217 FXUS62 KILM 031816 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 216 PM 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 2 PM SUNDAY...CHALLENGING FORECAST WITH POTENTIAL FOR ANOTHER ROUND OF SIGNIFICANT RAINFALL OVERNIGHT. CURRENTLY THE COASTAL TROUGH IS SLOWLY PUSHING INLAND. AS HAS BEEN THE CASE THE LAST FEW DAYS THE LATE NIGHT/EARLY MORNING PRECIP HAS SHUT OFF WITH THE ACTIVITY SHIFTING OFFSHORE. MAY START TO SEE SOME BREAKS IN THE CLOUD COVER ACROSS INLAND SC AS MID LEVEL DRY AIR TRIES TO MOVE IN FROM THE WEST. THINK BREAKS WOULD BE FEW AND FAR BETWEEN BUT ISOLATED CONVECTION COULD DEVELOP IN THESE REGIONS...ESPECIALLY IF THE TROUGH CAN PUSH A BIT FARTHER INLAND AND ADD SOME CONVERGENCE TO THE MEAGER INSTABILITY. DO NOT EXPECT MUCH WIDESPREAD HEAVY RAIN FOR THE REMAINDER OF THE AFTERNOON BUT THE PROBABILITY OF MEASURABLE PRECIP WILL REMAIN HIGH. FEEL CONFIDENT A BAND OF HEAVY RAIN...SIMILAR TO THIS MORNINGS WILL DEVELOP OVERNIGHT. IT APPEARS THERE WILL BE SEVERAL ELEMENTS IN PLACE FAVORING AN AREA OF ENHANCED PRECIP. WEAK SURFACE LOW TRAVELING NORTH ALONG THE COASTAL TROUGH WILL ENHANCE LOW LEVEL CONVERGENCE AND PUMPING MORE MOISTURE INTO THE REGION. ENHANCED SOUTH TO SOUTHEAST FLOW WILL KEEP PRECIPITABLE WATER VALUES OVER 2 INCHES...EXCEEDING 2.25 INCHES AT TIMES. MUCH OF THE GUIDANCE IS AGAIN SHOWING AN AREA OF ELEVATED FRONTOGENESIS DEVELOPING NEAR THE AXIS OF HIGHEST RH...THOUGH ISENTROPIC LIFT WILL BE WEAKER THAN THIS MORNING. THERE WILL BE A LOW LEVEL JET...SOMETHING THAT WAS MORE OR LESS LACKING LAST NIGHT...AND DIFFLUENCE ALOFT AS 70KT JET STREAK MOVES UP THE EASTERN SIDE OF THE TROUGH. ALL OF THESE FACTORS POINT TO MORE RAINFALL WITH POTENTIAL FOR EXCESSIVE RAINFALL. THE BIG QUESTION REMAINS WHERE WILL IT FALL. THE NAM...WHICH WAS FARTHER WEST WITH THIS MORNINGS BAND HAS A PRECIP BULLSEYE ON SOUTHEASTERN NC. THE GFS...WHICH WAS CLOSER TO REALITY EARLIER TODAY...HAS THE BAND SETTING UP ALONG THE COAST AND EXTENDING JUST OFFSHORE. FEEL THE GFS SOLUTION IS CLOSER TO WHAT WILL HAPPEN GIVEN ITS RECENT SUCCESS AND THE LESS THAN DESIRABLE HANDLING OF BERTHA BY THE NAM. THUS WILL MAINTAIN HIGHEST POP ALONG THE COAST BUT CONTINUE TO CARRY A MENTION OF PRECIP ACROSS THE FORECAST AREA. ALTHOUGH THE BULK OF THE PRECIP IS EXPECTED ALONG THE COAST LATER TODAY AND TONIGHT THE AMOUNT OF RAIN THAT FELL ACROSS INLAND AREAS COMBINED WITH POTENTIAL FOR HEAVY RAIN ONCE AGAIN TONIGHT WILL PROBABLY LEAD TO THE FLOOD WATCH...SET TO EXPIRE AT 8 PM TONIGHT...BEING EXTENDED INTO MON WITH THE AFTERNOON UPDATE. LOWS WILL CONTINUE TO RUN NEAR OR SLIGHTLY ABOVE CLIMO WITH COOLEST AREAS WELL INLAND AND WARMEST AREAS LONG THE COAST. && .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 /17Z SUNDAY THROUGH FRIDAY/... AS OF 18Z...CONVECTION HAS DIED DOWN FOR THE NEAR TERM...WITH ONLY LIGHT ACTIVITY EXPECTED INTO THE EVENING HOURS. LIGHT MAINLY NORTHEAST FLOW...WITH INTERMITTENT IFR STRATUS...PARTICULARLY INLAND. OVERNIGHT...ANOTHER SLUG OF MOISTURE WILL MOVE ONSHORE...WITH A INVERTED TROUGH COUPLED WITH THE DIVERGENT QUADRANT OF THE JET. RAIN COULD BE QUITE HEAVY ALONG THE COAST WITH POSSIBLY ANOTHER ROUND OF FLOODING. MODERATE TO HEAVY SHOWERS ARE EXPECTED THROUGH MOST OF THE FORECAST PERIOD. 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 THROUGH FRIDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 2 PM SUNDAY...SOUTHEAST FLOW WILL CONTINUE THROUGH THE PERIOD WITH A SLIGHT INCREASE IN SPEEDS EXPECTED LATER TONIGHT AHEAD OF WEAK LOW LIFTING NORTH FROM THE BAHAMAS. SPEEDS SHOULD REMAIN WITHIN THE 10 TO 15 KT RANGE THROUGH THE END OF THE PERIOD. SEAS WILL RUN 3 TO 4 FT...MAINLY AS SOUTHEAST WIND WAVE. 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 UNTIL 8 PM EDT THIS EVENING FOR SCZ017-023-024-032- 033-039-053>056. NC...FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR NCZ087-096-099- 105>110. MARINE...NONE. && $$ SYNOPSIS...MBB NEAR TERM...III SHORT TERM...MBB LONG TERM...MBB AVIATION...43