Area Forecast Discussion
Issued by NWS Wilmington, NC

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488
FXUS62 KILM 041152
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
652 AM EST Sun Dec 4 2016

.SYNOPSIS...
A weak wave of low pressure moving along the coast will bring
increasing rain chances through tonight. A more significant and
complex low pressure system will move in the vicinity late
Monday and Tuesday accompanied by periods of heavy rain. Two to
three inches of rainfall is forecast through Tuesday. Seasonable
weather will follow for mid-week before an Arctic front brings
very cold temperatures Friday and into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 600 AM Sunday...Patchy very light rain continues to move
across the area with more upstream headed in this direction.

Chilly high pressure centered to our N, will be moving offshore
tonight. A front will extend from low pressure along the Gulf
Coast eastward and will develop to our S and offshore along the
Carolina coast tonight. A wave of low pressure is expected to
develop along the front to our S and move NE along the Carolina
coast. This will allow precipitable water values to increase
through the day with the lowest levels of the column becoming
saturated by/during this evening. The best isentropic lift
arrives late tonight and this is when we expect the highest
rainfall rates. We will show POPs increasing through the day
with widespread rain expected tonight. Light rain today will
turn moderate to briefly heavy late tonight.

Cloudy skies through the period will minimize the diurnal range with
highs in the upper 40s to lower 50s and mid 50s along portions of
the immediate coast. Lows will be mainly in the mid and upper 40s
with upper 40s to around 50 near the coast.

&&

.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 300 AM Sunday...Rain should be temporarily tapering off from W
to E, in both coverage and intensity on Monday. A frontal boundary
will be draped to our S Monday and extend up the Carolina coast
across the coastal waters. A wave of low pressure will be positioned
on this front. The low is expected to be along the Carolina coast in
the morning, lifting away from the area and shoving the front
further S and E during the day. As this occurs, upward vertical
motion will greatly diminish as will the depth and magnitude of
moisture. We do not think the warm sector will bleed onto land
Monday morning, thus any thunderstorms will be kept offshore.

The main area of low pressure along the western Gulf Coast Monday
will lift NE across the mid south Monday night and up the Ohio
Valley Tuesday. This low pressure will actually fill/weaken late
Tuesday and Tuesday night as the upper support wanes and energy is
transfered to developing low pressure along the coast of North
Carolina and Virginia. The primary low early Wednesday morning will
be off the Del-Mar-Va.

The front to our S is expected to advance N as a warm front Monday
night and Tuesday as a 50 to 60 kt low level jet impinges on the
area. Moisture depth increases dramatically and precipitable water
values climb to near 2 inches. Strong isentropic upglide will
increase rainfall rates and we expect periods of heavy rain late
Monday night into Tuesday. Also, we have added mention of
thunderstorms for portions of the area, especially near the coast
and southern portions of the forecast area where instability
increases with the arrival of the warm sector. Current timing would
suggest the first half of Tuesday will be wetter than the second
half. The risk for rain will end by/during Tuesday night as low
pressure and its associated frontal system moves away from the area,
allowing drier air in make inroads. Storm total rainfall is expected
to be in the 2 to 3 inch range. A good soaking and given the time of
year, we should expect low-lying areas to experience ponding despite
several weeks of mainly dry weather.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 300 AM Sunday...Big story this period will be a true
Arctic front progged to cross the Carolinas during Thursday.
Ahead of this feature, dry and seasonable weather is expected as
a diffuse pressure gradient sets up behind Tuesday`s cold
front. Highs Wed/Thu will be in the 60s, but these will crash
down with the arctic front late Thursday. 850mb temps are
forecast to fall as low as -10C across this area by Friday
morning, indicative of the coldest air mass we have seen since
last winter. Moist advection ahead of this front is weak, but a
few showers cannot be ruled out late Thursday along the front.
These will all be of the liquid variety however, no snow showers
this time around despite soundings forecasting dendritic
saturation, as any snowflakes will sublimate into the very dry
air below 700mb. Highs behind this front will drop to 15 degrees
below climo Fri/Sat with lows in the 20s by Saturday morning.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
As of 12Z...Expect conditions to gradually deteriorate today as
a weak wave of low pressure brings increasing coverage of
rainfall along with low cigs and fog to the area.

