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000
FXUS62 KILM 231754
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
154 PM EDT THU MAY 23 2013

.SYNOPSIS...
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SHOWERS AND THUNDERSTORMS WILL PRECEDE A COLD FRONT TODAY. THE
FRONT WILL MOVE THROUGH EARLY FRIDAY AND USHER COOLER AIR INTO THE
CAROLINAS OVER THE WEEKEND. NEXT WEEK WILL BRING A GRADUAL WARMUP.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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AS OF 1:45 PM THURSDAY...AS EXPECTED...SHOWERS AND THUNDERSTORMS
HAVE POPPED UP THIS AFTERNOON...FOR NOW MAINLY OVER OUR SC
COUNTIES. STORMS ARE MOVING TO THE NE THOUGH SO EXPECT EXPANDED
COVERAGE OVER SOUTHEASTERN NC LATER THIS AFTERNOON. HAVE FINE-
TUNED FORECAST ACCORDINGLY. PREVIOUS DISCUSSION FROM EARLIER THIS
MORNING FOLLOWS:

VAPOR ANALYSIS SHOWS ONE SHORT-WAVE MOVING OFF THE GA/SC COAST
EARLY THIS MORNING...TRIPPING OFF NOCTURNAL OCEAN CONVECTION FROM
CAPE FEAR SOUTH THROUGH EAST. AREAS OF LOW-LEVEL MOISTURE
CONVERGENCE OFFSHORE WAS ADDITIONALLY HELPFUL IN BLOSSOMING
SHOWERS WITH EMBEDDED TSTMS OVER THE WATERS. THE BERMUDA HIGH
CIRCULATION OVER OUR LOCALITY IS MARKED BY DEEP SOUTHERLY FLOW
THAT WILL GUIDE THE OCEAN CONVECTION ONSHORE THIS
MORNING...GENERALLY EAST OF A KMYR TO KCPC TO KEYF LINE. THIS
ACTIVITY WILL BEGIN TO WANE IN THE MID MORNING AS BUOYANCY OVER
THE WATER DECREASES WITH DIURNAL WARMING.

THE CONVECTIVE FOCUS WILL SHIFT FROM WATER TO LAND BY MIDDAY AND
LOW-LEVEL WIND CONVERGENCE WILL SPREAD INLAND ALONG A RESULTANT
SEA BREEZE BOUNDARY HELPING TO PRODUCE LIFT. SHORT-WAVE ENERGY
WILL APPROACH FROM THE WEST IN THE AFTERNOON TO PROVIDE UPPER
SUPPORT. THE INLAND ADVANCING MARINE LAYER WILL SHIFT THE HIGHEST
POP VALUES INLAND AWAY FROM THE COAST THROUGH THE AFTERNOON.
FORECAST SOUNDINGS INDICATE 1100-1700 J/KG OF CAPE AT 18Z INLAND
WITH PWAT VALUES AROUND 1.6 INCHES. PROJECTED STORM MOTION 210/10
KT. LIGHT ENVIRONMENTAL WINDS AND BULK SHEAR PARAMETERS WILL LIMIT
STRENGTH OF CONVECTION...BUT CERTAINLY SOME STRONG WET DOWN-BURSTS
CAN BE EXPECTED.

