-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KILM 190322
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1122 PM EDT SAT MAY 18 2013

.SYNOPSIS...
RAIN CHANCES WILL INCREASE THE NEXT COUPLE OF DAYS AS WEAK LOW
PRESSURE ALOFT DRIFTS ACROSS THE CAROLINAS...WITH DAY AND NIGHT
TIME TEMPERATURES RUNNING NEAR NORMAL FOR MIDDLE MAY. BERMUDA
HIGH PRESSURE WILL BUILD TOWARD THE EAST COAST MID THROUGH LATE
WEEK...BRINGING A DRYING AND WARMING TREND.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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AS OF 1100 PM SATURDAY...TWO AREAS OF CONVECTION...1 ACROSS THE
WESTERN ILM CWA...AND THE OTHER JUST NORTH OF THE ILM CWA...WILL
BOTH CONTINUE THE WEAKENING/DISSIPATING TREND AS NOTED BY THE KLTX
AND SURROUNDING 88DS. A SFC BASED MARINE STABLE AIR MASS ACROSS
THE FA WILL MODERATE OVERNIGHT...MEANING THE DEPTH OF THIS AIR
MASS TRANSPORTED INLAND BY THE SEA BREEZE WILL DECREASE. PCPN
DEVELOPMENT WEST OF THE ILM CWA HAS REMAINED STEADY OR HAS
SLIGHTLY INCREASED. THIS PCPN ACTIVITY HAS BEEN AIDED BY
FORCING/DYNAMICS FROM A MID-LEVEL VORT...THAT WAS ONCE ASSOCIATED
WITH THE CLOSED UPPER LOW THAT AFFECTED THE SOUTHERN U.S. DURING
THE PAST MID-WEEK PERIOD. WILL MAINTAIN CHANCE POPS ACROSS THE
WESTERN 1/3RD OF THE ILM CWA TO ACCOUNT FOR ANY OF THE EASTWARD
MOVING CONVECTION MAKING IT TO THE FA. IT WILL ENCOUNTER AN AIR
MASS HAVING BEEN DEPLETED BY PREVIOUS CONVECTION ALONG WITH A
MODERATING SFC BASED MARINE LAYER. WILL INDICATE NO POPS ALONG THE
IMMEDIATE COAST. HAVE INCLUDED PATCHY FOG ACROSS PORTIONS OF THE
FA. THIS A RESULT OF SFC DEWPOINTS IN THE 60S...PROGGED SFC
DEWPOINT DEPRESSIONS LESS THAN 5 DEGREES...WINDS LIKELY TO
DECOUPLE ACROSS PORTIONS OF THE FA...AND AVBL MOISTURE FROM RECENT
RAINS. DEBRIS CLOUDINESS WILL KEEP THE RADIATIONAL FOG COVERAGE TO
A MINIMUM.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
AS OF 3 PM SATURDAY...BATCHES OF SHORT-WAVE ENERGY EVIDENT IN
VAPOR ANIMATIONS TWISTING AND CURLING WELL UPSTREAM OVER THE MID
MISSISSIPPI VALLEY WILL APPROACH AND MOVE ACROSS THE CAROLINAS
SUNDAY AND MONDAY. COLUMN MOISTURE/PWAT VALUES WILL INCREASE AND
WE MAY SEE A FEW DEGREES OF H7 COOLING AS THESE DISTURBANCES MOVE
ACROSS THE AREA. THESE SUBTLE FEATURES OF SLIGHT COOLING ALOFT AND
INCREASING MID-LEVEL MOISTURE MAKE A LARGER DIFFERENCE THIS TIME
OF YEAR WHEN CONVECTION BREWS. WILL MAINTAIN HIGH SCATTERED TO
LIKELY POP VALUES SUNDAY INTO MONDAY GIVEN THESE ANTICIPATED
INGREDIENTS. CONSIDERABLE CLOUDINESS WILL TEMPER MAX TEMPS IN THE
LOW 80S MOST LOCATIONS BOTH SUNDAY AND MONDAY...WHILE KEEPING
NIGHT TIME READINGS VERY MILD. AN H7 COLD FRONT WILL BRING A
WIND-SHIFT AND DRYING ALOFT LATE MONDAY AND HAVE TAPERED POP VALUES
INTO VERY EARLY TUESDAY. EXPECTED RAIN AMOUNTS/QPF BOTH DAYS ADDS UP
TO A 1/2 TO 1 INCH ALONG AND NEAR THE COAST...AND POTENTIALLY 1-2
INCHES OVER OUR WESTERN ZONES AND FAR INTERIOR FOR THE PERIOD SUNDAY
AND MONDAY.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 3 PM SATURDAY...BROAD UPPER RIDGING IN PLACE ON TUESDAY AS
WILL BE WEST ATLANTIC SURFACE HIGH PRESSURE. MAIN POINT OF
UNCERTAINTY REGARDING MID LEVEL SHORTWAVE/PRONOUNCED SHEAR AXIS.
SOME GUIDANCE HAS IT ALREADY OFFSHORE FOR WHAT SHOULD BE A RATHER
QUIET AFTERNOON WITH NEAR SEASONABLE TEMPS WHILE OTHERS HAVE IT
ALONG THE COAST FOR SLIGHTLY MORE ACTIVE AFTERNOON OF CONVECTION.
GIVEN HOW WEAK THE FLOW IS WILL SHOW LOW END CHANCE POPS. WITH THIS
FEATURE OUT OF THE PICTURE WEDNESDAY EXPECT A FURTHER WARMUP AND
MERELY ISOLATED CONVECTION ALONG BOUNDARIES LIKE THE SEA BREEZE AND
OUTFLOW FROM ANY ACTIVITY FROM THE PRIOR AFTERNOON. A VERY GRADUAL
UPTICK IN MID LEVEL SWRLY FLOW EXPECTED THURSDAY AHEAD OF TROUGHINESS
STRENGTHENING OVER OH/UPPER MS VALLEYS. THURSDAY THUS BEGINS AN
UPWARD TREND IN CONVECTIVE COVERAGE AS MOISTURE MAY DEEPEN. THE
ACTUAL CYCLONIC FLOW ASSOC WITH THE TROUGH WILL OVERSPREAD THE
REGION THURSDAY NIGHT INTO FRIDAY FURTHER BOLSTERING RAIN CHANCES
AND TEMPERING DAYTIME HIGHS BACK TOWARDS CLIMO.

