Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 150735

Area Forecast Discussion
National Weather Service Wilmington NC
235 AM EST Mon Jan 15 2018

Cold and dry high pressure will hold into Tuesday. An area of
low pressure will develop off the coast Wednesday, bringing a
chance of rain or snow Wednesday. Arctic air will build into the
area Wednesday night and Thursday. Temperatures will begin to
climb again by Friday.


As of 300 AM Monday...Shortwave energy passing overhead by around
12Z will have no available moisture to produce much in the way of
weather. This feature will swing the mid level flow to westerly or
west-southwesterly while a large trough develops from the Great
Lakes into the Mississippi/Ohio Valley region. At the surface a
weakening ridge of high pressure holds on along the eastern
seaboard, while a strong cold front impinges from the west. Cold
advection is maintained through this evening in a weakening state,
though the low level thermal trough moving offshore allows for some
slightly higher BL and surface temperatures. Cold advection
reversing briefly to weak warm advection late tonight for not quite
the chilly readings of this morning yet lows still 10 degrees below
climatology. The exception may be far western zones where predawn
winds go calm under the axis of the weakening surface ridge.


As of 300 AM Monday...Despite our earnest wishes, winter is not
done with us yet. A deep upper air trough will dig into the
eastern U.S. for the middle portion of this week. Cirrus clouds
ahead of the system will spread overhead Tuesday and thicken
Tuesday night. By Wednesday morning a 140 knot jet at 250 mb will
move across the Carolinas in advance of the trough.

Model consensus is that low-level baroclinicity will remain too
far east of the best vorticity advection for any significant
deepening of the low that forms along the East Coast Wednesday.
This means despite very impressive dynamics aloft, we will
likely see no Atlantic moisture circulated back onshore like we
did during the January 4th snow event. Tracing trajectories at
700 mb backwards, it appears what little moisture does move
across the Carolinas is of Pacific origin routed across the
northern Rockies and down through the Plains states.

We see no compelling reason to raise PoPs for Wednesday which
remain in the "chance" range, as high as 40 percent in the
Bennettsville-Lumberton-Elizabethtown corridor. Using GFS/NAM
thermal profiles as a guide, any precip that falls during the
day Wednesday could be a rain/snow mix across the interior
eastern Carolinas, with any shot at seeing snowflakes along the
coast occurring after dark as drier and colder air chases the
moisture offshore. QPF is expected to only be 0.05 inches at
best, and our deterministic snowfall forecast is zero across the

Very chilly air will race into the area Wednesday night on
northwest winds that could gust to 25 mph during the evening.
850 mb temps plunging to -10C argue for a very chilly night,
tempered only by the wind that will tend to keep low-level lapse
rates steep. We`re forecasting upper teens inland to lower 20s
at the coast, with wind chills falling to near 10 degrees


As of 300 PM Sunday...Arctic high pressure will build strongly
across the region Thu with its center passing to our S Fri and
then offshore Sat and Sun. Southerly return flow will bring
gradually higher temps and humidity levels during this time. A
cold front will approach Sun night and may bring some showers,
but otherwise it will be dry Thu through Sun.

Highs will be around 40 Thu. High temps should rebound into the
50s Fri and Sat and 60s Sun. Some locations could again sneak
down into the teens Thu night with strong radiational cooling.
Lows will then trend from upper 20s and lower 30s Fri night to
40s by Sun night.


As of 06Z...Low cloudiness entering parts of Pender County but not
expected to get near ILM overnight. The remainder of the area will
see clear skies and light N to NE winds through the period.

Extended Outlook...Rain/MVFR/IFR/with a slight chance for
wintry precipitation late Wed, otherwise VFR.


As of 300 AM Monday...The pinched northerly gradient flow
continues to relax albeit at quite a gradual pace. Seas down to
5ft at Frying Pan and still 4 ft at Masonboro Inlet buoy 41110
and so would feel more comfortable extending SCEC from 3am to
12Z. Georgetown County zone benefiting enough from wave
shadowing to not require cautionary headlines. Predominant seas
are a combination of 8 second NE swell and 5 second wind chop.
This likely not changing late today and tonight, but overall
significant wave height to drop by about a foot as the gradient
eases from the approach of weak high pressure.

As of 300 AM Monday...A weak wave of low pressure will develop
along a coastal trough out over the Gulf Stream off the Outer
Banks Tuesday morning. Other than keeping a light northwesterly
wind across our waters, little direct impact is expected on our
weather. Attention will shift to a strong upper level system
developing to our west Tuesday night into Wednesday. Several
areas of low pressure developing across the Carolinas and Mid-
Atlantic region will consolidate into a low off the New Jersey
coast Wednesday morning. Offshore winds will increase
substantially late Wednesday afternoon and continue through the
night, likely necessitating Small Craft Advisories. In addition,
there is a chance of some rain mixing with or changing over to
snow before ending Wednesday night.

As of 300 PM Sunday...Small Craft Advisory conditions likely to
continue into Thu. Seas will peak in the 5 to 9 ft range Thu

Winds will decrease to 10 to 15 kt by Thu afternoon and then
hold around 10 kt Thu night and Fri. The direction will back to
NW during Thu, W Fri morning and to SW Fri afternoon. Seas will
subside to 4 to 5 ft Thu afternoon with 2 to 4 ft seas generally
expected Thu night and Fri.





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