-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KILM 191732
AFDILM

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

.SYNOPSIS...
LOW PRESSURE ALOFT DRIFTING EAST ACROSS THE REGION WILL BRING
SCATTERED SHOWERS AND THUNDERSTORMS THROUGH MONDAY. A DRYING
AND WARMING TREND WILL FOLLOW THROUGH MID WEEK AS BERMUDA HIGH
PRESSURE BUILDS TOWARD THE COAST. A COLD FRONT WILL APPROACH
FRIDAY...BRINGING A RENEWED CHANCE FOR THUNDERSTORMS AND COOLER
TEMPERATURES INTO NEXT WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 132 PM SUNDAY...VAPOR ANIMATIONS SHOWING A MYRIAD OF UPPER
IMPULSES CURRENTLY DROPPING SLOWLY ESE INTO THE AREA AHEAD OF A
PRIMARY MID-LEVEL COOL POOL APPROACHING THE CAROLINA MOUNTAINS.
THE HIGH PRECIPITABLE WATER CONTENT AND MAY HEATING WAS ALLOWING
RESPONSIVE CUMULUS DEVELOPMENT...KEEPING MAXIMUM TEMPERATURES FROM
CLIMBING VERY QUICKLY. ONE IMPULSE APPEARS POISED TO INCREASE
CONVECTION OVER OUR WESTERN ZONES INTO THE MIDDLE AFTERNOON WHILE
ACTIVITY OVER OUR NE NC ZONES LIFTS NORTHWARD AHEAD OF A SECONDARY
IMPULSE MOVING TOWARD THE NORTH CAROLINA COAST. THE CONVECTION
ENTERING OUR WESTERN ZONES WILL HAVE A MORE WESTERLY COMPONENT TO
ITS MOVEMENT AND THEY MAY BE STRONGER AS WE APPROACH MAXIMUM
DIURNAL SURFACE HEATING AND 700 MB TEMPS COOL A DEGREE OR TWO.
WILL MAINTAIN HIGH SCATTERED TO LIKELY POP VALUES THROUGH THE NEAR
TERM AS THESE FEATURES CONTINUE TO PROVIDE FAVORABLE UPPER SUPPORT
IN A MOIST ENVIRONMENT.
-- End Changed Discussion --

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...COMBINATION OF BERMUDA HIGH PRESSURE AND WEAK
MID-LEVEL IMPULSE WILL CREATE SCATTERED TO WIDESPREAD CONVECTION
DURING THE FIRST PART OF THE WEEK.

BERMUDA HIGH PRESSURE WHICH HAS BEEN DOMINATING THE SYNOPTIC REGIME
FOR SEVERAL DAYS NOW WILL CONTINUE TO SIT IN PLACE
OFFSHORE...PUMPING WARM MOIST AIR INTO THE CAROLINAS. WHILE THIS
TYPICALLY SUPPORTS TEMPS NEAR TO ABOVE CLIMO...ITS ALSO A SETUP THAT
FEATURES DIURNAL CONVECTION. THIS CASE WILL BE NO DIFFERENT...EXCEPT
THAT TSTMS ARE EXPECTED TO BE MORE WIDESPREAD THAN "TYPICAL" DUE TO
THE PRESENCE OF THE SHORTWAVE ALOFT. SLIGHTLY COOLER MID-LEVEL TEMPS
WILL ENHANCE LAPSE RATES...WHILE MODERATE PVA ASSOCIATED WITH THE
IMPULSE WILL HELP DRIVE LIFT. WITH INSTABILITY PROGGED TO BE 1000 -
2000 J/KG...EVEN WITH AMPLE CLOUD COVER CONVECTION SHOULD TRIGGER
DURING THE EARLY AFTN ALONG THE PIEDMONT TROUGH AND SEA BREEZE
BOUNDARY EACH DAY. ADDITIONALLY...MONDAY NIGHT CONVECTION WILL
LIKELY LINGER MANY HOURS AFTER NIGHTFALL AS RESIDUAL OUTFLOW
BOUNDARIES TAP REMNANT ELEVATED CAPE ALLOWING FOR SHOWERS/TSTMS TO
PERSIST.

