-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KILM 181727
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
127 PM EDT SAT MAY 18 2013

.SYNOPSIS...
HIGH PRESSURE ANCHORED OFFSHORE WILL CONTINUE TO BRING WARM
TEMPERATURES INTO EARLY NEXT WEEK. WEAK LOW PRESSURE ALOFT WILL
BRING INCREASING CHANCES FOR AFTERNOON AND EVENING THUNDERSTORMS
THIS WEEKEND AND EARLY NEXT WEEK. DRIER WEATHER WITH CONTINUED
WARM TEMPERATURES IS EXPECTED FOR THE MIDDLE AND LATTER PORTIONS
OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 1:30 PM SATURDAY...SLOW MOVING AND DIFFUSE MID LEVEL TROUGH
WILL BEGIN TO IMPACT THE AREA IN A MORE SIGNIFICANT MANNER THIS
AFTERNOON AND EVENING. MOST OF THE HIGH RESOLUTION GUIDANCE AS
WELL AS THE SREF IS AGGRESSIVE ON QPF ACROSS THE WESTERN ZONES BY
0000 UTC AND HAVE RAISED POPS TO LIKELY IN THESE AREAS. THE COAST
SHOULD REMAIN RELATIVELY FREE OF ACTIVITY AS THE MARINE INFLUENCE
AND THE DISPLACEMENT FROM THE BETTER MID LEVEL FORCING TAKES ITS
TOLL. THERE REMAINS A DEFINITE CONVECTIVE NATURE TO THE ACTIVITY
SO I HAVE INCREMENTALLY LOWERED POPS FOR THE OVERNIGHT HOURS. THE
LACK OF THUNDER PROBABLY WARRANTS A CHANGE IN WEATHER TYPE WITH
ONLY ISOLATED THUNDER BEING MORE APPROPRIATE.

WITH ALL THE MOISTURE AND NO WEAK FRONTS AROUND TO DISTORT OVERNIGHT
LOWS...SLIGHTLY WARMER VALUES THAN MOS IS ADVERTISING APPEARS TO BE
THE BEST STRATEGY.
-- End Changed Discussion --

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 300 AM SATURDAY...SLOWLY WEAKENING SHORTWAVE TROUGH WILL DRIFT
OVERHEAD DURING THE SHORT TERM...COMBINING WITH RICH THETA-E AIR ON
RETURN FLOW TO CREATE SCATTERED-TO-WIDESPREAD CONVECTION EACH AFTN.
BERMUDA HIGH PRESSURE ANCHORED OFFSHORE WILL CONTINUALLY PUMP
WARM/MOIST AIR INTO THE REGION WITH PWATS RISING TO 1.6-1.8 INCHES.
THIS IS A PATTERN WHICH TYPICALLY SUPPORTS SCATTERED AFTN
CONVECTION. IN THIS CASE HOWEVER...THANKS TO THE PRESENCE OF THE 5H
SHORTWAVE ENHANCING LIFT AND PROMOTING STEEPER LAPSE RATES DUE TO A
COOL POOL ALOFT...EXPECT CONVECTION TO BE MORE WIDESPREAD THAN IS
USUAL FOR THIS SETUP. WITH TEMPS RISING INTO THE LOW/MID 80S EACH
AFTN...MLCAPE WILL RISE WELL ABOVE 1000 J/KG...FUELING CONVECTION
ALONG THE SEA BREEZE FRONT AND PIEDMONT TROUGH. SREF PROBS FOR 0.01"
RISE TO 100% (TYPICALLY A SIGNAL THAT QPF IS LIKELY) BOTH SUN AND
MON ACROSS THE WESTERN HALF OF THE CWA. WILL BUMP POP TO LIKELY FOR
THIS AREA BOTH AFTNS. WHILE SEVERE CONVECTION SEEMS UNLIKELY WITH
STORM ORGANIZATION LIMITED...BRIEFLY TORRENTIAL RAIN WILL OCCUR
WITHIN TSTMS DUE TO THE SATURATED COLUMN.

