHT. DRY AND SEASONABLE WEATHER RETURNS CHRISTMAS AND THE DAYS THAT FOLLOW. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... AS OF 1230 AM TUESDAY...NO SIGNIFICANT CHANGES WERE NEEDED TO THE FORECAST. THE NAM AND ITS TWO HIGH-RES COUSINS (WRF-NMM AND WRF-ARW) CONTINUE TO PERFORM BETTER THAN ANY OTHER GUIDANCE WITH THE LOCATION OF THE COASTAL FRONT OFFSHORE. PREVIOUS DISCUSSION FROM 930 PM FOLLOWS... LATEST SURFACE ANALYSIS SHOWS A COASTAL TROUGH POSITIONED OFFSHORE OF THE SC/NC COAST. SEVERAL MODEL SOLUTIONS BRING THIS FEATURE ONTO THE COAST BY DAYBREAK TUESDAY BUT RECENT PMSL LOOPS SHOW THE FEATURE HAS STALLED OFFSHORE LATE THIS EVENING. THE NE WIND FLOW REMAINS A SHALLOW ONE AND THE KLTX VAD WIND PROFILE DEPICTS DEEP SW WIND FLOW ABOVE 2000 FEET WITH SPEEDS OF 15-75 KT BOTTOM TO TOP. MOST RAIN PRESENTLY HAS MOVED WELL OFFSHORE AND CURRENTLY SUBSIDENCE ALOFT IN WAKE OF EXITING SHORT WAVE ENERGY HAS QUIETED PCPN. IN RECENT RADAR SCANS LIGHT SHOWERS WERE DEVELOPING OVER CENTRAL SC...WHICH MAY BE A SIGN THAT WEAK SHORT-WAVE ENERGY APPROACHING IS HELPING TO PRODUCE WEAK LIFT. THIS IS DEPICTED IN RECENT NAM PCPN FIELDS BUT QPF VALUES REMAIN VERY LOW OVERNIGHT TRACE-0.07". SO FAR THE LOW/HIGH TEMP AT ILM IS 44/47 AND LATEST HOURLY TEMP GUIDANCE SUGGEST LITTLE CHANGE IN TEMPERATURES THIS EVENING THEN WARMING A FEW DEGREES INTO THE PRE-DAWN HOURS AS MOUNTING SW WINDS CONTINUE TO SCOUR THE WET AND SHALLOW MARITIME WEDGE IN OVERCAST OF LOW ALTITUDE AND SATURATED AIR. THE WARMING MAY BE OVERDONE AND WAS ONLY RAISED A FEW DEGREES IN THE LATEST FORECASTS. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... AS OF 3 PM MONDAY...SHORT TERM WILL BE QUITE ACTIVE WITH A COMPLEX STORM SYSTEM AFFECTING THE EASTERN CONUS. PERIOD BEGINS WITH HIGH PRESSURE RIDGING DOWN THE COAST AND FRONT STALLED OFFSHORE. AS IS TYPICAL THE GUIDANCE WANTS TO MOVE THE FRONT ONSHORE EARLY TUE...BUT THIS PROBABLY WONT HAPPEN SAVE FOR THE COAST UNTIL LATE IN THE DAY TUE OR EVEN TUE EVENING. THE RESULT WILL BE CONTINUATION OF LIGHT PATCHY RAIN ALONG WITH POTENTIAL FOR SOME EMBEDDED ELEVATED CONVECTION. THE FRONT AND ITS LOCATION ON TUE WILL DETERMINE HIGH TEMPERATURE GRADIENT...WHICH IS LIKELY TO BE SIGNIFICANT. ALONG THE COAST MID TO UPPER 60S IS POSSIBLE WHILE WEST OF I-95 HIGHS MAY STRUGGLE TO REACH 50. COASTAL FRONT PUSHES NORTHWEST OF THE AREA TUE NIGHT WITH STRONG WARM ADVECTION AND IMPRESSIVE LOW LEVEL JETTING IN THE AREA. FORECAST SOUNDINGS SHOW 45 KT DEVELOPING BY WED MORNING WHICH WILL KEEP LOWS ABOVE TO WELL ABOVE CLIMO. INLAND AREAS MAY END UP WITH TUE HIGHS AND TUE NIGHT LOWS BEING THE SAME OR WITHIN A DEGREE OF EACH OTHER. FORECAST SOUNDINGS SHOW SOME WEAK INSTABILITY ABOVE 900MB ALONG WITH PVA AHEAD OF SHORTWAVES