Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 050231 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 931 PM EST WED MAR 4 2015 .SYNOPSIS... A COLD FRONT WITH A GOOD CHANCE OF RAIN AND SHARPLY COLDER TEMPERATURES WILL MOVE ACROSS THE AREA TOMORROW AFTER ANOTHER BALMY EVENING. THERE IS A CHANCE OF SOME LIGHT FROZEN PRECIPITATION IN SOME AREAS EARLY FRIDAY BEFORE THE PRECIPITATION ENDS. THE WEEKEND WILL FEATURE SLOWLY MODERATING TEMPERATURES. THE SLOW WARMUP WILL CONTINUE NEXT WEEK WITH SHOWERS POSSIBLE. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... AS OF 830 PM WEDNESDAY...MID-LEVEL RIDGING WITH 500MB HEIGHTS AT 590+ CENTERED OVER THE BAHAMAS. THIS FLATTENING STRONG UPPER RIDGING WILL AID IN THE SLOW PROGRESSION OF THE SFC ARCTIC FRONT TO THE SE AND LIKELY BE ON THE DOORSTEPS OF THE ILM CWA BY DAYBREAK THU. A STRONG POSITIVELY TILTED UPPER S/W TROF WILL HAVE DROPPED TO THE MISSOURI-KANSAS AREA BY DAYBREAK THU. THIS WILL EVIDENTLY PROVIDE THE NECESSARY PUSH THIS SFC ARCTIC FRONT NEEDS TO FINALLY GAIN SOME MOMENTUM. THE MAJORITY OF THIS ACTION WILL OCCUR DURING THE SHORT-TERM PERIOD. THE MAIN CLOUDINESS AND PCPN WILL OCCUR AFTER THE CFP. THUS WILL CONTINUE WITH THE DRY OVERNIGHT FORECAST...ALONG WITH AN ACTIVE SSW-SW WIND AT 10 TO 20+ MPH DUE TO A TIGHTENED SFC PG. WIDESPREAD 60S FOR TONIGHTS LOWS REMAIN ON TARGET AND SEE NO REASON TO DETOUR FROM THESE PROGGED LOWS. WITH SFC DEWPOINTS ALSO IN THE 60S...WILL BE LOOKING FOR SEA FOG ACROSS THE ADJACENT ATLANTIC WATERS AND THE INTRA-COASTAL WATERWAY TO OCCASIONALLY BLEED ONSHORE AND ALSO TRACK SLIGHTLY FURTHER INLAND. HAVE RE-ITERATED THE DENSE FOG ADV FOR THE PARTIAL COASTAL COUNTIES THAT BORDER THE LOCAL ATLANTIC WATERS. PREVIOUS DISCUSSION........................................... AS OF 400 PM WEDNESDAY...AREAS OF DENSE FOG APT TO ENSHROUD OUR COASTAL LAND ZONES AGAIN OVERNIGHT AS DAYTIME MIXING WANES AND ONSHORE SEA WINDS BRING IN A CHILLED SATURATION. THIS MAY PUSH INTO THE COASTAL INTERIOR BUT TAILING OFF TO PATCHY COVERAGE. ROBUST NOCTURNAL WINDS AND HIGH DEWPOINTS WILL PROMOTE STRATUS DEVELOPMENT LATE TONIGHT FARTHER INLAND...WITH WIDESPREAD MILD CONDITIONS. AFTER AN INITIAL FALL TONIGHT OF TEMPERATURES WITH LOSS OF DAY HEATING INTO THE LOWER AND MIDDLE 60S...HOURLY TEMPERATURES WILL LEVEL OFF OVERNIGHT AT THESE VALUES...UPPER 50S BEACHES. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... AS OF 400 PM WEDNESDAY...SPRING IS TYPICALLY A SEASON OF EXTREMES...AND THURSDAY BY ITSELF WILL BE A MICROCOSM OF THE SEASON AS A WHOLE. A VERY DYNAMIC SYSTEM AND ASSOCIATED COLD FRONT WILL BRING VERY WARM TEMPS...VERY COLD TEMPS...CONVECTION...AND EVEN WINTRY PRECIP. THE GRIDS REQUIRED USE OF BOTH SUMMER TIME CONVECTIVE PROCEDURES...AND WINTER WEATHER PROCEDURES. IN OTHER WORDS...IT IS NOT AN EASY FORECAST. VERY WARM TEMPERATURES WILL START THURSDAY. HIGH