Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 180525 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 123 AM EDT Wed Oct 18 2017 .SYNOPSIS... Canadian high pressure building into the Mid-Atlantic states will bring several days of cool, dry weather to the Carolinas. Temperatures should begin to warm up this weekend as the high moves off the coast. && .NEAR TERM /THROUGH WEDNESDAY/... As of 1000 PM Tuesday...Surface high north-northwest of the region will maintain dry and cool conditions through the period. In the mid-levels a 5h trough will move off the coast and a weak shortwave ridge will try to build north. High clouds have shifted offshore, leaving clear skies overnight. Deep northerly flow aloft will contribute to an abundance of dry air, as will subsidence behind the exiting 5h trough and along the top of the marginal 5h ridge. Low level dry air and boundary layer winds around 15kt should keep surface mixed enough to prevent any fog development. Mixing will also limit the effectiveness of radiational cooling, although overnight lows will end up around 5 degrees below climo. Inland cold spots will be right around 40 with locations along the coast near 50. A slight increase in thicknesses Wed (both low level and 1000-500mb) as the air mass starts to modify, mainly due to sunny to mostly sunny skies, will result in highs topping out around climo. Low level convergence off the coast may lead to some marine clouds and showers, but do not see much cloud moving onshore, let alone any precipitation. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 300 PM Tuesday...High pressure becomes elongated from the southern Appalachians northeast into the Atlantic waters Wed eve. This will allow for a greater on shore component to the low level winds which should give a push to some of the maritime moisture from the coastal waters associated with a bit of shortwave energy riding by. This enhanced low level moisture should move down from the NE Wed eve brushing the coast. Moisture profiles show a very dry column above 5k ft but a decent shallow layer below with mainly some strato cu clouds expected overnight Wed into early Thurs. By Thurs aftn, the high pressure becomes centered over the southern Appalachians allowing for a deeper northerly flow, cutting off the Atlantic moisture and providing a reinforcing push of dry air. Another minor shortwave passes by Thurs aftn but the column remains too dry to produce anything more than a few clouds. Pcp water up near an inch along the coast Wed night will be down to a half inch by Thurs aftn. Inland remains near a half inch through the period. Overall, aside from some passing clouds, expect dry and seasonable weather through the period. Better radiational cooling Thurs night with lighter winds and mainly clear skies expected but basically a gradual warming trend should keep overnight temps roughly the same both nights...within a few degrees on either side of 50. The high temp on Thurs should be nearing 80 most places. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 300 PM Tuesday...It will remain high and dry into Sunday as high pressure remains in control of area weather. An approaching cold front and return flow around the high will bring increasing clouds Sunday and Sunday night with a small chance of showers. Chances for showers will continue Monday and Tuesday as the front moves into and through the area. Max temperatures Friday through Monday will be in the upper 70s to around 80 and in the mid 70s Tuesday. Minimums will moderate from the low to mid 50s Friday morning to the low to mid 60s Monday and Tuesday morning. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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As of 06Z...High confidence for VFR conditions through the forecast period. Light northeast winds through the TAF period as high pressure remains to our north. The deep layer column will be too dry to support any clouds. Extended Outlook...Possible MVFR cigs Thurs AM. Possible showers on Monday. Otherwise VFR.
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&& .MARINE... NEAR TERM /THROUGH WEDNESDAY/... As of 1000 PM Tuesday...Northeast winds of 20 to 25 kt with higher gusts and seas up to 6 ft will necessitate the continuation of a Small Craft Advisory into at least Wed afternoon. The exception will be in AMZ254 where the bulk of the north-northeast winds/swell have been sheltered by land. The Small Craft Advisory has been downgraded to a Small Craft Should Exercise Caution for this segment of the coastal waters where seas will be 4 to 5 ft with wave periods 5 sec or less. It is also possible that the end time of the SCA may need to be extended beyond 6 PM EDT Wed. However have low confidence in this for now and do not plan any adjustments to the headlines. SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 300 PM Tuesday...High pressure will be more elongated from SW to NE north of the area which will produce a slightly more easterly component to the wind through Wed night. This NE push of winds up to 20 kts will continue to produce seas up near or slightly above SCA thresholds, near 6 ft, through Wed evening. WNA model shows a decrease in seas to below SCA criteria after midnight as gradient relaxes slowly into Thurs. Also, the winds will become more northerly in direction through Thurs which should help keep strongest winds off shore. Seas 4 to 6 ft initially will be down to 3 to 5 ft by Thurs aftn and 2 to 4 ft by Thurs night. LONG TERM /FRIDAY THROUGH SUNDAY/... As of 300 PM Tuesday...Northeast winds of 10 to 15 KT Friday will gradually become easterly by Sunday morning then southeast by Sunday night. Seas of 2 to 4 FT Friday will diminish to 2 to 3 FT Saturday then increase to 3 to 5 FT by Sunday evening. && .TIDES/COASTAL FLOODING... As of 300 PM Tuesday...Astronomical tides are increasing as we approach a new moon on Thu. This coupled with strong NE winds, may breach minor coastal flooding thresholds at Wrightsville Beach and advisories may be needed along portions of the North Carolina coast around the time of high tide for the next several days. The same will be true of the lower Cape Fear River to include downtown Wilmington. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until 6 PM EDT Wednesday for AMZ250-252- 256. && $$ NEAR TERM...RJD SHORT TERM...RGZ LONG TERM...RAN AVIATION...MBB TIDES/COASTAL FLOODING...TRL/RJD

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