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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KILM 212313
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
613 PM EST Mon Jan 21 2019

.SYNOPSIS...
Chilly and dry high pressure will slowly modify as it shifts off
the coast late Tuesday into Wednesday. Warming will take place
through mid week with increasing chance of showers ahead of next
cold front Wednesday night into Thursday. Cool and dry High
pressure will build in Friday through the weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 630 PM Monday...The Arctic High will remain well to our
north tonight, dropping as far south as central Virginia by
daybreak. While clear skies and bone-dry air will promote
efficient radiational cooling, boundary layer winds are not
going to become calm. In fact, most models actually show an
increase in winds just above the surface after midnight as the
low-level flow veers more northeasterly.

Raw model output shows lows in the mid to upper 20s tonight.
This seems unreasonably warm given that we`re already near
freezing here at 6 pm. GFS, NAM, and ECWMF MOS guidance shows
lows in the 15-19 range overnight, and that seems unreasonably
cold given still-warm soils and inferred boundary layer
turbulence from the 15 knot wind expected to persist just 500
feet above ground level. The National Blend Guidance set shows
generally lower 20s across the area -- a couple degrees cooler
near Lumberton and Burgaw, and a bit warmer along the SC
beaches. This seems to be a good compromise and is the basis for
our forecast this evening. Assuming our forecast lows work
out, tonight will have the coldest temperatures since the middle
of of January 2018. -TRA

Discussion from 300 PM follows...

High pressure sliding into the Carolinas has brought strong
northwest winds and cold air advection to the region today.
Temperatures across the region as of the early afternoon were
between the mid to upper 30s, which was about 20 degrees colder
than this time yesterday. Winds were gusting between 15 and 20
mph, which was a bit lower than earlier windspeeds this morning.
Skies across the forecast area were clear under the dry
Canadian air mass.

Winds will continue to decrease tonight as the center of high
pressure moves into the coastal plain, with lows in the upper
teens to lower 20s, which is about 10 to 15 degrees below
average low temperatures for this time of year. As high pressure
shifts eastward offshore Tuesday, surface winds will shift to
the east and tap into some warmer air and increase highs in to
the low to mid 40s, which is still about 10 to 15 degrees below
normal high temperatures for January.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 AM Monday...Transition from cold to warm through this
period. High pressure reaching down the eastern seaboard will be
centered just to our north at the start of the period, before
shifting further off the Outer Banks on Wednesday. This will
allow winds to shift around, becoming on shore Tues night and
then southerly on Wed. The very light flow and lack of clouds Tues
eve should produce decent radiational cooling allowing temps to
drop out, but as the night progresses, isentropic lift will
increase slightly as coastal trough/warm front pushes on shore.
Overnight lows should occur Tues night before midnight, down
into the 30s most places. Expect some low clouds and light pcp
possible into Wed morning with temps warming into the 40s fairly
rapidly. On Wednesday, deep S to SW flow will produce plenty of
WAA with temps increasing a good 30 degrees into the mid 60s.

By late Wed into Wed night, increasing southerly flow may
produce some sea fog before showers with moderate to heavy rain
spread across the area from west to east ahead of a cold front.
the heaviest rain should reach the I-95 corridor by Thurs
morning. Temps will remain well above normal Wed night, between
55 and 60 under cloudy skies and increasing showers.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 300 PM Monday...Period will start out wet, as cold front
progresses east across the area moving rapidly off shore by
Thurs eve. Increasing LLJ combined with deep moisture and deep
mid to upper trough will provide some decent support for showers
with moderate to heavy rain and gusty winds. Although, overall
instability is lacking, temps and dewpoints will reach into the
60s.

Drying through the mid levels will occur from west to east
through Thurs aftn with skies clearing and temps dropping
through Thurs night. Cold and dry high pressure will build in
with temps on the cool side Friday through the weekend. Next
storm system should begin to affect the area Sun night into Mon,
although there is quite a spread in the guidance solutions with
this system.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 00Z...Clear skies and VFR throughout the forecast period.
Northerly winds calming to around 5 knots at the coast and a little
lighter inland this evening. Very cold and very dry; no fog with dew
points near 0. Winds stay light and become northeasterly on Tuesday
as an area of high pressure moves southeastward and centers itself
over Delmarva by Tuesday evening. No aviation concerns other than a
few high clouds near the end of the period.

Extended Outlook...VFR becoming MVFR Wednesday morning as a warm
front approaches continuing into Thursday. VFR Friday into
Saturday.

&&

.MARINE...
NEAR TERM /THROUGH TUESDAY/...
As of 630 PM Sunday...Winds reported by area buoys and piers
were a couple knots stronger across the board than forecast. A
blend of the latest GFS, NAM, and ARW-NMM model were used for
forecast wind speeds overnight, which may reach 15-20 knots
late as the arctic high drops into northern Virginia and our
wind directions veer northeasterly. This should also lead to an
increase in seas, approaching 4 feet after midnight in a short
5-second wind chop. Discussion from 300 PM follows...

Conditions are improving offshore as winds and significant wave
heights decrease. Some locations may see elevated winds and
waves into this evening, especially further offshore beyond 20
NM. As high pressure continues to move offshore tomorrow, winds
will shift from offshore to more of an onshore direction
Tuesday. Otherwise, expect waves 2 to 4 feet Tuesday at 5 to 6
second periods with northeast winds 10 to 15 kts.

Astronomical low tides and offshore winds will result in abnormally
low-water levels overnight along the coastline.  Boaters should use
extra caution if navigating inlets tonight watching for sand bars
and increased shoaling potential.  Water levels should rise after 2
AM Tuesday.

SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 PM Monday...High pressure north of the waters will
shift further off the Outer Banks Tues night into Wed. This will
shift winds around, becoming on shore Tues night as a coastal
trough/warm front pushes on shore. Seas will 2 to 4 ft until
Wed morning.

Winds will increase out of the south through Wed into Wed night as
a cold front approaches from the west. This increasing southerly
push will drive seas up through Wed, reaching above SCA
thresholds by Wed eve. Seas should peak right ahead of the cold
front early Thurs morning, possibly reaching up to 8 to 10 ft.

LONG TERM /THURSDAY THROUGH SATURDAY/...
As of 300 PM Monday...Winds and seas will be peaking Thurs
morning up to 20 to 30 kts out of the south, before veering to
the west behind cold front by Thurs aftn. Seas up to 8 to 10 ft
Thurs morning will begin to diminish through late Thurs and
should drop below advisory thresholds by Fri morning in
diminishing off shore flow. Winds will become northerly on Fri
as high pressure builds in.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.

&&

$$

SYNOPSIS...
NEAR TERM...TRA/MCK
SHORT TERM...RGZ
LONG TERM...RGZ
AVIATION...21