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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KILM 211447
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1045 AM EDT TUE MAY 21 2013

.SYNOPSIS...
A WEAK UPPER LEVEL DISTURBANCE AND HIGH PRESSURE OFFSHORE WILL
CONTINUE TO PRODUCE SCATTERED SHOWERS AND THUNDERSTORMS TODAY. DRIER
AND WARMER WEATHER IS EXPECTED FOR MID-WEEK. A COLD FRONT WILL
APPROACH AND CROSS THE REGION EARLY FRIDAY. COOLER AND DRIER WEATHER
WILL DEVELOP FOR THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 1030 AM TUESDAY...ITS PRETTY HARD TO ADD MUCH SPECIFICITY TO
THE FORECAST ON A DAY LIKE TODAY. CURRENTLY CONVECTION IS WINDING
DOWN OVER THE WRN ZONES WHILE THE SEABREEZE IS LIGHTING UP NICELY
WITH SHOWERS THAT WHILE HEAVY WILL BE SO SHORT-LIVED THE ACTUAL
RAINFALL AMOUNTS WILL BE QUITE LIGHT OVER A GIVEN LOCATION. HOW MUCH
ACTIVITY REFIRES OVER WESTERN ZONES WILL LARGELY BE A FUNCTION OF
HEATING DUE THE ABSENCE OF ANY MEANINGFUL LARGE SCALE LIFT. THERE
WILL ALSO BE A TENDENCY FOR THE IMMEDIATE COAST TO SEE LESS ACTIVITY
EAST OF THE SEA BREEZE...WHICH WILL NOT MOVE MUCH INLAND AT ALL
TODAY. IN FACT IT MAY NOT MOVE MUCH FROM ITS CURRENT LOCATION WHICH
COULD NECESSITATE RAISING POPS ALONG THE GRAND STRAND. STORM MOTION
ALSO SHOWING CONSIDERABLE VARIABILITY TODAY DUE TO THE LEFTOVER
UPPER SHEAR AXIS OVER THE REGION.

AS OF 700 AM TUESDAY...A LARGE CLUSTER OF THUNDERSTORMS PRODUCING
HEAVY RAIN HAS DEVELOPED ACROSS THE SANDHILLS AND SOUTHERN PIEDMONT
OF NC. THIS CONVECTION IS DRIFTING SOUTHEASTWARD...PIVOTING AROUND
THE INLAND SIDE OF THE UPPER SHEAR AXIS THAT IS LINED UP ALONG THE
INTERSTATE 95 CORRIDOR. THE LATEST SEVERAL HRRR MODEL RUNS TAKE THIS
CONVECTION SOUTHEASTWARD INTO THE BENNETTSVILLE AND DARLINGTON AREA
OVER THE NEXT COUPLE OF HOURS...BUT DIVERGE FROM RUN TO RUN AS TO
WHAT HAPPENS LATER THIS MORNING. PRIOR RUNS SHOWED THE CONVECTION
CONTINUING TO RUN SOUTH/SOUTHEASTWARD THROUGH NOON...WHILE THE
LATEST RUN (08Z) DISSIPATES THE CURRENT CLUSTER WHILE DEVELOPING NEW
CONVECTION JUST INLAND FROM THE COAST BY LATE MORNING AHEAD OF THE
DEVELOPING SEABREEZE BOUNDARY.

THE TAKE-HOME MESSAGE FROM ALL THIS IS THAT WE HAVE AN AIRMASS THAT
REALLY WANTS TO PRODUCE CONVECTION GIVEN ANY POSSIBLE REASON.
CONVECTIVE OUTFLOW BOUNDARIES FROM THE CURRENT ACTIVITY PLUS THE
DEVELOPMENT OF A SEABREEZE THIS AFTERNOON SHOULD ENSURE THERE ARE
PLENTY OF REASONS FOR NEW CONVECTIVE DEVELOPMENT...THEREFORE I HAVE
RAISED POPS INTO THE LIKELY CATEGORY FOR MOST AREAS MORE THAN 20
MILES INLAND FROM THE COAST TODAY. WEST OF INTERSTATE 95 I HAVE
RAISED POPS INTO THE 70-90 PERCENT RANGE...ANTICIPATING THE CURRENT
SANDHILLS CONVECTION WILL SOAK THIS AREA IN THE NEXT FEW HOURS.

