-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KILM 191431
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1031 AM EDT WED JUN 19 2013

.SYNOPSIS...
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A COLD FRONT WILL SAG ACROSS THE AREA FROM NORTH TO SOUTH THROUGH
THIS EVENING. THE RISK FOR HEAVY RAINFALL WILL SLOWLY END FROM NORTH
TO SOUTH. HIGH PRESSURE WILL BRING DRIER AIR INTO THE EASTERN
CAROLINAS THURSDAY AND FRIDAY. THE FRONT MAY MOVE BACK TO THE NORTH
THIS WEEKEND.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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AS OF 1030 AM WEDNESDAY...A COLD FRONT HAS SLID THROUGH THROUGH
OVER HALF OF OUR FORECAST AREA...CURRENTLY EXTENDING ALONG A LINE
FROM NORTH MYRTLE BEACH WEST ACROSS CONWAY...THROUGH CENTRAL MARION
COUNTY TO NEAR LAKE CITY. ALTHOUGH THERE IS NO CONVECTIVE ACTIVITY
ALONG THE ACTUAL FRONT...THIS WILL CHANGE THIS AFTERNOON. A
PERSISTENT LINE OF SHOWERS EXTENDING FROM BENNETTSVILLE THROUGH
LUMBERTON INTO NORTHERN BLADEN COUNTY APPEARS TO BE THE RESULT OF
ELEVATED INSTABILITY JUST ABOVE A WEAK CAP AT 850 MB INTERACTING
WITH UPPER DIVERGENCE IN THE RIGHT-ENTRANCE REGION OF A DEPARTING
300 MB JET STREAK ACROSS THE MID-ATLANTIC STATES. AS WIND SPEEDS
DIMINISH TO NEAR CALM AT THE 850 MB LEVEL EARLY THIS AFTERNOON THESE
SHOWERS SHOULD TAPER OFF.

THIS AFTERNOON THE FOCUS FOR NEW CONVECTION WILL SHIFT SOUTH TO THE
FRONT ITSELF AND TO THE AREA OF BUILDING INSTABILITY SOUTH OF THE
FRONT ACROSS COASTAL SOUTH CAROLINA. I HAVE INCREASED POPS FOR
TODAY TO 70 PERCENT FROM SOUTHERN FLORENCE COUNTY EAST ACROSS THE
GRAND STRAND INTO THE CAPE FEAR AREA. AS 0-6 KM STORM MOTION VECTORS
SHRINK WITH WEAKENING LOW-MID LEVEL WINDS THIS AFTERNOON BUT
PRECIPITABLE WATER VALUES REMAIN VERY HIGH (NEAR 2.0 INCHES) THE
POTENTIAL FOR SLOW-MOVING THUNDERSTORMS WITH HEAVY RAIN WILL
INCREASE. MOST SYNOPTIC GUIDANCE PLUS THE LATEST FEW RUNS OF THE
HRRR PLACE THE HIGHEST RISK FOR HEAVY RAINFALL ACROSS HORRY COUNTY
DURING THE EARLY TO MID AFTERNOON HOURS.

WITH PLENTY OF CLOUD COVER I HAVE BACKED HIGHS DOWN A DEGREE OR TWO
IN MOST SPOTS...WITH LOWER 80S NOW FORECAST. CONVECTIVE ACTIVITY
SHOULD SHIFT TO THE OCEAN THIS EVENING WITH INLAND AREAS DRYING OUT.
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&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 3 AM WEDNESDAY...HIGH PRESSURE RIDGES DOWN THE COAST DURING
THE PERIOD WHILE COLD FRONT REMAINS JUST OFF THE COAST. FIRST HALF
OF THE PERIOD SHOULD BE DRY AS WESTERLY FLOW ALOFT IN CONJUNCTION
WITH SLOWLY BUILDING 5H RIDGE HELPS DRY THE REGION OUT. AT THIS
POINT IT LOOKS LIKE THE DEEP MOISTURE ASSOCIATED WITH THE FRONT
REMAINS JUST OFFSHORE AND FORECAST SOUNDINGS DROP PRECIPITABLE
WATER VALUES CLOSE TO 1 INCH LATE THU AFTERNOON. LOW LEVEL
NORTHEAST FLOW WILL PROVIDE SOME LOW LEVEL MOISTURE WHICH IS
LIKELY TO MANIFEST ITSELF AS A SCATTERED TO BROKEN FLAT STRATOCU
DECK IN THE AFTERNOON. CLOUD COVER ALONG WITH THE NORTHEAST FLOW
WILL KEEP HIGHS BELOW CLIMO. CANNOT RULE OUT SOME LIGHT SPRINKLES
NEAR THE COAST FROM ACTIVITY MOVING ON SHORE BUT DEEP DRY AIR
SHOULD PREVENT ANYTHING MEASURABLE.