EJECTED NORTHEAST FROM THE BASE OF THE 5H TROUGH. ALTHOUGH HARD TO PIN DOWN A FAVORED LOCATION/TIME TUE NIGHT SHOULD BE FAIRLY ACTIVE AND WILL MAINTAIN INHERITED CATEGORICAL POP. ALTHOUGH THERE WILL BE ELEVATED INSTABILITY AND IMPRESSIVE JETTING DO NOT THINK DAMAGING WINDS WILL BE AN ISSUE. THE BOUNDARY LAYER IS QUITE STABLE SO WHILE SURFACE WINDS WILL BE GUSTY DUE TO THE ENHANCED GRADIENT DO NOT FORESEE SIGNIFICANT SEVERE THREAT. IMPRESSIVE WARM ADVECTION CONTINUES WED AHEAD OF THE APPROACHING COLD FRONT. HIGHS WILL CLIMB INTO THE 70S IN A LOT OF AREAS DESPITE CLOUD COVER. ONCE AGAIN THERE WILL BE STRONG LOW LEVEL JETTING AND AN ABUNDANCE OF SHEAR BUT INSTABILITY WILL BE LACKING. FORECAST SOUNDINGS PEAK MLCAPE VALUES BETWEEN 100 AND 200 J/KG WED AFTERNOON WITH LOW LEVEL LAPSE RATES MARGINAL AT BEST. CONTINUE TO EXPECT WIDESPREAD PRECIP BUT NOT AS CONFIDENT ON POTENTIAL FOR STRONG TO SEVERE STORMS. STORM MOTIONS WILL BE ON THE ORDER OF 35 KT AND WITH POTENTIAL FOR SOME CONVECTION CANNOT RULE OUT SEVERE WEATHER BUT IT SEEMS LIKE A LONG SHOT AT THIS POINT...HENCE SPC HAVING MOST OF THE FORECAST AREA IN MARGINAL RISK FOR DAY 3. DO THINK RAIN COULD BE HEAVY AT TIMES WITH PRECIPITABLE WATER VALUES IN FORECAST SOUNDINGS AROUND 2 INCHES. WORTH NOTING 2 INCHES WOULD BE RIGHT AROUND THE HIGHEST EVER RECORDED FOR LATE DEC. COLD FRONT MOVES ACROSS THE FORECAST AREA LATE WED NIGHT BRINGING AN END TO PRECIP. LATE ARRIVAL/PASSAGE OF FRONT WILL NECESSITATE KEEPING HIGH POP IN THE WED NIGHT PERIOD THOUGH BASED ON LATEST TIMING THINK PRECIP WILL BE OVER IN MOST AREAS AROUND MIDNIGHT. THE EXCEPTION WOULD BE THE NC COAST WHERE PRECIP MAY LINGER A FEW HOURS AFTER MIDNIGHT. MID LEVEL TROUGH AXIS REMAINS WEST OF THE AREA INTO THU KEEPING WHAT COLD AIR IS PRESENT WELL TO THE WEST. FORECAST SOUNDINGS SHOW LOW LEVEL DRY AIR SPREADING OVER THE REGION BUT MOISTURE ALOFT WILL KEEP CLOUD COVER IN PLACE THROUGH THE END OF THE PERIOD. CLOUD COVER AND DEEP WESTERLY FLOW WILL KEEP WED NIGHT LOWS ABOVE TO WELL ABOVE CLIMO. && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 3 PM MONDAY...SUNSHINE WILL MAKE A REAPPEARANCE FINALLY ON CHRISTMAS DAY. THE MID TO UPPER TROUGH JUST ENTERING THE CAROLINAS THURS MORNING WILL PUSH THE COLD FRONT FARTHER OFF SHORE THROUGH THE DAY LEAVING A DEEP W-NW FLOW OF DRIER AND SOMEWHAT COOLER AIR. DEWPOINT TEMPS WILL DROP THROUGH THE DAY WITH A 20 PLUS DEGREE DROP FROM PREVIOUS DAY. PCP WATER VALUES WILL DROP LESS THAN A HALF INCH BY NOON AS COLUMN DRIES OUT. OVERALL EXPECT CLEARING THROUGH THE MORNING WITH INCREASING SUNSHINE...GUSTY WINDS AND SEASONABLE TEMPS CLOSER TO 60. HIGH PRESSURE WILL BUILD UP FROM THE GULF COAST OVER THE SOUTHEAST THURS INTO FRI. GUSTY WESTERLY WINDS ON THURS WILL