RAINFALL OVER THE PAST THREE DAYS HAS AVERAGED 2 TO 5 INCHES WEST OF
INTERSTATE 95 EXCEPT FOR THE WESTERN THIRD OF DARLINGTON COUNTY
WHERE BARELY ONE INCH HAS FALLEN. GIVEN SOME OF THE RADAR-ESTIMATED
TOTALS FROM ROCKINGHAM TO WEST OF CHERAW THIS MORNING IT IS POSSIBLE
FLOOD ADVISORIES OR WARNINGS MAY BE NEEDED IN MY PEE DEE COUNTIES IN
THE NEXT SEVERAL HOURS.

PREVIOUS DISCUSSION FROM 300 AM FOLLOWS...

THE WEAK UPPER LEVEL DISTURBANCE THAT BEGAN THIS RECENT WET PERIOD
SEVERAL DAYS AGO HAS DEGENERATED INTO A 500-TO-700 MB SHEAR AXIS.
WIND SPEEDS SURROUNDING THE UPPER FEATURE ARE TOO WEAK AT THIS POINT
TO SUPPORT DYNAMIC LIFT...BUT RICH LOW AND MID LEVEL MOISTURE
REMAINS IN PLACE ACROSS THE EASTERN CAROLINAS WITH PRECIPITABLE
WATER VALUES AROUND 1.7 INCHES. THE LACK OF ANY CONVECTIVE
CAP...DEEP-LAYER ENVIRONMENTAL LAPSE RATES SLIGHTLY STEEPER THAN THE
MOIST ADIABATIC LAPSE RATE...AND THIS AFTERNOON`S SEABREEZE BOUNDARY
SHOULD HELP PRODUCE ANOTHER ROUND OF SCATTERED SHOWERS AND
THUNDERSTORMS. SLOW STORM MOTION AND A DEEP REGION (NEARLY 10000
FEET DEEP) WHERE EFFICIENT WARM-CLOUD COALESCENCE PROCESSES WILL
DOMINATE SHOULD ALLOW HEAVY RAINFALL TO OCCUR. HIGHS THIS AFTERNOON
SHOULD REACH THE LOWER 80S FOR MOST AREAS AWAY FROM THE BEACHES.

SHOWER ACTIVITY SHOULD END QUICKLY THIS EVENING...ALTHOUGH PLENTY OF
RESIDUAL MOISTURE SHOULD ENSURE SKIES REMAIN PARTLY CLOUDY
OVERNIGHT. MODELS HINT AT SOME NOCTURNAL CONVECTIVE DEVELOPMENT OVER
THE OCEAN WHICH MAY MAKE A RUN AT CAPE FEAR LATE TONIGHT. WITH A
LITTLE LESS CLOUD COVER THAN WE HAVE SEEN OVER THE PAST FEW
NIGHTS...LOWS SHOULD DROP INTO THE MID 60S INLAND WITH UPPER 60S AT
THE COAST.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 300 AM TUESDAY...MID LEVEL RIDGING AND BERMUDA HIGH PRESSURE
PERSIST ON WEDNESDAY BEFORE PATTERN CHANGE FINALLY OCCURS LATE IN
THE PERIOD. WHILE TEMPS BOTH DAYS WILL CONTINUE TO BE SEVERAL
DEGREES ABOVE CLIMO...MID AND UPPER 80S...WEDNESDAY IS LIKELY TO BE
A DRIER DAY WITH ONLY ISOLATED CONVECTION DUE TO SUBSIDENCE/CAPPING
BENEATH THE 5H RIDGE. 5H RIDGE...AS QUOTED BY THE PREVIOUS
FORECASTER...BREAKS DOWN SURPRISINGLY QUICKLY...THURSDAY AS LONGWAVE
TROUGH EXITS THE MIDWEST AND PUSHES EAST. THIS IN ITSELF WILL LEAD
TO INCREASED CONVECTION CHANCES THURSDAY DUE TO COOLER TEMPS ALOFT
STEEPENING LAPSE RATES. AN ADDITIONAL FACTOR TO CONVECTION THURSDAY
WILL BE THE APPROACH OF A COLD FRONT WHICH IS NOW PROGGED TO CROSS
THE AREA OVERNIGHT THURSDAY NIGHT. WITH GOOD THETA-E ADVECTION AHEAD
OF THIS BOUNDARY...WILL BUMP POP TO HIGH CHC EVEN THURSDAY NIGHT FOR
SHOWERS/TSTMS...WITH DRYING OCCURRING IN THE COLUMN AT THE VERY END
OF THE PERIOD.

