Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 032233 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 632 PM EDT SUN MAY 3 2015 .SYNOPSIS... THE CENTER OF HIGH PRESSURE WILL DRIFT SLOWLY OFFSHORE THROUGH EARLY WEEK...PROVIDING SUNSHINE AND SEASONABLE MAY TEMPERATURES. A COASTAL LOW IS EXPECTED TO FORM IN THE BAHAMAS MID-WEEK...AND MEANDER ALONG THE SOUTHEAST COAST THROUGH THE END OF THE WEEK INTO NEXT WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 3 PM SUNDAY...DRY AND SEASONABLE WEATHER WILL CONTINUE THROUGH TONIGHT AS HIGH PRESSURE SLIPS OFF SHORE WITH A LIGHT RETURN FLOW SETTING UP. THERE WILL BE PLENTY OF SUBSIDENCE AND DRY AIR THROUGH THE MID TO UPPER LEVELS WITH ONLY LIMITED LOW LEVEL MOISTURE THROUGH THE COLUMN. THIS WILL ONLY ALLOW FOR SOME FLAT CU AS SOUNDINGS SHOW A DECENT SUBSIDENCE INVERSION RIGHT AROUND 8-9K FT WHICH WILL LIMIT THE VERTICAL GROWTH OF ANY CU. AS THE CENTER OF THE HIGH REMAINS NEARLY OVERHEAD THIS AFTERNOON...EXPECT A VERY WEAK GRADIENT AND THEREFORE VERY LIGHT PREVAILING WINDS BUT THIS WILL LEAD TO A STRONGER SEA BREEZE PUSHING WELL INLAND. EXPECT A GREATER AMOUNT OF CU ASSOCIATED WITH CONVERGENCE ALONG SEA BREEZE BOUNDARY AS IT PUSHES INLAND AND AROUND WESTERN PERIPHERY OF HIGH AS IT SHIFTS EAST THROUGH LATER TODAY. TEMPS WILL HOLD BETWEEN 75 AND 80 MOST PLACES THROUGH THE REMAINDER OF THE AFTERNOON...SLIGHTLY COOLER ALONG BEACHES. OTHERWISE EXPECT MID TO UPPER RIDGE TO TRY AND BUILD OVERHEAD WITH PLENTY OF SUBSIDENCE AND DRY AIR BUT IT WILL BE DISRUPTED BY A COUPLE OF SHORTWAVES MOVING DOWN IN THE NORTHWEST FLOW ALOFT TONIGHT. THESE SHOULD NOT PRODUCE ANYTHING MORE THAN SOME MID TO HIGH CLOUDS. THE AIR MASS WILL CONTINUE TO MODIFY IN E-SE RETURN FLOW AS SFC HIGH SHIFTS FARTHER EAST OVERNIGHT. THIS WILL ALLOW FOR MODEST MOISTURE RETURN WITH DEWPOINT TEMPS REACHING BACK FROM LOWER 40S THIS AFTERNOON UP TO THE MID 50S OVERNIGHT. EXPECT TEMPS TO DROP OFF AS ATMOSPHERE DECOUPLES LATE THIS EVENING WITH TEMPS DROPPING TO 50S FOR LOWS MOST PLACES. ALSO EXPECT PATCHY TO AREAS OF FOG AS TEMPS DROP WITH LIGHT TO CALM WINDS AND LIMITED CLOUD COVER. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 3 PM SUNDAY...SEASONABLE MAY SUNSHINE ON TAP THIS PERIOD WITH WEAK LOW-LEVEL ONSHORE FLOW AND DRY AIR PERCHED ABOVE 600MB AND LIGHT WINDS ALOFT. WEAK SHORT-WAVE IMPULSES WILL MEANDER OVER THE AREA AS NOTED IN H7-H5 VORTICITY FIELDS BUT WITHOUT FANFARE OTHER THAN MODERATE CUMULUS BUILD-UPS WITH ASSISTANCE FROM MAY SUN ANGLE AND RESULTING AFTERNOON INSOLATION. MAXIMUMS A FEW DEG EITHER SIDE OF 80 WARMEST INLAND...AND MINIMUMS IN THE UPPER 50S TO LOW 60S CLOSER TO THE COAST. TUESDAY LOOKS WARMER OVER THE INTERIOR AS THE UPPER RIDGE BECOMES SLIGHTLY MORE ESTABLISHED. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 3 PM SUNDAY...THE ENTIRETY OF THE LONG TERM WILL FOCUS ON WHAT IS EXPECTED TO BECOME A HYBRID/SUB-TROPICAL LOW OFF MEANDERING OFF THE SOUTHEAST COAST. LARGE AREA OF DISTURBED WEATHER WILL MOVE OUT OF THE CARIBBEAN AND THEN STRENGTHEN INTO A LOW PRESSURE SYSTEM WELL OFFSHORE. THIS OCCURS IN A REGION OF VERY WEAK STEERING FLOW IN THE VICINITY OF A LARGE MID-LEVEL RIDGE ACROSS THE SOUTHEAST...AND THUS THERE IS VERY LITTLE CONFIDENCE IN WHAT THIS SYSTEM WILL DO ONCE IT DEVELOPS...AND GUIDANCE IS ALL OVER THE PLACE IN HOW THE LOW WILL TRACK. HOWEVER...THERE IS INCREASING CONFIDENCE THAT A HYBRID- LOW WILL DEVELOP...BECOMING WARM CORE AND LIKELY STRENGTHENING THANKS TO A COMBINATION OF LATENT HEAT RELEASE FROM 