Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 070756 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 356 AM EDT THU MAY 7 2015 .SYNOPSIS... LOW PRESSURE SOUTH OF CAPE FEAR MAY BECOME A SUBTROPICAL CYCLONE OVER THE NEXT COUPLE OF DAYS. THE SYSTEM IS EXPECTED TO APPROACH THE COAST OF SOUTH CAROLINA OR SOUTHERN NORTH CAROLINA FRIDAY AND SATURDAY WITH INCREASING CHANCES FOR HEAVY RAIN...GUSTY WINDS... AND DANGEROUS RIP CURRENTS AT THE BEACHES. THIS SYSTEM WILL ONLY GRADUALLY LIFT NORTH AWAY FROM THE AREA EARLY NEXT WEEK. A COLD FRONT WILL APPROACH NEXT WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 330 AM THURSDAY...EXTENSIVE RAIN SHIELD APPROACHING AND NOW SKIRTING THE COAST IS HAVING TROUBLE HOLDING TOGETHER OVER LAND AS IT HAS TO OVERCOME A VERY DRY MID LAYER. THE TEMP-DEWPOINT SPREAD AT THE 850 MB LEVEL IS AROUND 45 DEGREES JUST INLAND OF THE COASTAL COUNTIES THIS MORNING ACCORDING TO MODEL SOUNDINGS...SO ALTHOUGH THE BEACHES ARE FINALLY SEEING SOME PATCHY LIGHT RAIN WITH CIGS AROUND 10 KFT...PROGRESS FURTHER WESTWARD WILL CONTINUE TO BE SLOW AND UNEVEN. RADAR SHOWS A NARROW BAND OF HEAVIER RAIN ABOUT 20 NM OFFSHORE. UNLESS THAT BAND GETS HERE INTACT WE CAN EXPECT ANY ACCUMULATIONS TO BE ONLY ON THE VERY LIGHT SIDE THIS MORNING. NHC NOW HAS THE NON-TROPICAL LOW PRESSURE SYSTEM AROUND 220 MILES SSE OF THE SC/NC BORDER AND GIVES A 70 PERCENT CHANCE OF CYCLONE FORMATION WITHIN 48 HOURS. SATELLITE LOOPS SHOW BETTER ORGANIZATION AND A MORE DISTINCT CIRCULATION CENTER...WHICH IS BEING ANALYZED AT AROUND 1009 MB. GUIDANCE IN REL GOOD AGREEMENT FOR THE NEAR TERM AS FAR AS MOVEMENT GOES...WITH THE SYSTEM DRIFTING NW TOWARDS COASTAL NC/SC. ALL MODELS SHOW DEEPENING WITH THE NAM BEING THE MOST AGGRESSIVE. HAVE LEANED ON A BLEND OF GUIDANCE TO ACCOUNT FOR BOTH THE UNCERTAINTY OF THE SITUATION AND AGREEMENT BETWEEN GUIDANCE. EXPECT WINDS TO PICK UP FROM THE NE TODAY AS THE SYSTEM MOVES NW...BUT THE RELATIVELY MODERATE ASSOCIATED GRADIENT WILL KEEP WINDS IN THE 15 KT RANGE THIS AFTERNOON WITH GUSTS OF 20 KTS OR SO. PRECIP WILL BE THE TRICKY ELEMENT OF THE FORECAST. GIVEN RECENT TRENDS AND PROJECTED MOVEMENT OF THE SYSTEM HAVE UPPED POPS TO CATEGORICAL FOR TODAY FOR THE COASTAL COUNTIES...TRENDING DOWNWARD AS ONE MOVES INLAND. RETAINING POSSIBILITY OF THUNDER OVERNIGHT AS SYSTEM APPROACHES THE COAST. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 330 AM THURSDAY...THE CHALLENGE...UNSURPRISINGLY...THROUGH THE SHORT TERM REMAINS DETERMINING WHAT KIND OF IMPACT A STRENGTHENING LOW PRESSURE WILL HAVE ON THE AREA. RECON FROM NHC WAS CANCELLED YESTERDAY AFTN DUE TO LACK OF ORGANIZATION...AND CURRENT WV/IR IMAGERY IS LESS THAN IMPRESSIVE...ALTHOUGH IMPROVING. HOWEVER...GUIDANCE IS STARTING TO COME TO SOME GENERAL CONSENSUS ON A SLOWER AND OVERALL WEAKER SYSTEM MEANDERING JUST OFF THE COAST THROUGH THE PERIOD. LOW PRESSURE WILL LIFT NORTH TO SOME WHERE JUST OFF THE SC COAST BEFORE THE PERIOD...AND THEN STALL...LOOP...OR RETROGRADE BACK TOWARDS THE SW AS ITS MOTION GETS HALTED BY RIDGE TO THE NORTH. VERY SLOW MOVEMENT IS EXPECTED REGARDLESS OF