WHILE CONVECTION WILL BE LIKELY ON MONDAY...THERE IS SLIGHTLY MORE
UNCERTAINTY TUESDAY DUE TO THE DISAGREEMENT IN MODEL OUTCOMES ON
THE EVOLUTION OF THE SHORTWAVE ALOFT. FEEL THE SLOWER GFS MAY BE
CORRECT DUE TO THE ALREADY SLOW-MOVEMENT OF THIS FEATURE...SO
ANOTHER DAY OF ENHANCED LIFT IS POSSIBLE TUESDAY AND THUS WILL CARRY
HIGH CHC POP TUESDAY AFTN. IF THE FASTER SOLUTION ENDS UP BEING
CORRECT...SOME SUBSIDENCE BEHIND THE VORT MAY LIMIT OVERALL
CONVECTIVE COVERAGE TUESDAY.

TEMPS MON/TUE WILL BE AROUND CLIMO...TEMPERED SLIGHTLY BY CLOUD
COVER. EXPECT HIGHS IN THE LOW 80S AWAY FROM THE IMMEDIATE COAST
MONDAY...AND THEN A FEW DEGREES WARMER TUESDAY. LOWS WILL BE HELD UP
BY CLOUD COVER...FALLING ONLY INTO THE UPPER 60S BOTH NIGHTS.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 300 AM SUNDAY...BUILDING HEIGHTS ALOFT AND BERMUDA-TYPE
SURFACE HIGH OFFSHORE WILL CREATE SUMMER LIKE CONDITIONS THROUGH THE
MAJORITY OF NEXT WEEK. WHILE THE FIRST TWO DAYS...WED/THU...ARE
LIKELY TO BE THE WARMEST...THERE IS SOME UNCERTAINTY DUE TO THE
PRESENCE OF A DEPARTING SHORTWAVE ALOFT. ATTM EXPECT THE IMPULSE TO
BE OFFSHORE...SO SOME SUBSIDENCE BEHIND THIS FEATURE AND BENEATH
BUILDING 1000-500MB THICKNESSES WILL BUMP TEMPS AND LOWER OVERALL
CONVECTIVE POTENTIAL. HOWEVER...WITH THETA-E RIDGING CONTINUING AND
TEMPS RISING INTO THE MID 80S...TSTMS WILL STILL BE POSSIBLE EACH
DAY. ALTHOUGH CONVECTION SHOULD NOT BE WIDESPREAD WED/THU...AND
FOCUSED ON THE USUAL BOUNDARIES (SEA BREEZE FRONT AND PIEDMONT
TROUGH)...WILL CARRY SCHC POP ACROSS THE ENTIRETY OF THE CWA SINCE
IT WOULD BE SUPERFLUOUS TO TRY TO NAIL DOWN SPATIAL EXTENT OF
COVERAGE THIS FAR OUT.

LATE IN THE WEEK...FULL LATITUDE TROUGH WILL BEGIN TO DISPLACE THE
UPPER RIDGE ACROSS THE EAST...LEADING TO INCREASING CONVECTIVE
POTENTIAL FRI AHEAD OF A COLD FRONT WHICH IS CURRENTLY PROGGED TO
CROSS FRIDAY AFTN. WOULD EXPECT FROPA TO SLOW WITH LATER MODEL RUNS
DUE TO DEEP SOUTHERLY FLOW AHEAD OF IT AND THE KNOWN MODEL BIAS TO
BREAK DOWN RIDGES TOO QUICKLY. WILL CONTINUE INHERITED LOW-CHC POP
FRIDAY AND SCHC SATURDAY...BUT IT IS POSSIBLE THAT COOLER AND DRIER
AIR WILL WORK INTO THE REGION BY NEXT WEEKEND.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
-- Changed Discussion --
AS OF 18Z...EXPECT TO SEE SCATTERED SHOWERS AND STORMS TO CONTINUE
THE PATTERN OF REDEVELOPMENT AND DISSIPATION DURING THE TAF PERIOD
AS WE HAVE SEEN DURING THE PREVIOUS 24 HOURS.  INITIALLY...THE
GREATEST POTENTIAL FOR ADDITIONAL CONVECTION WILL BE OVER SOUTHERN
AND WESTERN AREAS TODAY WITH A SHIFT EAST AND NORTH TONIGHT INTO
MONDAY.  THE EXACT TIMING THAT EACH TERMINAL WILL BE AFFECTED DURING
THE NEXT 24 HOURS IS SOMEWHAT UP TO CHANCE SO PILOTS SHOULD BE
PREPARED TO DEAL WITH THE ATTENDANT MVFR OR BRIEF IFR CIGS AND VSBYS
AT ALMOST ANY TIME DURING THE NEXT 24 HOURS.  OUTSIDE CONVECTION
EXPECT S WINDS OF 5 TO 10 KT WITH SLIGHTLY HIGHER WINDS POSSIBLE
NEARER THE COAST THIS AFTERNOON.

