Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 050832 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 332 AM EST THU MAR 5 2015 .SYNOPSIS... A POWERFUL COLD FRONT WILL BRING SHARPLY COLDER TEMPERATURES BEGINNING THIS EVENING. THERE IS A CHANCE OF SOME LIGHT FROZEN PRECIPITATION FRIDAY MORNING. THE WEEKEND WILL FEATURE SLOWLY MODERATING TEMPERATURES. THE SLOW WARMUP WILL CONTINUE NEXT WEEK WITH SHOWERS POSSIBLE. && .NEAR TERM /THROUGH TONIGHT/... AS OF 3 AM THURSDAY...LOTS OF INTERESTING WEATHER OVER THE NEXT 24 HOURS. IT BEGINS WITH MOIST SOUTHWEST WINDS PRODUCING SEA FOG ACROSS THE COASTAL WATERS AND ADJACENT LAND AREAS. ASOS/AWOS OBS AT KCRE AND KSUT HAVE SHOWN LOW VSBYS ALL MORNING...AND THIS SHOULD CONTINUE THROUGH ABOUT NOON. AS WE SAW YESTERDAY...THIS SAME AIRMASS ALSO HAPPENS TO BE EXCEPTIONALLY WARM. EVEN THOUGH MID-LEVEL CLOUDS WILL BE INCREASING ALONG THE I-95 CORRIDOR THIS MORNING AND SPREADING DOWN TO THE COAST THIS AFTERNOON THERE SHOULD STILL BE ENOUGH SUNSHINE TO PUSH TEMPS INTO THE UPPER 70S TO AROUND 80 DEGREES EAST OF I-95. ALONG THE SOUTH- OR SOUTHEAST-FACING BEACHES...COOL ONSHORE WINDS WILL KEEP TEMPERATURES ~10 DEGREES COOLER. A POWERFUL COLD FRONT STILL SHARPENING UP THROUGH THE SOUTHERN APPALACHIANS AND ACROSS SOUTHERN VIRGINIA WILL SAG SOUTHWARD INTO THE AREA THIS AFTERNOON. MODEL TRENDS OVER THE PAST FEW DAYS HAVE BEEN FOR A SLOWER ARRIVAL OF THIS FRONT...AND IT NOW APPEARS THE FRONT SHOULD ARRIVE IN BENNETTSVILLE-LUMBERTON-ELIZABETHTOWN AROUND 2 PM...FLORENCE-MARION-SOUTHPORT AND WILMINGTON BETWEEN 3-4 PM...AND SOUTHWARD ACROSS MYRTLE BEACH-GEORGETOWN-KINGSTREE BETWEEN 4-5 PM. THE TEMPERATURE DROP BEHIND THIS FRONT WILL BE PHENOMENAL: UPWARDS OF 12-15 DEGREES IN THE FIRST HOUR AFTER FROPA WITH A 30-35 DEGREE DROP OVER A 6 HOUR PERIOD GOING INTO THIS EVENING. BEHIND THE SURFACE FRONT LIGHT TO OCCASIONALLY MODERATE RAIN SHOULD DEVELOP AND LAST INTO THE EVENING HOURS. THIS RAIN WILL BE DUE TO ISENTROPIC LIFT ALONG THE 300K SURFACE WHICH SHOULD HAVE A FAIR AMOUNT OF SLOPE OVER THE INCREASINGLY COLD AIR NOSING SOUTHWARD INTO THE AREA. MOISTURE ON THIS ISENTROPIC SURFACE CLEARS OUT BY MIDNIGHT WITH A SUBSTANTIAL REDUCTION IN PRECIPITATION EXPECTED BY THIS TIME. AFTER MIDNIGHT...SHALLOWER MOISTURE WILL REMAIN OVER THE AREA AS THE ATMOSPHERE DRIES FROM THE TOP DOWN. BY 3 AM FRIDAY MORNING FORECAST ISENTROPIC MOTION IS DOWNWARD THROUGHOUT THE ENTIRE MOIST LAYER... WHICH USUALLY SPELLS THE END OF PRECIPITATION. HOWEVER AN IMPRESSIVE 300 MB JET STREAK OFF THE MID-ATLANTIC COAST WILL REMAIN FAVORABLY ORIENTED TO SQUEEZE EVERY LITTLE BIT OF MOISTURE OUT OF THE REMAINING CLOUD DECK. THE 00Z NAM IS QUITE A BIT MORE MOIST THAN THE 00Z GFS...AND 00Z SREF MEMBERS SHOW 30-50 PERCENT CHANCES FOR LINGERING LIGHT PRECIPITATION AS SURFACE TEMPERATURES PLUNGE TO NEAR FREEZING. FORECAST