LIGHTEN UP BECOMING NEAR CALM THURS NIGHT AS THE CENTER OF THE HIGH SETTLES OVER THE CAROLINAS. THE CLEAR SKIES AND LIGHT WINDS SHOULD ALLOW FOR SOME DECENT RADIATIONAL COOLING AND TEMPS DOWN IN THE 30S THURS NIGHT. A RETURN FLOW WILL SET UP THROUGH FRI AS RIDGE OF HIGH PRESSURE SHIFTS OFF SHORE. THIS SOUTHERLY FLOW WILL ALLOW FOR A RETURN OF MOISTURE AND WARMER TEMPS HEADING INTO THE WEEKEND. SHOULD SEE AN INCREASE IN CLOUDS THROUGH SATURDAY AHEAD OF COLD FRONT REACHING INTO THE CAROLINAS BY SAT NIGHT. BEST CHC OF PCP WILL COME SAT NIGHT AS THE FRONT MOVES THROUGH. THIS COLD FRONT SHOULD PUSH SOUTH THROUGH SUNDAY BUT THE FLOW ALOFT WILL REMAIN SW AS RIDGE HOLDS ON TO OUR SOUTHEAST. THEREFORE WILL END UP WITH LOW CLOUDS HANGING ON THROUGH THE START OF NEXT WEEK. TEMPS UP IN THE 60S ON SATURDAY WILL BE BACK DOWN IN THE 50S MOST PLACES SUN AND MON ESPECIALLY IF LOW CLOUDS HANG AROUND. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... AS OF 06Z...EXPECT IFR/LIFR TO PERSIST THIS MORNING DUE TO LOW CIGS...AREAS OF FOG AND -RA. IMPROVEMENT TO MVFR AT KCRE/KMYR POSSIBLE LATE AFTERNOON/EARLY EVENING AS WARM FRONT NEARS THE AREA. OBSERVATIONS CURRENTLY ARE REPORTING WIDESPREAD LIFR DUE TO LOW CIGS AND FOG. WILL SEE THESE CONDITIONS CONTINUE THROUGH THE EARLY MORNING HOURS WITH LIGHT NORTH-NORTHEASTERLY WINDS. AFTER DAYBREAK...BAD CONDITIONS WILL CONTINUE WITH LOW CIGS ALONG WITH AREAS OF FOG AND ISOLATED TO SCATTERED -RA. WINDS MAY BECOME SOUTHEASTERLY IN THE AFTERNOON NEAR THE COAST. COULD SEE SOME IMPROVEMENT TO MVFR TOWARDS THE END OF THE PERIOD...ESPECIALLY AT KCRE/KMYR...AS A WARM FRONT BEGINS TO LIFT NORTHWARD INTO THE AREA. OTHERWISE...EXPECT IFR TO PERSIST WITH WINDS BECOMING LIGHT AND AREAS OF -RA. EXTENDED OUTLOOK...EXPECT SHOWERS/MVFR AND GUSTY WINDS AHEAD OF A COLD FRONT ON WEDNESDAY. GUSTY WEST WINDS AND VFR THU BEHIND THE FRONT. EXPECT VFR FRIDAY AND SATURDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1230 AM TUESDAY...TWO BIG CHANGES TO THE FORECAST. THE FIRST WAS THE ISSUANCE OF A MARINE DENSE FOG ADVISORY. UNLIKE THE LAND VERSION OF A DENSE FOG ADVISORY ONLY 1 NAUTICAL MILE VSBYS ARE NEEDED FOR CONSTITUTE DENSE FOG FOR MARINERS...AND MANY COASTAL OBSERVATIONS ARE SHOWING THESE VSBYS CURRENTLY. SECONDLY I HAVE LOWERED FORECAST NEARSHORE SEAS SUBSTANTIALLY BASED ON BUOYS SHOWING 1-2 FEET WITHIN 10 MILES OF THE COAST AT SUNSET BEACH...THE HARBOR BUOY NEAR CAPE FEAR...AND AT THE NEARSHORE WRIGHTSVILLE BEACH BUOY. THE FRYING PAN SHOALS CONTINUES TO REPORT HIGHER SEAS NEAR 4 FEET. PREVIOUS DISCUSSION FROM 930 PM FOLLOWS... COASTAL FRONT HAS RETROGRADED SLIGHTLY AND FRYING PAN SHOALS NOW BACK TO REPORTING NE WIND. ALTHOUGH RECENT RECENT NUMERICAL MODELS BRING THIS FEATURE CLOSE TO SHORE