Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 300828 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 428 AM EDT THU OCT 30 2014 .SYNOPSIS... SEASONABLE WEATHER WILL RETURN TODAY WHILE FRIDAY TURNS A BIT COOLER. SATURDAY WILL TURN ABRUPTLY COLDER WITH SOME LIGHT RAIN AND A WINTER-LIKE CHILL IN THE AFTERNOON BREEZE. SUNDAY WILL BE ALMOST AS COLD BUT NOT AS WINDY AND BOTH NIGHTS OF THE WEEKEND WILL BRING LOWS IN THE 30S, SUNDAY NIGHT THE COLDER OF THE TWO. MONDAY AND TUESDAY BRING A GRADUAL WARMUP THAT BECOMES MORE PRONOUNCED WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 345 AM THURSDAY...HAVE BEEN FOLLOWING THE PROGRESSION OF THE SFC COLD FRONT ACROSS THE ILM CWA USING KLTX SRM/V PRODUCTS AT THE 0.5 DEGREE SLICE. AT THIS POINT IN TIME...THE COLD FRONT HAS PUSHED OFF THE COAST FROM THE ILM NC COUNTIES...AND EXTENDS FROM MYRTLE BEACH SW TO TRIO OF WILLIAMSBURG COUNTY. CONTINUED SSE PROGRESSION OF THIS FRONT WILL TAKE IT OFF THE ILM SC COAST AND LIKELY REACHING THE OFFSHORE WATERS OFF BOTH THE NC AND SC COASTS BY DAYBREAK THU. THE SFC COLD FRONT WILL BECOME ORIENTED WITH THE FLOW ALOFT...FROM SW TO NE...TO A POSITION JUST OFFSHORE FROM THE CAROLINA COASTS BEFORE STALLING LATER TODAY. MORE PCPN THEN EXPECTED IMMEDIATELY BEHIND THE COLD FRONT WITH SOME OF THESE CELLS EXHIBITING LIGHTNING. POPS WILL BE ADJUSTED WITH THE LAST OF THE PCPN OFF THE COAST BEFORE NOON TODAY. THE NEXT PROBLEM DEALS WITH THE EXTENT OF THE POST FRONTAL CLOUDINESS AS BOTH THE NAM AND GFS MODEL TIME HEIGHT DISPLAYS ACROSS THE FA QUITE DIFFERENT. THE NAM LOOKS OVERDONE WITH THE MOISTURE FOR BOTH CLOUDS AND PCPN CHANCES AND THUS WILL LEAN TOWARD THE DRIER GFS. DID KEEP CLOUDY SKIES WELL INTO THE AFTN ACROSS THE COASTAL COUNTIES BUT CONTINUED THE PARTIAL CLEARING TREND INLAND. FOR TONIGHT...MAINLY CLEAR WITH PARTLY CLOUDY ALONG THE IMMEDIATE COAST. DRY CONDITIONS TO PREVAIL WITH POPS REMAINING OFF THE COAST AS MODELS INDICATE A WEAK SFC LOW MOVING ALONG THE STALLED FRONT. FOR MAX/MIN TEMPS...BASICALLY DID A BLEND OF THE NAM/GFS MODEL MOS GUIDANCE WITH THE THINKING IS THE NAM BEING TOO LOW AND THE GFS RUNNING A BIT HIGH.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 3 AM THURSDAY...FRIDAY WILL BE RATHER NONDESCRIPT ESPECIALLY WHEN COMPARED TO THE PERIOD SOON THEREAFTER. DEEP EASTERN U.S. TROUGHINESS AND A COLD FRONT AND FLAT WAVE OF LOW PRESSURE WELL OFFSHORE WILL YIELD A GRADUAL INCREASE IN CLOUDINESS WHILE THE AFTERNOON REMAINS ON THE COOL SIDE OF CLIMATOLOGY. MEANWHILE A VERY ENERGETIC SYSTEM WILL BE DIGGING INTO THE WESTERN GREAT LAKES...TO THE TUNE OF A 36S-1 VORT MAX JUST EAST OF A NORTHERN JET OF 80KT AT 500MB AND 120KT AT 250MB. WITH SUCH ENERGY ALOFT IT FOLLOWS THAT SOME DOWNRIGHT COLD AIR WILL BE BEING DRAWN SOUTH OUT OF CANADA. THE COLD BLAST IS SLATED FOR A SATURDAY ARRIVAL. THIS MEGA-VORT IS NOT YET BEING SAMPLED BY THE DENSE UPPER AIR OF THE U.S. SO THERE IS A LITTLE UNCERTAINTY AS TO HOW IT WILL MOVE THROUGH AND WHAT SURFACE REFLECTION WILL RESULT. THIS MAINLY BEING RELEVANT SINCE THE CURRENTLY DISCOUNTED