Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 070237
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1037 PM EDT WED MAY 6 2015

.SYNOPSIS...
LOW PRESSURE SOUTH OF CAPE FEAR MAY BECOME A SUBTROPICAL CYCLONE
OVER THE NEXT COUPLE OF DAYS. THE SYSTEM IS EXPECTED TO APPROACH
THE COAST OF SOUTH CAROLINA OR SOUTHERN NORTH CAROLINA FRIDAY AND
SATURDAY WITH INCREASING CHANCES FOR HEAVY RAIN...GUSTY WINDS...
AND DANGEROUS RIP CURRENTS AT THE BEACHES. UNSETTLED WEATHER
SHOULD PERSIST INTO EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
AS OF 1030 PM WEDNESDAY...I HAVE MADE SMALL TWEAKS TO
TEMPERATURES BASED ON OBSERVED HOURLY TEMP CURVES. PRECIP SHIELD
IS ONLY 20 MILES FROM BALD HEAD ISLAND AND MEASURABLE RAIN MAY
ONLY BE 4 HOURS AWAY FROM REACHING LAND. 00Z MHX SOUNDING
REVEALED CONSIDERABLE DRY AIR IN THE 4000-15000 FT LAYER THAT WILL
LIMIT WESTWARD PROGRESS OF THE RAIN AS PREVIOUSLY FORECAST.
DISCUSSION FROM 730 PM FOLLOWS...

THE LOW SEVERAL HUNDRED MILES SOUTH OF CAPE FEAR HAS CHANGED
LITTLE IN ORGANIZATION THIS AFTERNOON. THE LATEST WORD FROM THE
HURRICANE CENTER IS STILL FOR A 60 PERCENT CHANCE OF DEVELOPMENT
INTO A NAMED SUBTROPICAL STORM OVER THE NEXT FEW DAYS. THE NASA
GLOBAL PRECIPITATION MISSION (GPM) SATELLITE OVERFLEW THE SYSTEM
EARLY THIS AFTERNOON AND SHOWED RAINFALL ECHOES LARGELY DISLOCATED
FROM THE SATELLITE-INFERRED CIRCULATION CENTER. (SEE OUR LATEST
FACEBOOK/TWITTER POSTS) THIS DOES NOT BODE WELL FOR RAPID
STRENGTHENING...ALTHOUGH THIS COULD CHANGE AS THE SYSTEM REMAINS
NEAR THE WARM GULF STREAM CURRENT FOR AT LEAST ANOTHER 36 HOURS.

