Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 061121
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
621 AM EST Tue Dec 6 2016

.SYNOPSIS...
A strong storm system will bring periods of heavy rainfall
through today. Dry and seasonable weather will follow for mid-
week ahead of an arctic front which will cross offshore late
Thursday. Very cold temperatures will follow for Friday and
Saturday. A warming trend will begin Sunday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 620 AM Tuesday...Miller type B storm system to affect the
area today. At the sfc, currently a rather strong wedge has
developed across the Carolinas with the offshore frontal system
now slowly backing to the north. What once was a closed mid-
level low over TX last night, has opened up into a s/w mid-
level trof now over LA and MS early this morning. Modest Sfc low
is basically underneath this upper s/w trof. The dynamics aloft
will track to the NE today, staying west and north of the ILM
CWA this morning and afternoon. The sfc low underneath is
progged to weaken and fill in while off the southeast NC coast a
new low will develop early this afternoon on a frontal system
that has been back and forth across the coastal and adjacent
offshore waters the past couple days. Models bring this frontal
system to the coast and just like the previous scenario, the
front may temporarily push just inland from the coast by midday
thru this afternoon. This will play havoc with temperatures,
with 40s and 50s west and north of this front and 60s to around
70 south and east of the coastal front. In addition, the frontal
position will become the focus of isolated thunderstorms due to
enough instability either sfc based or elevated for convection
to key off of. West and north of this front, expect overrunning
ie. isentropic lift, light to moderate rains with embedded
heavier showers. The low will slowly intensify as it moves
northeast along the coastal front this afternoon, reaching off
the Outer Banks early this evening. The pcpn will come to an end
from southwest to northeast during the mid to late afternoon
hours. QPF from this storm system will observe a nice uniform 1
to 1.5 inches of rainfall. Tonight, will see a drying trend with
residual low cloudiness possible given various models rh time
height displays. Lows will drop back into the 40s. Northwest
winds during this evening with diminish enough for possible
patchy fog.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 400 AM Tuesday...Looking at benign weather Wednesday thru
Thursday afternoon as weak high pressure prevails with basically
the FA under a rather low amplitude longwave trof aloft that
affects much of the U.S. with Pacific origins. The trof aloft
amplifies-some during Thu into Fri enabling a piece of a 1050+
mb Arctic High to break and push toward the area late Thu
night. The cold or arctic front ahead of it is progged to push
across Thu afternoon and early evening. A thin band of moisture
along this front may be enough to squeeze out a few hundredths
of an inch of rain. With no tapping of any moisture, this front
may end up being a dry passage. The sfc pg tightens after its
passage Thu night and combined with excellent CAA as evidenced
with a nice packing of the various thickness fields dropping
across the FA, especially in the low levels when looking at the
1000-850mb thicknesses. Have basically stayed with a blend of
model guidance for max/min temps this period with temps running
at or slightly higher than the 30 year normals.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 300 AM Tuesday...Very cold temperatures greet the extended
as an arctic front will be well offshore Friday morning. Highs
and lows Fri/Sat will be 10-15 degrees below climo, peaking in
the upper 40s both aftns, and dropping into the low 20s by
Saturday morning. This will be the coldest air since last
winter, and gusty winds Friday will create an even more
significant "bite" to the air despite full sunshine. The cold
Canadian high pressure responsible for this chill will push
offshore quickly by Sunday thanks to broad cyclonic flow aloft,
setting up a warming trend back to seasonable values Sunday and
into early next week. As this high moves offshore, return flow
develops, and a weak coastal trough may develop offshore,
advecting warm and moist air into the region for Monday ahead of
a rapidly approaching cold front for Monday night. This will
allow Monday to warm to above seasonable temps, but at the same
time rain chances will increase ahead of the front late on
Monday.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
As of 06Z...High confidence in IFR overnight, and persisting
through much of this valid period. Low pressure consolidating
near Florida will ride up a stalled front just offshore through
this period, creating widespread rain, heavy at times. IFR cigs
are slowly advancing NE tonight, and will envelop all terminals
in the next few hours. Once this occurs, cigs will slowly lower,
and LIFR is forecast much of Tuesday. VSBYS will fluctuate
considerably during periods of heavier rainfall, but MVFR is
forecast to be predominant. Winds will increase from the NE
overnight to 10-15 kts, but will then back to the NW as the low
pulls away during Tuesday, driving the front offshore. This wind
shift will create subtle dry advection, and cigs will gradually
improve late Tuesday, with VFR possibly developing inland by
the end of this valid period.

Extended Outlook...Fog possible Tuesday and Wednesday nights.
VFR conditions expected to prevail late week through this
weekend.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 620 AM Tuesday...Small Craft Advisory raised for all
waters due to effects from this Miller Type B storm system.

Modest to strong wedge in place across the Carolinas with the
frontal system offshore now returning north and west toward the
coasts later this morning. The positioning of this frontal
boundary will make wind direction forecasts across the local
waters rather difficult. Models indicate this front will
temporarily progress onshore but just if and how far inland and
how long it meanders across the local waters. For now will go
with the scenario of temporarily pushing 5 to possibly 10 miles
inland around midday. Low pressure will develop off Cape Fear,
on the front by midday and intensify as it tracks northeast
away from the local waters this afternoon. This will pull the
front as a cold front back off the coast and offshore this
afternoon and evening. The sfc pg tightens enough to produce 15
to 25 kt wind speeds, with gusts on the warm side of the front
30+ kt. Significant seas will peak in the 5 to 8 foot range this
aftn and mainly dominated by wind driven waves at 4 to 6 second
periods.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 415 AM Tuesday...Leftover SCA or SCEC conditions possible
Wed morning. Overall, winds and seas will diminish and
subside respectively Wed thru Thu as weak high pressure
prevails. By late Wed afternoon thru early Thu, winds will
have become variable in direction at 10 kt or less. In lieu of
forecasting variable, will indicate a predominate direction.
A cold or arctic front is progged to push off the coast late Thu
afternoon and across the local waters and well offshore during
Thu evening. After the CFP, the sfc pg will tighten dramatically
and excellent CAA will prevail across the area waters Thu night.
Guidance indicates NW winds increasing to 15 to 25 kt with gusts
over 30 kt possible as the core of the cold air begins pushing
across the local waters during the pre-dawn Fri hours.
Significant seas having mellowed to around 2 ft early Thu, will
rapidly build Thu night. With a NW wind direction, an offshore
trajectory, will indicate a range of seas building. Could see 1
to 3 ft near shore and 3 to 6 ft across the outer waters from
10 to 20 nm out.

LONG TERM /FRIDAY THROUGH SATURDAY/...
As of 300 AM Tuesday...SCA conditions possible to greet Friday
morning as an arctic front will be positioned well offshore. In
the wake of this front early Friday, NW winds of 20-25 kts will
push seas up to 4-6 ft, and an SCA may be required. These winds
and elevated seas will fall through Friday however as high
pressure builds eastward. As this surface high moves eastward
and offshore the Mid-Atlantic region during the wknd, winds will
weaken to around 10 kts by late Saturday, with a slow veering
to the NW. Seas fall quickly late Friday and on Saturday as
well, from 3-5 ft Friday aftn to just 1-2 ft at the end of the
period.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory until noon EST Wednesday for AMZ250-252-
     254-256.

&&

$$
SYNOPSIS...JDW
NEAR TERM...DCH
SHORT TERM...DCH
LONG TERM...JDW
AVIATION...SGL


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