PRESSURE OFF THE COAST WILL CONTINUE TO PUMP WARM RETURN FLOW INTO THE AREA...AND TEMPS WILL SOAR THE FIRST HALF OF THURSDAY. GUIDANCE CONTINUES TO SLOW TIMING OF THE COLD FRONT...THANKS IN PART TO THE PERSISTENT RIDGE AND THE DRAWN OUT/WEAKENING DRIVING VORTICITY IMPULSE. THIS SUGGESTS THAT GUIDANCE MAY BE TOO COOL WITH HIGHS THURSDAY...AND EXPECT MOST OF THE AREA TO AGAIN RISE TO 70 OR GREATER BY LATE MORNING. SREF PLUMES SUGGEST TEMPS RISING AS HIGH AS THE MID 70S LATE THURSDAY MORNING...AND PLAN TO HEDGE TOWARDS THE WARM END OF THE SREF PLUME ENVELOPE THANKS TO A WARM START AND DELAYED FROPA. THE COLD FRONT WILL CROSS THE REGION THURSDAY DURING THE LATE AFTN THROUGH EARLY EVE...BUT MOST OF THE PRECIP ASSOCIATED WITH IT WILL BE POST-FRONTAL. SPC HAS MOST OF THE AREA OUTLINED IN A "GENERAL RISK" FOR SWODY2...MENTIONING POTENTIAL ELEVATED CONVECTION BEHIND THE FRONT. FORECAST PROFILES DO SUGGEST A SMALL AMOUNT OF INSTABILITY WITHIN THE 700-500MB LAYER...BUT THIS IS ACCOMPANIED BY VERY WEAK MID-LEVEL FORCING AND ONLY MARGINAL JET-LEVEL DIFFLUENCE. ADDITIONALLY...THE ATMOSPHERE ABOVE 700MB LOOKS TO REMAIN QUITE DRY...SO DRIVING SATURATED PARCELS INTO THE CHARGE SEPARATION ZONE WILL BE DIFFICULT TO ACHIEVE...AND THUS WILL CARRY JUST RW AND LEAVE OUT ANY THUNDER MENTION THURSDAY EVE. WHAT WILL NOT BE DIFFICULT TO ACHIEVE WILL BE RAPIDLY COOLING TEMPS...AS VERY STRONG CAA FOLLOWS BEHIND THE COLD FRONT. TEMPS BETWEEN THURSDAY EVE AND FRIDAY MORNING WILL DROP SOME 40 DEGREES ACROSS THE CWA...AND EXPECT THE ENTIRE CWA TO DROP TO FREEZING OR BELOW FOR THURSDAY NIGHT MINS. TEMPS BELOW FREEZING WILL BE ACCOMPANIED BY LIGHT...BUT STILL OCCURRING PRECIP. THUS...FREEZING RAIN IS LOOKING MORE LIKELY LATE THURSDAY NIGHT INTO FRIDAY. GUIDANCE DIFFERS INTO HOW LONG PRECIP WILL PERSIST ON FRIDAY...BUT WITH THE VORT STRUNG OUT AND HANGING WELL BACK TO THE WEST...COULD SEE PRECIP LINGER INTO FRIDAY AFTN...ESPECIALLY ALONG THE COAST. WWD GRAPHICS PAINT A LARGE AREA OF UP TO 0.10 ICE ACCRUAL...AND THIS SEEMS REASONABLE ATTM. COLD AIR CHASING MOISTURE IS NEVER A GOOD SETUP FOR WINTRY PRECIP...BUT THE STRENGTH AND RAPIDITY OF THE COLD AIR DROPPING SOUTH SHOULD OVERCOME THE TYPICAL BIAS...AND FROZEN PRECIP IS EXPECTED FOR AT LEAST A SHORT DURATION. FORTUNATELY...ANY ZR WILL BE FALLING ONTO WET AND WARM GROUNDS SO ONLY ELEVATED SURFACES MAY ACTUALLY SEE ACCUMULATION. THE HIGHEST ICE ACCRETION IS EXPECTED ALONG THE CAPE FEAR AREA WHERE THE LONGEST CROSSOVER OF COLD TEMPS AND PRECIP IS EXPECTED. DRYING WILL OCCUR FRIDAY AFTN/EVE AS COLD HIGH PRESSURE RIDGES EASTWARD...AND A CLEAR FRIDAY NIGHT IS EXPECTED WITH LIGHT NORTH WINDS. WITH HIGHS FRIDAY AFTN EXPECTED TO BE ONLY IN THE LOW 30S (!!)...MINS FRIDAY NIGHT SHOULD DROP WELL INTO THE 20S...AND MAY APPROACH RECORD LOWS FOR THE DATE. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 400 PM WEDNESDAY...OVERALL THE MID LEVEL PATTERN FOR THE EXTENDED HAS CHANGED LITTLE FROM THIS TIME YESTERDAY. STILL EXPECTING CONSIDERABLE TROUGHING OVER THE EASTERN THIRD OF THE CONUS. THROUGH EARLY TUESDAY WITH A RELAXING OF THE PATTERN THEREAFTER. SOME DETAILS WITH SURFACE FEATURES HAVE CHANGED HOWEVER. ANY POPS WITH A GLANCING SHORTWAVE SYSTEM FOR SATURDAY HAVE BEEN REMOVED. THE SYSTEM EMANATING FROM THE GULF OF MEXICO SHOULD OCCUR SUNDAY AND SOME OF MEDIUM RANGE GUIDANCE IS NOW KEEPING ANY AFFECTS WELL OFFSHORE. A MORE SIGNIFICANT SYSTEM WITH SLIGHTLY BETTER MODEL AGREEMENT DEVELOPS LATE MONDAY AND TUESDAY. I HAVE MAINTAINED THE SLIGHT CHANCE POPS FOR THIS TIME AND THE NEW DAY WEDNESDAY. TEMPERATURE TRENDS REMAIN INTACT AS WELL WITH A DELIBERATE WARMING TREND BASICALLY DUE TO AIRMASS MODIFICATION UNDER A VERY WEAK PRESSURE PATTERN AFTER A COLD START SATURDAY. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... AS OF 00Z...TERMINALS ARE CURRENTLY VFR BUT SEA FOG IS LOOMING FROM JUST EAST OF KCRE TO SE OF KILM. IFR/LIFR/VLIFR IS POSSIBLE AT THE COASTAL TERMINALS THIS EVENING. POTENTIALLY THE LOWEST CONDITIONS THIS EVENING SHOULD BE AT KCRE WITH THE HIGHEST AT KILM/KMYR. KMYR WOULD HAVE THE LEAST CHANCE OF SEA FOG OCCURRENCE. BY 06Z THROUGH THE OVERNIGHT HOURS POTENTIAL FOR IFR/LIFR/VLIFR WILL BE THE HIGHEST AT THE COASTAL TERMINALS. LOW STRATUS CIGS 300-500 FEET WILL BE POSSIBLE AT KFLO/KLBT GENERALLY AFTER 08Z. LOW LEVEL WIND SHEAR IS A GOOD POSSIBILITY WITH 30-40KT WINDS AROUND A 1K FOOT INVERSION. IFR OR LOWER CIGS SHOULD BREAK UP 14-15Z WITH VFR EXPECTED...EXCEPT MVFR AT KLBT. A STRONG COLD FRONT WILL MOVE THROUGH THE TERMINALS DURING THE AFTERNOON WITH POST FRONTAL MVFR CIGS/-RA AT THE COASTAL TERMINALS AND POST FRONTAL IFR/-RA AT THE INLAND TERMINALS. WINDS WILL SHIFT TO THE NORTH WITH GUSTS TO 18-25 KT. EXTENDED OUTLOOK...IFR CONDITIONS ON THURSDAY...AND POSSIBLY INTO FRIDAY ALONG THE COAST. OTHERWISE EXPECT VFR. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 830 PM WEDNESDAY...THIS UPDATE TO BLEND CURRENT WINDS AND SEAS TO THE CURRENT OVERNIGHT FORECAST WHICH STILL LOOKS AOK. TIGHTENED SFC PG AND PATTERN TO YIELD A SSW-SW WIND AT 10 TO 20 KT OVERNIGHT. THERE WILL BE A FEW POSSIBLE GUSTS UP TO 25 KT ACROSS THE LOCALLY WARMER SSTS THAT ARE APPROACHING 60. LATEST 41013 BUOY INDICATES SSTS IN THE MID 60S JUST OUTSIDE THE ILM COASTAL WATERS. THUS THE HIER WINDS ALOFT ARE ABLE TO MIX DOWN TO THE OCEAN SFC. HOWEVER...THE MAJORITYY OF THE LOCAL WATERS ARE IN THE 40S AND THUS THE WINDS WILL BE PRIMARILY DRIVEN BY THE TIGHTENED SFC PG. SIGNIFICANT SEAS WILL RANGE BETWEEN 3 AND 5 FT. THE PSEUDO 5 TO 7 SECOND PERIOD GROUND SWELL WILL DOMINATE THE SEAS SPECTRUM BUT AS WINDS FURTHER INCREASE...THE WIND DRIVEN WAVES WILL LIKELY BECOME THE MORE DOMINANT. SEA FOG WILL PLAGUE THE LOCAL WATERS OVERNIGHT...MAINLY OCCURRING OVER LOCAL SSTS THAT ARE IN THE 40S. THE DENSE FOG ADV WILL CONTINUE INTO THU. PREVIOUS DISCUSSION........................................ AS OF 400 PM WEDNESDAY...NOT A JOY RIDE TONIGHT WITH AREAS OF DENSE MARINE FOG AND 10-20 KT SW WINDS...BUT NO ADVISORIES ARE NEEDED. HIGHEST WINDS OFFSHORE...AND SEAS 3-4 INSHORE AND 4 TO 5 FT OUTER PORTION. SOME FRESH SWELL ENERGY IS KEEPING SEAS SLIGHTLY ELEVATED FOR CORRESPONDING WINDS. SEA SPECTRUM A MIX OF SSW WAVES 2-4 FT EVERY 4-5 SECONDS AND ESE WAVES 1-2 FEET EVERY 9-10 SECONDS. NO TSTMS BUT VSBYS AT TIMES LESS THAN 1/4 NM. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 400 PM WEDNESDAY...HIGH PRESSURE OFFSHORE AND A COLD FRONT APPROACHING FROM THE WEST WILL KEEP A PINCHED GRADIENT WITH GUSTY SW WINDS THE FIRST PART OF THURSDAY. WIND SPEEDS OF AROUND 15 KTS ARE EXPECTED TO CONTINUE INTO THURSDAY AFTN BEFORE VEERING MORE TO THE W/SW IN THE EVE. THIS WILL KEEP SEAS 3-5 FT...BUT WILL ALSO CONTINUE THE POTENTIAL FOR AREA OF DENSE MARINE FOG AS THE WARM MOIST AIR ADVECTS ACROSS STILL VERY COLD SHELF WATERS. HAVE OPTED NOT TO EXTEND THE MARINE DFA ATTM...BUT A LOCAL EXTENSION INTO THURSDAY AFTN MAY BE REQUIRED TONIGHT. COLD FRONT APPROACHES AND THEN CROSSES THE WATERS FROM NORTH TO SOUTH THURSDAY NIGHT. THIS IS A POWERFUL FRONT...AND WILL BE ACCOMPANIED BY AN ABRUPT WIND SHIFT TO THE NORTH AND A QUICK RISE IN SPEEDS TO 20-30 KTS FRIDAY MORNING. A GALE WATCH HAS BEEN ISSUED BEGINNING AT 11PM THURSDAY NIGHT FOR FREQUENT GUSTS ABOVE GALE FORCE DURING THIS TIME PERIOD...AND LASTING INTO LATE FRIDAY MORNING. HIGH PRESSURE WILL BUILD EAST DURING FRIDAY AND FRIDAY NIGHT...MAINTAINING THE NORTH WINDS BUT WITH SLOWLY DECREASING SPEEDS. SEAS...WHICH WILL RISE TO AS HIGH 5-9 FT OVERNIGHT THURSDAY INTO FRIDAY...WILL FALL THROUGH FRIDAY...BECOMING 2-4 FT AT THE END OF THE PERIOD. LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 400 PM WEDNESDAY...SOME RESIDUAL STRONGER WINDS CONTINUE ACROSS THE WATERS EARLY SATURDAY WITH A NORTHERLY FLOW OF 10-15 KNOTS. AFTER THIS A VERY WEAK AND PROLONGED PRESSURE PATTERN DEVELOPS UNDER A RELAXING MID LEVEL PATTERN. DIFFICULT TO EVEN PINPOINT A PREDOMINANT WIND DIRECTION BUT NORTHEAST BACKING TO WESTERLY SEEMS LIKE IT WILL WORK. SPEEDS WILL BE TEN KNOTS OR LESS AND PROBABLY MUCH LESS IN SOME CASES. SEAS WILL BE 2-4 FEET FOR A FEW HOURS SATURDAY THEN SUBSIDE TO 1-2 FEET SUNDAY AND MONDAY. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...DENSE FOG ADVISORY UNTIL 6 AM EST THURSDAY FOR SCZ054-056. NC...DENSE FOG ADVISORY UNTIL 6 AM EST THURSDAY FOR NCZ106-108-110. MARINE...DENSE FOG ADVISORY UNTIL 6 AM EST THURSDAY FOR AMZ250-252-254- 256. GALE WATCH FROM THURSDAY EVENING THROUGH FRIDAY MORNING FOR AMZ250-252-254-256. && $$ SYNOPSIS...SHK NEAR TERM...DCH/MJC SHORT TERM...JDW LONG TERM...SHK AVIATION...MRR

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