Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 031801 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 201 PM EDT SUN MAY 3 2015 .SYNOPSIS... HIGH PRESSURE WILL MOVE OVERHEAD THROUGH TONIGHT...AND EAST OF THE AREA INTO THE MID-WEEK PERIOD. THIS HIGH PRESSURE SYSTEM WILL CONTINUE TO RIDGE BACK ACROSS THE FORECAST AREA. A DEVELOPING COASTAL LOW OVER THE BAHAMAS DURING THE MID-WEEK PERIOD...WILL LIFT NORTHEAST AND PARALLEL THE SOUTHEAST U.S. COAST DURING THE UPCOMING MID TO LATE WEEK PERIOD. && .NEAR TERM /THROUGH TONIGHT/... AS OF 200 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 AM SUNDAY...BERMUDA HIGH WILL REMAIN THE MAIN SURFACE FEATURE DURING THE PERIOD WHILE ALOFT WEAK 5H RIDGE WILL TRY TO BUILD OVER THE SOUTHEAST. INITIALLY THERE WILL BE RESISTANCE FROM THE REMAINS OF A WEAK 5H SHORTWAVE TROUGH BUT EVENTUALLY THIS WILL BE OVERPOWERED. AS FAR AS LOCAL WEATHER GOES THE REGION WILL REMAIN DRY WITH PLENTY OF SUN AND TEMPERATURES NEAR TO SLIGHTLY ABOVE CLIMO WITH THE EXCEPTION OF HIGHS ALONG THE COAST RUNNING A LITTLE COOLER. THE AFOREMENTIONED SHORTWAVE TROUGH MAY RESULT IN A LITTLE MORE CLOUD COVER ACROSS WESTERN PORTION OF THE FORECAST AREA...ESPECIALLY MON AFTERNOON BUT PRECIP CHANCES WILL REMAIN NEAR ZERO THROUGH TUE NIGHT. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... AS OF 3 AM SUNDAY...BIG STORY IN THE EXTENDED CONTINUES TO BE THE SYSTEM EXPECTED TO EMERGE FROM THE CARIBBEAN/BAHAMAS MID WEEK. GUIDANCE CONTINUES TO STRUGGLE WITH THE EVOLUTION OF THE SYSTEM AND BOTH THE GFS/ECMWF HAVE BEEN SWINGING BACK AND FORTH BETWEEN A WELL DEFINED HYBRID SYSTEM AND A WEAK BARELY CLOSED OFF LOW ALONG A TROPICAL WAVE. ONE THING THAT SEEMS TO BE FAIRLY CERTAIN IS THE STATE OF THE STEERING FLOW. THE SYSTEM WILL TAKE SHAPE UNDER 5H RIDGING OVER THE SOUTHEAST AND WESTERN ATLANTIC LATER THIS WEEK. THIS WILL WILL LEAD TO THE LOW MEANDERING OFF THE SOUTHEAST COAST FOR MUCH IF NOT ALL OF THE PERIOD. INITIALLY THE LOW IS FAR ENOUGH FROM THE COAST THAT PRECIP IS NOT A CONCERN THUS WILL MAINTAIN THE INHERITED DRY FORECAST WED. POP FORECAST FOR THU THROUGH SAT IS LESS CLEAR. COLD FRONT TRIES TO DROP IN FROM THE NORTH BUT NOT SURE HOW MUCH SUCCESS IT WILL HAVE. HOWEVER THE LOW OFF THE COAST WILL BE WORKING TO SPREAD A SIGNIFICANT AMOUNT OF LOW LEVEL MOISTURE OVER THE SOUTHEAST. THIS SHOULD LEAD TO AN INCREASE IN PRECIP CHANCES LATE IN THE WEEK...ESPECIALLY AS THE MID LEVEL RIDGE SHOULD BE WEAKENING. CONFIDENCE IN THE ULTIMATE TRACK OF THE LOW REMAINS RATHER LOW...ESPECIALLY GIVEN THE VERY WEAK STEERING FLOW SO AT THIS POINT IT IS HARD TO PIN DOWN ANY ONE DAY AS A FAVORED DAY FOR PRECIP. FOR NOW PLAN TO BUMP PRECIP CHANCES LATE IN THE PERIOD A BIT BUT NOT A SIGNIFICANT AMOUNT. HIGH WILL BE NEAR TO SLIGHTLY BELOW CLIMO WITH LOWS RUNNING SLIGHTLY ABOVE. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... AS OF 18Z...POTENTIAL FOR MVFR/IFR DUE TO FOG OVERNIGHT INTO MONDAY MORNING. OTHERWISE EXPECT VFR. FEW/SCT CU WILL CONTINUE TO DEVELOP THIS AFTERNOON WITH NORTH- NORTHEAST AROUND 5 TO 10 KTS BECOMING SOUTHEAST AOB 12 KTS AS THE AFTERNOON SEABREEZE PUSHES INLAND. INTO THE OVERNIGHT HOURS AS HIGH PRESSURE GRADUALLY SHIFTS OFFSHORE...LIGHT WINDS AND NEARLY CLEAR SKIES WILL PREVAIL. CANNOT RULE OUT PATCHY FOG DEVELOPMENT LATE OVERNIGHT INTO EARLY MORNING HOURS...POTENTIALLY CREATING MVFR/IFR. ON MONDAY...VFR WILL PREVAIL WITH LIGHT SOUTHEAST TO SOUTHWEST WINDS. EXTENDED OUTLOOK...PRE-DAWN MORNING FOG IS POSSIBLE EACH DAY THAT COULD RESULT IN MVFR/IFR CONDITIONS...OTHERWISE EXPECT VFR. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 200 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 AM SUNDAY...BERMUDA HIGH EXTENDING WEST WILL MAINTAIN EAST TO SOUTHEAST FLOW THROUGH THE PERIOD. GRADIENT WILL REMAIN WEAK WITH SPEEDS 10 KT OR LESS. SOME NEAR SHORE ENHANCEMENT WILL BE POSSIBLE EACH AFTERNOON BUT ONSHORE FLOW WILL LIKELY MINIMIZE THE EFFECT OF THE SEA BREEZE. PROLONGED ONSHORE FLOW WILL PUSH 2 FT SEAS ON MON TO 2 TO 3 FT TUE. LONG TERM /WEDNESDAY THROUGH THURSDAY/... AS OF 3 AM SUNDAY...MAIN CONCERN CONTINUES TO BE THE SYSTEM EMERGING FROM THE BAHAMAS AND THE UNCERTAINTY ASSOCIATED WITH IT. BERMUDA HIGH WILL RETREAT ON WED AS THE LOW SLOWLY DRIFTS NORTH. THE LACK OF STEERING FLOW MEANS THE LOW WILL DRIFT SLOWLY ALTHOUGH THE DIRECTION REMAINS A QUESTION. FOR NOW WILL SHOW WINDS BACKING TO NORTHEAST WED AND REMAINING NORTHEAST THU. GRADIENT SHOULD START TO INCREASE LATER IN THE PERIOD ALTHOUGH THE INCREASE IS NOT LIKELY TO BE A LOT. WILL SHOW NORTHEAST FLOW INCREASING LATE BUT STILL HAVE SPEEDS BELOW HEADLINE CRITERIA. EXTENDED PERIOD OF NORTHEAST FETCH WILL SLOWLY BUILD SEAS FROM 2 TO 4 FT WED MORNING TO 3 TO 6 FT BY THE END OF THE PERIOD. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...RGZ SHORT TERM...III LONG TERM...III AVIATION...SGL

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