Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 261724 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 124 PM EDT THU MAY 26 2016 .SYNOPSIS... Summer-like warmth will prevail today and Friday as an upper ridge holds across the region. An area of low pressure organizing near the Bahamas will drift west towards the southeast United States coast this weekend. This slow moving feature will waver in the vicinity through early next week, bringing a good chance for showers and thunderstorms. && .NEAR TERM /THROUGH TONIGHT/... As of 1235 PM Thursday...A band of cu marking the sea breeze front has developed just inland of the coast but development has been arrested by very dry air aloft. Elsewhere we see just isolated cu and some cirrus. Still expecting a dry and warm afternoon, followed by a mainly clear overnight period as diurnal cu fades with the sunset. Mild S-SSW winds overnight will slow the late night temperatures drops, settling at 64-68 degrees daybreak Friday. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 3 AM Thursday...Prime headline this period is arrival of the leading edge of an elevated precipitable water surge onto the Carolina coasts Friday night. This will set a trend of rising dewpoints and layered absolute humidity. A continued trend of deepening moisture through Saturday will deliver precipitable water values near 2 inches and dewpoints around 70. By this time a surface low will be positioned offshore somewhere between JAX and CHS. One discernible consensus among the GFS/ECMWF/NAM solutions is that despite exactly where...a slow drift landward toward the NW is portrayed for Saturday into Sunday. Even given the abundant vapor, forcing and details precludes likely or wash- out pops and values were held in a 35-50 percent range Saturday. MAX-T Saturday around 3-6 degrees cooler than Friday due to clouds and moisture, but because of the elevated humidity Saturday, heat indices are similar both days. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 300 AM Thursday...The forecast challenge for the extended continues to be exclusively about a potential tropical/sub-tropical low which will meander in the vicinity. Guidance remains in very good agreement that a low pressure will be off the southeast coast Saturday and then waver through the middle of next week - but any fine details are still very far from being ironed out. That being said...it does appear an unsettled period is becoming more certain...although a 3-4 day washout is not expected. The surface low will likely track WSW Sunday as the western Atlantic ridge holds firm...before finally...and very slowly...moving NNE through the remainder of the period. The steering flow is exceedingly weak until a mid-level trough digs across the northern tier states causing the ridge to open up and allowing the system to move northward...but that may not happen until Tue. This suggests all 4 days will be partly cloudy with periods of heavy rainfall and thunderstorms in an environment characterized by increasing PWATs on deep and moist easterly flow. Still...timing when the heaviest rainfall is likely is challenging. Sunday may actually be the quietest day as some subsidence moves overhead as shown on time-heights and the low stays pretty far to the south of the ILM CWA. As it starts to lift north...especially Mon/Tue...850mb wind u-vectors reach -3 SD`s which combined with the approach of the low will favor increasingly heavy rainfall chances...and will try to show at least somewhat better certainty in rainfall then. Even so...Sun/Wed will also likely feature periods of showers/tstms in the moist/unstable environment...but the coverage may be less on these days. Winds will likely not be too much of a factor regardless of whether the system acquires tropical characteristics as the STRONGEST of the guidance keeps min SLP well above 1000mb with a weak PG otherwise. So heavy rainfall...as well as strong rip currents...will be the primary hazards in the timeframe surrounding Memorial Day. It is important to note that all of this is dependent on a system that has yet to develop so changes can and will likely occur. Once the system begins to organize the finer details will become more clear. Temps will be warm but likely below climo due to clouds and rainfall...but breaks would allow for short duration heating and will show highs just below guidance...with lows struggling to fall much below 70 each night. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... As of 18Z...Essentially a persistence forecast with VFR conditions expected through the period. Diurnal ceilings have once again developed this afternoon but should fade quickly with the loss of daytime heating this evening. Some concern about an hour or two of MVFR tomorrow morning inland but it should be fleeting. Extended Outlook...MVFR possible in scattered to numerous showers, isolated TSTMS this weekend. Otherwise expect VFR. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1235 PM Thursday...light SW winds and 2 ft seas continue to be the obs this morning except near the coast. Near the coast a sea breeze circulation has set up, bringing winds around to the south. Still expect SW winds of around 10 kt to become S 15 kt this afternoon, with a few higher inshore gusts during the heart of the sea breeze middle to late afternoon. Seas will be a composite of SE waves 2 FT every 8 seconds and a light to moderate S-SW chop. No TSTMS or VSBY restrictions expected today through tonight. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 3 AM Thursday...Marine conditions will become more challenging into the weekend as seas build due to growing wave energy from the ESE in dominant periods of 8-9 seconds. An advisory is not out of the question by Saturday as wave heights approach 6 feet. Showers and isolated TSTMS can be expected beginning Friday night and mariners should get a check on conditions before heading out this holiday weekend, including a look at radar trends. E winds 10 kt Friday will ramp up to NE 15 kt gusts to 20 kt Friday night into Saturday. The National Hurricane Center is monitoring low pressure from the Bahamas for potential development into the weekend, please stay tuned. LONG TERM /SUNDAY THROUGH MONDAY/... As of 300 AM Thursday...Marine conditions will be significantly dependent on a low pressure system progged to move out of the Bahamas and towards the coast this weekend. Guidance still differs on the exact timing...placement...and strength of this feature...but it is most likely a weak low pressure will move across the coastal waters Sunday and Monday. Although the low pressure will be weak...prolonged easterly fetch will build a long period swell to 4- 7ft at 8 sec...creating seas of 3-5 ft...with 6 footers possible. Most of the contribution to the sea spectrum will be from this swell...as winds are forecast to remain rather light...from the E/SE at 10-15 kts...barring any unforeseen strengthening of the low pressure. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...JDW NEAR TERM...MJC/REK SHORT TERM...MJC LONG TERM...JDW AVIATION...SHK MARINE...MJC/REK/JDW

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