Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 302319 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 718 PM EDT SAT MAY 30 2015 .SYNOPSIS... HIGH PRESSURE CENTERED WELL OFF THE EAST COAST WILL SLOWLY LOSE ITS INFLUENCE THROUGH MONDAY. A COLD FRONT WILL APPROACH FROM THE NORTH EARLY NEXT WEEK AND WILL BE IN CLOSE PROXIMITY MID AND LATE NEXT WEEK. THERE IS A RISK FOR SHOWERS AND THUNDERSTORMS EACH DAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 200 PM SATURDAY...SYNOPTIC PATTERN REMAINS ONE THAT CAN BE BEST DESCRIBED AS A "HYBRID SUMMER TYPE SETUP" THANKS TO THE PERSISTENT HIGH PRESSURE OFFSHORE BEING WELL DISPLACED FROM THE MORE TYPICAL BERMUDA RIDGE SETUP. WHILE THE NORMAL SETUP IN THE DOLDRUMS OF SUMMER WOULD HAVE THE HIGH CENTER MUCH FURTHER SW THAN WHERE IT CURRENTLY RESIDES...THE PATTERN IS BASICALLY THE SAME...WITH THE MAJOR DIFFERENCE BEING THE AIRMASS ADVECTING INTO THE REGION. AS HAS BEEN DISCUSSED PREVIOUSLY...AIR PARCELS MOVING INTO THE CAROLINAS ACTUALLY HAVE ORIGINATED IN SOUTHERN CANADA AND HAVE MADE THE 8 DAY TRANS-ATLANTIC TRIP AROUND THE SURFACE HIGH BEFORE REACHING THIS AREA. THIS IS CLEARLY EVIDENT ON HYSPLIT BACK TRAJECTORIES...AND THIS MODIFIED CONTINENTAL AIRMASS CARRIES MUCH LESS MOISTURE THAN THE TYPICAL SUB-TROPICAL AIRMASS ENCOUNTERED DURING THE SUMMER. IT IS PRIMARILY THIS REASON THAT SHOWERS/CONVECTION HAVE BEEN ONLY ISOLATED IN NATURE. THAT BEING SAID...LONG RESIDENCE TIMES OVER THE OPEN OCEAN STILL TRANSPORT MOISTURE LOCALLY...AND ISOLATED SHOWERS HAVE DEVELOPED ACROSS THE AREA...AND WILL CONTINUE TO DO SO THROUGH NIGHTFALL. THE BEST CHANCE FOR THIS WILL BE THE CENTRAL PORTIONS OF THE CWA WEST OF THE RESULTANT...AS WELL AS ALONG THE SEA BREEZE "NOTCH" WHICH WILL BE ORIENTED SE TO NW ACROSS BRUNSWICK AND COLUMBUS COUNTIES. HAVE CARRIED ONLY THE ISOLATED WORDING IN THE WX GRIDS...AND DO NOT HAVE ANY LIGHTNING AS DRY AIR ALOFT WILL SUPPRESS ANY UPDRAFTS FROM REACHING CHARGE SEPARATION TEMPERATURES. SHOWER ACTIVITY WILL WANE AFTER DARK WITH LOSS OF HEATING...BUT RENEWED SHOWER ACTIVITY MAY ONCE AGAIN DEVELOP OFFSHORE AND ADVECT TOWARDS THE COAST. HAVE KEPT MENTIONABLE POP JUST EAST OF THE CAPE FEAR REGION...BUT WOULD NOT BE SURPRISED IF A FEW SHOWERS AGAIN REACH THE SHORE FROM CAPE FEAR NORTH BY SUNRISE. THE OTHER CONCERN TONIGHT WILL BE FOG POTENTIAL. MOS NUMBERS ARE HIGHLY VARIABLE...BUT MINS HAVE BEEN COOLER THAN FORECAST THE PAST FEW NIGHTS. HAVE SIDED WITH THE COOLER MET NUMBERS AGAIN TONIGHT WITH LOW 60S INLAND AND MID 60S AT THE COAST. THIS IS IMPORTANT BECAUSE CROSSOVER TEMPERATURES ARE FORECAST TO BE REACHED IN SOME LOCATIONS...AND THE LOCAL UPS FOG PROCEDURE USING THE MODIFIED RICHARDSON NUMBER DOES PRODUCE A LARGE AREA OF FOG LOCALLY. HAVE OPTED TO KEEP FOG OUT OF THE OFFICIAL FORECAST (NOT EXPECTING 2SM VSBY) BUT SOME FOG SEEMS PLAUSIBLE INLAND FROM THE COAST WHERE WINDS WILL GO CALM AND HYDROLAPSE RATES APPEAR TO SUPPORT AT LEAST SHALLOW FOG. