Swell Matrix

Area Forecast Discussion

National Weather Service Newport/Morehead City Nc

640 am EDT Sat Oct 21 2017

Synopsis

High pressure will build over the region through tonight and then slide offshore Sunday into Monday. A strong cold front will approach from the west Tuesday and move across the area Tuesday night. High pressure will build over the area mid to late week.

Near Term

Until 6 pm this evening As of 640 AM Saturday, High pressure surface and aloft will continue over the region through the weekend. Expect a continuation of the nice weather of the past several days with mostly sunny skies and warm temperatures. Shallow fog patches will dissipate early this morning. Highs today inland will be in the upper 70s to lower 80s with mid 70s beaches.

Short Term

6 pm this evening through 6 am Sunday As of 640 AM Saturday, Mostly clear skies/light winds will result in good radiational cooling conditions and fog patches developing in the late evening and overnight hours. Due to the strong expected radiational cooling and lows from the past several nights, will use the coolest (MET) MOS for lows with min temps ranging from the upper 40s inland to the lower 60s beaches.

Long Term

Sunday through Friday As of 315 AM Sat, Sunday, High pressure will move off the coast Sunday though flow will remain E to NE and continued lowered humidity vals expected, even though daytime highs will rise a bit on increasing low level thicknesses. It will continue to be mainly sunny with highs in the lower 80s most places, with 70s on the OBX. Morning lows will be in the 50-55 degree range interior to low 60s beaches.

Monday, The high moves further offshore Monday and significant deepening shortwave and cold front begins to advance into the deep south and TN valley. This will bring slight strengthening return southeasterly flow, so some iso/sct showers may advect onshore across the FA as boundary layer moisture increases through the day and into Monday night. Monday appears to be the warmest day through the period with low lvl thicknesses maxing out around 1390M, indicative of highs in the 80-84 degree range for the entire area, save for the beaches which will remain in the upr 70s.

Tuesday, Raised pops to categorical as 21/00Z global model suite in good agreement with timing/strength of deep upper trough and strong cold front progged to move through the region. Vorticity advection increases as models depict dampening shortwave trough pivoting through the TN/Ohio valleys, and will spur sfc cyclogenesis in the southern Appalachians acting to increase dynamics and strengthening southerly flow on 50+ kt LLJ. Dewpoints will be quite high in the 60s on Tuesday and would be sufficient for marginal instability, and the combination of significant wind shear and marginal instability could spell a high shear/low CAPE scenario for strong or severe storms. Any heavy showers or isolated thunderstorms could produce strong gusty winds due to momentum transfer to the sfc from strong winds aloft.

Wednesday through Friday, Rapid drying and cooling expected Wednesday as the front should move off the coast by early morning. Have retained the small PoPs for Wednesday though confined them to the extreme eastern areas mainly the OBX as the deep upper low moves through E NC with lingering deep layer moisture across the OBX. Dry WNW flow on Thursday as upper low finally exits off the Mid Atlantic coast and high pressure builds into the region. Temps will be much cooler for the mid week period with Wednesday and Thursday both in the 60s to near 70 for highs. High pressure slides offshore Friday with return flow bringing gradually warming temps with highs in the 70s. Low temps fall back into the 50s inland to around 60 coast for Wednesday morning, then into the 40s inland and low 50s beaches for Thursday/Friday mornings.

Aviation

12z Saturday through Wednesday Through tonight As of 640 AM Saturday, Very shallow fog patches early this morning with rapidly changing visibilities will dissipate around 13Z (9 AM) with VFR conditions then prevailing through this evening. Conditions again will be favorable for fog patches to develop again after midnight tonight.

Sunday through Wednesday As of 320 AM Sat, Pred VFR conditions expected Sunday into Monday, however there may be overnight/early morning fog all TAF sites as low level moisture increases and skies remain mostly clear with calm winds each night. Brief periods of sub-VFR possible with isolated to scattered showers spreading onshore Monday into Monday night. Much better chance of widespread MVFR/IFR arrives on Tuesday as periods of heavy rain ahead of a strong cold front. Gusty southerly winds also expected on Tuesday ahead of the front. Pred VFR expected to return Tuesday night through mid week as drier air moves into the region behind the front.

Marine

Through tonight As of 640 AM Saturday, High pressure will continue over the waters through the weekend producing light winds 10 kt or less through tonight. Light/variable winds this morning will become NE/E 5 to 10 kt later today into tonight then tend to become light and variable again late tonight. Seas will continue mainly 2 to 3 ft through tonight.

Sunday through Wednesday As of 320 AM Sat, High pressure continues over the waters Sunday with northeast to east winds around 5-10 kt and seas around 2-3 ft. Winds will veer to southeast on Monday as high pressure moves further offshore and slowly increase from 5-10 kt in the morning to 10-15 kt by late in the afternoon. Seas will be around 2-4 ft. Southerly winds increase drastically Monday night and peak around 20-30 kt with some gale force gusts possible on Tuesday ahead of a strong cold front approaching from the west. Seas build to 8-12 feet by Tuesday afternoon into the evening hours. The cold front pushes across the region late Tuesday night with winds becoming NW around 10-15 kt and seas gradually subsiding to 4-6 ft by Wednesday afternoon.

Watches, Warnings, Advisories

Nc, none. Marine, none.

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