WRF BRINGS IN A PREFRONTAL WARM SECTOR ALONG THE IMMEDIATE CAPE FEAR COAST. BARRING THAT THE FORECAST IS MORE SLANTED TOWARDS GFS/EC/PREV FCST. SATURDAY MORNING FINDS AN APPROXIMATE 5 SIGMA 500MB TROUGH IN THE EAST WITH THE AMAZING 536 DAM CUTOFF RIGHT OVER ILM BY 18Z...THE FINE FOLKS AT WPC DESCRIBING AS A NEARLY 50 YEAR EVENT. LIGHT TO MODERATE RAIN SHOULD BREAK OUT WITH SOUTHERN ZONES OPERATING OFF OF PURE DYNAMICS WHILE NORTHERN ZONES WILL BENEFIT FROM FURTHER FORCING FROM LOW LEVEL WARM ADVECTION...FROM THE NORTHEAST! THIS SYSTEM IS SO STRONG AND COLD ALOFT THAT THE POSSIBILITY OF GRAUPEL WAS DISCUSSED WITH NEIGHBORING WFO. ITS A FAST MOVING SYSTEM THOUGH SO THE CHILLY AND RAW AFTERNOON WILL BE MORE NOTEWORTHY THAN THE RAINFALL AMOUNTS IN ANY GIVEN LOCATION. AS THE AFTERNOON WEARS ON AND THE DEPARTING/DEEPENING SURFACE LOW ACCELERATES OFF TO THE NORTHEAST A STRONG GRADIENT OF WELL-ALIGNED NORTHWESTERLY FLOW SHOULD REALLY GET THE WINDS QUITE GUSTY. THE COLD ADVECTION EASES SATURDAY NIGHT BUT NOT BEFORE THE AIRMASS IS COLD ENOUGH TO SUPPORT LOW TEMPS IN THE UPPER 30S. THE WIND STAYS UP WITH THE GRADIENT PRECLUDING RAD COOLING BUT FOR THE SAME REASON SUCH CHILL SHOULD MAKE ITS WAY RIGHT UP TO THE BEACHES. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 3 AM THURSDAY...SUNDAY IS THE POST COLD ADVECTION DAY WHEREIN LARGE HIGH PRESSURE BUILDS IN. ALTHOUGH THE COLD ADVECTION HAS ALREADY TYPICALLY REVERSED BY THIS TIME THE MIXING IS SHALLOWER AND TEMPERATURE DEVIATIONS FROM CLIMO ARE ALMOST AS LARGE AS THE PRIOR DAY BUT NOT QUITE. ALL OF THIS SHOULD APPLY ON SUNDAY. SIMILARLY THE STAGE WILL BE SET FOR RAD COOLING...AS THE COLDEST NIGHT OF AN OUTBREAK IS USUALLY THE SECOND NIGHT. THERE APPEARS TO BE A LINGERING FEW MPH OF NE WINDS THAT MAY SPARE INLAND ZONES FREEZING TEMPS WHEREAS WEAK OCEAN INFLUENCE SHOULD FAVOR UPPER 30S COAST. THE CENTER OF THE HIGH IS HESITANT TO GET EAST OF THE REGION ON TUESDAY PRECLUDING BONA FIDE RETURN FLOW AND SO THE CLIMO TEMPS SEEN IN MOS BULLETINS SEEM TOO OPTIMISTIC...AND HAVE BEEN UNDERCUT BY JUST A FEW DEGREES. THE ACTUAL RETURN FLOW SHOULD GET UNDERWAY TUESDAY NIGHT INTO WEDNESDAY. WILL ADD SOME LOW POPS IN THE RETURN FLOW BUT MOST OF THE MOISTENING MAY STILL BE DEDICATED TO PW RECOVERY FROM THE COLD AIRMASS AS OPPOSED TO ACTUAL RAINFALL. && .AVIATION /08Z THURSDAY THROUGH MONDAY/... AS OF 07Z...POTENTIAL FOR MVFR/IFR DUE TO LOW CIGS ALONG WITH SCATTERED SHOWERS THROUGH THE PRE-DAWN THU HOURS ALONG WITH THE PASSING OF A COLD FRONT. OTHERWISE EXPECT VFR. EXPECT SCATTERED VFR POSSIBLY MVFR VSBY FROM -SHRA ALONG AND JUST AFTER FROPA. OTHERWISE...CLOUD COVER ALONG AND LONG AFTER THE PASSAGE OF THE COLD FRONT WILL BE THE PROBLEM CHILD WELL INTO THE DAYTIME THU HRS. BROKEN VFR CEILINGS DURING THE DAY WILL RUN AOA 4K FT...WITH SOME DRYING OVER THE INLAND TERMINALS RESULTING IN THESE CEILINGS BECOMING SCATTERED. VFR WILL CONTINUE INTO TONIGHT WITH NE WINDS DROPPING TO AOB 6 KTS. EXTENDED OUTLOOK...VFR ON FRIDAY. A CHANCE OF MVFR POSSIBLY IFR PCPN SATURDAY WITH BREEZY TO WINDY CONDITIONS BOTH SATURDAY INTO SUNDAY. VFR ON MONDAY. