Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 180759

Area Forecast Discussion
National Weather Service Marquette MI
359 AM EDT Fri Aug 18 2017

.SHORT TERM...(Today and tonight)
Issued at 359 AM EDT FRI AUG 18 2017

Water vapor imagery shows troughing across the Upper Great Lakes
region this morning with the associated surface low tracking across
eastern Lake Superior. Upstream of the area, additional shortwave
activity is also apparent as it digs across the northern and central
Plains. A few lingering showers continued to impact portions of
Upper Michigan both ahead of and behind the main surface low. A few
areas of fog were observed across the area, primarily across the
Keweenaw Peninsula where upslope flow is most prevalent.

Today, as the above mentioned low pressure system continues to lift
northeast out of the area, cold air advection and lingering cloud
cover will help keep temperatures about 10 degrees below normal for
this time of year. Some locations, especially those downwind of Lake
Superior across the north central and eastern portions of Upper
Michigan will struggle to climb into the mid 60s. In fact, some
locations may see high temperatures occur this morning, with a
cooling trend through the afternoon. Given the track of the system,
it looks like we will see more northwesterly than northerly winds on
the back side of the system. Given this flow orientation with the
terrain, this should limit the temporal extent of any lingering
drizzle chances across the north central portions of the area to at
least the morning hours. Across the Keweenaw where upslope flow will
be better oriented with the terrain, expect the fog to linger across
the higher terrain this morning and possibly into the early
afternoon hours. Further east, wrap around showers will linger
through a good portion of the day. Not expecting widespread showers,
but a few locations may pick up a tenth to a quarter of an inch of
additional rainfall. As the pressure gradient and pressure rises
behind the exiting system linger across the region, expect winds to
be rather gusty today. These gusty winds will be strongest near the
shores of Lake Superior and will create a high swim risk for
Marquette and Alger counties.

Late this afternoon through the overnight hours, as the upstream
shortwave activity previously mentioned begins to dig across the
Upper Great Lakes region, it isn`t out of the question that we could
see scattered showers track southeast across the area.

.LONG TERM...(Friday night through Thursday)
Issued at 332 PM EDT THU AUG 17 2017

Saturday and Sunday: As the upper-level trough and surface low
continue to shift eastward, weak upper level ridging and a suface
high pressure system are expected to build across the Upper Great
Lakes Region for Saturday into Sunday morning. This will allow winds
to diminish across the area and allow skies to become clear to
partly cloudy through Sunday morning. There may be a few afternoon
showers that develop over the eastern U.P. on any lake breezes that
develop; however, the coverage should remain isolated for the day
Saturday. Sunday afternoon a weak surface trough is expected to
slide in from the west, which will bring scattered showers and
thunderstorms from west to east across much of the U.P. through the
evening hours. Sunday afternoon will be very warm ahead of the
surface trough with many locations warming into the mid 80s.

Monday into Tuesday: The next area of broader troughing will shift
eastward toward the Upper Great Lakes for this time period. As this
happens, a cold front is expected to shift into the area Monday
afternoon and then slowly shift eastward into Tuesday afternoon. As
moisture, forcing and instability increase along and ahead of the
front, expect showers, thunderstorms and cloud cover to increase
across the area Monday afternoon through Tuesday.

Rest of the extended: The front will be east of the area on
Wednesday allowing condtions to dry out a bit; however, the upper
level trough axis nearby along with the potential for a shortwave
passing through will allow for at least increased afternoon cloud
cover and possibly some diuranl afternoon rain showers. Temperatures
will be near normal for this time period. At this point, will stick
with a consensus of the models for this time period.

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 119 AM EDT FRI AUG 18 2017

Upslope, moist flow on the back side of a surface low pressure
system currently near KSAW will promote low CIGs, rain and reduced
VIS at all sites into Friday morning. Gradual improvement from W to
E will be noted on Fri as the low exits the region.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 359 AM EDT FRI AUG 18 2017

Today, as low pressure continues to lift northeast across eastern
portions of Lake Superior and up into Canada, expect winds behind
the system to be 20-30 knots across the central and eastern portions
of the lake. A few gale force gusts will be possible, especially
closer to the lake shore where winds may become locally enhanced.
Further to the west, winds will begin to relax through the afternoon
to around 10 to 20 knots.

Tonight as the pressure gradient relaxes across the area, expect
winds to decrease to around 10 to 20 knots. Winds are expected to
remain below 20 knots through the weekend and a good portions of
next week.

Upper Michigan...
  Beach Hazards Statement through this evening for MIZ005-006.

Lake Superior...
Lake Michigan...


SHORT TERM...Ritzman
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