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000
FXUS62 KILM 221103
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
703 AM 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/...
AS OF 700 AM WEDNESDAY...EARLIER SHOWER ACTIVITY OFFSHORE AND OVER
WILMINGTON DISSIPATED A COUPLE HOURS AGO. THE ATMOSPHERE REMAINS
SUPPORTIVE OF AT LEAST SHALLOW CONVECTION...BUT CERTAINLY WITH LESS
COVERAGE THAN WHAT WAS EXPERIENCED YESTERDAY GIVEN DRIER AIR ALOFT
AND SUBSEQUENT LOWER PRECIPITABLE WATER VALUES. THIS WILL REDUCE
PRECIPITATION EFFICIENCY AND SHOULD LEAD TO LOWER RAINFALL TOTALS
EVEN WHERE IT DOES RAIN. NO SIGNIFICANT CHANGES ARE NEEDED TO THE
FORECAST EARLY THIS MORNING. PREVIOUS DISCUSSION FROM 300 AM
FOLLOWS...

THE WEAK UPPER LEVEL SHEAR AXIS THAT HAS BEEN NEARLY STATIONARY
ACROSS THE EASTERN CAROLINAS FOR THE PAST TWO DAYS HAS DECAYED AS
LIGHT SOUTHERLY FLOW HAS ESTABLISHED ITSELF THROUGHOUT THE 500-700
MB LAYER. ALTHOUGH THE OVERALL AIRMASS REMAINS THE SAME AS
YESTERDAY...TRIGGERS FOR TODAY`S CONVECTION WILL BE SURFACE
BOUNDARIES ONLY. EARLY MORNING CONVECTION MOVING ONSHORE ACROSS OAK
ISLAND THROUGH WILMINGTON IS ASSOCIATED WITH A LOW-LEVEL CONVERGENCE
AXIS WHERE SOUTHWEST WINDS ACROSS THE SC COASTAL WATERS CONVERGE
WITH SOUTH WINDS CLOSER TO THE GULF STREAM. THIS CONVECTIVE ACTIVITY
SHOULD BECOME MORE ISOLATED IN NATURE TOWARD DAYBREAK...BUT THE
REMNANT CONVERGENCE AXIS MAY BECOME ACTIVE AGAIN BY LATE MORNING AS
THE DEVELOPING SEABREEZE CIRCULATION CREATES ADDITIONAL CONVERGENCE
IN THE LOW LEVELS.

BY EARLY AFTERNOON WE SHOULD HAVE A DEVELOPING FIELD OF SCATTERED
SHOWERS ACROSS MOST OF THE AREA EAST OF I-95 AND WEST OF THE
BEACHES. AS THE SEABREEZE MAKES GOOD PROGRESS INLAND THIS AFTERNOON
EXPECT CLEARING CONDITIONS WITHIN 20 MILES OF THE COAST...BUT
SHOWER AND T-STORM CHANCES WILL INCREASE TO 30-40 PERCENT WEST OF
THE SEABREEZE BOUNDARY IN A MODERATELY UNSTABLE AND COMPLETELY
UNCAPPED AIRMASS. 850 MB TEMPS IN THE +15C TO +17C RANGE WILL
SUPPORT TEMPERATURES IN THE MID 80S INLAND TODAY...WITH LOWER 80S
CLOSER TO THE COAST.

SOUTHWESTERLY WINDS WILL INCREASE ABOVE THE SURFACE TONIGHT AS A
MID-LATITUDE STORM SYSTEM SWEEPS EAST INTO THE GREAT LAKES. A WEAK
VORTICITY MAXIMUM LOCATED ACROSS GEORGIA THIS EVENING WILL MOVE
EASTWARD AND SHOULD SUSTAIN ISOLATED TO SCATTERED SHOWER AND T-STORM
POTENTIAL THROUGH THE NIGHT ACROSS THE EASTERN CAROLINAS. WHILE THE
SC PEE DEE REGION WILL BE THE CLOSEST GEOGRAPHICALLY TO THE INCOMING
VORT ALOFT...PRECIP CHANCES MAY ACTUALLY BECOME GREATEST IN THE
WILMINGTON AREA AS MODELS ARE INSISTENT THAT A BLOB OF GULF STREAM
CONVECTION WILL MOVE NORTH INTO THE CAPE FEAR REGION OVERNIGHT. LOWS
SHOULD FALL TO 66-70...WARMEST AT THE BEACHES.

&&

.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 /12Z WEDNESDAY THROUGH SUNDAY/...
AS OF 12Z...A BIT LESS DEEP MOISTURE TODAY WITH MAINLY SOUTHERLY
FLOW. A LOW LCL INDICATES A MVFR CEILING COULD FORM AN HOUR OR SO
AFTER SUNRISE. HRRR MODEL INDICATES AN EARLY START TO CONVECTION
ALONG THE SEA BREEZE TODAY...WITH SHOWERS LIKELY NOT AS STRONG DUE
TO LACK OF MOISTURE. MOST OF THE ACTIVITY WILL ACTUALLY BE BETWEEN
THE INLAND AND COASTAL TERMINALS...NEARING THE INLAND TERMINALS BY
18Z. SOUTHERLY FLOW WILL BE A BIT GUSTY THIS AFTERNOON...DIMINISHING
DIURNALLY THIS EVENING. WILL REEVALUATE BACK END OF TAFS ON THE NEXT
MODEL RUN AS ANOTHER SLUG OF MOISTURE ADVECTS IN FROM THE SOUTH.

EXTENDED OUTLOOK...SHOWERS/T-STORMS POSSIBLE THURSDAY THROUGH EARLY
FRIDAY. OTHERWISE VFR.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 700 AM WEDNESDAY...ISOLATED SHOWERS MAY CONTINUE THROUGH THE
MORNING HOURS BUT SHOULD DISSIPATE WITH THE AFTERNOON SEABREEZE
CIRCULATION. NO SIGNIFICANT CHANGES ARE NEEDED TO THE FORECAST.
PREVIOUS DISCUSSION FROM 300 AM FOLLOWS...

BERMUDA HIGH PRESSURE WILL MOVE LITTLE THROUGH TONIGHT...CONTINUING
TO PUMP AIR FROM THE CARIBBEAN NORTHWARD ACROSS THE CAROLINA COASTAL
WATERS. LOW PRESSURE WILL MOVE EAST ACROSS THE GREAT LAKES...TOO FAR
AWAY FOR ANY DIRECT AFFECTS JUST YET. A TYPICAL SUMMER/TROPICAL
WEATHER REGIME IS EXPECTED WITH SCATTERED SHOWERS AND THUNDERSTORMS
OVER THE COASTAL WATERS ENDING THIS MORNING...THEN REDEVELOPING
TONIGHT. MODELS ARE ACTUALLY QUITE INSISTENT THAT AT LEAST ONE
CONCENTRATED BATCH OF CONVECTION COULD ROLL IN OFF THE GULF STREAM
OVERNIGHT AND TOWARD COASTAL NORTH CAROLINA.

OUTSIDE OF ANY SHOWER AND THUNDERSTORM ACTIVITY...SOUTH WINDS SHOULD
AVERAGE 10-15 KNOTS WITH 3-4 FT SEAS. DOMINANT WAVE PERIODS AT THE
FRYING PAN SHOALS BUOY ARE 6 SECONDS...WITH YESTERDAY`S 10 SECOND
EASTERLY SWELL HARDLY REGISTERING ANYMORE.

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.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.

&&

$$

SYNOPSIS...DCH/TRA
NEAR TERM...TRA
SHORT TERM...DCH
LONG TERM...DCH
AVIATION...43