REINFORCING SHOT OF DRY AIR ARRIVES THU NIGHT BUT IS SHORT LIVED AS
STALLED BOUNDARY MOVES CLOSER TO THE COAST FRI MORNING. LOWS WILL
BE NEAR TO SLIGHTLY BELOW CLIMO THU NIGHT WITH SKIES CLEARING AND
LIGHT NORTHEAST FLOW CONTINUING.

FORECAST SOUNDINGS SHOW A RETURN OF DEEPER MOISTURE DURING THE DAY
FRI AS THE BOUNDARY TRIES TO MOVE ONSHORE. BOUNDARY BECOMES SOMEWHAT
DIFFUSE AT THIS POINT BUT MOISTURE ASSOCIATED WITH IT MOVES ONSHORE
DURING THE AFTERNOON AND EVENING...OPENING UP THE POSSIBILITY OF
SOME ISOLATED CONVECTION. GIVEN THE PROXIMITY TO THE DRY AIR AND THE
WEAK SUBSIDENCE DO NOT THINK COVERAGE WILL BE SIGNIFICANT BUT FEEL
IT DOES WARRANT A SLIGHT CHC POP...MAINLY CONFINED TO COASTAL
COUNTIES. DESPITE CONTINUED NORTHEAST FLOW MORE SUN SHOULD LEAD
TO HIGHS A LITTLE CLOSER TO CLIMO. CLOUD COVER AND LOW LEVEL
MOISTURE ALONG THE COAST WILL CREATE A LARGER SPREAD FOR LOWS FRI
NIGHT. TEMPS WILL RANGE FROM NEAR TO SLIGHTLY ABOVE CLIMO ALONG
THE COAST TO NEAR TO SLIGHTLY BELOW CLIMO WELL INLAND.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 3 AM WEDNESDAY...UNCERTAINTY ABOUNDS FOR THE DURATION OF THE
LONG TERM. THE DECENT AGREEMENT SEEN LAST NIGHT HAS EVAPORATED
LEAVING SEVERAL POSSIBLE SOLUTIONS TO PONDER. THESE RANGE FROM
MOSTLY DRY FOR THE WEEKEND AND START OF NEXT WEEK TO VERY WET WITH
POSSIBLE FOR WEAK LOW PRESSURE ALONG THE CAROLINA COAST. COMMON
THEME AMONG THEM IS THE EVOLUTION OF THE MID LEVEL AND SURFACE
PATTERNS AND THE PRESENCE OF LINGER SURFACE BOUNDARY OFF THE
SOUTHEAST COAST. ALL OF THE GUIDANCE SHOW MID LEVEL RIDGE BUILDING
OVER THE SOUTHEAST WHILE AT THE SURFACE BERMUDA HIGH TAKES HOLD.

