Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 130637

Area Forecast Discussion
National Weather Service Marquette MI
237 AM EDT Fri Oct 13 2017

.SHORT TERM...(Today and tonight)
Issued at 232 AM EDT FRI OCT 13 2017

Early this morning, a trailing cold front continued to push eastward
across the Arrowhead of Minnesota. With moisture lacking, along
this cold front, precipitation failed to develop early this
morning. However, head of this front, southerly flow has brought
additional low-level moisture northward across Upper Michigan this
morning, resulting in areas of extensive cloud cover, and drizzle
and/or light rain at times. This light precipitation was observed
across the far east where frictional convergence off of lake
Michigan aided in localized enhanced lift, along with areas that
saw upslope conditions due to southerly winds.

Today, as the cold front continues to push east across the area, due
to the enhanced low-level moisture, we could see scattered light
rain showers and/or pockets of drizzle develop. Overall, the deeper
moisture is expected to remain well south of the area, so not
expected much in the way of rainfall accumulations. Temperatures are
expected to remain rather seasonable today with lingering cloud
cover out ahead of the cold front. Once the front passes through,
much drier air will work into the region and allow for skies to
gradually start to clear across the west by the late afternoon
hours. Winds will be breezy at times today, especially closer to the
Great Lakes and across the Keweenaw.

Tonight, skies will continue to clear across the central and eastern
portions of the area as the cold front drop south of Upper Michigan
and the above mentioned drier air continues to filter eastward.
Surface high pressure will quickly fill in behind the exiting cold
front, which will provide the appropriate conditions for a crisp
fall night, especially across the west and central, as light winds
and clearing skies will give way to ample radiational cooling. Some
locations across the interior west and central could see
temperatures drop down in the lower 30s.

.LONG TERM...(Friday night through Thursday)
Issued at 414 PM EDT THU OCT 12 2017

Only significant impacts in the long term are due to winds and waves
late Sat through late Sun.

Models have generally trended farther N and strong with a shortwave
and SFC low. For the most part there are two camps with the low
track/strength. The GFS and NAM are very similar in deepening the
low from around 1,000mb over SW WI 00Z Sun to mid 990s mb over S-
central Upper MI 06Z Sun to 986mb over far eastern Lake Superior 12-
15Z Sun, then quickly E into Quebec by 18Z Sun. The CMC and ECMWF
are weaker, only deepening to the mid 990s mb, and tracking farther
south over northern Lake Michigan and eastern Upper MI. Still plenty
of uncertainty with the exact track and strength so definitely favor
the blended guidance for winds. Current "middle of the road"
forecast has increasing E-NE winds Sat afternoon into early Sat
night, but nothing significant over land through that time. Winds
switch to N-NNW through the rest of the night while increasing up to
gusts up to 35mph in land areas near central and western Lake
Superior. Stronger NW winds and CAA then kick in Sun morning and
early afternoon, with shorelines gusts to 45-50mph east of
marquette, and gusts of 35-45mph elsewhere near Lake Superior. Winds
then decrease Sun evening and night. This will lead to waves in
excess of 8ft along all exposed Lake Superior shorelines in the CWA,
and in excess of 12ft east of Marquette. Last season we saw beach
erosion issues at 8ft and lakeshore flood issues around 14ft.
However, lake levels are 6 inches higher than this time last year,
so those thresholds may be lower. Of course, if the NAM/GFS
solutions verify, winds will be stronger, with potential for
shorelines gusts to 60mph. If the ECMWF/CMC verify, winds will be
weaker. Will continue to promote the impacts in the HWO/EHWO.

Only changes made to blended initialization was to pull winds to
downwind shore areas late Sat through late Sun. Otherwise, no
significant impacts expected and blends performed well.

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 123 AM EDT FRI OCT 13 2017

Advection of low-level moisture around high pressure to the east of
Upper Michigan has resulted in large area of stratus over the
region. MVFR conditions to IFR conditions are expected tonight
through the early morning hours Friday. There could also be some
light drizzle or sprinkles tonight into Friday morning. By late
Friday morning into early Friday afternoon, drier air will begin to
push in from the west allowing for steadily improving conditions as
a cold front pushes to the east of the area. Most sites will likely
become VFR by late morning and remain VFR through the rest of the
TAF period at each site.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 232 AM EDT FRI OCT 13 2017

...Northeast to North gales possible on Lake Superior Saturday night
through Sunday...

Today as a cold front traverses the lake, winds of 20 to 30 knots
are expected. Tonight, winds will decrease in speed from west to
east across the lake as high pressure quickly tracks across the
region. However, the surface pressure gradient will increase from
west to east late Saturday through the end of the weekend as a
strengthening low pressure system lifts northeast across the Western
Great Lakes. Initially winds will be out of the east-northeast by
late Saturday at speeds of 20 to 30 knots. As the above mentioned
system lifts northeast into Ontario by Sunday morning, winds will
switch around to the north, with gales up to 35 to 40 knots.
Thankfully, this system is progged to exit the region rather
quickly, and the gales should subside from west to east through
the day Sunday. We will see a brief lull in the winds as speeds
lessen to around or less than 20 knots by Monday. Winds will ramp
back up to 20 to 30 knots Monday night into Tuesday as a system
rapidly digs just east of Lake Superior across Ontario and
enhances the surface pressure gradient. It is not out of the
question that we could see a few gale force gusts during that time
period as well. Otherwise, through the middle/end of next week,
winds will subside to be around or less than 20 knots.

Upper Michigan...
Lake Superior...
Lake Michigan...


SHORT TERM...Ritzman
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