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 400 AM THURSDAY...COLD FRONTAL PASSAGE TO PUSH SSE ACROSS THE COASTAL WATERS EARLY THIS MORNING...AND OFFSHORE AROUND DAYBREAK. WINDS WILL VEER TO THE N AND NE AFTER THE CFP AND INCREASE TO AROUND 15 KT...WITH GUSTS UP TO 20 KT POSSIBLE. THE COLD FRONT WILL STALL OFFSHORE...BECOMING ORIENTED NE-SW. WEAK SFC LOW IS PROGGED TO MOVE NE ALONG THIS FRONT AND WILL THUS KEEP A SEMI-TIGHTENED SFC PG ACROSS THE AREA WATERS. THEREFORE...WILL KEEP NNE TO NE WINDS AT 10 TO AROUND 15 KT...WITH AN OCCASIONAL GUSTS UP TO 20 KT FOR THE ILM NC WATERS WHICH WILL BE CLOSER TO THIS SFC LOW. SIGNIFICANT SEAS WILL RUN 2 TO 4 FT AND BE COMPRISED INITIALLY OF SW WIND DRIVEN WAVES BECOMING N-NE WIND DRIVEN. A MORE SOLID 3 TO 4 FT WILL EXIST OVER THE ILM NC WATERS...FROM CAPE FEAR NORTHWARD. DOMINANT PERIODS WILL RUN 3 TO 6 SECONDS. POST FRONTAL PCPN WILL PUSH OFFSHORE THIS AFTERNOON. PCPN ASSOCIATED WITH THE WEAK LOW LATER TONIGHT...SHOULD REMAIN JUST OFFSHORE. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 3 AM THURSDAY...COLD FRONT STALLED FAIRLY FAR OFF THE COAST ON FRIDAY WITH A FLAT/ELONGATED WAVE OF LOW PRESSURE RUNNING MUCH OF ITS LENGTH OFF THE SOUTHEAST COAST. THIS WAVE WILL HELP TO BOOST THE GRADIENT AND THE RESULTING NE WINDS AND SEAS WILL RUN CLOSE TO CAUTIONARY THRESHOLDS. AS THIS LOW CONGEALS INTO A MORE CIRCULAR SYSTEM AND PULLS AWAY TO THE NE LOCAL FLOW WILL BACK TO NORTHWESTERLY. THERE MAY EVEN BE A BRIEF LULL AS THE NEXT LOW AND COLD FRONT APPROACH FROM THE NW. THIS SYSTEM WILL DEFINE THE PERIOD HOWEVER. THE STRENGTH OF THE SYSTEM ALOFT WILL BE EXCEPTIONAL AND A BLAST OF COLD AIR AND SURGE IN GRADIENT WILL GET UNDERWAY IMMEDIATELY ON SATURDAY AND STRENGTHEN THROUGH THE AFTERNOON. THERE ARE SOME UNCERTAINTIES YET AS THE MAIN UPPER LEVEL DISTURBANCE IS NOT BEING SAMPLED BY THE CONUS UPPER AIR BALLOONS. THIS WILL CHANGE HEADING INTO FRIDAY AND IT WILL BECOME MORE CLEAR AS TO WHETHER OR NOT A GALE WATCH WILL BE NEEDED. GALE FORCE GUSTS ARE CERTAINLY EXPECTED GIVEN THE STRENGTH OF THE LOW LEVEL FLOW AND STRONG MIXING OF THE COLD AIR FLOWING OVER THE WARMER SSTS. STILL ENOUGH UNCERTAINTY ABOUT SUSTAINED WINDS FOR A GALE WATCH AT THIS TIME...WHICH WOULD BE A BIT LONGER FUSED THAN NORMAL ANYWAY. LONG TERM /SUNDAY THROUGH MONDAY/... AS OF 3 AM THURSDAY...THE GRADIENT WILL STILL BE QUITE STRONG EARLY SUNDAY ESPECIALLY OVER NORTHERN ZONES. HOWEVER THERE WILL BE A MARKED ABATING TREND AS THE DAY WEARS ON DUE TO THE RAPID NORTHEASTERLY MOVEMENT OF THE STILL DEEPENING LOW THAT AFFECTED US DIRECTLY DURING THE SHORT TERM. IN FACT AS IT APPEARS NOW THERE MAY BE NO HEADLINES NEEDED BY MIDDAY OR SO. FOR MUCH OF MONDAY HIGH PRESSURE WILL ELONGATE UP AND DOWN THE CAROLINAS WITH A LATE DAY SHIFT TOWARDS THE COASTLINE. N WINDS WILL VEER TO THE NE AND GROW LIGHTER.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...MBB NEAR TERM...DCH SHORT TERM...MBB LONG TERM...MBB AVIATION...DCH

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