Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 221809 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 209 PM EDT WED MAY 22 2013 .SYNOPSIS... BERMUDA HIGH PRESSURE WILL DOMINATE THE WEATHER ACROSS THE EASTERN CAROLINAS THROUGH THURSDAY. SHOWERS AND THUNDERSTORMS WILL INCREASE THURSDAY AND THURSDAY NIGHT AHEAD OF AN APPROACHING COLD FRONT. THE FRONT WILL CROSS THE REGION FRIDAY MORNING. A MUCH COOLER AND DRIER AIRMASS WILL FOLLOW...COMPLEMENTS OF A CANADIAN HIGH PRESSURE...AND AFFECT THE AREA THIS WEEKEND. THE HIGH WILL SLIDE OFF THE EAST COAST EARLY NEXT WEEK WITH TEMPERATURES REBOUNDING TO NEAR NORMAL...ALONG WITH AN INCREASE IN AFTERNOON SHOWERS AND THUNDERSTORMS. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1:45 PM WEDNESDAY...A BAND OF LIGHT TO MODERATE SHOWER ACTIVITY WITH THE ISOLATED RUMBLE OF THUNDER IS MOVING RAPIDLY INLAND ALONG THE SEA BREEZE FRONT THIS AFTERNOON. CONVECTIVE BAND NOW APPROACHING THE I-95 CORRIDOR WITH WHICH IT IS ALIGNED WITH. SOME LIGHT SHOWERS ARE MOVING IN OFF THE OCEAN SOUTH OF CAPE FEAR. OTHERWISE...THE COASTAL COUNTIES WILL BE ON THE DRY SIDE FOR THE REMAINDER OF THE AFTERNOON. FOR TONIGHT GUIDANCE IS STILL IN GOOD AGREEMENT ON REDEVELOPMENT OF CONVECTION...ESPECIALLY ALONG THE COAST IN THE VICINITY OF THE CAPE FEAR REGION...AS AN UPPER IMPULSE LIFTS AN AREA OF SHOWERS AND THUNDERSTORMS ASHORE FROM OVER THE WESTERN ATLANTIC. HAVE GONE WITH SCATTERED CONVECTION TONIGHT FOR MUCH OF THE FORECAST AREA. EXTENSIVE CLOUD COVER AND CONTINUED WARM...MOIST SOUTHERLY FLOW WILL KEEP MINIMUM TEMPERATURES ABOVE NORMAL...IN THE MID 60S MOST PLACES AND THE UPPER 60S AT THE COAST.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 300 AM WEDNESDAY...THIS PERIOD WILL BE HIGHLIGHTED BY THE EVOLUTION OF A RATHER DEEP MID-LEVEL TROF THAT WILL DOMINATE THE WEATHER ACROSS THE FA BY THE END OF THIS PERIOD. AT THE BEGINNING OF THE SHORT TERM...THE AMPLIFYING UPPER TROF IS PROGGED TO BE JUST EAST OF THE MISSISSIPPI RIVER...AND BY LATE FRIDAY NIGHT ITS NORTH TO SOUTH TROF AXIS WILL HAVE MOVED JUST OFF THE NORTH AND SOUTH CAROLINA COASTS...VIA NAM AND GFS MODELS. MODELS AT TIMES HAVE TRIED TO MAKE THIS AN AMPLIFIED FULL LATITUDE TROF BUT INDIVIDUAL VORTS/IMPULSES ROTATING THROUGH THIS UPPER FEATURE...ARE PROGGED TO MOVE AT DIFFERENT SPEEDS AND THUS PREVENTING THE CARVING OF A TRUE FULL LATITUDE TROF. ONE OF THE STRONGER VORTS IS PROGGED TO TRACK ACROSS THE FA FRIDAY AFTERNOON/EVENING AS DYNAMICS FROM THIS FEATURE AND COLDER TEMPS ALOFT PROVIDE ENOUGH INSTABILITY FOR ISOLATED CONVECTION. AT THE SURFACE...WESTERN ATLANTIC RIDGING WILL CONTINUE ACROSS THE FA EARLY THURSDAY. A PRE-FRONTAL OR LEE SIDE TROF ORIENTED N-S WILL DEVELOP ACROSS THE WEST-CENTRAL CAROLINAS AND BECOME THE FOCUS FOR CONVECTION DEVELOPMENT AS IT SLOWLY PROGRESSES EASTWARD. IN ADDITION MID-DAY/AFTERNOON DIURNALLY INDUCED CONVECTION WILL BREAK OUT ACROSS THE COASTAL PORTIONS OF THE ILM CWA. WILL INDICATE 50 POPS INLAND...WITH 30-40 CLOSER TO THE COAST DURING THE DAY THURSDAY. FOR THURSDAY NIGHT...THE APPROACHING COLD FRONT WILL BECOME THE PRIMARY FORCE FOR INDUCING CONVECTION. HOWEVER...THE SUB-TROPICAL/TROPICAL MOISTURE FEED WILL