Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 210155 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 955 PM EDT Wed Sep 20 2017 .SYNOPSIS... A few disturbances aloft will bring isolated showers through Friday. High pressure will build in from the north for the remainder of the week, while Jose spins nearly stationary off the Mid-Atlantic coast. Dangerous hurricane Maria will bring increasing southeast swell and strengthening rip currents to the Carolinas beginning late this week. Maria is expected to move north and offshore of the Carolinas early next week. && .NEAR TERM /THROUGH THURSDAY/... As of 930 PM Wednesday...Not much change from previous thinking was concerned about earlier convection reaching the coast thie evening but last half hour the precipition has diminshed greatly and should be gone in about an hour. I did raise the pops to slight chance ahead of this batch of showers but that is the only change to this package. From previous discussion...POPS will remain quite low but become distributed area-wide late tonight into Thursday as temps aloft cool with the upper low. Future forecasts may be able to suggest that northern zones warrant slightly higher POPS, being closer to the cold pool aloft. Temperatures will continue to average above climatology through the period. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 330 PM Wednesday...Region will remain in an area of weak mid level troughing through the period. Mid level moisture will be limited by northeast flow below 20k ft and westerly flow above 20k ft. Cannot rule out some isolated diurnal convection, especially on Fri, but the environment is not particularly favorable for development of deeper convection. What few shortwaves are present remain on the weak side and offer little in the way of enhancement. Some diurnal convection may linger into Thu night but best chances will be during the afternoon and evening Fri. A very weak front will move south across the area during the day and convection may develop along the boundary. Appears SC will be favored but timing/location of the surface boundary will be key in deciding where any convection fires. Temperatures will run close to 10 degrees above climo Thu night. The minimal cool surge behind the boundary will drop temps a bit for Fri and Fri night but highs and lows will still run 5-8 degrees above climo. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 330 PM Wednesday...If NHC Maria forecast tracks hold, the extended forecast will feature a healthy dose of warm late summer weather and mainly dry, with daytime temperatures running 2-5 degrees above normal for this time of the year. Dry air aloft remains in place of an extent that only showers are advertised in the extended period. The exception is Tuesday when we have the deepest moisture in place as Maria passes between the Carolinas and Bermuda, an outer band may fling ashore. Otherwise mainly dry and warm this period. && .AVIATION /01Z THURSDAY THROUGH MONDAY/... As of 23Z...Still expecting VFR conditions across the terminals this evening into the overnight period except for possible predawn MVFR fog. A few showers across the region are slowly diminishing with the loss of daytime heating and will past just north of KLBT. Models indicate patchy fog across the cwa with IFR hinted at for FLO but given anticipated gradual increase in cloud cover this was not given much credence. Winds will be light across the terminals overnight. Will mention prob30 across the coastal terminals for chance of afternoon tstms with sea breeze front but VFR looks likely across all terminals on Thursday. Extended Outlook...Mainly VFR conditions through the period are expected with the exception of a few hours of early morning low clouds or fog most mornings through the period. The highest risk of IFR conditions will be in the 0900-1200Z timeframe each morning. && .MARINE... NEAR TERM /THROUGH THURSDAY/... As of 930 PM Wednesday...No changes at this time to the previous thinking. from previous discussion...Not much of a pressure gradient out there and marine conditions showing as such with a mere 10kt of wind and 2.5 ft seas all the way out at 41013. In fact model wave guidance running a tad too high likely since it is still seeing the dominant period being about 9 sec Jose swell. Winds to stay light and quite variable through the period...seas not expected to change much from current values. SHORT TERM /THURSDAY NIGHT SATURDAY NIGHT/... As of 330 PM Wednesday...Gradient over the waters will remain on the weak side through the period with high pressure to the northwest maintaining light northeast flow. Speeds will remain under 10 kt through Fri night. Seas will be a different story, running 2 to 3 ft at the start of the period but steadily increasing later Fri and Fri night as swell from Hurricane Maria starts reaching the area. Much will depend on structure/strength of Maria but headlines will be possible as the period ends. LONG TERM /SUNDAY THROUGH MONDAY/... As of 330 PM Monday...Increasingly dangerous marine conditions this period as Maria generates large SE swell, as she moves north, east of the Bahamas. If NHC forecast tracks hold, we can expect increasing NE and N winds late Sunday and Monday but probably below Gale force through Monday. Even if winds do not become strong this period, we will still likely require a headline for large swell-heights. This will produce inlet turbulence during the outgoing tides as well, and larger than breakers near ocean sandbars, while extending the width of the surf zone. Expect seas of 6-10 feet, mainly in SE swell by late Monday. && .TIDES/COASTAL FLOODING... As of 930 PM Wednesday..High tide on the Cape Fear River downtown will occur at 1043 this evening. latest reading showed the riverfront at 5.42 feet which appears to be about a half foot below the forecast so once again there appears to be about a two hour window of Advisory- worthy coastal flooding. Beaches are forecast to remain below thresholds though they were yesterday as well and WB did marginally meet criteria for two hours so evening shift may have to monitor the model`s handling of the departures once the tide starts rising. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...Coastal Flood Advisory until midnight EDT tonight for NCZ107. MARINE...None. && $$ SYNOPSIS...REK NEAR TERM...SHK/MAC SHORT TERM...REK LONG TERM...99 AVIATION...MAC MARINE...99/REK/SHK TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.