THE ACTUAL TRACK...AND IT IS NEARLY GUARANTEED THAT THIS WILL BE IMPACTING THE AREA ALL FRIDAY AND SATURDAY. A SLOWLY LOOPING SYSTEM JUST OFFSHORE WILL MAINTAIN RAIN CHANCES...SOME OF WHICH MAY BE HEAVY AT TIMES...THE CHANCE FOR SOME GUSTY WINDS (FOCUSED ALMOST EXCLUSIVELY ALONG THE COAST HOWEVER)...AS WELL AS HIGH WAVE ACTION/MINOR BEACH EROSION/STRONG RIP CURRENTS. THE BIGGEST IMPACT LOCALLY IS LIKELY TO END UP BEING RAINFALL...ESPECIALLY FROM MYRTLE BEACH NORTHWARD ACROSS THE CAPE FEAR COAST. GUIDANCE SUGGESTING THAT 250MB DIFFLUENCE WILL BE ALMOST EXCLUSIVELY ON THE N AND E SIDE OF THE SYSTEM (MORE EVIDENT IT WILL NEVER TRULY BECOME TROPICAL EVEN AS FSU PHASE DIAGRAMS SUGGEST SYMMETRIC WARM CORE DEVELOPMENT) WHICH SUGGESTS CONVECTION WILL BE CONFINED TO THE N/E SIDE OF THE SYSTEM. WITH THE LOW STALLING JUST SE OF THE AREA...COPIOUS MOISTURE WILL ADVECT FROM AN ANOMALOUSLY HIGH PWAT AIRMASS...SO SOME VERY HEAVY RAIN WILL AT LEAST LURK OFFSHORE...AND MAY ADVECT INLAND. A TIGHT AND SIGNIFICANT GRADIENT WILL EXIST...AND CONVECTIVE ELEMENTS ARE POSSIBLE AS MOIST-ADIABATIC LAPSE RATES EXIST DEEP INTO THE COLUMN. HIGHEST POP WILL REMAIN FRIDAY ESP ALONG THE COAST...BUT A GOOD CHC FOR RAINFALL WILL CONTINUE RIGHT TROUGH SATURDAY NIGHT. TEMPS WILL STRUGGLE EVEN IN THE TROPICAL AIR MASS DUE TO WIDESPREAD CLOUDS AND RAIN. HIGHS WILL REMAIN BELOW CLIMO...MID 70S FRIDAY AND UPR 70S SATURDAY...BUT TEMPERED DIURNAL RANGES WILL KEEP MINS IN THE UPR 60S OR CLOSE TO 70 BOTH NIGHTS. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 330 AM THURSDAY...FIRST HALF OF THE EXTENDED WILL CONTINUE TO FEATURE A SLOW MOVING LOW PRESSURE SYSTEM SOMEWHERE IN THE VICINITY. THIS LOW PRESSURE WILL MEANDER JUST OFFSHORE OR POSSIBLY JUST INLAND OF THE COAST SUNDAY AND MONDAY AS STEERING FLOW REMAINS GENERALLY WEAK. WHILE A WEAKENING TREND IS EXPECTED DURING THE LONG TERM...THE HIGHEST PWAT AIR MAY ACTUALLY MOVE ACROSS THE CWA SUNDAY...SO PERIODS OF HEAVY RAINFALL COULD CONTINUE AT LEAST INTO MONDAY. WILL NOT FOCUS ON ANY SPECIFICS AT THIS TIME RANGE...AND JUST SHOW CONTINUED UNSETTLED WEATHER WITH CHC POP...HIGHEST ACROSS THE CAPE FEAR REGION...WITH PERIODS OF MDT TO POSSIBLY HVY RAINFALL. THE LOW WILL FINALLY KICK OUT TO THE NE ON TUESDAY AS AN UPPER TROUGH DIGS INTO THE GREAT LAKES REGION. THE UNSETTLED CONDITIONS WILL PERSIST INTO WEDNESDAY HOWEVER AS A COLD FRONT DIGS ACROSS THE CAROLINAS AT THE END OF THE PERIOD. THERE IS GOOD NEWS HOWEVER...AS THIS FRONT SHOULD BRING IN A PERIOD OF MUCH DRIER CONDITIONS BEYOND THIS FORECAST PERIOD. && .AVIATION /08Z THURSDAY THROUGH MONDAY/... AS OF 06Z...CONFIDENCE IS STILL RATHER LOW...BUT IMPROVING AS THE MODELS ARE STARTING TO GET A BIT MORE IN SYNC. LOW PRESSURE WILL SLOWLY APPROACH THE REGION TOWARD MORNING...WITH SHOWERS AND MVFR CONDITIONS EXPECTED AN HOUR OR TWO AFTER DAYBREAK ALONG THE COAST. AGAIN...THE UNCERTAINTY IS THERE AS THE HRRR MODEL IS SLOWER THAN THIS. THE GRADIENT WILL TIGHTEN ALSO AROUND DAYBREAK...WITH GUSTS OVER 20 KTS A GOOD BET AFTER 14Z. THE INLAND TERMINALS WILL TAKE A WHILE TO GET ANY PRECIP...PERHAPS BY MID AFTERNOON. THE COLUMN OF DEEP MOISTURE WILL REMAIN OVER THE REGION THROUGH THE END OF THE FORECAST PERIOD...WITH INTERMITTENT IFR POSSIBLE IN THE HEAVIER PRECIP. EXTENDED OUTLOOK...RAIN/MVFR. TEMPO IFR IN HEAVIER SHOWERS HIGHEST CONFIDENCE COASTAL TERMINALS. BECOMING VFR/SHOWERS SUNDAY. VFR ISOLATED SHOWERS MON. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 330 AM THURSDAY...SMALL CRAFT ADVISORY WILL CONTINUE THROUGH THE NEAR TERM AS A LOW PRESSURE SYSTEM 220 MILES SSE OF THE NC/SC BORDER DRIFTS NW. EXPECT WINDS AND SEAS TO BE HIGHEST OVER OUR SC WATERS...WITH 20 TO 25 KTS AND 5 TO 8 FT RESPECTIVELY FOR TODAY. CONDITIONS WILL BE A BIT BETTER FOR OUR NC WATERS...BUT WILL STILL BE HAZARDOUS WITH SEAS IN THE 5 TO 7 FT RANGE. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 330 AM THURSDAY...STRENGTHENING LOW PRESSURE WILL MEANDER VERY NEAR THE COASTAL WATERS THROUGH THE ENTIRE PERIOD...CREATING PERIODS OF GUSTY WINDS AND LARGE WAVES. WHILE UNCERTAINTY REMAINS IN THE EXACT INTENSITY AND PLACEMENT OF THIS SYSTEM AS IT EVOLVES...REGARDLESS OF THE EVENTUAL SOLUTION CONDITIONS WILL BE DIFFICULT FOR MARINERS. WITH THE CURRENT FORECAST PATH EXPECTED TO KEEP THE LOW CENTER EAST OF THE SC...WINDS WILL BE GENERALLY EASTERLY ACROSS AMZ250 AND AMZ252...AND NORTHERLY OVER AMZ254 AND AMZ256. THESE SHOULD REMAIN FAIRLY CONSISTENT THROUGH THE PERIOD...ALTHOUGH SOME FLUCTUATION CAN BE EXPECTED...ESPECIALLY AS THE LOW WOBBLES IN THE VICINITY. SPEEDS REGARDLESS OF DIRECTION WILL BE 15-25 KTS...WITH SOME GUSTS OVER 30 KTS POSSIBLE...PRIMARILY OVER THE NC WATERS. WAVE HEIGHTS WILL BE HIGHEST ACROSS NC WATERS THANKS TO THE ONSHORE FLOW WHERE 5-9 FT SEAS ARE EXPECTED FRIDAY. 4-7 FTERS ARE ANTICIPATED ACROSS THE SC WATERS. SEAS WILL GRADUALLY START TO COME DOWN THE LATTER HALF OF THE PERIOD BUT THIS WILL OBVIOUSLY DEPEND ON EXACTLY HOW THE SYSTEM EVOLVES BEYOND FRIDAY. ATTM SHOW WAVE HEIGHTS LOWERING TO 3-5 FT SATURDAY AND THE CURRENT SCA ENDING AT 8AM SATURDAY ACROSS THE SOUTHERN WATERS. NC SEAS WILL LIKELY REMAIN ELEVATED BEYOND THE 8AM SCA END-TIME BUT WILL EXTEND AS NEEDED WITH FUTURE UPDATES. LONG TERM /SUNDAY THROUGH MONDAY/... AS OF 330 AM THURSDAY...GUSTY WINDS TO START SUNDAY...ESPECIALLY ACROSS THE NC WATERS...AS THE PERSISTENT LOW PRESSURE SYSTEM MOVES SLOWLY NEAR THE AREA. ATTM THE BEST FORECAST TAKES THE LOW INLAND ACROSS HORRY/BRUNSWICK COUNTIES...AND THUS WINDS THE FIRST HALF OF SUNDAY WILL STILL BE GUSTY AROUND 20 KTS FROM THE EAST ACROSS AMZ250/252...BUT MUCH WEAKER AND NORTHERLY OVER THE SC WATERS. THIS SYSTEM WILL FINALLY BEGIN TO LIFT NE THROUGH SUNDAY AND INTO MONDAY...SO WINDS WILL VEER TO THE SW AND BECOME 10-15 KTS ACROSS ALL THE COASTAL WATERS. SEAS INITIALLY MAY STILL BE ABOVE SCA THRESHOLDS ACROSS THE NC WATERS BUT SHOULD FALL THROUGH THE DAY...AND 3-4 FT SEAS ARE FORECAST FOR MOST OF THE EXTENDED. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT SATURDAY FOR AMZ250-252-254-256. && $$ SYNOPSIS...JDW NEAR TERM...REK SHORT TERM...JDW LONG TERM...JDW AVIATION...REK MARINE...REK/JDW

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