Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 031131
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
631 AM EST Sat Dec 3 2016

.SYNOPSIS...
High pressure will move offshore Sunday night. A complex storm
system will bring periods of heavy rainfall late Sunday through
Tuesday. Cool and dry high pressure will follow this system for
mid-week. A true Arctic front will cross early Friday, ushering
in the coldest air since last winter.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 600 AM Saturday...Chilly and dry high pressure will be in
place through tonight.

The low level flow will be from the N and NE. Satellite imagery
shows considerable higher clouds racing across the southern CONUS.
Model profiles show this moisture increasing above 15 kft today with
mid level ceilings beginning to materialize tonight. Thus, sunshine
will be more filtered as compared to recent days. Given temps
at 850 mb will only be in the single numbers and sunshine will
be increasingly filtered, forecast highs are not expected to
exceed the mid 50s. The clouds tonight should help to keep temps
from falling below the mid 30s to around 40.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 300 AM Saturday...Chilly high pressure will be centered just
to our N Sunday. The high will move off the coast Sunday night. At
the same time, a very wet southern stream system will be organizing
along the Gulf Coast. Warm and moist air will override the cool
airmass near the surface and isentropic lift will be on the
increase. Clouds should be plentiful on Sunday. Moisture should be
streaming N and E and it is possible light rain will break out
during Sunday afternoon, especially across the Pee Dee and
Interstate-95 corridor. A warm front is expected to develop to our S
and along the southeast coast Sunday night. The lift associated with
this feature is expected to increase the risk for rainfall and have
increased POPs to categorical.

Monday and Monday night, strengthening low pressure is expected to
move from the western Gulf Coast and across the mid south. A warm
front will extend eastward from the low. Another area of low
pressure may begin to develop along the offshore coastal front. A
southwest low level jet of 50-60 kt will bring copious moisture up
and over the front to our S. Precipitable water values will be near
2 inches while the depth of moisture becomes very deep. Thus, will
show POPs as high as categorical. Rainfall rates should increase
given the increasing lift and moisture supply. Will add mention of
heavy rain. The frontal system is expected to remain to our S and E
through 12z Tue and so will keep any mention of thunderstorms
offshore where instability should be highest. We are still expecting
a soaking rain with amounts through Tue in the 1 to 2 inch range and
as high as 3 inches.

High temperatures will be below normal through the period, mainly in
the lower to mid 50s Sunday and mid and upper 50s Monday. Low
temperatures will be in the 40s Sunday night and mid 40s to mid 50s
Monday night, highest at the coast.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 300 AM Saturday...An active pattern continues next week, and
the extended will begin with a potentially high-QPF rain event. Low
pressure developing along the Gulf Coast will move NE, with
secondary re-development likely along the Carolinas Coasts. High
pressure in place ahead of this feature will slowly erode to the NE,
with strong isentropic lift in an environment with increasing PWAT
driving periods of heavy rainfall Tuesday. While initially the
precip characteristic will be stratiform, recent guidance has
shifted the secondary low track just inland, which could allow for
more dynamic/convective rainfall late Tuesday. This can be ironed
out as we get closer to the event, and what is more certain is
significant rainfall, with the GFS ensemble plume mean centering
near 2 inches in the timeframe ending Tuesday night.

A cold front trails this system Tuesday night and seasonably cool
and dry weather is forecast Wed/Thu before a strong trough digs into
the Great Lakes driving an arctic cold front through the Carolinas
on Friday. Moisture return ahead of this feature may be limited, so
showers along the front are currently forecast to be light early
Friday. More noteworthy is the polar air mass behind this front, and
850mb temps may approach -10C by the end of the period, signaling
well below normal temperatures beginning Friday.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
As of 06Z...High confidence in VFR through the valid period.
High pressure ridging into the area from the west will be the
dominant weather feature, maintaining dry weather and VFR. A
surge of northerly winds are expected a few hours either side of
dawn, and have added tempo wind gusts of 15-20 kts at all
terminals, but otherwise winds will become generally from the
north at 6-10 kts. High level cloud cover streaming from the
west will gradually lower into mid-level cigs, but this is not
expected until Saturday night.

Extended Outlook...A storm system will bring periods of MVFR/IFR
late Sunday through Tuesday. VFR Wednesday.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 600 AM Saturday...A Small Craft Should Exercise Caution
headline is in effect from Cape Fear to Surf City. High pressure
building from the NW will keep the wind direction from the N
today and NE tonight. Wind speeds will be up to 15 to 20 kt this
morning with gusts up to 25 kt. Wind speeds for the remainder
of the period will be 10 to 15 kt. Seas will be up to 4 to 5 ft
this morning, highest across the outermost waters. Seas will
subside to 2 to 4 ft this afternoon and 2 to 3 ft tonight.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 300 AM Saturday...The center of high pressure to out N on
Sunday will shift offshore Sunday night. A warm front and coastal
front will develop Sunday night and then remain in close proximity
Monday and Monday night. Return flow around the departing high will
allow winds to veer from NE Sunday to E and SE Sunday night. The
juxtaposition of the front will ultimately determine the wind
direction for the remainder of the period. At this time, we think
winds will tend to veer to S and SW across the waters late Sunday
night into Monday as high pressure moves offshore. Developing low
pressure along the front would tend to shift winds back to the NE
during Monday with winds perhaps returning to E and SE overnight
Monday depending on the evolution of the the coastal front. Wind
speeds will be in the range of 10 to 20 kt through the period. Seas
of 2 to 3 ft Sunday and Sunday night will build to 3 to 4 ft Monday
and Monday night.

LONG TERM /TUESDAY THROUGH WEDNESDAY/...
As of 300 AM Saturday...Low pressure moving along the coast will
create SCA conditions on Tuesday. Uncertainty remains into the
strength and position of this system, but if the low stays along the
coast or just inland as currently projected, S/SW winds of 15-25 kts
will envelop the waters Tuesday, driving seas to 4-7 ft, and an SCA
is likely. As the low pulls away Tuesday night, a trailing cold
front will cross the waters turning winds to the NW, with wind
speeds then slowly falling to around 10 kts by the end of the
period. These lighter winds combined with the offshore direction
will allow seas to fall to 2-3 ft during Wednesday.

&&

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

&&

$$

NEAR TERM...RJD
SHORT TERM...RJD
LONG TERM...JDW
AVIATION...JDW



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