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 200 PM SATURDAY...WESTERN ATLANTIC RIDGE WILL VERY SLOWLY LOSE ITS INFLUENCE ACROSS THE EASTERN CAROLINAS THROUGH THE PERIOD. THIS WILL ALLOW A COLD FRONT TO THE NORTH AND NORTHWEST TO APPROACH AS WE MOVE INTO TUE. PRECIPITABLE WATER VALUES WILL INCREASE AS DRIER AIR AND SUBSIDENCE ERODE AND WE BEGIN TO TAP GULF OF MEXICO MOISTURE AHEAD OF APPROACHING TROUGH. INLAND AREAS WILL EXPERIENCE THE GREATEST SURGE...CLIMBING IN EXCESS OF AN INCH AND A HALF. STILL NO SIGNIFICANT UPPER LEVEL SUPPORT...ALTHOUGH A SUBTLE MID-LEVEL DISTURBANCE DOES REACH THE AREA FROM THE WEST AND NORTHWEST MON AFTERNOON AND EVE. MIXED LAYER CAPE VALUES WILL RISE TO NEAR 1000 J/KG EACH AFTERNOON. WE DO EXPECT AN UPTICK IN SHOWER AND THUNDERSTORM ACTIVITY AND COVERAGE SHOULD BE AT LEAST SCATTERED WITH THE GREATEST COVERAGE LIKELY MON AFTERNOON AND EVE. AS WAS THE CASE THIS MORNING...AT LEAST ISOLATED SHOWERS WILL BE POSSIBLE ALONG THE COAST AS THE SEABREEZE PUSHES INLAND. THE BEACHES WILL BE MORE PRONE TO GETTING SOME RAINFALL IN THE MORNING WHILE ELSEWHERE POPS WILL BE HIGHER MIDDAY AND THROUGH THE AFTERNOON AND EVE. TYPICAL TEMPS FOR THE LAST DAY OF MAY AND JUNE 1ST. HIGHS INLAND WILL BE IN THE UPPER 80S TO 90 DEGREES. THE SEABREEZE SHOULD KEEP THE MORE COASTAL LOCATIONS IN THE LOWER 80S. LOWS WILL BE IN THE UPPER 60S AND LOWER 70S. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 200 PM SATURDAY...MEDIUM RANGE GUIDANCE SHOWS A CUTOFF LOW MEANDERING ACROSS THE GULF COAST INITIALLY WITH A GENERAL WEAKENING TREND BY THE END OF THE PERIOD. IN TYPICAL SUMMER TIME PATTERN FORM...THE LOW ESSENTIALLY BECOMES A WEAKNESS IN THE 500MB HEIGHT PATTERN. AT THE SURFACE...A WEAK COLD FRONT TRUDGES ACROSS THE CAROLINAS AND ENDS UP OFFSHORE BY SATURDAY. THESE ELEMENTS WILL COMBINE TO KEEP UNSETTLED CONDITIONS IN THE FORECAST FOR MOST IF NOT ALL OF THE PERIOD. THE HIGHEST CHANCES OCCUR TUESDAY AND TREND DOWN SOMEWHAT THEREAFTER. BY THURSDAY THE FORCING WEAKENS SUFFICIENTLY TO APPLY A MORE ENHANCED DIURNAL TREND TO THE POPS. WPC IS PAINTING DECENT RAINFALL AMOUNTS ACROSS THE AREA WITH SEVEN DAY TOTALS RANGING FROM 2-3 INCHES. THE CAVEAT WITH THE LATEST GUIDANCE IS THE AXIS OF THE HEAVIEST QPF COULD SET UP JUST OFFSHORE. REGARDING TEMPERATURES...READINGS...BEYOND A WARMER TUESDAY...WILL BE NEAR SEASONABLE VALUES WITH HIGHS IN THE LOWER TO MIDDLE 80S AND OVERNIGHT LOWS IN THE MIDDLE TO UPPER 60S. DEPENDING ON THE ACTUAL COVERAGE OF CONVECTION...THESE RANGES MAY END UP SOMEWHAT LOWER. && .AVIATION /00Z SATURDAY THROUGH THURSDAY/...