&&

.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
AS OF 00Z...PERIODS OF MVFR ASSOCIATED WITH HEAVIER RAINFALL AT
INLAND TERMINALS POSSIBLE THROUGH THE OVERNIGHT HOURS ALONG WITH THE
POTENTIAL FOR MVFR DUE TO LOWERED CIGS OVERNIGHT. OTHERWISE EXPECT
VFR WITH PERIODS OF MVFR/IFR POSSIBLE ON SATURDAY WITH ISOLATED TO
SCATTERED SHOWERS AND THUNDERSTORMS.

PLENTY OF SCT/BKN HIGH CLOUD COVER ACROSS THE AREA THIS EVENING WITH
MAINLY SOUTH WINDS AOB 10 KTS AND SHOWERS/ISOLATED CONVECTION
AFFECTING THE INLAND SITES. EXPECT SHOWER ACTIVITY TO LINGER INTO
THE OVERNIGHT HOURS...THOUGH WILL NOT REACH THE COASTAL SITES.
TIME-HEIGHT ANALYSIS AND FCST SOUNDINGS SUGGEST THE POSSIBILITY OF
LOWERED CIGS WHICH MAY CREATE MVFR INTO THE EARLY MORNING
HOURS...THUS HAVE INTRODUCED INTO GOING FORECAST. AFTER DAYBREAK ON
SATURDAY...SOUTH TO SOUTHWEST WINDS WILL PREVAIL AOB 10 KTS WITH
GUSTS UP TO 20 KTS ALONG THE COAST LATER IN THE DAY AND INCREASING
CHANCES FOR ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS

EXTENDED OUTLOOK...AFTN SHOWERS/TSTMS POSSIBLE THROUGH MONDAY.
OTHERWISE VFR.

