Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 220830
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
330 AM EST Sun Jan 22 2017

.SYNOPSIS...
A complex and potent storm system will affect the Carolinas
today through Monday with potential for severe weather during
this afternoon and evening. Total rainfall amounts through
Monday should amount to one to three inches. This storm system
will slowly depart through Monday leaving high pressure for
Tuesday and Wednesday. The next cold front will move across the
area on Thursday. Much colder weather will follow Friday and
into next weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1030 PM Saturday...This evening`s round of rain has ended,
other than some lingering sprinkles over the Cape Fear region.
Guidance brings our next round in from the SW by around daybreak.
Previous discussion from earlier this afternoon follows:

Sfc winds coming around to the SE to S most places and will see
a deep warm and moist S-SW flow across the area by tonight as
warm front lifts north. Models continue to show a sfc low moving
along this boundary as a shortwave tracks up from the SW. As
the low exits off to the north a line of convection will move
E-NE through SC. The warm front boundary will get a slight push
south again as low pulls off to the NE but it looks like it
should be aligned closer to the VA/NC border by Sun morning
leaving our forecast area well entrenched in a warm and moist
air mass overnight. The best shortwave energy will move across
the area this afternoon through this evening with better chc of
thunderstorms and showers with heavier rain. Strongest
convection to the southeast will weaken as it moves toward the
area but could see some stronger storms reach the area into this
evening. Best chc of convection with heavy rain and gusty winds
will be between 4 and 8pm over northeast SC, but overall expect
weakening with time.

Expect a break in pcp overnight with another period of low
stratus and fog with temps and dewpoints remaining near 60.

&&

.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 300 PM Saturday...SPC latest forecast continues to keep
slight risk over northern fringe of forecast area and enhanced
risk elsewhere for Sunday. Therefore we are still looking at an
active late day on Sunday with potential for damaging winds and
potential for tornadoes.

Similar to Sat morning, areas of fog will start out the morning
and low pressure will be lifting off to the N-NE off the VA
coast. This will swing boundary back around but should be just
north of local forecast area Sun morning as potent storm system
tracks up from the southwest. The parent low will be stacked
over the lower Mississippi Valley Sun morning and will track
slowly east to northeast through Sun into Monday. Strong upper
level energy will rotate around this system into the southeast
through late Sunday. Although some pcp will brush over the area
through Sun morning, the main threat of stronger convection and
heavier rain will come later in the day on Sunday as the upper
low shifts east over the Carolinas. It looks like the brunt of
the convection will reach the eastern Carolinas between 6p and
midnight. The models differ in terms of exact location of low
and timing and therefore will keep a wider window for now. The
position of the low will be key in terms of potential for
tornadoes, but either way, the enhanced upper level support will
produce potential for strong to severe storms storms with
damaging winds. Gearing up for a high shear, low cape event with
main threat Sun evening. LLJ cranks up to 50 to 60 kts running
right up through the tip of Cape Fear around 7 to 10 pm. Pcp
water reaches up close to 1.7 inches at this time with CAPE
values up 500 to 800 j/kg through late Sun evening.

This potent low will move slowly off to the E-NE reaching the VA
coast Mon evening. The cold front extending south will push
well east of the FA late Sunday night into early Monday. Some dry
air will wrap around the back end into the Carolinas through
Mon morning but stacked low will drift across VA and off the VA
Cape by Tuesday daybreak. Enough moisture will continue to wrap around
maintaining a good deal of clouds along with a low end pcp
chances. The 850 temps will drop from 13c Sun aftn down to 5 to
6 c by Mon aftn as cooler air makes its way in on the back end.
This will bring temps down a good 5 to 10 degrees on Monday but
still keeping well above normal temps for this time of year.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 3 AM Sunday...Period begins warm and dry with surface high off
the east coast and mid level ridge axis overhead. Ridging aloft
shifts off the coast during Wed but subsidence will continue
suppressing upward motion while pushing highs close to 70 degrees.
Cold front moves across the area Thu morning possibly accompanied by
isolated showers, however low level convergence is weak and the
front lacks strong dynamical support. Inherited low chc pop may be a
little generous but will not make any changes at this time.
Regardless of shower coverage any rainfall would be meager if
forecast soundings are correct in showing a brief 6 hour period of
precipitable water values over 1 inch.  By Thu afternoon PWATs are
around 0.30 inch.