DENSE CIRRUS ALONG THE COAST SHOULD CONTINUE OVERNIGHT AS THE
UPPER LOW OFFSHORE MAINTAINS A SOUTHERLY FLOW AT 200-300 MB.
MOISTURE AT 700 MB IS REMAINING 50+ MILES OFFSHORE WITH RATHER DRY
AIR ACROSS THE EASTERN CAROLINAS AT THIS TIME. AS WINDS THROUGHOUT
THIS LEVEL TURN MORE EASTERLY TONIGHT THE LARGE SHIELD OF RAIN
VISIBLE ON THE PERIPHERY OF OUR RADAR SHOULD SHIFT
WESTWARD. I HAVE SLOWED DOWN THE WESTWARD ADVANCE OF
PRECIPITATION FROM PREVIOUS FORECASTS A BIT...WITH CHANCES OF
MEASURABLE RAIN BY DAYBREAK 30-50 PERCENT AT THE COAST AND 10
PERCENT OR LESS ALONG I-95. NO SIGNIFICANT CHANGES HAVE BEEN MADE
TO LOWS...STILL EXPECTED TO RANGE FROM THE UPPER 50S INLAND TO THE
LOWER 60S AT THE COAST.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
AS OF 300 PM WEDNESDAY...A LARGE SWATCH OF SHOWERS AND THUNDERSTORMS
OFF THE FLORIDA EAST COAST AND IN THE VICINITY OF THE BAHAMAS HAS
BEEN RELUCTANT TO BECOME MUCH MORE ORGANIZED TODAY. THE NATIONAL
HURRICANE CENTER CONTINUES TO MONITOR AND MAY SEND A PLANE INTO
THE SYSTEM ON THURSDAY TO BETTER EVALUATE ITS STRUCTURE AND
INTENSITY. MODELS ARE RATHER CONSISTENT IN SHOWING A VERY SLOW
EVOLUTION AS THE SHOWERS AND THUNDERSTORMS CONTINUE TO ADVANCE/
EXPAND FURTHER NORTH ACROSS THE EASTERN CAROLINAS. HAVE INCLUDED
LIKELY TO WIDESPREAD CONVECTION FOR MUCH OF THE PERIOD. THE
PERSISTENCE OF THE RAINFALL MAY LEAD TO A RISK FOR SIGNIFICANT
PONDING AND PERHAPS SOME FLOODING. AT THIS TIME...IT IS DIFFICULT
TO PINPOINT WHERE THE HEAVIEST OF RAIN WILL FALL. CERTAINLY THERE
WILL BE PLENTY OF VERY HEAVY RAINFALL OFFSHORE. IF DEVELOPING LOW
PRESSURE IS ABLE TO DRIFT OR REDEVELOP WESTWARD AND CLOSER TO THE
COAST...THEN THE RISK FOR EXCESSIVE RAINFALL WILL MOVE ACROSS THE
EASTERN CAROLINAS. AT THIS TIME...RAINFALL AMOUNTS UP TO 1 TO 2
INCHES IS CERTAINLY POSSIBLE WITH AGAIN A POTENTIAL FOR MUCH
HIGHER AMOUNTS. THE COASTAL AREAS SHOULD BE PRONE TO THE HIGHER
RAINFALL TOTALS. OTHERWISE...GUSTY WINDS ARE EXPECTED WITH THE
STRONGEST WINDS NOW EXPECTED ON FRI...UP TO 20 TO 30 MPH AND FROM
THE NE. THE SURF ZONE WILL LIKELY BECOME DANGEROUS WITH BUILDING
BREAKERS...ROUGH SURF...STRONG RIP CURRENTS AND SIGNIFICANT BEACH
EROSION.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 300 PM WEDNESDAY...SYSTEM STILL SLOW TO ORGANIZE TODAY OFF THE
SOUTHEAST COAST. SO SLOW IN FACT THAT THE RECON HAS BEEN POSTPONED.
UNTIL THIS SYSTEM BEGINS TO CONGEAL (AT WHICH TIME AIRCRAFT RECON
WILL BECOME LIKELY) ITS STILL VERY TOUGH TO ASCERTAIN HOW THINGS
WILL PAN OUT. IN THE VERY NEAR TERM THE SOUTHERN CENTER JUST NORTH
OF THE BAHAMAS SEEMS TO BE WEAKENING IN FAVOR OF THE NORTHERN CENTER
ROUGHLY EAST OF JACKSONVILLE, FL. THE FORMER IS A WEAK REFLECTION OF
THE UPPER LOW WHILE THE LATTER IS THE MORE TYPICAL FRONTAL LOW. MOST
MODELS INDICATE THAT THE FRONTAL LOW REMAINS DOMINANT AND THAT THE
FRONTAL STRUCTURE WEAKENS AS THE SYSTEM MOVES SLOWLY TO THE NORTH.
THIS CONTINUES TO BE SUPPORTED BY THE FLORIDA STATE CYCLONE PHASE
DIAGRAMS THAT EVENTUALLY INDICATE A WEAKLY WARM CORE SYMMETRIC
SYSTEM. SSTS ARE MARGINAL TO SAY THE LEAST SO A HYBRID SYSTEM
APPEARS MORE LIKELY THAN PURELY TROPICAL BUT IN THE END NHC WILL
HAVE THAT CALL. LOCALLY THE CHANCE FOR HEAVY RAINFALL SEEMS TO BE
GOING UP MORE NOTABLY THAN THE CHANCE FOR ANY MEMORABLE WINDS.
ASSUMING AT LEAST SOME WARM RAIN PROCESSES THE TRACK OF THIS SYSTEM
(IT WILL BE A VERY SLOW MOVER AND MAY EVEN STALL, LOOP, OR
RETROGRADE) WE COULD SEE ANYTHING FROM A BENEFICIALLY VERY WET
WEEKEND TO SOME ARRANT FLOODING ISSUES. ANOTHER FACTOR THAT
COMPLICATES THE RAINFALL POTENTIAL IS THE SEEMING LIKELIHOOD OF A
HYBRID SYSTEM. THE RAINFALL DISTRIBUTION WILL NOT BE VERY SYMMETRICAL
ABOUT THE CIRCULATION. RATHER, THERE SHOULD BE A FOCUSED CHANNEL OF
SOUTHEASTERLY FLOW WHERE A FAIRLY LOCALIZED BULLSEYE OF HEAVY
RAINFALL IS FOCUSED. GIVEN THE AFOREMENTIONED POSSIBILITY OF A
STALLED OUT SYSTEM THE POP FORECAST WILL ONLY GRADUALLY DECREASE
HEADING INTO EARLY NEXT WEEK. MOISTURE FROM THIS SYSTEM COULD
CONCEIVABLY LINGER INTO TUESDAY OR WEDNESDAY AT WHICH TIME A COLD
FRONT WILL BE APPROACHING FROM THE NORTHWEST.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
AS OF 00Z...CONFIDENCE IS STILL RATHER LOW...BUT IMPROVING AS THE
MODELS ARE STARTING TO GET A BIT MORE IN SYNC. LOW PRESSURE WILL
SLOWLY APPROACH THE REGION TOWARD MORNING...WITH SHOWERS AND MVFR
CONDITIONS EXPECTED AROUND DAYBREAK ALONG THE COAST. THE GRADIENT
WILL TIGHTEN ALSO AROUND DAYBREAK...WITH GUSTS OVER 20 KTS A GOOD
BET AFTER 13Z. THE INLAND TERMINALS WILL TAKE A WHILE TO GET
ANY PRECIP...PERHAPS BY EARLY AFTERNOON. THE COLUMN OF DEEP MOISTURE
WILL REMAIN OVER THE REGION THROUGH THE END OF THE FORECAST
PERIOD...WITH INTERMITTENT IFR IN THE HEAVIER PRECIP.

