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000
FXUS62 KILM 200341
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1141 PM EDT SUN MAY 19 2013

.SYNOPSIS...
WESTERN ATLANTIC HIGH PRESSURE WILL RIDGE ACROSS THE FORECAST AREA
FOR THE MAJORITY OF THIS WEEK. A DISTURBANCE ALOFT MOVING ACROSS
THE AREA EARLY IN THE WEEK...WILL MAINTAIN THE THREAT FOR CONVECTION
TONIGHT THROUGH TUESDAY. FOR THE REMAINDER OF THE WEEK...EXPECT A
RETURN BACK TO THE NORMAL DIURNALLY INDUCED CONVECTION THREAT. FOR
LATE THURSDAY AND FRIDAY...A COLD FRONT WILL PUSH ACROSS THE AREA.
IN ITS WAKE...DRY CANADIAN HIGH PRESSURE WILL RIDGE ACROSS THE REGION
DURING THE UPCOMING HOLIDAY WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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AS OF 1100 PM SUNDAY...VIA LATEST 88D TRENDS...EARLIER WIDESPREAD
CONVECTIVE ACTIVITY ACROSS THE FA HAS DISSIPATED TO ISOLATED IN
AREAL COVERAGE AS OF LATE THIS EVENING. IN GENERAL...THE ATM HAS
BEEN WORKED OVER INLAND...WHERE-AS CLOSER TO THE COAST THE ATM
HAS HAD TIME TO RECOVER SOME FROM THE ITS EARLIER ACTIVITY. THIS
TREND WILL ALSO OCCUR INLAND LATER TONIGHT. WITH A 1ST LOOK AT THE
00Z NAM...AID FROM DYNAMICS ALOFT...PVA ASSOCIATED WITH THE MAIN
5H VORT ASSOCIATED WITH THE WEAK S/W MID-LEVEL S/W TROF HAVING
CRASHED INTO THE UPPER RIDGE EARLIER THIS WEEKEND...CONVECTION
SHOULD BEGIN TO FIRE ACROSS THE CENTRAL CAROLINAS JUST OUTSIDE
WEST OF THE ILM CWA...AND DRIFT INTO THE FA DURING THE PRE-DAWN
HRS. ACROSS THE ADJACENT ATL WATERS...CONVECTION WILL FIRE UP
ACROSS THE WARMER WATERS JUST OUTSIDE OF THE ILM COASTAL
WATERS...AND PUSH ACROSS THE COASTAL WATERS AND ONSHORE DURING
THE PRE-DAWN MON HRS. WITH THE SLIGHTLY COOLER THEN NORMAL SHELF
WATERS IN PLACE FOR THIS TIME OF THE YEAR...THE QUESTION RESIDES
OF JUST HOW MUCH OF A NEGATIVE/WEAKENING INFLUENCE WILL IT HAVE ON
THIS CONVECTION PRIOR TO MOVING ONSHORE. POPS AGAIN HAVE BEEN RE-
ADJUSTED/RE-STRUCTURED TO ACCOUNT FOR CURRENT RADAR TRENDS...AND
THE INCREASED CONVECTIVE POTENTIAL LATER OVERNIGHT. 00Z RAOBS
INDICATE PWS OF 1.4 MHX TO 1.8 CHS INCHES. HAVE INCLUDED A HEAVY
RAIN SUFFIX TO THE PCPN WHICH ALSO RESULTED IN A RE-TOOLING OF
THE QPF ACROSS THE FA. OVERNIGHT MIN TEMPS AND HOURLY DEWPOINTS
REMAIN ON QUE.
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&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
AS OF 300 PM SUNDAY...MAIN FORECAST CHALLENGE WILL BE POPS AND THE
TIMING THEREOF AT LEAST THROUGH THE FIRST DAY...MONDAY. THE MID
LEVEL PATTERN WILL CONSIST OF A WEAK RIDGE EXTENDING INTO THE
TENNESSEE VALLEY/WESTERN NORTH CAROLINA REGION WITH A BROAD
WEAKNESS ALONG THE EAST COAST AT LEAST FROM FLORIDA NORTH TO THE
DELMARVA. PRECIPITABLE WATER VALUES REMAIN ELEVATED MONDAY INTO
MONDAY EVENING NEAR ONE AND THREE QUARTERS OF AN INCH. THE FORCING
WILL BASICALLY CONSIST OF THE WEAK MID LEVEL FORCING...A BROAD
DEFORMATION ZONE IN THE 700-300MB LAYER...AND DIFFERENTIAL HEATING
VIA THE SEA BREEZE AND INTERVALS OF CLOUDS.

