Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 201730
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
1230 PM EST Fri Jan 20 2017

.SYNOPSIS...
A warm front will lift north across the area today. The front
will then remain in close proximity through the weekend. Waves
of low pressure will move along this boundary with the last and
deepest Sunday night and Monday. This will result in a wet
weekend with total rainfall amounts of one to three inches.
Thunderstorms will have the potential to produce severe weather
Sunday and Sunday night. As the deep low departs, high pressure
will build toward the area Tuesday and Wednesday. A weak cold
front will stall in the region on Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1000 AM Friday...Pcp remains fairly inexistent over the
forecast area as a warm front makes its way north. Winds have
been coming around to the E-SE through the morning and expect
further veering as the warm front continues its northward
movement. Soundings show drying through the column as drier air
through the mid to upper levels works its way down through this
afternoon. This will allow for breaks in the clouds and
increasing sunshine. This will combine with continued waa in
deep S-SW flow to bring temps into the 70s except the immediate
coast. Can not rule out a spotty shower but overall amounts will
be negligible.

A weak wave of low pressure will skirt the coast as it moves N
of the area today. The front will then have a tendency to sag S
tonight as the wave moves NE and well offshore. Winds will
become very light and variable at the surface tonight while low
level flow will veer from SW to W before backing around to the
SW again by morning. This will allow moisture to increase
through the column once again. Not expecting measurable
rainfall tonight, although some spotty drizzle may occur
tonight, as well as, low stratus and fog development and have
included areas of fog in the grids at this time. Widespread fog
may turn dense overnight as dewpoints remain elevated.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 400 AM Friday...A front will be in close proximity
through the period. A wave of surface low pressure is expected
to move NE along this front coincident with mid-level shortwave
energy Sat. Precipitable water values ramp up Sat, especially
by/during the afternoon and will show POPs ramping up in kind.
This wave moves by and if the timing holds, and this of course
is not a certainty, we should experience a lull in the coverage
of convection sometime Sat eve. However, our Forecast Area will
remain ripe for more significant rainfall as another wave moves
NE along the front. A 50 to 60 kt low level jet at 2-3 kft will
impinge on the area overnight Sat into Sun morning and
precipitable water values again peak near 1.5 inches. This
supports another round of categorical POPs. Then perhaps a lull
before the vertically stacked area of strong low pressure
reaches the area Sun night and Mon.

As you can see, the forecast is froth with complexity. However,
the bottom line is we are expecting a very wet and stormy
weekend with bouts of showers and some thunderstorms. Our
current storm total rainfall forecast through Sun night is 1 to
3 inches of rain and this will be enough to cause localized
ponding and perhaps some flooding in the most urbanized areas
where drainage is poor.

The other major concern is whether any of the thunderstorms will
produce severe weather. Here the signals are a bit mixed with
the strongest low-level jet not quite in sync with the strongest
lift nor the better instability and shear. The strongest low-
level jet is currently slated to arrive during Sun morning, a
diurnal minimum. Still the severe weather potential late in the
weekend exists with mixed layer CAPE values on the order of 500
J/kg with significantly higher instability not too far to our S
where the warm sector will be deepest. However, as is often
the case in the winter season with these powerful systems, there
will be very strong shear. The 0-6 km Bulk Shear values reach
up to 70-80 kt Sun and Sun night and these are very high. These
values heighten the tornado risk. So it still remains to be seen
whether there will be sufficient instability in the lowest
levels of the atmosphere to produce damaging winds or tornadoes
in our area. SPC currently has a good portion of the eastern
Carolinas in a slight risk for severe weather Sun and Sun night.
We continue to highlight the weekend hazards in the Hazardous
Weather Outlook.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 300 AM Friday...A complex storm system will be on the
move to the east/northeast Monday with some residual moisture
and forcing aloft continued to advertise good chance pops
winding down in the evening.

In the wake of this system a broad and deliberate pattern change
begins to take shape. Brief mid level ridging moves across Tuesday
as strong troughing takes shape out west. This feature will deepen
and move east with a full cyclonic flow in place by the end of next
week.

At the surface, weak high pressure Tuesday and Wednesday will give
way to a cold front Thursday. A decent southwest flow of moisture
with this system warrants at least some mention of pops for
Thursday. Colder temperatures arrive for next weekend with the
expectation of below freezing readings (overnight lows) returning
for the first time in a while.

&&

.AVIATION /18Z FRIDAY THROUGH TUESDAY/...
As of 1730Z...VFR conditions will deteriorate after midnight
tonight as elevated dewpoints and low-level moisture transport
work into the area. IFR ceilings expected AFT 6Z, with VSBYS of
1/2-2SM overnight through end of the taf cycle. IFR conditions
may not be widespread but will prevail over a large portion of
SE NC and NE SC from late tonight through Saturday morning with
OCNL -RA AFT 15Z.

Extended outlook...IFR/LIFR likely continuing Saturday morning.
Tempo MVFR or lower ceilings and visibility expected in showers and
thunderstorms Saturday afternoon through Sunday night. Thunderstorms
will have the potential for strong to severe wind gusts Sunday
afternoon and night.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 1000 AM Friday...A warm front will continue to move north
through tonight with E-SE winds shifting around to the S-SW
behind the front. Satellite winds show weak low just east of
Cape Fear and this should continue to move north through today.
Seas of 1 to 2 ft this morning will build to 2 to 3 ft this
afternoon in S to SW winds 10 to 15 kts.

As the low moves north tonight the front may drop south
producing more variable winds, but remaining very light. Seas
will remain 2 to 3 ft. Winds in the northern waters may be E-NE
overnight but will come back around to the E-SE through Sat
morning while winds above the surface will shift back to the SW
by morning. There is some concern for sea fog development and
reduced visibility late tonight and have included in the gridded
forecast at this time and through the day Sat.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 300 AM Friday...Sea fog may result in reduced visibility
through a good portion of the day Sat. A front will be in close on
Sat and a wave of surface low pressure is expected to move NE along
this front. This will bring widespread showers and some
thunderstorms across the waters, especially Sat afternoon. Then on
Sun, another wave will be moving along this wavering front and then
finally the strongest and deepest area of stacked low pressure will
make its way across the area beginning Sun night. Waves of
widespread showers and some thunderstorms are expected with each of
these features. Convection will have the potential to produce at
least gale force gusts Sun and Sun night. Small Craft Advisory
conditions are expected to get underway Sun morning and then to
persist into the early part of the work week. Sustained winds will
peak around 25 kt with higher wind gusts expected. Seas will peak in
the 6 to 9 ft range.

LONG TERM /MONDAY THROUGH TUESDAY/...
As of 300 AM Friday...Low pressure will be departing to the northeast
leading to a continuation of strong southwest winds at least for a
few hours Monday. Expect speeds of 20-25 knots through midday
dropping to 15-20 by the evening. A more offshore flow develops
Tuesday with similar speeds of 15-20 knots although leaning toward
the lower end of the range most of the day. Significant seas will
show a similar trend with very high values early in the period (7-10
feet) dropping considerably Tuesday.

&&

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

&&

$$

NEAR TERM...RGZ
SHORT TERM...RJD
LONG TERM...SHK
AVIATION...8



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