MINS WED NIGHT WILL BE WELL ABOVE NORMAL...UPPER 60S TO NEAR 70.
SEVERAL DEGREES COOLER THURSDAY NIGHT AS THE FROPA OCCURS...FALLING
INTO THE LOW/MID 60S.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 300 AM TUESDAY...BEAUTIFUL LATE MAY WEATHER EXPECTED FOR THE
EXTENDED AS DRIER BUT STILL SEASONABLE AIR DEVELOPS ACROSS THE
CAROLINAS. COLD FRONT WILL BE JUST EXITING OFFSHORE AT THE START OF
THE PERIOD...WITH MUCH DRIER AIR FLOODING IN BEHIND IT AS A HIGH
PRESSURE BUILDS DOWN FROM THE NW. WHILE A FEW SHOWERS MAY LINGER
VERY EARLY FRIDAY...WILL QUICKLY RAMP POP DOWN TO SILENT FRIDAY
THROUGH MONDAY AS HIGH PRESSURE BUILDS ACROSS THE AREA HELPING PWATS
DROP TO WELL BELOW ONE INCH. EVEN WITH HIGH PRESSURE BUILDING DOWN
FROM THE NW...THE OVERALL AIR MASS CHANGE WILL BE ONE TO MUCH DRIER
CONDITIONS AS OPPOSED TO MUCH COOLER...WITH TEMPS FALLING TO JUST A
FEW DEGREES BELOW CLIMO...AND A NEAR PERFECT LATE-SPRING WKND
APPEARS TO BE IN STORE FOR THIS AREA.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
AS OF 12Z...CURRENT RADAR IMAGERY SHOWS SCT SHOWERS/T-STORMS NEAR
AND WEST OF KFLO WITH MORE SHOWERS OFFSHORE. THERE ARE POCKETS OF
IFR CIGS WITHIN THE CWA...AND KFLO COULD DEVELOP IFR SHORTLY WITH
STORMS MOVING OVERHEAD. HAVE INCLUDED TEMPO -SHRA IN THE NEAR TERM
TO ACCOUNT FOR CURRENT ACTIVITY BASED ON RADAR TRENDS AND LATEST
HRRR RUNS. MORE SHOWERS/T-STORMS WILL DEVELOP TODAY WITH DAYTIME
HEATING. EXPECT VFR/MVFR TO PREVAIL WITH BRIEF PERIODS OF IFR IN
HEAVIER PCPN. BETTER PCPN CHCS WILL BE INLAND THIS AFTN...BUT SOME
SEA BREEZE STORMS COULD DRIFT BACK TOWARDS THE COAST AS WELL. S-SW
WINDS AOB 10 KTS THIS MORNING WILL BECOME SOUTH AROUND 10 KTS THIS
AFTN. MVFR/IFR CIGS/VSBYS ARE CERTAINLY POSSIBLE OVERNIGHT WITH THE
ABUNDANT LOW-LEVEL MOISTURE IN PLACE.