HAVE BEEN PUSHED OFFSHORE AND NO LONGER THE PRIMARY SOURCE. THINKING IS THAT ENOUGH MOISTURE WILL REMAIN FOR ADDITIONAL CONVECTION TO FIRE AHEAD OF THE COLD FRONT...DEPENDING HOW MUCH THE ATM IS ABLE TO DE-STABILIZE FROM THE CONVECTION THAT DEVELOPED EARLIER IN THE DAY. AS A RESULT...WILL HIGHLIGHT 40-50 POPS IN THE EVENING AND SLOWLY DROP THEM TO SLIGHT CHANCE OVERNIGHT. MODELS AFTER MIDNIGHT FRIDAY...DIVERGE FROM ONE ANOTHER WITH RESPECT TO THEIR SOLUTIONS RELATED TO THE TIMING AND PLACEMENT OF THE COLD FRONT. FOR EXAMPLE THE NAM AND CANADIAN HAVE THE FRONT OFF THE CAROLINA COASTS BY DAYBREAK FRI...WHEREAS THE GFS LAGS BEHIND AND ONLY HAS IT PROGRESSING THROUGH THE COASTAL CAROLINAS BY DAYBREAK FRI. WILL LEAN TOWARD THE SLIGHTLY SLOWER PROGRESSION OF THE CFP. POST FRONTAL DRIER AIR FINALLY ADVECTS ACROSS THE FA DURING THE DAY FRI. CANADIAN HIGH PRESSURE WILL FINALLY PROVIDE RELIEF FROM THE HUMID SUBTROPICAL/TROPICAL AIR MASS THAT AFFECTED THE FA FOR MUCH OF THIS WEEK. AS FOR MAX/MIN TEMPS...A RANGE OF 80 TO 85 FOR HIGHS THU...SIMILAR TO WHAT THE NAM/GFS MOS GUIDANCE SHOWS. THE COLD AIR ADVECTION BEHIND THE CFP WILL LAG BEHIND...AND BE OFFSET BY A DOWNSLOPE TRAJECTORY IN THE WIND FIELDS. AS A RESULT...HAVE GONE ABOVE GUIDANCE FOR FRIDAYS HIGHS WITH THE COASTAL COUNTIES LIKELY TO BE WARMER THAN INLAND. A COMPROMISED MOS GUIDANCE MIN FORECAST WAS USED. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 300 AM WEDNESDAY...FOR SATURDAY THRU MONDAY MID LEVEL FEATURES REMAIN RELATIVELY UNCHANGED WITH THE TROF AXIS ASSOCIATED WITH THE UPPER TROF HAVING ONLY PROGRESSED JUST OFF THE EAST COAST. THE CENTRAL U.S. WILL BE HIGHLIGHTED BY AN UPPER RIDGE WITH ITS AXIS RUNNING N-S ALONG THE MISSISSIPPI RIVER. BY TUESDAY...THE EUROPEAN FLATTENS THIS RIDGE WHEREAS THE GFS PROGRESSES IT EASTWARD AND MAINTAINING ITS IDENTITY. PREFERRED THE GFS SOLUTION AT THIS POINT. AT THE SFC...CANADIAN HIGH PRESSURE TO RIDGE ACROSS THE FA SATURDAY. ITS CENTER IS PROGGED TO BREAK APART BY SUNDAY...WITH THE SOUTHERN EXTENT OF ITS CENTER MOVING ACROSS AND OFFSHORE FROM THE CAROLINAS MONDAY AND TUESDAY. SUBSIDENCE ALOFT WILL KEEP A LID ON THE DIURNALLY DRIVEN CU FROM DEVELOPING IN THE VERTICAL. THEREFORE NO POPS THROUGH SUNDAY. FOR LATE SUNDAY NIGHT THRU TUESDAY...MODELS ARE HINTING AT A BACK-DOOR COLD FRONT DROPPING SOUTHWARD...AND BECOMING STATIONARY JUST NORTH OF THE FA. THIS MAY BECOME AN AID TO POSSIBLE MCS/MCC THAT DEVELOP WELL UPSTREAM MON AND TUE...WHICH WILL FOLLOW THE NW-SE UPPER FLOW. TOO FAR OUT IN TIME TO PREDICT THEIR TIMING...HOWEVER ENOUGH OF A POSSIBILITY TO PLACE A LOW CHANCE POP IN THE GOING FORECAST. FOR THIS UPCOMING MEMORIAL DAY WEEKEND...SATURDAY THROUGH MONDAY MORNING TEMPS ACROSS THE FA WILL RUN 5 TO 10 DEGREES BELOW NORMAL...ESPECIALLY WITH OVERNIGHT LOWS. FOR MONDAY THRU TUESDAY...WILL BE LOOKING AT NEAR NORMAL TEMPS. IF THE BACK-DOOR COLD FRONT DROPS FURTHER SOUTH THAN ANTICIPATED...THE NW FLOW AHEAD OF IT COULD PUSH TEMPS WELL INTO THE 80S TO AROUND 90...MUCH HIGHER THAN THE CURRENT MOS GUIDANCE. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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AS OF 18Z...MOST OF THE CONVECTION THIS AFTERNOON WILL BE BETWEEN THE INLAND AND COASTAL TERMINALS...HOWEVER THINK FLO WILL SEE SOME ACTION SOMETIME AFTER 18Z. VISIBILITIES COULD BE BRIEFLY IFR IN THE SHOWERS. MOST OF THE ACTIVITY WILL BE DYING DOWN BY EVENING...BUT ANOTHER SLUG OF MOISTURE WILL ADVECT IN FROM THE SOUTH AT THE COASTAL TERMINALS BY MID TO LATE EVENING. EXPECT SHOWERS TO CONTINUE OVERNIGHT WITH CEILINGS LOWERING TO NEAR IFR. INLAND...EXPECT POSSIBLE IFR CONDITIONS AFTER MIDNIGHT WITH ABUNDANT LOW LEVEL MOISTURE. THURSDAY...MORE SHOWERS ARE EXPECTED WITH TROPICAL MOISTURE FLOWING NORTHWARD. EXTENDED OUTLOOK...SHOWERS/T-STORMS POSSIBLE THURSDAY THROUGH EARLY FRIDAY. OTHERWISE VFR.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 1:45 PM WEDNESDAY...THE SEA BREEZE CIRCULATION HAS TURNED WINDS NEAR-SHORE MORE EASTERLY. OTHERWISE...LATEST OBS SHOW LIGHT SE WINDS WITH SEAS IN THE 3 TO 4 FT RANGE. FOR THE REMAINDER OF THIS AFTERNOON AND OVERNIGHT WE WILL SEE LITTLE CHANGE FROM PRESENT CONDITIONS. A STATIONARY BERMUDA HIGH OVER THE WESTERN ATLANTIC WILL KEEP SOUTHERLY WINDS IN THE 10 TO 15 KT RANGE...WITH 2 TO 4 FT SEAS. WINDS WILL BE GUSTY THIS AFTERNOON NEAR SHORE DUE TO THE SEA BREEZE CIRCULATION...WITH GUSTS UP TO AROUND 20 KTS. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 300 AM WEDNESDAY...WESTERN ATLANTIC RIDGING WILL PROVIDE A RATHER SOLID 15 KT SOUTHERLY FLOW DURING THU...BECOMING SW LATE THU AFTERNOON AND NIGHT. THE SFC PG WILL TIGHTEN BETWEEN THE APPROACHING COLD FRONT AND THE WESTERN ATLANTIC HIGH CENTERED WELL OFFSHORE FROM THE SE U.S.COAST. COULD SEE 15 TO 20 KT WITH SOME HIGHER GUSTS. CFP SLATED FOR AFTER DAYBREAK FRI...WITH WINDS VEERING TO W TO NW 10 TO 15 KT...INCREASING TO 15 TO 25 KT FRIDAY NIGHT DUE TO COLD AIR ADVECTION COMBINED WITH A TIGHTENED SFC PG. SIGNIFICANT SEAS WILL RANGE FROM 2 TO 4 FT THU...BUILDING TO 3 TO 5 FT LATE THU THROUGH EARLY FRI. TEMPORARILY DROPPING BACK TO 2 TO 4 FT DURING FRIDAY...THEN BUILDING BACK TO 3 TO 5 FT FRI NIGHT WITH 6 FOOTERS POSSIBLE OUTER WATERS OFF CAPE FEAR. SIG. SEAS WILL PRIMARILY BE DRIVEN BY AN ESE GROUND SWELL AT 8 TO 9 SECOND PERIODS DURING EARLY THU...WITH 4 TO 6 SECOND PERIOD WIND DRIVEN WAVES TO DOMINATE LATE THU THRU FRI NITE. SCEC CONDITIONS POSSIBLE FOR ALL WATERS...WITH A BORDERLINE SCA FOR THE ILM NC WATERS DURING THE INFLUX OF COLD AIR FRI NIGHT. LONG TERM /SATURDAY THROUGH SUNDAY/... AS OF 300 AM WEDNESDAY...POSSIBLE SCEC OR SCA CONDITIONS WILL PEAK DURING EARLY SATURDAY...WITH A DIMINISHING AND SUBSIDING TREND FOR WINDS AND SIGNIFICANT SEAS RESPECTIVELY DURING THE LATTER 2/3RDS OF THIS PERIOD. ALL IN RESPONSE TO THE CENTER OF THE MODERATING CANADIAN HIGH PUSHING ACROSS THE LOCAL WATERS SUNDAY THROUGH SUNDAY NIGHT. WINDS ARE PROGGED TO BECOME VARIABLE IN DIRECTION DURING SUNDAY AND SUNDAY NIGHT AT 10 KT OR LESS. SIGNIFICANT SEAS WILL BE DRIVEN BY LOCALLY PRODUCED SHORT PERIOD WIND DRIVEN WAVES ON SATURDAY...WITH AN 8 TO 9 SECOND PERIOD SMALL EASTERLY SWELL DOMINATING ON SUNDAY.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...DCH NEAR TERM...REK SHORT TERM...DCH LONG TERM...DCH AVIATION...DL MARINE...DCH/REK

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