80 DEGREE WATERS IN THE GULF STREAM...BAROCLINIC INSTABILITY DUE TO CHANGE IN WATER TEMPS NEAR THE COAST...AND GOOD VENTILATION THROUGH DIFFLUENCE ALOFT. WILL NOT MAKE ANY WHOLESALE CHANGES TO POP/WX IN THE EXTENDED DUE TO SUCH LOW CONFIDENCE...AND WILL MAINTAIN THE INHERITED POP FOR THE THU-SUN TIMEFRAME...HIGHEST CHANCE AT THE COAST. STILL...CANNOT FOCUS ON ANY SPECIFIC DAY BEING THE MOST FAVORABLE FOR PRECIP AS THE GUIDANCE ENVELOPE IS SO WIDE. ON THE BRIGHT SIDE...TEMPS THROUGH THE PERIOD SHOULD BE ABOVE CLIMO...ESPECIALLY AWAY FROM THE COAST. && .AVIATION /00Z MONDAY THROUGH SATURDAY/... AS OF 00Z...NOT MUCH SYNOPICALLY DIFFERENT FROM YESTERDAY...WITH HIGH PRESSURE OFFSHORE GIVING US SOUTHEAST FLOW. THERE IS FOG POTENTIAL AGAIN OVERNIGHT...MAINLY AFTER 08Z. CRE STANDS THE BEST CHANCE AGAIN...BUT COULD NOT RULE OUT INLAND FOG EITHER. DO NOT THINK WE WILL SEE THE LIFR CONDITIONS THAT WE EXPERIENCED LAST NIGHT. MONDAY...BECOMING VFR AT ALL LOCATIONS WITH CONTINUED SOUTHEAST FLOW...STRONGEST ALONG THE COAST. EXTENDED OUTLOOK...PRE-DAWN MORNING FOG IS POSSIBLE EACH DAY THAT COULD RESULT IN MVFR/IFR CONDITIONS. UNSETTLED WEATHER THURSDAY NIGHT THROUGH SATURDAY WITH A SUBTROPICAL LOW. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 3 PM SUNDAY...HIGH PRESSURE OVERHEAD THIS AFTERNOON WILL SHIFT FARTHER OFF SHORE THROUGH TONIGHT. THEREFORE EXPECT VERY LIGHT WINDS TODAY SHIFTING AROUND TO AN ON SHORE RETURN FLOW AS HIGH MOVES EAST WHILE EXTENDING BACK WEST. EXPECT A DECENT SEA BREEZE TO DEVELOP WHICH WILL LEAD TO SOME CHOPPY SEAS IN THE AFTERNOON INTO THE EVENING WITH WINDS NEARSHORE BECOMING E-SE TO S-SE AT 10 KT...AND UP TO 10 TO 15 KT AND GUSTY AT THE HEIGHT OF THE SEA BREEZE. SIGNIFICANT SEAS WILL RUN AROUND 2 TO 4 FT WITH A VERY SLOW DECLINE THROUGH TONIGHT AS SEA BREEZE CUTS OFF AND BACKSWELL FROM THE LOW MOVING OFF INTO THE DISTANT ATLANTIC WATERS BEGINS TO SLOWLY WANE. OVERALL THE LONGER PERIOD E-NE 9 TO 11 SECOND SWELL WILL CONTINUE TO DOMINATE THE WATERS WITH ONLY A SPIKE IN WIND WAVES THROUGH LATE THIS AFTN DUE TO THE SEA BREEZE. SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 3 PM SUNDAY...FRIENDLY MARINE ENVIRONMENT EXPECTED THIS PERIOD AS LIGHT ONSHORE FLOW PREVAILS WITH MINIMAL WAVE ENERGY. A MODERATE AFTERNOON SEA BREEZE MAY DRIVE ONSHORE GUSTS TO 17 KT INSHORE ACCOMPANIED BY MODERATE CHOP...OTHERWISE ONSHORE 10 KT MON/TUE. WITH LIGHT CHOP AND WEAK SWELL DOMINANT WAVE PERIOD OF 7-9 SECONDS EXPECTED...EXCEPT INSHORE DURING THE AFTERNOON THE CHOP MAY BRIEFLY BECOME THE PRIMARY ENERGY. NO TSTMS OR VSBY RESTRICTIONS EXPECTED MONDAY OR TUESDAY. LONG TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 3 PM SUNDAY...ALL EYES WILL BE ON A HYBRID-TYPE LOW PRESSURE SYSTEM DEVELOPING WELL OFF THE SOUTHEAST COAST. THIS LOW IS EXPECTED TO BEGIN FORMATION WEDNESDAY...AND THEN STRENGTHEN SLOWLY WHILE MEANDERING IN WEAK STEERING FLOW. STILL MUCH UNCERTAINTY REGARDING THIS PORTION OF THE FORECAST...BUT CONSENSUS AT THIS TIME KEEPS WINDS E/NE THROUGH THE PERIOD WITH SPEEDS PRIMARILY 10-15 KTS...HIGHER AT TIMES. OF COURSE...THESE COULD CHANGE SIGNIFICANTLY DEPENDING ON HOW THIS STORM SYSTEM EVOLVES. PROLONGED E/NE FETCH COMBINED WITH THE ELEVATED WINDS WILL DRIVE SEAS UP FROM 3-5 FT WEDNESDAY...TO 4-7 FT THU/FRI...AND AN EXTENDED SCA MAY BE NEEDED FOR MUCH OF THE PERIOD. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...8 NEAR TERM...RGZ SHORT TERM...COLBY LONG TERM...JDW AVIATION...43

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