EXTENDED OUTLOOK...RAIN/MVFR. TEMPO IFR IN HEAVIER SHOWERS HIGHEST
CONFIDENCE COASTAL TERMINALS. BECOMING VFR/SHOWERS SUNDAY. VFR
ISOLATED SHOWERS MON.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 PM WEDNESDAY...LOW PRESSURE A FEW HUNDRED MILES SOUTH
OF CAPE FEAR IS NOT BECOMING APPRECIABLY BETTER ORGANIZED THIS
EVENING...BUT CONTINUES TO HAVE A BETTER THAN A 50-50 CHANCE OF
BECOMING A NAMED SUBTROPICAL CYCLONE IN THE NEXT FEW DAYS.
REGARDLESS OF ITS DESIGNATION...A LARGE COUNTERCLOCKWISE SWIRL OF
WINDS FROM CAPE HATTERAS INTO THE NORTHERN BAHAMAS IS BUILDING SEA
HEIGHTS AT A PRETTY GOOD RATE EARLY THIS EVENING. DATA FROM THE
FRYING PAN SHOALS BUOY INDICATES SEAS ARE ALREADY 7.2 FEET...WITH
4.5-5 FOOT SEAS SHOWING UP VERY CLOSE TO SHORE AT THE TWO CORMP
BUOYS NEAR CAPE FEAR.

RADAR SHOWS RAIN OFFSHORE ON THE NORTHERN PERIPHERY OF THE CYCLONE
HAS PUSHED UP TO ABOUT 20 MILES FROM CAPE FEAR. RELATIVELY DRY
AIR SHOULD IMPEDE THIS RAIN FROM MOVING WESTWARD TOO RAPIDLY...BUT
SHOWERS SHOULD BE LIKELY ACROSS MOST OF THE WATERS BY DAYBREAK.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 300 PM WEDNESDAY...SMALL CRAFT ADVISORY FLAGS WILL BE FLYING
THROUGH THE PERIOD. HOWEVER...THESE FLAGS MAY BE REPLACED BY A
TROPICAL STORM WATCH OR WARNING DURING/BY THURSDAY. IN EITHER
CASE...THE SLOW EVOLUTION AND MOVEMENT OF THIS SYSTEM UP THE
SOUTHEAST COAST AND ITS EXPANSIVE CONVECTION WILL CHURN UP SEAS
AND WE ARE EXPECTING SEAS TO BUILD UP TO 6 TO 10 FT...PERHAPS
PEAKING THU NIGHT AND FRI. WIND SPEEDS WILL BE UP TO 20 TO 30 KT
WITH HIGHER GUSTS AND THE DIRECTION WILL PRIMARILY BE FROM THE NE
AND E THU AND THU NIGHT AND E OR SE FRI AND FRI NIGHT.

LONG TERM /SATURDAY THROUGH MONDAY/...
AS OF 300 PM WEDNESDAY...WE WILL HAVE ADVISORIES UP ON SATURDAY
IF NOT TROPICAL WARNINGS FROM NHC. THE POSSIBLE SLOW AND ERRATIC
MOVEMENT OF THE SYSTEM WILL MAKE IT TOUGH TO SAY AT WHAT SPEED
CONDITIONS WILL IMPROVE AND AT WHAT TIME SUCH HEADLINES CAN BE
STEPPED DOWN. A STALLING OF THE STORM COULD ALSO MEAN THAT THE
WIND DIRECTION FORECAST IS OFF. IN THE END UNTIL THIS SYSTEM
STARTS TO CONGEAL INTO A MORE ORGANIZED AREA OF LOW PRESSURE
(TOMORROW OR FRIDAY) THERE IS JUST TOO MUCH UNCERTAINTY TO CHANGE
THE FORECAST MUCH AT ALL AT THIS TIME.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT FRIDAY FOR AMZ250-252-254-
     256.

&&

$$

SYNOPSIS...TRA
NEAR TERM...TRA
SHORT TERM...RJD
LONG TERM...MBB
AVIATION...HDL


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