469 FXUS62 KILM 031027 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 627 AM EDT SUN AUG 3 2014 .SYNOPSIS... A COASTAL FRONT WILL KEEP THE WEATHER UNSETTLED TODAY. RAIN CHANCES CONTINUE OR POSSIBLY INCREASE ON MONDAY AS A TROPICAL WAVE MOVES NORTHWARD BY THE AREA. BERTHA WILL REMAIN MUCH TOO FAR OFFSHORE FOR ANY DIRECT IMPACTS THROUGH TUESDAY. MORE SEASONABLE WEATHER RETURNS WEDNESDAY AND THURSDAY. COOLER WEATHER IS THEN SLATED FOR THE LATE WEEK PERIOD BEHIND A COLD FRONT. && .NEAR TERM /THROUGH TONIGHT/... AS OF 6:30 AM SUNDAY...NO CHANGES TO THE FORECAST WITH THE LATEST UPDATE. PREVIOUS DISCUSSION FOLLOWS: LATEST WRINKLE IN THE NEAR TERM FORECAST CONCERNS FORMATION OF A TROPICAL DISTURBANCE OVER THE BAHAMAS. SYSTEM IS MOVING NORTH AT AROUND 10 MPH. ALTHOUGH THE NHC SAYS DISTURBANCE IS SHOWING NO SIGNS OF ORGANIZATION AND ONLY GIVES IT A 10 PERCENT CHANCE OF FORMATION OUT THROUGH 5 DAYS...NAM AND TO A LESSER EXTEND THE GFS HINT AT AN INTERACTION BETWEEN THIS FEATURE AND AN INVERTED TROUGH/TROPICAL WAVE FEATURE JUST OFFSHORE THAT COULD MARKEDLY INCREASE PRECIPITATION CHANCES OVERNIGHT. THE ECMWF IS ALSO IN THIS CAMP WITH THEIR LATEST AVAILABLE GUIDANCE. IF THIS SCENARIO COME TO PASS...WE WILL HAVE TO CONSIDER EXTENDING THE PRESENT FLOOD WATCH THROUGH TONIGHT. IN ANY CASE...CONDITIONS REMAIN FAVORABLE FOR PERIODS OF HEAVY RAIN AT LEAST THROUGH THE DAYLIGHT HOURS..SO WILL BE KEEPING THE RESENT FLOOD WATCH UP INTO THE NEAR TERM. A PERSISTENT AND NEARLY STATIONARY FRONT IS ANALYZED OVER OUR NC AND SC COASTAL PLAIN COUNTIES THIS MORNING. MODEL CONSENSUS HAS THIS FRONT WAVERING BACK AND FORTH THROUGH THE PERIOD...ALTHOUGH TIMING OF FRONT PLACEMENT IS LOW CONFIDENCE DUE TO MODEL SPREAD IN ITS MOTION. AT THE UPPER LEVELS A LONG-WAVE TROUGH WILL MAINTAIN ITS HOLD OVER EASTERN CONUS AS A SERIES OF WEAK DISTURBANCES ROUND ITS BASE AND MOVE NE OVER THE EASTERN CAROLINAS. WATER VAPOR LOOPS CONTINUE TO SHOW A TROPICAL PLUME OF MOISTURE ADVECTING NE OVER THE FORECAST AREA...ESPECIALLY OVER THE COASTAL PLAIN. MODEL SOUNDINGS ALSO CONTINUE TO SHOW A DEEPLY MOIST COLUMN THROUGH THE PERIOD...WITH A MODERATELY UNSTABLE AIRMASS AND P/W VALUES WELL IN EXCESS OF 2 INCHES. ALL ELEMENTS REMAIN IN PLACE FOR POTENTIAL WIDESPREAD SHOWER AND THUNDERSTORM ACTIVITY...WITH THE ATTENDANT HEAVY RAIN THREAT CONTINUING WELL INTO TODAY. GUIDANCE HAS BEEN WOEFULLY POOR LATELY IN CAPTURING THE UNUSUALLY LOW MAXIMUM TEMPERATURES BROUGHT ABOUT BY EXTENSIVE CLOUD COVER AND PRECIPITATION. SO...WILL GO SIGNIFICANTLY UNDER GUIDANCE BY LIMITING MAXIMUM TEMPERATURES TO THE LOWER 80S FOR TODAY. OVERNIGHT LOWS WILL HOVER AROUND 70. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 3 AM SUNDAY...MONDAYS FORECAST WILL NOW HINGE UPON WHAT MAY END UP BEING A COMPLEX (AND POORLY SAMPLED) INTERACTION BETWEEN TWO CIRCULATIONS OFF THE EAST COAST...BERTHA AND TROPICAL WAVE NOW IN THE BAHAMAS. WRF SCORED A BIT OF A COUP WHEN IT STARTED SHOWING THIS LAST NIGHT. THE QUESTION THAT NOW REMAINS TO BE SEEN...WHICH CIRCULATION BECOMES THE DOMINANT ONE? WRF MAINTAINS THAT IT WILL BE THE WESTERN SYSTEM AND THAT THE COAST IS IN FOR QUITE A RAINSTORM FOLLOWING A WET WEEKEND AND OUR CURRENT FLOOD WATCH WILL LIKELY NEED TO BE EXTENDED. BERTHA CURRENTLY UNDERGOING LAND INTERACTION WITH HISPANIOLA...AND SEEMINGLY MAINTAINING A FAIR AMOUNT OF CONVECTION...AND SO RIGHT NOW IT SEEMS THAT THE WRF IS A BIT EXTREME. GFS LAST NIGHT PRETTY MUCH IGNORED THE BAHAMA LOW BUT NOW GIVES IT AN IDENTITY THROUGH THE PERIOD WHILE SEEMINGLY PLAUSIBLY KEEPING BERTHA AS A SEPARATE ENTITY. THE MAIN PROBLEM WITH THE GFS IS IT SEEMS ERRONEOUSLY SLOW WITH THE WESTERN LOW AND SHOWS SURPRISINGLY LITTLE QPF FOR A SYSTEM THAT IS NOT ONLY OF TROPICAL ORIGIN BUT ALSO POSSIBLY TAPPING SOME MOISTURE FROM A TROPICAL STORM. THIS SYSTEM WILL LIKELY STILL BE PUSHING MOISTURE TOWARDS THE COAST MONDAY NIGHT INTO TUESDAY MORNING. TUESDAY AFTERNOON WILL BRING A DRYING TREND AT LEAST IN THE MID LEVELS. RAIN CHANCES WILL BE ON THE DECLINE AND THE AREA MAY START TO SEE SOME MORE BREAKS OF SUN THAN IT HAS RECENTLY. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... AS OF 3 PM SUNDAY...WEDNESDAY WILL OFFER UP SEASONABLY WARM WEATHER AND MINIMAL RAIN CHANCES. NEARLY ZONAL/WESTERLY MID LEVEL FLOW LOCALLY AROUND PERSISTENT TROUGHINESS IN THE NORTHEAST TO KEEP THINGS FAIRLY DRY. VERY LOW RAIN CHANCES COMING FROM SEA BREEZE AND PIEDMONT TROUGH WHERE AN ISOLATED SHOWER OR TSTM CANNOT BE RULED OUT. AFOREMENTIONED UPPER TROUGH SHARPENS ON THURSDAY DRIVING A LATE DAY COLD FRONT INTO THE REGION. WITH THE LACK OF MID LEVEL MOISTURE AND EVEN NO APPRECIABLE INFLUX OF GULF OR ATLANTIC LOW LEVEL MOISTURE AHEAD OF THE BOUNDARY ITS HARD TO IMAGINE HOW IT BRINGS AN APPRECIABLE INCREASE IN RAIN CHANCES. AS IT STALLS TO OUR SOUTH IT WILL USHER IN SOME COOLER AIR OVER THE WEEKEND. TOUGH TO SAY HOW MUCH PENDING HOW CLOUDY IT GETS VS THE ACTUAL AIRMASS CHANGE/COOL ADVECTION. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... AS OF 06Z...LIFR CONDITIONS WILL CONTINUE THROUGH 14Z AT KFLO/KLBT WITH IMPROVEMENT TO MVFR EXPECTED AFTERWARDS. SHOWERS DEVELOP BY 14Z. PROGS ARE IN GENERAL AGREEMENT PRECIPITATION WILL PERSIST AT LEAST THROUGH 14Z AT THE COASTAL TERMINALS. ATTM THE CHANCE OF TS APPEARS TOO LOW TO INCLUDE IN TAFS. MVFR EXPECTED WITH SHOWERS ALTHOUGH IFR/LIFR CIGS COULD ALSO OCCUR AROUND 12Z...WITH THE BEST CONFIDENCE OF OCCURRENCE...ALBEIT LOW...AT KCRE/KMYR. VFR EXPECTED AFTER THE PRECIPITATION ENDS MID-MORNING. EXTENDED OUTLOOK...SHRA/TSRA LIKELY WITH PERIODS OF MVFR CONDITIONS THROUGH TUESDAY AS A FRONT STALLS AND FINALLY DISSIPATES OVER THE EASTERN CAROLINAS. A CHANCE OF SHOWERS CONTINUES ON WEDNESDAY LATE INTO THURSDAY MORNING. