Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 150124 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 924 PM EDT Sat Oct 14 2017 .SYNOPSIS... Onshore winds will bring a good share of clouds over the eastern Carolinas through the weekend, accompanied by mild daytime temperatures. A cold front will cross the coast Monday, bringing much cooler, and drier air Tuesday through mid-week. A slow warming trend will prevail into late week. && .NEAR TERM /THROUGH SUNDAY/...
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As of 900 PM Saturday...The back-edge of the low level stratus cloud shield has pushed to a Myrtle Beach to Whiteville to Elizabethtown line via latest IR satellite trends. Without the days insolation and mixing, this back edge will likely hold in its position or may even increase in coverage. Areas where skies cleared will see prime rad cooling conditions with winds having already decoupled. This will likely result in fog development during this evening becoming widespread, especially areas outside the stratus cloud deck. GFS and NAM Mos guidance at odds with one another as the NAM wants more stratus and less fog while the GFS wants to place dense fog even across locations underneath the stratus cloud deck. For now will carry areas of fog at most locations. Tonights lows look aok, only massaging needed was the hourly sfc temps and dewpoints based on latest trends. Previous................................................... As of 300 PM Saturday...Weak surface low development off Hatteras was triggering a sustained NW surface wind locally, which has been instrumental in creating a growing `split` in the stratus layer this afternoon. It may very well be this fills back in overnight, as winds veer onshore or simply become light and variable to calm, coupled with the onset of diurnal cooling. As a result, have indicated a return to LOW stratus conditions across the region overnight into early Sunday. One consequence was to raise minimums a couple degrees compared to previous forecasts to account for insulating effects. Very weak and shallow over-running late tonight may prompt patches of light drizzle. Sunday, the return flow is a weak one, and scouring of any low stratus will be a slow process potentially once again. The dry and mild air aloft will cap any thermals handily and no pop values are near mentionable thresholds, but a trace from late night episodes of drizzle should be a shock. Did undercut the MAX-T model consensus curve a degree or two based on expectation of a slowly eroding cloud deck Sunday morning.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 300 PM Saturday...It looks like that first crisp and cool Fall airmass is slated for the short term. Sunday night will be one last period where we remain in the warm and humid prefrontal regime. Clouds increase late from NW to SE just prior to the front`s arrival close to daybreak Monday. The boundary will power across the region with enough speed and force for a non- diurnal temperature curve. The prefrontal airmass does not saturate in the mid and upper levels so most of the very light rainfall will be post-frontal. The cold air advection Monday night is impressive. Forecast soundings initially show a typical shallow cold airmass with a very strong frontal inversion from 1500-3000 ft to a heart-of-winter looking sounding by 12Z Tuesday showing a near isothermal layer to 11,000 ft. As such expect area-wide lows in the 40s except for the beaches where low 50s more likely, mainly SC beaches. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 330 PM Saturday...With a recently passed cold front, high pressure will quickly build in across the area early next week where it will remain through the period. A brief cool down on Tuesday will be short-lived as upper level ridging moves in across the eastern US in to the latter part of the week. High temperatures on Tuesday will be in the upper 60`s inland to around 70 at the coast, with a gradual increase into the mid 70`s throughout the week. Overnight lows will range in the low to mid 50`s. In regards to precipitation, moisture supply to the area will remain extremely minimal given placement of the ridge. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/... As of 00Z...MVFR/IFR and eventually LIFR conditions will overspread the local terminals starting this evening with the LIFR conditions occurring during the pre-dawn Sun hours up to several hrs after sunrise. Model guidance suggests low stratus the primary driver for IFR/LIFR conditions with some models indicating dense fog that reduces vsby to IFR/LIFR thresholds mainly in the 09Z to 13Z time range. Improvements to both vsby and ceilings to VFR conditions across all terminals by midday Sun. High pressure centered over the FA tonight will result in mainly calm winds across all terminals tonight thru daylight Sunday morning. The center of the sfc high will begin to slowly sink southward during Sun resulting in S to SSW winds around 5 kt. Extended Outlook...Isolated to scattered MVFR/IFR produced convection is possible on Monday ahead of a strong cold front. MVFR stratus possible near the coast TUE/WED morning in blustery post-frontal NE wind. && .MARINE...
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NEAR TERM /THROUGH SUNDAY/... As of 915 PM Saturday...The center of sfc high pressure will extend across the local waters tonight into Sunday. With the sfc pg quite relaxed, the local waters will generally see wind speeds at 5 to a generous 10 knots. Wind directions will remain variable but will carry a best guess direction by the models until the center of the sfc high drops south of the local waters during Sunday. Significant seas will run at 2 to 3 ft with an easterly ground swell at 10 second periods dominating the seas. Previous................................................. As of 300 PM Saturday...Friendly marine conditions in the near term period as a generally light onshore wind flow prevails. A veering and easing wind trend is expected into Sunday, and a light southerly breeze should take residence over the 0-20 NM waters much of the day, with no TSTMS or showers expected. Several low amplitude wave trains will propagate ashore tonight through Sunday, SE waves 1-2 ft every 9 seconds and E waves 2-3 feet every 9 seconds. Very little chop or wind-wave expected and thus the bulk of wave energy will reside in the 9 second swells. SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 300 PM Saturday...Light winds will be veering Sunday night due to the approach of a powerful cold front, possibly turning all the way from S to W ahead of the boundary by Monday morning. The highlight of the period however will be FROPA itself soon thereafter. The surface surge comes quickly by midday monday and wave faces should steepen precipitously. Wind direction becomes better aligned with height Monday night at which time wind and/or seas should reach Advisory levels. LONG TERM /TUESDAY THROUGH THURSDAY/... As of 330 PM Saturday...Small Craft Advisory possible on Tuesday. A recently passed cold front across the waters will keep northeast winds and seas elevated early on Tuesday. Sustained winds around 20 kts and seas of 5 to 7 feet will gradually decrease throughout the day. Late Tuesday evening into Wednesday and Thursday, expect northeasterly winds around 15 kts with seas 3 to 5 ft.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...MJC NEAR TERM...DCH/MJC SHORT TERM...MBB LONG TERM...SGL AVIATION...DCH

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