THE KEY TO THE PERIOD WILL BE HOW DEFINED THE BOUNDARY REMAINS AND
HOW MUCH DEEP MOISTURE LINGERS WHEN THE BOUNDARY COMES ONSHORE AND
THEN LIFTS NORTH. THE ECMWF IS CURRENTLY THE DRIEST AND ALSO THE
SOLUTION WITH THE LEAST AMOUNT OF QUESTIONS CONCERNING ITS VALIDITY.
THE GFS APPEARS TO BE AFFECTED BY FEEDBACK WHICH MAY BE HELPING
MAINTAIN A STRONGER SURFACE BOUNDARY AND DEEPER MOISTURE. THE
CANADIAN DEVELOPS A CLOSED LOW WHICH MAY OR MAY NOT IMPACT THE
CAROLINAS...DEPENDING ON THE RUN. THIS HAS BEEN SOMEWHAT COMMON
FOR THE CANADIAN RECENTLY AS IT HAS BEEN TRYING TO TURN WEAK WAVES
ALONG STALLED COASTAL FRONTS INTO MORE SIGNIFICANT CLOSED LOWS
WITH LITTLE SUCCESS. FOR NOW WILL IGNORE ITS SOLUTION GIVEN
RECENT PERFORMANCES AND THE LACK OF CONSISTENCY. THE RESULT IS
MINIMAL CHANGES TO PREVIOUS FORECAST WITH SLIGHT CHC TO LOW CHC
POP EACH DAY AND TEMPERATURES GRADUALLY INCREASING FROM BELOW
CLIMO TO ABOVE CLIMO BY THE END OF THE PERIOD.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
AS OF 12Z...PERIODS OF MVFR/IFR WITH SCATTERED SHOWERS AND
THUNDERSTORMS EXPECTED TODAY THROUGH THE EVENING HOURS. MVFR/IFR DUE
TO LOWERED CIGS/AREAS OF FOG OVERNIGHT INTO THE EARLY MORNING HOURS
ON THURSDAY. OTHERWISE EXPECT VFR.

AS A COLD FRONT DRAPED ACROSS THE FORECAST AREA CONTINUES TO
SLOWLY DROP SOUTHWARD THIS MORNING...ANTICIPATE
ISOLATED SHOWERS WITH TEMPO MVFR/IFR CIGS TO CONTINUE. THE FRONT
IS EXPECTED TO BECOME STALLED AS IT NEARS THE COAST...AND GIVEN
LATEST GUIDANCE AND ANALYSIS...EXPECT SHOWERS AND THUNDERSTORMS TO
CONTINUE ACROSS THE AREA THROUGH THE REST OF THE DAY AND THIS
EVENING...ESPECIALLY ALONG THE COAST. GIVEN UNCERTAINTY OF TIMING
OF ACTIVITY...HAVE OPTED TO KEEP IN VCTS WITH PERIODS OF
ANTICIPATED RAINFALL/REDUCED RESTRICTIONS. INTO THE LATE EVENING
HOURS...ACTIVITY WILL TAPER OFF...WITH A FEW SHOWERS STILL
POSSIBLE ALONG THE COAST. ANTICIPATE STRATUS TO CREATE MVFR/IFR
CONDITIONS..WITH AREAS OF FOG ALONG THE COAST OVERNIGHT...WITH
NORTH-NORTHEAST WINDS WILL AOB 8 KTS.

EXTENDED OUTLOOK...VFR THURSDAY THROUGH SATURDAY. SLIGHT CHANCE OF
SHOWERS ON SUNDAY.

&&

.MARINE...
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NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 AM WEDNESDAY...A COLD FRONT HAS PUSHED SOUTH AS FAR AS
BALD HEAD ISLAND AND OAK ISLAND WHERE WINDS ARE NOW REPORTED ON
MESONET STATIONS TO BE FROM THE NORTH. WEST WINDS CONTINUE IN THE
MYRTLE BEACH AREA WHERE THE FRONT HAS YET TO REACH. THE FRONT SHOULD
SLOW ITS SOUTHWARD PROGRESS THIS AFTERNOON AS WARMING INLAND
TEMPERATURES FORCE A WEAK SEABREEZE CIRCULATION TO COUNTER THE
FRONT. IN FACT ONSHORE WINDS COULD TEMPORARILY REDEVELOP ALONG THE
BRUNSWICK COUNTY COAST BEFORE BECOMING NORTHEAST TONIGHT AS THE
LARGE HIGH PRESSURE CENTER OVER THE EASTERN GREAT LAKES BUILDS SOUTH.