INTERESTING TO LOOK AT THE CURRENT MESOSCALE CONVECTIVE SYSTEMS WEST
OF OUR AREA AND THE DEFORMATION. THESE APPEAR TO BE THE PRODUCT OF
THIS BROAD ZONE. HOWEVER THIS AREA OF FORCING...WHILE STILL PRESENT
IN A WEAKER STATE MONDAY AND OVER OUR AREA...MOVES LITTLE AND DO NOT
ANTICIPATE AS MUCH ORGANIZED CONFECTION...MORESO OF WHAT WE ARE
SEEING TODAY. MORE OF A SOUTHWEST FLOW DEVELOPS TUESDAY WITH PW
VALUES DROPPING SOMEWHAT AND THIS IS REFLECTED IN LOWER POP VALUES.

FOR TEMPERATURES...LOW CONFIDENCE FORECAST BUT I FOLLOWED A
CONSISTENT TREND OF LOWER VALUES MET NUMBERS MONDAY VIA HIGHER POPS
AND WARMER NUMBERS TUESDAY...MAV NUMBERS.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 300 PM SUNDAY...WEDNESDAY SHOULD BE THE LAST DAY WITH THE
ABSENCE OF ANY SYNOPTIC SCALE ASCENT AS WEST ATLANTIC SURFACE AND
UPPER RIDGE HOLD ON. THE LATTER WILL BE WEAKENING HOWEVER AND LARGE
SCALE WEAK FORCING MAY KICK IN AS EARLY AS WEDNESDAY NIGHT. THE
AFTERNOON HOURS WILL STILL BE SUSCEPTIBLE TO ISOLATED COVERAGE OF
CONVECTION BORNE OF MESOSCALE BOUNDARIES ESPECIALLY WITH
TEMPERATURES ON THE WARM SIDE OF CLIMO...YIELDING EXTRA INSTABILITY.
THURSDAY AND FRIDAY MAY TURN ACTIVE WITH UPPER TROUGH AND SURFACE
COLD FRONT BOTH IMPINGING UPON THE REGION FROM THE NW. THE SPEED
AND AMPLITUDE OF THE TROUGH AND ENSUING COOLER/DRIER AIR IS NOT
AGREED UPON BY MODEL GUIDANCE. THE SLOWER AND LESS AMPLIFIED 00Z
EC SEEMS AT ODDS WITH THE MORE AGGRESSIVE GFS/GEM. THE QUICKER
SOLUTIONS OF CONTINUITY HAVE BEEN PRESERVED...IMPLYING THAT SOME
CONSIDERABLY DRIER AIR WILL WORKING OVER THE WEEKEND.

&&

.AVIATION /03Z MONDAY THROUGH FRIDAY/...
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AS OF 00Z...PERIODS OF MVFR/IFR POSSIBLE OVERNIGHT...ESPECIALLY
INLAND...DUE TO LOW CIGS AND AREAS OF FOG. OTHERWISE EXPECT VFR
WITH PERIODS OF MVFR/IFR POSSIBLE ON SUNDAY WITH ISOLATED TO
SCATTERED SHOWERS AND THUNDERSTORMS.

SCT/BKN LOW/MID/HIGH LEVEL CLOUDS AS WELL AS SHOWERS ARE SPREAD
ACROSS THE AREA THIS EVENING. LATEST OBS ALSO DEPICTING SOME
AREAS OF FOG...BUT CURRENTLY NOT AFFECTING ANY OF THE TERMINALS.
EXPECT SOUTH WINDS AOB 8 KTS AND LINGERING ISOLATED SHOWERS
THROUGH THE OVERNIGHT HOURS...WITH LOW CIGS CREATING MVFR/BRIEF
IFR CONDITIONS POSSIBLE GIVEN FCST SOUNDINGS AND TIME-HEIGHT
ANALYSIS. ALSO CANNOT RULE OUT FOG INLAND LATE OVERNIGHT INTO THE
EARLY MORNING HOURS...WHICH MAY CREATE MVFR/BRIEF IFR. AFTER
DAYBREAK...ANY LINGERING FOG WILL DISSIPATE AND CIGS WILL
GRADUALLY LIFT GIVING WAY TO VFR AREA-WIDE. SOUTHWEST WINDS WILL
PREVAIL AOB 10 KTS WITH GUSTS UP TO 18 KTS ALONG THE COAST LATER
IN THE DAY. CHANCE FOR ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS THROUGHOUT THE DAY.