VFR prevails across the area this morning with light northeast winds
and scattered light showers as seen from latest radar imagery. A
gradual deterioration of conditions is expected this morning into
the afternoon hours as rainfall coverage becomes more widespread and
lower cigs infiltrate into the area. As a result, a mixture of
MVFR/IFR is expected today with winds becoming east-northeasterly, 5
to 10 kts. Into tonight, IFR is expected to prevail with low cigs
and areas of fog as rainfall continues well into the morning hours
on Monday. A veering of the winds will continue to the southeast and
then south towards morning, with sustained winds remaining around 10
kts.

Extended Outlook...Periods of IFR likely through Tuesday night due
to rainfall and low cigs/reduced visibilities. MVFR developing
on Wednesday, with VFR returning on Thursday.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 600 AM Sunday...High pressure centered to our N will be
moving offshore tonight. A front is expected to develop to our S
and up along the offshore waters of the Carolinas tonight. A
wave of low pressure will develop to our S tonight and then move
up along the offshore front overnight and into Monday morning.
This may bring a brief period of Small Craft Advisory conditions
late tonight into Monday morning, especially across the
northern waters where the pressure gradient should be tightest.
A Small Craft Should Exercise Caution headline is most probable
across the southern waters. Wind directions will be quite varied
over the course of the next 48 hours or so. Mariners should
consider this as well as the deteriorating conditions before
venturing out. NE winds today will veer to E and SE tonight and
then S and SW overnight in response to a developing front and
wave of low pressure. Wind speeds will be 10 to 15 kt this
morning, increasing to 15 to 20 kt by/during this eve and up to
20 to 25 kt overnight. Seas will respond, building from 2 to 3
ft this morning to 3 to 4 ft this afternoon and up to 5 to 6 ft
late tonight.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 400 AM Sunday...A complex storm system will bring poor
marine conditions along with changeable wind directions. One
area of low pressure will be departing to the NE during Monday,
taking a front further offshore. Then another area of low
pressure will move from the Gulf Coast through the mid south
and up the Ohio Valley. This low will transfer its energy to
developing low pressure off the North Carolina and Virginia
coast late Tuesday and Tuesday night. SW winds Monday morning
should veer back to the N and NE Monday afternoon and night.
Winds should then veer to E and SE overnight Monday and S and SW
Tuesday as a warm front reaches the area. As the low lifts away
from the area and the front moves offshore, the wind direction
will veer to W and then NW Tuesday night. The strongest winds
this period should be late Monday night and on Tuesday although
winds Monday morning will be nearly equivalent. Seas will be as
high as 5 to 6 ft Monday morning and then again later Tuesday
into Tuesday night. Small Craft Advisory conditions will be
possible Monday morning and then again Tuesday into Tuesday
night. Mariners should expect widespread rain and some
thunderstorms. The highest risk for thunderstorms will be late
Monday night and during Tuesday.

LONG TERM /WEDNESDAY THROUGH THURSDAY/...
As of 300 AM Sunday...Cold front offshore Wednesday morning
will leave winds of 10-15 kts from the NW across the waters.
These winds will gradually ease through Wednesday as the
gradient relaxes, and begin to back to the west into Thursday
morning ahead of an arctic front. Seas Wednesday of 3-5 ft very
early will fall to 2-3 ft through the day. A very strong arctic
front will then cross the waters on Thursday, causing winds to
veer again to the NW and increase to 15-25 kts late, pushing
seas back to 2-4 ft, lowest near- shore. Attm forecast
conditions are just below any cautionary thresholds, but a SCEC
or SCA may be needed late Thursday if winds increase a bit more
than current forecasts suggest.

&&

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

&&

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



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