EVEN THOUGH CONVECTION WILL BE DIURNALLY FORCED...RESIDUAL ELEVATED
INSTABILITY NOTED IN FORECAST SOUNDINGS SUGGESTS THAT OUTFLOW
BOUNDARIES WILL ALLOW TSTMS TO LIVE ON SEVERAL HOURS BEYOND
NOCTURNAL COOLING...AND HAVE CONTINUED AT LEAST SCHC EACH NIGHT
DURING THE SHORT TERM. MINS EACH NIGHT WILL BE WELL ABOVE CLIMO FOR
MID-MAY...FALLING INTO THE MID 60S...UPR 60S AT THE COAST.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 300 AM SATURDAY...WARM AND SUMMER-LIKE CONDITIONS PERSIST
DURING THE EXTENDED AS BERMUDA HIGH SITS OFFSHORE AND MID-LEVEL
RIDGING BULGES FROM THE GULF COAST. WHILE DIURNAL CONVECTION WILL BE
POSSIBLE EACH AFTN...COMBINATION OF SOME SUBSIDENCE BEHIND A
DEPARTING SHORTWAVE AND BUILDING HEIGHTS ALOFT SHOULD LIMIT OVERALL
TSTM POTENTIAL...ESPECIALLY WED/THU. BY LATE IN THE WEEK...UPPER
TROUGH BEGINS TO DISPLACE THE RIDGE...AND A COLD FRONT APPROACHES
FROM THE NW. DO NOT EXPECT ANY SIGNIFICANT AIRMASS CHANGES OR COLD
FRONT IMPACTS BEFORE NEXT WEEKEND...BUT TSTM POTENTIAL WILL AGAIN
INCREASE LATE IN THE PERIOD. WARMEST DAYS WILL BE WED/THU...BUT ALL
DAYS WILL BE CLIMO...TO SLIGHTLY ABOVE...FOR BOTH HIGHS AND LOWS.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
-- Changed Discussion --
AS OF 18Z...IN GENERAL...EXPECT VFR THROUGH MUCH OF THE PERIOD.
HOWEVER...SCATTERED SHOWERS AND STORMS SHOULD DEVELOP THIS AFTERNOON
AND IMPACT THE INLAND TERMINALS DIRECTLY AND AFFECT THE COASTAL
TERMINALS WITH DEBRIS CLOUDS. SHOWERS AND STORMS...DEBRIS CLOUDS AND
THE PERIOD FOR ABOUT 3 HOURS AFTER SUNRISE SUNDAY MAY RESULT IN
BRIEF PERIODS OF MVFR CONDITIONS AT ALL TERMINALS WITH THE GREATEST
POTENTIAL AT LBT/FLO.  LINGERING CLOUDS AND THE PROXIMITY OF THE
UPPER LEVEL ENERGY TRIGGERING THE STORMS SHOULD PRECLUDE THE
DEVELOPMENT OF SIGNIFICANT FOG TONIGHT.  OUTSIDE STORMS...S TO SW
WINDS OF 5 TO 10 KT ARE EXPECTED DURING DAYLIGHT HOURS THROUGH THE
PERIOD.

EXTENDED OUTLOOK...AFTN SHOWERS/TSTMS POSSIBLE THROUGH MONDAY.
OTHERWISE VFR.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
NEAR TERM /THROUGH TONIGHT/...
AS OF 1:30 PM SATURDAY...THE ONLY SURFACE FEATURE TO IMPACT THE COASTAL
WATERS IS THE SEA BREEZE AND THIS IS TYPICAL OF A SUMMERTIME
PATTERN. OTHERWISE...LOW LEVEL WIND PROFILES...THROUGH 850MB...SHOW
ONLY A MARGINAL INCREASE OVERNIGHT TO ABOUT 16 KNOTS...UP FROM ABOUT
TEN KNOTS. THIS WILL WARRANT AN INCREASE IN THE FORECAST TO A RANGE
OF 10-15 KNOTS FROM THE SOUTH. SIGNIFICANT SEAS WILL SEE AN INCREASE
FROM AROUND TWO FEET TO 2-3 FEET.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 300 AM SATURDAY...FAIRLY STAGNANT PATTERN FOR THE SHORT TERM
AS BERMUDA HIGH PRESSURE SITS OFFSHORE. WHILE OVERALL GRADIENT WILL
NOT BE VERY STRONG...S/SW WINDS AROUND THIS HIGH PRESSURE WILL BE
10-15 KTS THROUGH THE PERIOD WITH LITTLE DIURNAL OR DIRECTIONAL
FLUCTUATION. WITH BERMUDA HIGH SITTING OFFSHORE...PERSISTENT EAST
AND SOUTH WINDS AROUND IT WILL PROMOTE AN INCREASINGLY LONG-PERIOD
SWELL...BECOMING 2-3 FT AT 10 SEC ON MONDAY. THIS COMBINED WITH THE
S/SW WINDS WILL DRIVE SEAS UP TO 3-5 FT EACH DAY DURING THE PERIOD.

LONG TERM /TUESDAY THROUGH WEDNESDAY/...
AS OF 300 AM SATURDAY...CONTINUED BERMUDA RIDGE SITTING OFFSHORE
WILL KEEP PERSISTENT 10-15 KTS OF S/SW WINDS OVER THE WATERS. THE
LONG TEMPORAL DURATION OF THIS FETCH AROUND THE OFFSHORE HIGH WILL
KEEP A 2FT/10 SEC SE SWELL IN THE WAVE SPECTRUM...WHICH WILL COMBINE
WITH 3-4 FT SOUTHERLY WIND CHOP. THESE TWO WILL DRIVE SEAS TO 3-4 FT
THROUGH THE PERIOD WITH LITTLE VARIABILITY.
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...JDW
NEAR TERM...SHK
SHORT TERM...JDW
LONG TERM...JDW
AVIATION...RAN