Following the cold front cooler air will start building into the
region, but its arrival is likely to be later Thu which will result
in one last day with temperatures above climo. 850 temps drop 5-10
degrees C between Thu morning and Fri morning and highs on Fri may
struggle to reach climo (mid 50s). Temperatures will trend even
cooler for the weekend with a reinforcing shot of cold air Sat
keeping highs around 50 with lows hover around freezing. Deep
westerly flow will keep skies mostly clear and prevent any
rainfall.

&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
As of 06Z...With the exit of the 1st round of pcpn, the FA has
become more stable due to the subsidence in the wake of the pcpn
now exiting off the Outer Banks. Sfc SSW-SW winds will remain
active across the FA keeping dense fog development to a minimum
early this morning. As winds back to the SSW and S later this
morning, will have to keep an eye on any sea fog development and
any inland push to it.

The next round of pcpn is already making headway from the Gulf
Coast states as a warm front lifts northward early this morning.
This pcpn should be pushing across the FA from SW to NE, roughly
between 08Z thru 15z. The pcpn will be moving over an airmass
that has been stabilized and thus the thunderstorm activity, if
any, will be held to a minimum.

And finally, the final round of pcpn, with an increased
potential for severe Thunderstorms, will occur between 1/22 at
21Z thru 1/23 at 05Z. This will be associated with the
intensifying upper closed low and its accompanying sfc low, both
finally lifting NE from the Gulf Coast States to the western
Carolinas by 1/23 06Z. The dry punch in the mid-levels will
push across the area during the mid to late evening hours,
ending the pcpn after pushing across. Plenty of atmospheric
dynamics associated with this final round of pcpn along with a
meandering sfc boundary. Enough to warrant placing Gusts up to
45 kt during the convection this evening.

Extended outlook...Expect mainly VFR, except for possible
MVFR/IFR during Mon from clouds and reduced vsby from pcpn.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 100 AM Sunday...Cancelled dense fog advisory over the
waters.

As of 1030 PM Saturday...Dense Fog Advisory remains in effect
for all waters for areas of fog with vsbys less than a mile. SCA
for all coastal waters beginning at 6 am Sunday and persisting
thru 6 pm Tuesday.

A sfc frontal boundary will move back north as a warm front as
low pressure tracks up into the Carolinas through this evening.
Winds to the north of this boundary will shift from E-SE to
S-SW and south of the boundary the winds will be S to SW. Winds
10 kts or so will pick up to 10 to 20 kt overnight into Sunday
morning as southerly winds increase ahead of next system. This
southerly push will drive seas from 2 to 3 ft this afternoon up
tp 3 to 5 ft by Sun morning.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 300 PM Saturday...Strong SCA conditions through the period
as a potent low pressure system moves across the Carolinas and
up to the VA coast by Mon night. Increasing SW winds ahead of
this system on Sunday will reach up to 20 to 30 kts. This strong
southerly push will drive seas rapidly up to SCA thresholds
through the morning and possibly as high as 7 to 9 ft by Sun
night. Winds will begin to veer to the W-SW through the day on
Monday which will help to lower the heights near shore but still
expect seas up to 6 to 8 ft through much of the day on Monday
in SW winds up to 20 to 30 kts. Winds will continue to veer with
strong off shore westerly winds by Tues morning keeping the
highest seas in the outer waters but strong winds will persist
through the period with SCA conditions throughout.

LONG TERM /WEDNESDAY THROUGH THURSDAY/...
As of 3 AM Sunday...Southwest flow around western side of high
pressure will gradually increase Wed and Wed night as gradient
increases ahead of a cold front. Front moves across the waters
late Thu morning with offshore flow developing in the afternoon.
Ahead of the front southwest winds will peak around 20 kt Wed
night and Thu morning. Winds veer to west-northwest Thu
afternoon with speeds remaining 15 to 20 kt into Fri morning.
Seas 2 to 3 ft at the start of the period will build to 3 to 5
ft later Wed and could exceed 6 ft in some areas late Wed night.
Cannot rule out short duration SCA just prior to the front
passing. Post front offshore flow will knock seas down, from 3
to 5 ft Thu afternoon to 1 to 3 ft Fri morning.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory until 6 PM EST Tuesday for AMZ250-252-254-
     256.

&&

$$

NEAR TERM...REK/RGZ
SHORT TERM...RGZ
LONG TERM...III
AVIATION...DCH



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