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AS OF 00Z...VFR CONDITIONS ARE OVER THE AREA ATTM WITH SE TO S WINDS GENERALLY AOB 10 KT. THIS EVENING WINDS WILL BECOME LIGHT AND VARIABLE. MODELS AGAIN ARE SUGGESTING MVFR VSBYS DUE TO BR...MAINLY AT THE INLAND TERMINALS. HAVE MAINTAINED PREDOMINANT MVFR AT CRE/FLO/LBT. SOME SHOWERS MAY PRODUCE BRIEF MVFR CIGS AT ILM AFTER MIDNIGHT...BUT HAVE OPTED TO LEAVE IT OUT OF ILM TAF AS THE DURATION SHOULD BE BRIEF IF IT OCCURS AND SHOWER ACTIVITY SHOULD BE ISOLATED. EXPECT THE SAME CONDITIONS AS TODAY AFTER SUNRISE SUNDAY WITH TEMPO MVFR CIGS POSSIBLE BUT VFR FOR THE MOST PART. VCSH CONTINUES AT THE COASTAL TERMINALS WITH WINDS BECOMING SE AT ALL TERMINALS AFTER 14Z OR SO. EXTENDED OUTLOOK...MORNING MVFR CONDITIONS WITH MAINLY AFTERNOON ISOLATED/SCATTERED SHOWERS AND THUNDERSTORMS THROUGH THE PERIOD. AN INCREASED CHANCE FOR CONVECTION TUE AND WED. SHOWERS DECREASING FROM WEST TO EAST THU.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 200 PM SATURDAY...EXPANSIVE HIGH PRESSURE CENTERED WELL NE OF BERMUDA CONTINUES TO RIDGE BACK TOWARDS THE CAROLINAS THIS AFTN. THIS RIDGE IS MAINTAINING ITS INFLUENCE ACROSS THE WATERS...CREATING RATHER BENIGN MARINE CONDITIONS TODAY. WINDS HAVE BEEN PREDOMINANTLY FROM THE EAST WITH ONLY SLIGHT FLUCTUATION TO SE OR NE...AT SPEEDS OF LESS THAN 10 KT OUTSIDE OF THE SEA BREEZE. EVEN WITHIN THE NEAR SHORE SEA BREEZE...WINDS HAVE BEEN 10-15 KT WITH SIMILAR DIRECTION. WHILE NEAR-SHORE SEAS ARE LIKELY A BIT CHOPPY...THE PREDOMINANT WAVE GROUP IS FROM A 4FT/9SEC EASTERLY SWELL...DRIVING SEAS TO 2-4 FT ACROSS THE WATERS. LITTLE CHANGE IN THESE CONDITIONS IS EXPECTED THROUGH THE PERIOD...THE EXCEPTION BEING WITHIN THE WATERS IMPACTED BY THE SEA BREEZE WHERE WINDS WILL EASE WITH LOSS OF HEATING ALLOWING THE MEAN SYNOPTIC WIND TO TAKE OVER ONCE AGAIN. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 200 PM SATURDAY...WESTERN ATLANTIC HIGH PRESSURE WILL SLOWLY LOSE ITS GRIP ON THE WATERS. SSE TO S WINDS THROUGH MONDAY WILL BECOME SW MON NIGHT AS THE RIDGE FINALLY DEPARTS ALLOWING A FRONT TO APPROACH. WIND SPEEDS DURING THE PERIOD WILL BE NO HIGHER THAN 10 TO 15 KT...SOME HIGHER GUSTS ARE EXPECTED ACROSS THE NEAR SHORE WATERS DUE TO SEABREEZE INFLUENCES LATE MORNING THROUGH EARLY EVE EACH DAY. SEAS WILL BE MAINLY 3 TO 4 FT SUN AND SUN NIGHT...BUT THE 8 TO 9 SECOND EASTERLY SWELL SHOULD CONTINUE TO SLOWLY ABATE...ALLOWING SEAS TO SUBSIDE ABOUT A FOOT MON AND MON NIGHT. LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 200 PM SATURDAY...THE LATEST GUIDANCE HAS SHIFTED/DELAYED THE BACK DOOR FRONTAL PASSAGE UNTIL WEDNESDAY MORNING. FOR TUESDAY THE ONSHORE SOUTHEAST FLOW OF AROUND TEN KNOTS CONTINUES. THE AFOREMENTIONED FRONT ALTHOUGH STILL PROGGED TO MOVE ACROSS THE WATERS...IS WEAKER AND APPEARS TO WASH OUT WITH A BRIEF NORTHEASTERLY FLOW BECOMING SOUTHEAST AGAIN BY WEDNESDAY EVENING. WINDS ATTEMPT ANOTHER RUN AT A NORTHEASTERLY DIRECTION THURSDAY BUT THE SEA BREEZE INFLUENCE SHOULD TRUMP THE WEAKLY FORCED FRONT. SEAS WILL BE MODEST THROUGH THE PERIOD AT THE MERCY OF LOWER WIND SPEEDS AND THE CHANGEABLE FETCH. OVERALL EXPECT 1-3 FEET. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...JDW SHORT TERM...RJD LONG TERM...SHK AVIATION...31

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