A LINE OF STRONG THUNDERSTORMS HAS PUSHED WELL EAST OF THE NEARSHORE
WATERS AND WILL BE APPROACHING THE GULF STREAM IN THE NEXT FEW
HOURS. NEW SHOWERS ARE DEVELOPING INLAND AND SOME OF THESE MAY GROW
INTO THUNDERSTORMS WITH VERY HEAVY RAINFALL THIS AFTERNOON...
ESPECIALLY FROM JUST AROUND CAPE FEAR SOUTH THROUGH THE GRAND
STRAND.

PERSISTENT SOUTHWEST AND WEST WINDS OVERNIGHT BUILT SEAS TO 5 FT AT
THE OCEAN CREST PIER GAUGE AND 7 FT AT THE FRYING PAN SHOALS BUOY.
ADJUSTMENTS TO WAVE FORECASTS FOR THE NEXT FEW HOURS INCLUDE A LARGE
UPWARD ADJUSTMENT OF +3 FT ALONG THE BRUNSWICK COUNTY COAST WITHIN
5-8 MILES OF SHORE...TAPERING DOWN THROUGH THE AFTERNOON SINCE WEST
WINDS HAVE ENDED AND LIGHTER SPEEDS ARE DEVELOPING. THIS GIVES
FORECASTS OF GENERALLY 3-5 FT FOR THE NC WATERS...AND 3-4 FT FOR THE
SC WATERS THROUGH THE DAY.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 3 AM WEDNESDAY...PINCHED GRADIENT BETWEEN HIGH PRESSURE
BUILDING SOUTH AND STALLED FRONT OFF THE COAST WILL PRODUCE
NORTHEAST FLOW IN THE 15 TO 20 KT RANGE THU AND THU NIGHT. GRADIENT
STARTS TO WEAKEN LATE THU NIGHT WITH SPEEDS DROPPING TO A SOLID 15
KT BY FRI MORNING. FURTHER REDUCTION IN GRADIENT FRI WILL KEEP
NORTHEAST FLOW IN THE 10 TO 15 KT RANGE. FLOW BECOMES A LITTLE MORE
EASTERLY FRI NIGHT AS SURFACE RIDGE AXIS STARTS TO SETTLE SOUTH.
GRADIENT CONTINUES TO WEAKEN AS REMAINS OF STALLED FRONT LIFT INTO
THE AREA. AS A RESULT SPEEDS WILL DROP BELOW 10 KT BY THE END OF
THE PERIOD. SEAS 3 TO 5 FT THU IN RESPONSE TO STRONG NORTHEAST
FLOW SLOWLY SUBSIDE INTO FRI. GRADUALLY REDUCTION IN WINDS LATE
THU NIGHT AND FRI ALLOWS SEAS TO FALL TO 2 TO 3 FT BY THE END OF
THE PERIOD.

LONG TERM /SATURDAY THROUGH SUNDAY/...
AS OF 3 AM WEDNESDAY...WEAK COASTAL TROUGH IN THE VICINITY AND HIGH
PRESSURE WEAKLY BUILDING DOWN THE COAST DURING THE PERIOD WILL KEEP
WIND LIGHT AND VARIABLE. WINDS WILL BE FROM THE EAST AT 10 KT OR
LESS BUT COULD VARY FROM NORTHEAST TO SOUTHEAST AT ANY GIVEN
TIME...DEPENDING ON THE POSITION OF THE REMAINS OF THE SURFACE
BOUNDARY AND ANY MESOSCALE BOUNDARIES. LIGHT WIND FIELD WILL
MAINTAIN 2 TO 3 FT SEAS WITH HIGHEST SEAS SAT.
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&&

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

&&

$$

NEAR TERM...TRA
SHORT TERM...III
LONG TERM...III
AVIATION...SGL