486
FXUS63 KMQT 050808
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
308 AM EST Wed Feb 5 2025

.KEY MESSAGES...

- Two system snowfalls during this forecast cycle, the first
Wednesday night into Thursday morning and the second Saturday and
Saturday night. At this point, neither are expected to produce
significant snowfall as the probability of exceeding 6 inches is not
higher than 20% with the first event and not higher than 40% with
the second. Slippery travel conditions will occur with the snowfall.

- Strong west winds expected on the Keweenaw late Thursday afternoon
and evening. Probability of peak gusts in excess of 50mph is 75%.
The strong gusty winds bring potential of occasional whiteout
conditions in blowing snow and falling snow.

- Temperatures around normal to below normal into the weekend will
settle to prevailing below normal next week.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 116 AM EST Wed Feb 5 2025

As model guidance shows the center of a high pressure ridge moving
through the Upper Midwest early this morning, the last of the lake
effect snowfall is wrapping up over the eastern U.P. as winds
continue to weaken and back to the west. As the lake effect cloud
cover dies down, expect the low-level cloud cover over the U.P. to
clear out, allowing temperatures to bomb into the negative single
digits in the interior west this morning, possibly even down to -10F
in the coldest spots near the Wisconsin border. Thankfully with the
winds weakening, wind chills will not be a concern today. As partly
cloudy skies roll through the Upper Peninsula during the daylight
hours today, expect temperatures to be around normal for this time
of year; expect highs in the lower to mid 20s across the area. Cloud
cover increases from the west as the sun sets this evening thanks to
a shortwave low approaching from the Northern Plains.

&&

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
Issued at 324 PM EST Tue Feb 4 2025

Midlevel flow pattern to start the long term consists of low-
amplitude ridging centered just upstream, with low-amplitude
troughing over the Northeast. This configuration will favor
subsidence and surface high pressure leading to a tranquil day on
Wednesday with highs near normal in the mid-20s. Meanwhile, a deep
closed low sits offshore of the Pac NW. A shortwave trough emanating
from this low will shift quickly eastward, reaching the Great Lakes
Thursday morning. A second shortwave will precede this one but with
a further south track. This wave will not impact us directly, but
the better moisture will be associated with this one, and phasing
with the northern stream wave is not expected. The upshot is a
mainly nuisance-level snowfall Wednesday night into Thursday. Solid
isentropic lift with saturation for roughly 6-9 hours will provide
the forcing, and there are some hints at stronger banded structures
in the CAMs with neutral stability in a fairly deep layer about 600
mb, although they will be progressive. HREF mean hourly snowfall
rates are around 0.25-0.50" Wednesday night, although they could
briefly exceed 0.50" at times. All told, looking at a 1-4" event,
highest western UP/Keweenaw and lowest Menominee County.

The northern stream wave does become vigorously negatively tilted
with associated strong cyclogenesis resulting in a mid-990s mb low
just north of Lake Superior by late Thursday. This will set up a
strong pressure gradient between the departing low and a nearly 1030
mb high building over the northern Plains, with pressure rises of 9-
10 mb/6hr advertised by the GFS. Strong cold advection will
encourage deep mixing into a 40-45kt layer. This looks like a solid
wind advisory event for the Keweenaw, if not a high wind warning
(current NBM probs for 50 mph gusts are about 75%, and 50 kt about
30%). The combination of wind and recently fallen snow, along with
potential lake effect snow bands, may result in whiteout conditions
later Thursday into Thursday night. Advisory-level (45 mph) winds
are also likely along the Lake Superior shoreline in the western and
eastern UP, with gusts topping out from 30-40 mph elsewhere.

After high pressure briefly builds in Friday into Friday night, we
will have another system to deal with for Saturday/Saturday night.
An energetic mid/upper tropospheric wind pattern will be in place
with a low-amplitude and quick-moving wave shifting from the central
Rockies to the Northeastern US Sat/Sat night. A surface low will
spin up along the tight baroclinic zone in concert with this wave.
Ensemble means are in fairly good agreement with the track of the
surface low from the central Plains just north of the Ohio River to
near Lake Ontario, although there is a fair amount of spread in the
ensemble members as expected. This is too far south for a
significant snowfall, although modeled QPF fields are fairly
expansive northward as a coupled jet structure translating across
the area will likely enhance lift. At this time it looks like a
solid advisory event for much of the UP, although there is about a
20-40% chance of exceeding 6 inches for the US-2 corridor and points
south.

As we head into early next week, anomalous ridging over Alaska and
northern Europe will link up near the North Pole, which will
displace Arctic troughing southward. Although the deepest troughing
will be over the northern Rockies, high pressure setting up over
south-central Canada will funnel seasonably cold air into the Great
Lakes, leading to solidly below normal temperatures. Although early
next week looks mainly dry, the mid/late week period could get
active again with potential for accumulating snow as the mean
trough axis shifts east and ridging builds over the eastern US.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 308 AM EST Wed Feb 5 2025

VFR conditions will generally continue at SAW through the period and
eventually at KIWD by this afternoon. KCMX looks like it may have
MVFR cigs hang on until the afternoon hours or longer as lake effect
clouds are stubbornly not scattering out. KIWD looks to return to
IFR late this evening, with KCMX becoming MVFR once again (if not
already so) near the end of the period.

&&

.MARINE...
Issued at 324 PM EST Tue Feb 4 2025

25-30 kt northwesterlies gradually diminish this evening into
tonight and remain light through Wednesday. Southerly winds increase
to 20-25 kt Wednesday night ahead of a strengthening low. Behind
this system, winds will quickly increase later Thursday as they
shift westerly. There is nearly a 100% chance of gales over most of
the lake and about a 50% chance of storms to 50 kt from around the
Keweenaw eastward. Winds will gradually decrease through the day
Friday, becoming less than 20 kt Friday night through the weekend.

Moderate to heavy freezing spray is also expected during the strong
winds Thu aftn and Thu night.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Watch from Thursday morning through Friday morning for
     LSZ162-240>251-263>267.

Lake Michigan...
None.

&&

$$

SHORT TERM...TAP
LONG TERM...Thompson
AVIATION...TAP
MARINE...Thompson