EXTENDED OUTLOOK...AFTN SHOWERS/TSTMS POSSIBLE MONDAY AND
TUESDAY. OTHERWISE PREVAILING VFR.
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&&

.MARINE...
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NEAR TERM /THROUGH TONIGHT/...
AS OF 1111 PM SUNDAY...LATEST COASTAL AND MARITIME OBS INDICATE
WINDS GENERALLY NEAR 10 KT NEAR SHORE...AND UP TO 15 KT ACROSS
THE OUTER WATERS. BASED ON THE LATEST AND PROGGED SFC PRESSURE
PATTERN...160-190 DEGREE WIND DIRECTIONS TO OCCUR OVERNIGHT. THE
PROGGED SFC PG HAS WIND SPEEDS GENERALLY INCREASING TO 10-15 KT
THRUOUT THE AREA WATERS. SIGNIFICANT SEAS WILL GENERALLY BE 2 TO
3 FT...WITH 4 FOOTERS POSSIBLE ACROSS THE OUTER WATERS 10-20 NM
OUT. A 1 TO 2 FOOT EASTERLY PSEUDO GROUND SWELL AT 8 TO 9 SECOND
PERIODS...WILL MESH WITH LOCALLY GENERATED WIND WAVES AT 4 TO 5
SECOND PERIODS. CURRENT ISOLATED CONVECTIVE ACTIVITY...WILL
INCREASE TO SCATTERED TO AREAS IN COVERAGE DURING THE PRE-DAWN
HRS AND INTO DAYLIGHT MONDAY MORNING. COULD SEE WINDS GUSTING TO
20 TO 30 KT FROM THE STRONGER TSTMS...ESPECIALLY THOSE TRAVERSING
ACROSS SSTS OF 70 DEGREES OR HIGHER...IE THE OUTER WATERS OFF CAPE
FEAR.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 300 PM
SUNDAY...SURFACE PATTERN CHANGES LITTLE THROUGH THE PERIOD WITH IF
ANYTHING...A SLIGHT TURN IN THE WINDS TOWARD THE SOUTHWEST
TUESDAY. DIRECTION SHOULD REMAIN STRAIGHT SOUTHERLY MONDAY.
OVERALL WINDS WILL CONTINUE TO DISPLAY SUMMERTIME SPEEDS IN A
10-15 KNOT RANGE. SEAS WILL ALSO DISPLAY LITTLE IN THE WAY OF
VARIABILITY WITH 2-4 FEET AS PERIODS REMAIN DOMINATED BY WIND
WAVES.

LONG TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 300 PM SUNDAY...SOUTH TO SOUTHWESTERLY FLOW THROUGH THE
PERIOD WITH BERMUDA HIGH PRESSURE BEING THE MAIN PLAYER AT LEAST
INITIALLY. THE INCREASED DURATION OF FETCH WILL ALLOW FOR SOME
LONGER PERIOD SWELL ENERGY TO BEGIN MOVING INTO THE SOUTHEASTERN
U.S. AS A RESULT THERE SHOULD BE A DECREASE IN THE OVERALL WAVE
PERIOD WHILE SIGNIFICANT WAVE HEIGHT IS ON THE RISE. THERE COULD
EVEN BE SOME SCEC-WORTHY 5 FT SEAS ALONG THE OUTER EDGES OF THE
FCST ZONES BY THURSDAY. APPROACHING COLD FRONT ON FRIDAY COULD
VEER THE WIND SLIGHTLY. THIS BOUNDARY MAY BE COMING THROUGH AS
EARLY AS FRIDAY NIGHT BUT A SLOWER SOLUTION SEEMS LIKELY IN
FUTURE MODEL RUNS.
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&&

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

&&

$$
SYNOPSIS...SHK
NEAR TERM...DCH
SHORT TERM...SHK
LONG TERM...MBB
AVIATION...SGL