Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 210512
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
112 AM EDT Sat Oct 21 2017

.SYNOPSIS...
Warm temperatures and dry conditions are expected through the
weekend. A strong cold front will bring the likelihood for
showers and thunderstorms later Monday into Tuesday. Much cooler
temperatures are expected during the middle of next week as dry
weather returns.

&&

.NEAR TERM /THROUGH TODAY/...
As of 1000 PM Saturday...High pressure aloft will be centered
just south of the area while at the surface, high pressure will
ridge down the eastern seaboard through the period. This will
bring clear skies and virtually calm winds tonight. The low
levels are again not particularly susceptible to fog given the
lack of moisture. However, similar to last night, strong
radiational cooling should allow fog prone locations to
experience patchy fog, mainly within an hour or two of
daybreak. Lows will be in the 50s, coolest inland where a few
upper 40s will be sprinkled.

Models are showing precipitable water values remaining between
0.50 and 0.75 inches and the time heights are not showing
distinct layers of clouds developing on Saturday and so our
forecast will continue to advertise sunny skies. Highs on
Saturday will range from the upper 70s at the beaches to the
lower 80s inland.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
As of 300 PM Friday...Ridging sfc and aloft will dominate the
FA weather Sat night thru Sunday. Skies will mainly be clear
with mainly thin Cirrus overhead. Some increase in the low level
moisture, below 850mb, from onshore flow will likely be enough
for diurnal Cu with possible onshore movement of Stratocu
especially across the southern portions of the ILM CWA. For Sun
night, the upper ridge axis slides further off the Southeast
U.S. coast allowing more opaque cirrus to move overhead. The
center of the sfc high just off the Mid-Atlantic States Sat
night will slide well offshore Sun thru Sun night but will
continue to ridge back across the FA. Flow thruout this period
will be onshore with a slow veering trend from ENE at the start
of the period to ESE at the end of this period. This will
further increase the low level moisture in the form of low level
clouds. A weak low-mid level impulse riding up the backside of
the upper ridge across SC during Sun may interact with just
enough low level moisture for possible low topped showers to
occur. However, have kept a dry fcst across the FA, keeping the
chance of rain just south and west of the SC portions of the ILM
CWA. Onshore flow will limit max temps but nevertheless, low
80s for Sun highs and widespread 50s for Sat night lows and
widespread 60s for Sun night lows due to the deeper onshore flow
across SSTS that are in the 70s.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 300 PM Friday...Week begins with highly amplified pattern
over the eastern CONUS. Deep 5h trough, which may or may not
become briefly cutoff, will be over the Mississippi Valley Mon
morning and steadily moving east, pushing a cold front with it.
Mid-level ridging along the Southeast will also shift east, but
the rate at which these features move ultimately determines when
showers and thunderstorms ahead of and along the front reach
the area. Strong warm advection ahead of the front will push
temps close to 10 degrees above normal Mon while ensuring
abundant moisture. Still to early to say if strong or severe
storms are a threat but low level jet Mon night and Tue will be
40-50 kt so at least some potential exists.

Front crosses the area during Tue but cold advection will be delayed
and temps will be near to slightly above climo. A shortwave dropping
southeast across the western Great Lakes and into the OH/KY Valleys
Tue night drives a cold surge into the southeast Wed. Cold advection
will drop 850 temps from low teens late Tue to near zero Wed
night, ushering in a 36 to 48 hour period of temperatures 5 to
10 degrees below climo. Mid-level trough axis shifts off the
coast Thu morning and lifts northeast during the day. Warm
advection will already be under way at this point but cold air
will linger at the surface through Thu. Thu night or Fri will
see temperatures return to levels typical of late October in the
southeast.

&&

.AVIATION /05Z SATURDAY THROUGH WEDNESDAY/...
As of 05Z...Patchy ground fog is expected to develop in the
early morning hours, and best chance for IFR visibility is
expected to be KLBT, where dewpoint depressions reached zero at
04Z. Otherwise expect visibility to remain MVFR or better
through sunrise. High pressure centered over the Mid-Atlantic
region this morning will shift offshore, and although winds will
veer towards the east later today, they will remain light.

Extended Outlook...Showers and thunderstorms may result in flight
restrictions Mon-Tue.

&&

.MARINE...
NEAR TERM /THROUGH SATURDAY/...
As of 1000 PM Friday...High pressure will continue to be the
main influence across the waters. Winds will be under 10 kt
overnight as they back to the NE. An ENE wind direction will
prevail on Sat with wind speeds increasing to 10 to 15 kt during
the afternoon. Seas will be 2 to 3 ft as the easterly swell
continues to wane.

SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 300 PM Friday...This period will continue to be favorable
for Mariners navigating across the local waters. Onshore flow
will highlight this period, starting from the NE-ENE Sat night
veering slightly thru the period to ESE-SE by Monday morning.
This in response to the sfc high`s center migrating from the
Mid- Atlantic Coast Sat night to well offshore by Mon morning.
The sfc ridging from the high will extend inland from the coast
resulting in the onshore flow. The sfc pg will remain relaxed at
the start of this period with around 10 kt for speeds. The sfc
pg will begin to tighten-some Sun thru Sun night resulting in 10
to 15 kt speeds, except closer to around 15 kt for the
southernmost waters. Significant seas will run 2 to 3 ft Sat
night followed by a slow 1 foot building trend thru Mon morning
when seas will run 3 to 4 ft except around 4 ft southernmost
waters. Dominant periods thruout this time-line will run 8 to 9
seconds due to a persistent ESE ground swell.

LONG TERM /MONDAY THROUGH WEDNESDAY/...
As of 300 PM Friday...Cold front approaching from the west will
lead to increasing southerly flow on Mon. Winds start out east-
southeast 10 to 15 kt but turn more southerly during the day,
increasing to a solid 15 kt later in the day. Winds peak at 20
to 25 kt late Mon night and continue in the 20 to 25 kt range
into Tue evening before dropping under 20 kt Tue evening/night
and shifting to offshore as the front passes. Seas ahead of the
front will build to 5 to 7 ft Mon night and exceed 8 ft in
places on Tue. Headlines will likely be raised early Mon night
and continue through Tue and into the first part of Tue night.
Combination of offshore flow and decreased speeds late Tue night
and Wed should allow conditions to drop below headline
thresholds. Cold advection following the front is delayed so
offshore flow will not be strong right behind the front. However
cold air is expected to arrive near the end of the period and
offshore winds approach 20 kt Wed night.

&&

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

&&

$$
SYNOPSIS...
NEAR TERM...RJD/DRH
SHORT TERM...DCH
LONG TERM...III
AVIATION...CRM
MARINE...



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