LOSS OF HEATING WILL TAKE A TOLL ON CONVECTION THIS EVENING AND
DRYING IN THE MID LEVELS OF THE ATMOSPHERE AFTER 6Z TONIGHT SHOULD
BEGIN TO CURTAIL SHOWER ACTIVITY. MID-LEVEL DRYING WILL OUT-PACE
THE SURFACE FRONT. THE FRONT WILL BRING A WIND-SHIFT TO THE COAST
AROUND 12Z FRIDAY.
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&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
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AS OF 3 AM THURSDAY...STRONG UPPER TROUGH ESPECIALLY FOR LATE MAY
SWINGS ACROSS ON FRIDAY. THE COLD FRONT AND DEEP MOISTURE WILL BE
OFFSHORE BEFORE THE START OF THE PERIOD BUT IF THE TROUGH AXIS
LAGS ENOUGH TO PREVENT DOWNSLOPING/DRYING THEN THERE COULD BE
ENOUGH SW FLOW AND PVA FOR SOME INSTABILITY SPRINKLES. FCST
SOUNDINGS SHOW ENOUGH MID LEVEL DRY AIR TO PRECLUDE MEASURABLE
PRECIP AT THIS TIME SO THE FORECAST WILL REMAIN DRY. OTHERWISE
FRIDAY LOOKS INCREASINGLY BREEZY WITH PLUMMETING DEWPOINTS AND
PERHAPS EVEN STRONG ENOUGH LATE DAY CAA TO MAKE FOR A RATHER FLAT
DIURNAL TEMPERATURE CURVE. CAA SUFFICIENT TO BRING A DOWNRIGHT
COOL FRIDAY NIGHT. WIND STAYS UP TO PRECLUDE RAD COOLING BUT LOWS
COULD STILL DIP DOWN CLOSE TO RECORDS. NORTHERLY FLOW AND COLD
ADVECTION CONTINUES INTO SATURDAY KEEPING TEMPERATURES A SOLID
CATEGORY OR MORE BELOW CLIMO DESPITE FULL SUNSHINE. AS THE TROUGH
DEEPENS AND CUTS OFF OFF THE NEW ENGLAND COAST BY SATURDAY NIGHT
THE COLD ADVECTION WILL BE MAINTAINED INTO THE PERIOD. WITH THE
SOLAR MODIFICATION FIGHTING THE PROCESS THE WHOLE TIME SAT NIGHT
LOWS MAY END UP VERY NEAR THOSE OF FRIDAY NIGHT.
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&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 3 AM THURSDAY...LARGE VORTEX MORE TYPICAL OF COOLER SEASON
WEATHER TO ONLY VERY SLOWLY LIFT OUT OF NEW ENGLAND STATES MONDAY
THROUGH WEDNESDAY. LOCAL RESULT WILL BE AN ABATING OF THE SURFACE
HIGH PRESSURE THAT UNTIL THEN WILL HAVE BEEN PUSHING IN FROM
POINTS NORTH. THE SPEED AT WHICH THIS HAPPENS IS STILL UP FOR
DEBATE BUT THE TREND WILL BE ONE OF GRADUALLY INCREASING WARMTH
AND MOISTURE. AT SOME POINT MOISTURE MAY BE SUFFICIENT TO SUPPORT
ISO OR SCTD CONVECTION OR THERE COULD EVEN BE AN ACTUAL SURFACE
WARM FRONT THAT DEVELOPS IN THE RETURN FLOW...WHICH COULD ADD TO
COVERAGE A LITTLE BIT. EITHER WAY BOTH SCENARIOS SEEM TO OFFER
LITTLE IN THE WAY OF RAIN CHANCES AREA-WIDE. BY THE END OF THE
PERIOD THE SURFACE HIGH WILL BE OFF THE COAST AND AN UPPER LEVEL
RIDGE BUILDING SO TEMPS SHOULD END UP NEAR OR ABOVE CLIMO.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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AS OF 18Z...CONVECTION FIRING NEAR THE WESTERN TERMINALS...WITH
INTERMITTENT SHOWERS EXPECTED THROUGH THE AFTERNOON HOURS. WITH
PWAT VALUES AROUND 1.7 INCHES...EXPECT BRIEF HEAVY DOWNPOURS.
THUNDER IS A POSSIBILITY...HOWEVER COVERAGE WILL BE LIMITED. MOST
OF THE CONVECTION WILL BE ALONG AND WEST OF THE RESULTANT...SO THE
COASTAL TERMINALS MAY BE SPARED. TONIGHT...CONVECTION WILL DIE OFF
WITH A DRY COLD FRONT APPROACHING. WINDS WILL SHIFT TO THE
NORTHWEST FIRST AT THE WESTERN TERMINALS...SOMETIME AFTER 06Z. ILM
MAY SEE AN IFR CEILING JUST AHEAD OF THE FRONT FOR A FEW HOURS.
BECOMING VFR FRIDAY WITH A DRYING NORTHWEST WIND...GUSTY BY MID TO
LATE MORNING.

