547
FXUS63 KMQT 020958
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
458 AM EST Tue Dec 2 2025

.KEY MESSAGES...

- Winter Weather Advisory for moderate to possibly heavy lake effect
snowfall in Keweenaw County this morning. Uncertainty remains high
in the exact placement of the dominant band with a high boom/bust
scenario.

- The weather pattern through the week and into next weekend is
defined by periodic Clipper low pressure systems, which will not be
strong enough to deliver accumulating snow on their own, but the
proceeding lake effect snow will bring the potential for 4"/day
snowfall rates (50% chance) especially in the NW wind lake effect
snow belts, beginning Wednesday.

&&

.DISCUSSION...
Issued at 456 AM EST Tue Dec 2 2025

Early morning observations in Marquette County feature some light
snow showers, but nothing accumulating. Further west, ship obs, IWD,
and CMX have reported snowfall this morning, and lining up KDLH
radar returns of a SW-flow LES band with CAM modeled reflectivity
(as the Keweenaw has no low level radar coverage) shows that
dominant band brushing mainland Keweenaw County through this morning
before lifting north. Will keep the Winter Weather Advisory as-is,
given there is not much evidence that the previous forecast is much
different than what the given observations show. 00Z HREF LPMM plots
show that if the LES band does reside over approximately the Eagle
River vicinity, 6 inches of snowfall is possible, though more likely
outcomes are an additional 1 to 3 inches. Still, this could make for
a challenging morning commute along US-41 and M-26 in Keweenaw
County, so drivers beware of rapidly changing road conditions and
visibility.

As the LES band lifts offshore, expect a quiet day across the UP
today, with high temperatures in the 20s despite increasing
southwesterly flow, which usually brings warmer air to the region.
Aloft, few longwave features are noted at 500mb over North America,
with the dominant feature being a Hudson Bay closed low with a few
shortwaves embedded within the peripheral flow. Elsewhere, a Rex
Block is set up off the Pacific Coast, with the closed low
being off the coast of Los Angeles and the Baja California,
while the ridging is off the Pacific Northwest and British
Columbia coast. As this blocking pattern is in no hurry to
progress (especially as the number of longwave features
downstream is low), the weather pattern over Upper Michigan will
be dictated by the aforementioned embedded shortwaves within
the Hudson Low and any shortwaves embedded in the northwesterly
flow proceeding through the Canadian Rockies. Either shortwave
mechanism is primed to deliver clipper-type low pressure
systems, though given the diminutive size of the parent
troughing features, these clippers will not be particularly
strong. The first such clipper arrives tonight into Wednesday.
The HREF shows the synoptic snowfall from this event being not
terribly impressive with mean 6-hourly snowfall rates of 1"/6hr
or less widespread. However, as winds become northwesterly
behind the cold front, lake enhancement (850mb temps falling
into the -20s C over a Lake Superior still around 5 C) and
orographic enhancement do highlight the spine of the Keweenaw as
likely to see 2-4 inches of snowfall by Wednesday evening. Some
blowing and drifting snow is also possible as the cold
advection behind the front allows wind gusts of near 35 mph to
mix down to the surface Wednesday. The other area of concern
will be the east-half NW wind LES belts, as long-lake fetch with
the aforementioned supportive thermodynamics (and a not-yet
frozen Lake Nipigon in support as well) will provide the
ingredients for moderate snowfall. At this time, still
anticipating around 4"/day rates in the east by Thursday
morning. With the next 12Z HREF, expect some more clarity as to
whether further advisories are needed, though potential for
Winter Storm Warnings (8+ inches) is low (10% or less).

While high temperatures in the teens and 20s persist throughout this
week and into the weekend, not much change in Lake Superior`s
temperature is expected until some clearing skies can allow for more
efficient cooling. With persistent cool NW flow aloft over the warm
lake for the foreseeable future, expect some flavor of LES to
persist between rounds of clippers, the following of which, the
NBM brings increased PoPs with Thursday evening. Again, given
the weaker nature of these systems, the lake effect may be the
more noteworthy mechanism for delivering accumulating snowfall,
and with persistent background NW flow, expect the NW wind snow
belts to be the hardest hit this week and into the weekend.
Overnight lows in the single digits to occasionally subzero in
the interior west will bring some of the coolest temperatures of
the season, with Thursday morning being the most likely to have
wind chills below -10 (50-80% chance interior west).

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1240 AM EST Tue Dec 2 2025

MVFR prevails through the rest of the night. There remains a
potential for a lake effect snow band to pivot over the Keweenaw,
with heavy snowfall and IFR-or-worse restrictions possible at CMX.
However, confidence is low, so have continued to handle this
potential with a PROB30 the second half of the night. Otherwise,
expect VFR at all terminals after 12Z Tuesday. Another batch of snow
begins to move into the western UP Tuesday night, with a drop down
to MVFR possible at IWD and CMX towards the end of the forecast
period.

&&

.MARINE...
Issued at 456 AM EST Tue Dec 2 2025

Wind gusts of near 25 kt this morning ramp up to near 30 kt
especially between the Keweenaw Peninsula and Isle Royale ahead of a
cold front. As the cold front passes Wednesday, chances of gale
force gusts increase to around 50 percent over central Lake
Superior, though the timing is too uncertain to commit to a headline
at this time. Wind gusts fall down to near 25 kt for Thursday
morning before wind gusts ramp up once again ahead of the next
disturbance, arriving Thursday evening and ramping up wind gusts to
near gales in the far west (50% chance of exceedance) and around 30%
chances of gales further east. This pattern of weak clipper lows
followed by periodic chances of low end gales will continue into the
weekend. Each gale or near-gale looks to bring 8-11 ft waves, and
the coolest airmass of the season residing over the lake will
introduce some moderate to heavy freezing spray threats at times.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until 10 AM EST this morning for
     MIZ001.

Lake Superior...
None.
Lake Michigan...
None.

&&

$$

DISCUSSION...GS
AVIATION...LC/NL
MARINE...GS