EXTENDED OUTLOOK...SLIGHT CHC OF SHOWERS WEDNESDAY. SHOWERS/T-STORMS
POSSIBLE THURSDAY THROUGH EARLY FRIDAY. OTHERWISE VFR.

&&

.MARINE...
-- Changed Discussion --
NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 AM TUESDAY...NO SIGNIFICANT CHANGES ARE NEEDED TO THE
FORECAST. PREVIOUS DISCUSSION FROM 300 AM FOLLOWS...

THERE HAS BEEN AMAZINGLY LITTLE CHANGE IN THE OVERALL SYNOPTIC
WEATHER PATTERN OVER THE PAST 24 HOURS. HIGH PRESSURE HAS DROPPED
SOUTH TO NEAR BERMUDA WHILE LOW PRESSURE IN THE NORTHERN PLAINS IS
STILL SITTING OVER EASTERN SOUTH DAKOTA. THIS WILL ENSURE A SOUTH
WIND AT 10-15 KNOTS CONTINUES TODAY THROUGH TONIGHT. SCATTERED
SHOWERS AND POSSIBLY A FEW THUNDERSTORMS WILL BE MOST NUMEROUS THIS
MORNING...WITH SUBSIDENCE BEHIND THE SEABREEZE CLEARING OUT MOST OF
THIS ACTIVITY FROM THE COASTAL WATERS THIS AFTERNOON. SEAS CURRENTLY
RANGE FROM 3-4 FT ON BUOYS IN THE CAPE FEAR VICINITY...IN A
COMBINATION OF 10 SECOND EASTERLY SWELL AND A 6 SECOND SOUTHERLY
WIND WAVE.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 300 AM TUESDAY...BERMUDA HIGH PRESSURE REMAINS IN PLACE
WEDNESDAY BEFORE GRADUALLY PUSHING AWAY THURSDAY THANKS TO A COLD
FRONT WHICH WILL CROSS THE WATERS AT THE VERY END OF THE PERIOD.
WITH BERMUDA HIGH IN PLACE WED...RETURN FLOW CREATES S/SW WINDS OF
10-15 KTS...CREATING SEAS OF 2-4 FT WITH A 6 SEC SOUTHERLY WIND WAVE
DOMINANT IN THE WAVE SPECTRUM. BY THURSDAY...WINDS BEGIN TO VEER
SLOWLY AS COLD FRONT APPROACHES FROM THE WEST. WINDS WILL REMAIN
10-15 KTS...BUT VEER TO THE SW THU AFTN AND THEN FINALLY TO THE WEST
LATE THURSDAY NIGHT WITH THE ACTUAL FROPA. SEAS WILL BRIEFLY RISE TO
3-5 FT DURING THURSDAY...BEFORE FALLING BACK TO 2-4 FT AT THE END OF
THE PERIOD.

LONG TERM /FRIDAY THROUGH SATURDAY/...
AS OF 300 AM TUESDAY...COLD FRONT EXITING OFFSHORE AT THE START OF
THE PERIOD...WITH HIGH PRESSURE BUILDING DOWN FROM THE NW INTO
SATURDAY. WINDS WILL VEER SIGNIFICANTLY DURING THE PERIOD...FROM
WEST AROUND 10 KTS FRIDAY MORNING...TO NORTH AT 15 KTS FRIDAY
NIGHT...THEN NE AT 15-20 KTS ON SATURDAY THANKS TO A PINCHED
PRESSURE GRADIENT JUST OFFSHORE. SEAS WILL BE ENTIRELY WIND-WAVE
DOMINATED DURING THE EXTENDED...BUILDING FROM 2-4 FT FRIDAY...TO 3-5
FT ON SATURDAY WITH A NORTHERLY CHOP BECOMING PREDOMINANT.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...JDW
NEAR TERM...MBB/TRA
SHORT TERM...JDW
LONG TERM...JDW
AVIATION...BJR