EXTENDED OUTLOOK...VFR THROUGH SUNDAY. POSSIBLE MORNING FOG MONDAY
AND TUESDAY.
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&&

.MARINE...
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NEAR TERM/THROUGH TONIGHT/...
AS OF 1:45 PM THURSDAY...LATEST OBS SHOW SOUTHERLY WINDS IN THE 10
TO 15 KT RANGE WITH SEAS AROUND 4 FT. NO CHANGES TO THE FORECAST
WITH THE LATEST UPDATE. PREVIOUS DISCUSSION FOLLOWS:

SOUTH WINDS WILL INCREASE TODAY INTO THIS EVENING AHEAD OF AN
APPROACHING COLD FRONT. THE WINDS WILL REMAIN BELOW ADVISORY
LEVELS...BUT GUSTS TO 20 KT CAN BE EXPECTED THIS AFTERNOON AND
TONIGHT. SSW WINDS WILL SHIFT TO WNW AFTER DAYBREAK ON FRIDAY.
SEAS MAY REACH 5 FEET OUTER PORTION LATER TODAY AND TONIGHT...AND
3-4 FEET MOST LOCATION. SHOWERS AND TSTMS WILL IMPACT THE WATERS
THIS MORNING AND MOVING FROM SOUTH TO NORTH BUT DECREASING BY LATE
MORNING. SEAS WILL BE COMPOSED OF A MIX...SSE WAVES OF 3 FEET
EVERY 7 SEC AND SSW WAVES OF 1-2 FEET EVERY 4-5 SECONDS. WINDS AND
SEAS WILL BE LOCALLY HIGH IN AND NEAR TSTMS.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 3 AM THURSDAY...THE PERIOD BEGINS WITH A COLD FRONT MOVING
OFF TO THE EAST OF THE WATERS. THE SHARP VEER ASSOCIATED WITH
FROPA WILL GIVE WAY TO A MORE GRADUAL VEERING OF WIND DIRECTION AS
HIGH PRESSURE/COOL AIR SPILLS SOUTHWARD ACROSS THE EASTERN U.S.
FRIDAY NIGHT WILL ALSO BRING A CATEGORY OF SPEED INCREASE IN THE
COOL SURGE. TOO EARLY TO TELL WHETHER OR NOT ANY HEADLINES WILL BE
NEEDED AS MODEL GUIDANCE WIND SPEEDS SEEMS TO HAVE DECREASED
SLIGHTLY RESULTING IN SLIGHTLY LOWER SEAS IN SWAN OUTPUT. EVEN SO
EXPECT STEEP AND CHOPPY WAVES FROM ALL OF THE CHANGING WIND
DIRECTION. HIGH PRESSURE CONTINUES TO BUILD IN FROM THE N ON
SATURDAY KEEPING THE WINDS NORTHERLY BUT THERE SHOULD BE A
RELAXATION BY SATURDAY NIGHT AS RIDGE CENTER DRAWS CLOSER.

LONG TERM /SUNDAY THROUGH MONDAY/...
AS OF 3 AM THURSDAY...HIGH THAT BUILDS IN BEHIND FRIDAY COLD FRONT
WEAKENS AS LOW PRESSURE DEEPENS AND OCCLUDES NEW ENGLAND COAST. AS
THE LOW BECOMES THE DOMINANT WIND MAKER LOCALLY A NW TO W FLOW
WILL BE ESTABLISHED BUT WIND SPEEDS MAY STAY CAPPED AT 10 FT. WIND
WAVES FAIRLY DIMINUTIVE WITH A LITTLE BACKSWELL DEVELOPING FROM
THE STORM. AS THIS SYSTEM PULLS AWAY TO THE NE AND FILLS THE
GRADIENT LOCALLY WILL START TO BE MOST DEFINED BY WEAK HIGH
DEVELOPING OVER THE WEST ATLANTIC AND A LIGHT AND MORE TYPICAL
SOUTHERLY COMPONENT GETS RE-ESTABLISHED.
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&&

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

&&

$$

NEAR TERM...REK