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 6:30 AM SUNDAY...NO CHANGES TO THE FORECAST WITH THE LATEST UPDATE. PREVIOUS DISCUSSION FOLLOWS: AN INVERTED TROUGH/TROPICAL WAVE FEATURE OVER THE WATERS IS KEEPING WINDS LIGHT AND VARIABLE WITH SEAS IN THE 3 FT RANGE. A NEARLY STATIONARY FRONT WILL REMAIN INLAND OR JUST NEAR THE COAST TODAY AND TONIGHT. WINDS WILL BECOME SOUTHEASTERLY LATER THIS MORNING IN THE 10 TO 15 KT RANGE...WITH SEAS REMAINING AROUND 3 FT. THESE CONDITIONS WILL PERSIST THROUGH THE NEAR TERM. EXPECT EXTENSIVE SHOWER AND THUNDERSTORM ACTIVITY OVER THE WATERS AS A TROPICAL PLUME OF MOISTURE MOVES NORTH ACROSS THE WATERS. SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 3 AM SUNDAY...PRETTY DIFFICULT FORECAST ON MONDAY. WINDS WILL BE MAINLY A FUNCTION OF THE INTERACTION BETWEEN BERTHA AND A TROPICAL WAVE NOW OVER THE BAHAMAS. MODEL SOLUTIONS VARY CONSIDERABLY AS TO HOW THESE TWO WILL INTERACT AND WHICH ONE WILL END UP BECOMING A DOMINANT CIRCULATION AS THEY BOTH PASS NORTHWARD ACROSS OUR LATITUDE ON MONDAY. BERTHA CURRENTLY INTERACTING WITH HISPANIOLA FURTHER COMPLICATING THE ISSUE. SOUTHEASTERLY WINDS SHOULD BE PREDOMINANT LOCALLY EITHER WAY...ALTHOUGH THE STRENGTH OF THESE WINDS AND TO A LESSER EXTENT THE MAGNITUDE OF SEAS REALIZED WILL BE MODULATED BY WHICH SYSTEM TAKES OVER. SHOULD IT BE BERTHA THEN THE CURRENT FCST APPLIES. SHOULD THE WESTWARD WAVE TAKE OVER THEN WINDS MAY BE A BIT HIGHER IN SPEED AND CHANGE MORE THROUGH THE DAY AS THE FCST ZONES EXPERIENCE MORE CLOSED ISOBARS. A SMALL CRAFT ADVISORY IS GETTING TOUGH TO RULE OUT ESP FOR NRN ZONES BUT THERE IS JUST TOO MUCH UNCERTAINTY TO RAISE AT THIS POINT. EITHER WAY WINDS SHOULD SWING AROUND TO THE NORTH AND THEN WEST ON TUESDAY AS THE SYSTEMS ACCELERATE OFF TO THE NORTH AND EAST. SUCH A TURN TO OFFSHORE OFTEN ACTS TO DIMINISH NEARSHORE SEAS AS LANDMASS WAVE SHADOWING TAKES OVER BUT THERE WILL BE ENOUGH BACKSWELL TO MINIMIZE THIS FOR MUCH OF TUESDAY. THE EXCEPTION SHOULD BE BRUNSWICK WATERS WHERE THERE WILL NOT ONLY BE WESTERLY SHADOWING OF WIND WAVES BUT ALSO A SWELL SHADOWING FROM CAPE FEAR. LONG TERM /WEDNESDAY THROUGH THURSDAY/... AS OF 3 PM SUNDAY...WEAK PIEDMONT TROUGHINESS TAKES SHAPE ON WEDNESDAY YIELDING A SOUTHWESTERLY WIND OF FAIRLY 'SEASONABLE' SPEED. SEAS NORMALLY 2 TO 3 FT IN SUCH A SETUP BUT A REMNANT EASTERLY SWELL MAY STILL BE GIVING RISE TO 4 FT DOMINANT WAVES OVER NRN ZONES. THE TROUGH MOVES CLOSER TO THE COAST ON THURSDAY WHILE A COLD FRONT ALSO APPROACHES FROM THE NW. OVERALL THE GRADIENT WILL EASE AND THE FLOW MAY BACK TO SRLY. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...FLOOD WATCH THROUGH THIS EVENING FOR SCZ017-023-024-032-033- 039-053>056. NC...FLOOD WATCH THROUGH THIS EVENING FOR NCZ087-096-099-105>110. MARINE...NONE. && $$ SYNOPSIS...MBB NEAR TERM...REK SHORT TERM...MBB LONG TERM...MBB AVIATION...REK/MRR MARINE...REK/MBB