EXTENDED OUTLOOK...AFTN SHOWERS/TSTMS POSSIBLE AGAIN MONDAY AND
TUESDAY. OTHERWISE PREVAILING VFR.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
NEAR TERM /THROUGH TONIGHT/...
AS OF 132 PM SUNDAY...SEAS AROUND 2 FEET WILL BUILD TO 3 FT AND
POSSIBLY UP TO 4 FT OUT 20 MILES BY THIS EVENING...AS PERSISTENT
SOUTH WINDS ACROSS THE WESTERN ATLANTIC PREVAIL AND INCREASE A BIT
THROUGH AFTERNOON. SPECTRAL WAVE DATA FROM THE FRYING PAN SHOALS
BUOY SHOWS THE BULK OF THE WAVE ENERGY CURRENTLY IS EMBODIED IN A
9 SECOND SOUTHEAST SWELL...WHICH WILL CONTINUE INTO TONIGHT AS THE
4-5 SECOND SOUTH WIND WAVES BUILD ON TOP. NO ADVISORIES EXPECTED
BUT MARINERS SHOULD GET A RADAR FIX BEFORE HEADING OUT...AS TSTMS
INCREASE TONIGHT INTO MONDAY OVER THE WATERS.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...LITTLE VARIABILITY IN MARINE CONDITIONS FOR
THE EARLY PART OF THE WEEK AS BERMUDA HIGH PRESSURE RETAINS ITS
CONTROL OVER THE SYNOPTIC REGIME. THIS MANIFESTS ITSELF AS
PERSISTENT S/SW WINDS OF 10-15 KTS...WITH LITTLE FLUCTUATION DURING
THE PERIOD. WHILE THESE WINDS WILL CREATE A SOUTHERLY 5 SEC WIND
CHOP OF 3-4 FT...THE LONGEVITY OF THIS BERMUDA HIGH HAS ALLOWED A
2FT/10SEC SE SWELL TO DEVELOP IN THE WAVE SPECTRUM AS WELL. THESE
TWO WAVE GROUPS WILL COMBINE TO CREATE 2-4 FT SEAS THROUGH THE
PERIOD.

LONG TERM /WEDNESDAY THROUGH THURSDAY/...
AS OF 300 AM SUNDAY...PERSISTENT BERMUDA HIGH OFFSHORE WILL MAINTAIN
ITS POSITION THROUGH THE EXTENDED...KEEPING S/SW RETURN FLOW ONGOING
ACROSS THE WATERS AT 10-15 KTS. WHILE A WEAK SE SWELL WILL BE
EVIDENT WITHIN THE WAVE SPECTRUM THROUGH MID-WEEK...IT WILL FEATURE
A SLOWLY DECAYING AMPLITUDE...ALLOWING SEAS TO BECOME MORE WIND-WAVE
DOMINATED WITH A SHORTER AVERAGE PERIOD. AS THE SWELL DECAYS...3-6
FT SOUTHERLY WIND WAVES BECOME DOMINANT...AND THESE SHORTER PERIODS
HELP WAVE AMPLITUDES GROW WITHIN THE COASTAL WATERS. SEAS INITIALLY
OF 2-4 FT WILL INCREASE LATE THURSDAY AHEAD OF A COLD FRONT
ADVANCING FROM THE WEST...AND MAY APPROACH SMALL CRAFT ADVISORY
THRESHOLDS LATE.
-- End Changed Discussion --

&&

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

&&

$$

NEAR TERM...MJC
SHORT TERM...JDW
LONG TERM...JDW
AVIATION...RAN/MJC