&&

.MARINE...
-- Changed Discussion --
NEAR TERM /THROUGH TONIGHT/...
AS OF 1111 PM SATURDAY...LOWERED POPS RELATED TO THE CONVECTION
TRYING TO REMAIN TOGETHER AS IT MOVES OFF THE NORTH AND SOUTH
CAROLINA MAINLAND INTO THE ILM COASTAL WATERS. RATHER THICK SFC
BASED STABLE MARINE LAYER CONTINUES TO HAVE A NEGATIVE IMPACT ON
CONVECTION DEVELOPMENT AS A WHOLE...AS WELL AS ITS SUSTAINABILITY
AFTER MOVING OFF THE MAINLAND. THE SFC FRONTAL BOUNDARY WILL
CONTINUE RETURNING NORTHWARD OVERNIGHT INTO SUNDAY...FURTHER AWAY
FROM THE ILM COASTAL WATERS. PROGGED SFC PRESSURE PATTERN AND
GRADIENT WILL RESULT IN A SE-S WIND AROUND 10 KT...OCCASIONALLY
15 KT ACROSS THE ILM SC WATERS. SIGNIFICANT SEAS WILL RUN 2
FT...EXCEPT UP TO 3 FT FAR THE ILM SC WATERS. A 1 TO 2 FOOT
PSEUDO EASTERLY GROUND SWELL AT 8 TO 9 SECOND PERIODS WILL
DOMINATE SIG. SEAS...WITH ONLY A 1-2 FOOT CONTRIBUTION FROM A 3
TO 4 SECOND PERIOD WIND WAVE.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 3 PM SATURDAY...LESS THAN IDEAL MARINE CONDITIONS EXPECTED
SUNDAY AND MONDAY BUT NO HEADLINES OR CAUTIONARY STATEMENTS ARE
EXPECTED AT THIS TIME. SW WINDS OF 15-20 KT AND 4 FT SEAS WILL
MARK A GOOD PORTION OF THE MARINE FORECAST SUNDAY THROUGH MONDAY
AS BERMUDA HIGH PRESSURE BUILDS WEST TOWARD THE COAST AND LOWER
PRESSURE INLAND INTERACT. SEAS WILL BE COMPOSED OF GROWING S WAVES
WITH PERIODS AROUND 6 SECONDS AND LOW-AMPLITUDE ESE SWELL WAVES.
MARINERS SHOULD CONSIDER GETTING A FIX ON RADAR TRENDS BEFORE
HEADING OUT SINCE TSTMS MAY DOT THE WATERS...FAVORED MOSTLY LATE
SUNDAY INTO MONDAY. WINDS AND WAVES WILL BE LOCALLY HIGHER IN AND
NEAR TSTMS.

LONG TERM /TUESDAY THROUGH WEDNESDAY/...
AS OF 3 PM SATURDAY...SOUTHWESTERLY FLOW SHOULD PERVADE THE
ENTIRE PERIOD AS HIGH PRESSURE REMAINS NEARLY STATIONARY ACROSS
THE WESTERN ATLANTIC. THE FLOW MAY INCREASE TOWARDS THE END OF THE
PERIOD AS RIDGE AXIS INTO THE CAROLINAS DEVELOPS AND MOVES TO THE
NORTH. THIS COULD ALSO STEER JUST ENOUGH SWELL ENERGY INTO THE
REGION TO BUILD SEAS A FOOT OR TWO.
-- End Changed Discussion --

&&

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

&&

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