335
FXUS63 KMQT 310954
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
454 AM EST Fri Jan 31 2025

.KEY MESSAGES...

- Widespread wetter snow is expected Saturday night into Sunday.
  This will result in snow covered and possibly sloppy roadways
  Sunday morning.

- Westerly winds of 45 to 50 mph are possible in the Keweenaw
  Peninsula Sunday night into Monday morning. This may result in
  some power outages and some tree damage.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 323 AM EST Fri Jan 31 2025

Water vapor imagery and RAP analysis show weak, sheared shortwave
tracking from southern Manitoba across northern Ontario. This wave
is helping to push a sfc cold front s across the area early this
morning. As of 07z, front runs across western Lake Superior to near
Ontonagon then e to around Marquette and to around Newberry. Post
frontal n winds have led to stratus developing across portions of
northern Upper MI. Temps at 08z range from generally the teens F
across the s to the 20s F n. Cold spot is Peavy Falls at 7F and warm
spot is 32F at Copper Harbor, closely followed by 30F at Menominee.

Cold front will quickly move to the s of Upper MI over the next
several hrs. Rather vigorous CAA today in its wake will lower 850mb
temps from current readings of around 0C over s central Upper MI and
-10C over northern Lake Superior to -10C over s central Upper MI to
-15 to -18C across Lake Superior by sunset, allowing LES to develop
today, particularly for the aftn when the DGZ falls blo the
inversion. Speaking of which, the inversion will be low. Over the w,
inversion falls from around 5kft to 3-4kft. Over eastern Lake
Superior, inversion will be around 5kft. Roughly 45 degrees of
directional shear is noted from cloud base to around cloud top which
will be an impediment to organization. So, while the DGZ falling
into the convective layer will raise SLRs/fluff up the snow, the low
inversions and directional shear will keep snow accumulations on the
light side. Expect snow accumulations of an inch or less today,
except in the high terrain of Baraga/Marquette counties where
upsloping will provide a boost for 1-2 inches. Expect highs in the
mid 20s to lwr 30s F, warmest s central. However, temps will slowly
fall in the aftn under continued caa, and readings will be down to
the mid/upper teens Keweenaw to n central by sunset.

&&

.LONG TERM /TONIGHT THROUGH THURSDAY/...
Issued at 453 AM EST Fri Jan 31 2025

The long term forecast kicks off with a weak shortwave passing over
Lake Superior and closed low in the Ohio River Valley. These
features journey eastward, placing Upper Michigan in a brief period
of northerly CAA late Friday through Saturday morning, supporting
light lake effect snow showers over the north wind snowbelts.
Ridging builds in from the west early Saturday, sending Canadian
high pressure into the Upper Great Lakes through the morning.
Lingering light LES begins to dwindle as dry air aloft eats at lake
induced inversion heights, which lower to less than 5kt feet by the
afternoon. Overall, an inch or two of fluff is possible underneath
any persistent bands or where local terrain enhancement in the
central UP and Keweenaw provide a slight boost.

Our attention then shifts upstream to a series of shortwaves
ejecting out of the northern Rockies into the Great Lakes late
Saturday through Sunday. Guidance is in fairly good agreement with
the evolution of sfc low pressure developing and consolidating east
of the northern Rockies of Montana/Wyoming, then pressing along the
Dakota-Canadian border Sunday. WAA ahead of the systems mid-level
warm front will force wet snow across the region through the
overnight hours Saturday and most of Sunday afternoon before being
cut off by a dry slot. This dry slot and the following cold front
are still handled poorly. US models such as the GFS and NAM hold on
to QPF into Sunday evening and bring in additional precip along the
cold front boundary, whereas the Euro/Canadian abruptly ends precip
in the late afternoon hours. What remains is a signal for Lake
Michigan / upslope enhancement for the south-central counties. This
could be overdone given ice cover in the Green Bay. Additionally,
given the strong warm air advection aloft, there could even be a
brief period of rain/snow mix along Lake Michigan if WAA
overachieves, although guidance has trended slightly cooler over the
past 24 hours. Snowfall totals through Sunday afternoon have been
nudged down a tad seeing as ensemble probability for >6" by Sunday
evening has been reduce to zero. Chances for 3" remain ~50-70% for
the Michigamme Highlands, Keweenaw, and areas close to Lake
Michigan, although confidence is still somewhat low with the outlier
GEFS displaced further south than its EPS and CMC friends.
Regardless, expect wet snow covered roads and a slippery commute if
traveling late Saturday into Sunday morning.

Cold front will push through Sunday night. Pressure rises behind the
front, strong cold air advection, and an isallobaric wind
acceleration will make for gusty westerly winds. These strong winds
should continue into Monday when they gradually relax. Model
soundings and EC meteograms suggest potential for 45-50 mph winds in
the Keweenaw. Lake effect behind the front is expected to develop
thanks to lingering surface troughing over the region. Into the mid-
week, ensemble and deterministic guidance depict elongated troughing
with embedded shortwaves over the west-central conus and additional
chances for precipitation, however, specifics are not able to be
determined at this point.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1207 AM EST Fri Jan 31 2025

Winds will continue their shift from variable to northerly over the
next few hours, while low level clouds increase with a weak
disturbance. So, VFR conditions will continue into early morning
when flight conditions shift to MVFR. The exception until then will
be possible MVFR/IFR fog under clear skies at CMX over the next few
hours, which is highlighted with a tempo. Confidence is also now
high enough to mention IFR at IWD as well as SAW by mid to late
morning as the aforementioned disturbance phases with a closed upper
low over Missouri. Other impacts include some northerly wind gusts
up to 20 kts at CMX this afternoon.

&&

.MARINE...
Issued at 453 AM EST Fri Jan 31 2025

Calm winds this morning will being to increase as colder air pouring
into the area supports northerly winds increasing to near 25-30kts
by the late afternoon over the north and east lake. These should
lighten Saturday morning back to near 20kts or less. The next wave
move through the region at that point late Saturday. Southeast winds
to increase to near 30kts across lake by evening, with some low end
gales being possible north and east of Isle Royale. These lighten
Sunday before increasing to 30-40kts from the west Sunday night into
Monday with the passage of a cold front and strong pressure couplet.
The colder airmass building into the area behind the front,
alongside the stronger winds, will make ice accumulation on vessels
from freezing spray possible Monday into Monday evening.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

SHORT TERM...Rolfson
LONG TERM...BW
AVIATION...Rolfson
MARINE...BW