Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 240910

Area Forecast Discussion
National Weather Service Marquette MI
410 AM EST Fri Nov 24 2017

.SHORT TERM...(Today and tonight)
Issued at 408 AM EST FRI NOV 24 2017

Main impacts for the short-term will be above normal temperatures
today with rain moving into the area and then colder temperatures
moving in tonight with light lake effect snow.

Today: Low pressure, sliding across Ontario this morning, will reach
western Quebec this evening. Ahead of the low, WAA increasing across
the Upper Great Lakes will allow isentropic ascent to linger across
the area as more moisture steadily flows across the region. This
will allow for isolated to scattered rain showers to continue or
slowly increase by mid to late morning. As the low continues
eastward throughout the day, a cold front sagging southward across
western MN this morning, will slide into the western U.P. by
around 18Z/24 and then to the far eastern U.P. by 03Z/25. Along
and ahead of the cold front/strong shortwave, widespread rain showers
will push through the Upper Peninsula as forcing is amplified.
Current thinking is that most areas will end up seeing between a
tenth and a quarter inch of rain. The strong southerly flow into
the area will allow temperatures to warm to above normal by this
afternoon with most area reaching into at least the mid 40s. The
favored south wind downsloping areas may end up seeing upper 40s.
It may not feel overly warm; however, as winds may gust to around
20 to 25 mph, which will make temps feel a bit cooler.

Tonight: The aforementioned cold front and low pressure system will
continue off to the east of the U.P. tonight. As this happens, winds
will become westerly this evening and then more northwesterly
overnight. At the same time, CAA will increase into the Upper Great
Lakes Region, with 850mb temperatures falling from around 2-3C this
evening to around -10C to -12C overnight. This will allow for
favorable delta-T values for lake effect snow. The most favorable
time for this to happen will be after 06Z as this is when the colder
temperatures advect into the region. Overall not expecting too much
in the way of accumulation as inversion heights are generally around
5kft and only a small portion of the moisture and convective cloud
layer are progged to be in the DGZ. At this point, have only a half
inch to an inch in the northwest wind favored snow belts. The
greater fetch over the eastern U.P. would lead to better chances
of seeing closer to an inch late tonight. Again, not expecting
too much, but it will be colder and roads may become a bit
slippery. Winds will be fairly gusty tonight, which will make it
feel much cooler. In fact, the favored westerly wind over the
Keweenaw may enhance the gusts a bit with gusts possibly reaching
between 25 and 35 mph tonight. Much of the rest of the U.P. may
see gusts around 15 to 25 mph. The northwest flow will allow waves
to build as high as 8 to 11 feet for locations east of Marquette.
This will lead to minor lakeshore flooding and beach erosion.

.LONG TERM...(Saturday through Thursday)
Issued at 220 AM EST FRI NOV 24 2017

Nam shows a 500 mb ridge across the western U.S. and troughing in
the ern half of the U.S. 12z Sat. This ridge slowly moves into the
plains by 12z Mon. Lake effect winds down on Sat and then quiet
weather for the rest of the forecast period.

In the extended, GFS and ECMWF show a 500 mb trough on the west
coast, a broad ridge across the plains 12z Mon. Troughing moves into
the northern plains 12z Tue with a closed low over the desert sw.
Cold air moves through the area on Tue with this trough. The
troughing moves into New England on Wed as another trough moves into
the central and southern plains. More troughing moves into the
northern plains 12z Thu which moves into the upper Great Lakes on
Fri. Above normal temperatures will continue for this forecast
period with brief periods of lake effect pcpn.

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1222 AM EST FRI NOV 24 2017

VFR conditions will give way to MVFR conditions on Fri afternoon
with a lowering of ceilings under areas of rain developing ahead of
an approaching cold front from the west. Winds turning to an upslope
westerly direction will favor KCMX for possible IFR conditions for a
brief time Fri afternoon. LLWS will continue at all sites into Fri
morning as a low-level wind max moves across the area.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 408 AM EST FRI NOV 24 2017

South winds of 20 to 30 knots are expected to continue through
today. Gale force gusts to 35 knots are expected through this
morning so a gale warning remains in effect through mid morning for
most of Lake Superior. On the back side of the strong low pressure
system/cold front additional 35 knot gales are possible on colder
northwest flow into the area. Winds are then expected to remain in
the 20 to 30 knot range through at least mid week.

Upper Michigan...
Lake Superior...
  Gale Warning until 10 AM EST this morning for LSZ244>251-263>267.

Lake Michigan...
  Gale Warning until 1 PM EST this afternoon for LMZ221-248-250.



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