SOUNDINGS AT 09Z-12Z FRI REVEAL A HEALTHY SLUG OF COLD AIR BELOW 3000 FEET AGL WHICH SHOULD BE SUFFICIENT TO FREEZE FALLING HYDROMETERS INTO SLEET PELLETS. ANYTHING FALLING DURING THAT TIME SHOULD TAKE THE FORM OF SLEET...OR PERHAPS RAIN WHERE LOW-LEVEL TEMPERATURES ARE WARM ENOUGH TO REMELT PRECIPITATION. FORECAST QPF AFTER 06Z IS QUITE LOW (.02" OR LESS) AND WITH VERY WARM GROUND TEMPERATURES OVER THE PAST 48 HOURS IT APPEARS THIS SHOULD BE NOT BE A SIGNIFICANT WINTER WEATHER EVENT. && .SHORT TERM /FRIDAY THROUGH SATURDAY 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 /SUNDAY 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 /09Z THURSDAY THROUGH MONDAY/... AS OF 06Z...SEA FOG HAS PUSHED INTO KCRE AND IS LOOMING JUST EAST OF KMYR. THROUGH SUNRISE CONFIDENCE IS MODERATE TO HIGH SUB-IFR CONDITIONS WILL OCCUR AT THE COASTAL AIRPORTS. HIGHEST CONFIDENCE IS AT KCRE AND KILM (MAINLY CEILINGS AT KILM) WITH LESSER CONFIDENCE AT KMYR. LOW STRATUS CIGS 500-1000 FEET WILL BE POSSIBLE AT KFLO/KLBT GENERALLY AFTER 11Z. LOW LEVEL WIND SHEAR IS A GOOD POSSIBILITY WITH 30-35KT WINDS AROUND A 1K FOOT INVERSION. IFR OR LOWER CIGS SHOULD BREAK UP 14-15Z WITH GENERALLY VFR EXPECTED. 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 T0 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 3 AM THURSDAY...STEADY SOUTHWEST WINDS CONTINUE TO BRING SUBTROPICAL MOISTURE NORTH ACROSS THE AREA. WHERE THIS MOISTURE ENCOUNTERS THE VERY CHILLY OCEAN WATER WE HAVE A LONG-LIVED DENSE SEA FOG EVENT ONGOING. AIRPORT WEATHER OBSERVATIONS FROM NORTH MYRTLE BEACH & SOUTHPORT CONFIRM THE FOG IS STILL VERY DENSE. VERY LITTLE SHOULD CHANGE IN THE SYNOPTIC WIND SETUP THIS MORNING INTO THE EARLY AFTERNOON...UNTIL A POWERFUL COLD FRONT NOW TAKING SHAPE ACROSS SOUTHERN VIRGINIA SINKS SOUTHWARD INTO THE AREA. THIS FRONT WILL BRING AN INSTANTANEOUS SHIFT TO NORTH WINDS DURING THE MID TO LATE AFTERNOON HOURS...WITH WIND SPEEDS INCREASING TO 25-30 KNOTS TONIGHT. GUSTS TO GALE FORCE SHOULD OCCUR DURING THE PERIOD OF STRONGEST COLD AIR ADVECTION LATE THIS EVENING AND OVERNIGHT...AND WE HAVE TURNED THE GALE WATCH INTO A GALE WARNING BEGINNING AT 9 PM THIS EVENING. SEAS CURRENTLY 3-5 FEET ARE NEARLY STEADY-STATE WITH THE SOUTHWEST WINDS...BUT SHOULD INCREASE TO 6-9 FEET OVERNIGHT...HIGHEST EAST OF CAPE FEAR AND EAST OF WINYAH BAY WHERE NORTH WINDS WILL HAVE THE LONGEST EFFECTIVE FETCH TO WORK WITH. 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 10 AM EST THIS MORNING FOR SCZ054. NC...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR NCZ108-110. MARINE...DENSE FOG ADVISORY UNTIL NOON EST TODAY FOR AMZ250-252-254-256. GALE WARNING FROM 9 PM THIS EVENING TO 10 AM EST FRIDAY FOR AMZ250-252-254-256. && $$ NEAR TERM...TRA SHORT TERM... LONG TERM... AVIATION...TRA/MRR

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