INTO DAYBREAK TUESDAY...IT MAY NOT REACH SHORE. THIS FEATURE IS DECAYING AND WINDS WILL LIGHTEN AND PERHAPS BECOME VARIABLE OR SE OUTER WATERS AS THE DECAYING COASTAL TROUGH EDGES CLOSER. PERIODS OF LIGHT RAIN AND MIST COULD REDUCE VSBYS BELOW 2NM AT TIMES. SEAS 3 TO 4 FEET WITH EAST WAVES DOMINATING THE SPECTRUM IN 8 SECOND WAVE PERIODS. THIS WAVE REGIME WILL HOLD OVERNIGHT WITH WINDS 10 KT OR LESS...MAINLY NE WITHIN 20NM. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 3 PM MONDAY...COASTAL FRONT ACROSS THE WATERS TUE WILL MOVE ONSHORE LATER IN THE DAY. TIMING THE FRONT...AND THE RESULTING STRONG SOUTHERLY FLOW IS ALWAYS DIFFICULT. GUIDANCE IS USUALLY TOO FAST TO MOVE THE FRONT INTO THE COLDER AIR AND TUE APPEARS TO BE NO DIFFERENT. THUS CONTINUE FOLLOWING THE TREND FROM PREVIOUS FORECASTS WITH MOVEMENT OF THE FRONT DELAYED UNTIL TUE AFTERNOON/EVENING. THIS WILL KEEP WINDS OVER THE NEARSHORE WATERS LIGHT AND VARIABLE TOMORROW BEFORE SOUTHERLY FLOW INCREASES TUE NIGHT. SPEEDS LATE TUE NIGHT AND WED WILL BE INTO THE 20 TO 25 KT RANGE AT TIMES...BUILDING SEAS ACROSS ALL WATERS OVER 6 FT. SCA WILL BE NEEDED PROBABLY STARTING CLOSE TO MIDNIGHT AND LASTING THROUGH WED AND WED NIGHT. LATE IN THE PERIOD THE COLD FRONT MOVES ACROSS THE WATERS WITH OFFSHORE FLOW DEVELOPING. COLD ADVECTION IS LACKING BUT GRADIENT REMAINS TIGHT AND SPEEDS WILL REMAIN NEAR THE 20 TO 25 KT RANGE THROUGH THE END OF THE PERIOD. LONG TERM /THURSDAY THROUGH FRIDAY/... AS OF 3 PM MONDAY...COLD FRONT WILL SHIFT FARTHER OFF SHORE ON THURS AS HIGH PRESSURE BUILDS UP FROM THE GULF COAST. GUSTY W-SW WINDS EARLY THURS WILL VEER AROUND BECOMING WEST THROUGH THE DAY. SEAS UP AROUND 5 TO 7 FT SHOULD FALL BELOW SCA THRESHOLDS BY THURS AFTN WITH HIGHEST SEAS GETTING PUSHED FARTHER OFF SHORE IN STRONGER W-NW FLOW BEHIND FRONT. WINDS WILL VEER FURTHER TO THE NW AND LIGHTEN UP LATE THURS INTO FRI AS CENTER OF HIGH SHIFTS CLOSER OVERHEAD. SEAS WILL BE DOWN TO 2 TO 4 FT BY THURS NIGHT AND DOWN TO 3 FT OR LESS THROUGH FRI AS HIGH PRESSURE MOVES OVERHEAD WITH MORE VARIABLE WINDS EXPECTED. HIGH PRESSURE WILL SHIFT FARTHER OFF SHORE ON SATURDAY WITH A RETURN FLOW UNDER 15 KTS SETTING UP. A COLD FRONT WILL APPROACH SAT NIGHT WITH WINDS VEERING AROUND AND INCREASING SLIGHTLY. THIS WILL PUSH SEAS BACK UP CLOSER TO 3 TO 4 FT BY SUNDAY MORNING. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...COASTAL FLOOD ADVISORY FROM 7 AM TO 10 AM EST TUESDAY FOR SCZ054-056. NC...COASTAL FLOOD ADVISORY FROM 7 AM TO 10 AM EST TUESDAY FOR NCZ106-108. MARINE...DENSE FOG ADVISORY ALL ZONES UNTIL 10 AM TUESDAY. && $$ SYNOPSIS...3/MJC NEAR TERM...MJC/TRA SHORT TERM...III LONG TERM...RGZ AVIATION...SGL/TRA

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