130
FXUS63 KMQT 191132
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
632 AM EST Sun Jan 19 2025

.KEY MESSAGES...

- Dangerously cold arctic air settles into the area this weekend
  into early next week, leading to temperatures remaining
  subzero from tonight through at least Tuesday morning over the
  interior west half of Upper Michigan. Much of west and
  central Upper Michigan may see temperatures fail to rise above
  zero on Monday and maybe Tuesday.

- Homeowners and property managers should take action now for
  this cold period, especially if past very cold periods have
  yielded impacts. Ensure your Winter Car Survival Kit is up-to-
  date. This weekend through Tuesday, limit time outdoors for
  you and your pets, and check on vulnerable neighbors.

- Frequent whiteouts are expected in the northwest wind snow
  belts today through Tuesday morning due to the falling snow
  being a fine, powdery type snow that is highly effective at
  reducing visibility. Expect very hazardous driving conditions
  in the lake effect snow areas.

- No widespread, significant snowfalls for Upper MI through next
  week. Nearly all of the snow that occurs will be lake effect
  driven.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 538 AM EST Sun Jan 19 2025

Highly amplified flow across North America has allowed a broad mid-
upper level trough to envelop much of the CONUS and central Canada.
As a result, very cold Arctic air has been able to push into the
Northern Plains and Upper Great Lakes this weekend. 850 mb temps
around -25C this morning will continue to get even colder today into
tonight reaching from -26C east to colder than -30C west by 12Z
Monday. This has resulted in bitter cold surface temps across Upper
Michigan early this morning with temps ranging from near 0F east and
near Lake Superior to 5 below to nearly 20 below over much of the
interior west half. Highs today are only expected to get in the
single digits above zero east half and will only be in the single
digits blo zero west half. Lows tonight will be even colder across
the interior with 10 below to 25 below zero readings, coldest
interior west, while near the Lake Superior shore readings will be
in the zero to 10 below zero range. Cold advisories in effect over
the west today will expand across most of the central counties later
tonight. If you must go outside today, dress warmly in layers and
make sure to have a winter survival kit in your vehicle in case of
emergency. Limit exposure outside for you, your family and your
pets!

The cold air moving across Lake Superior continues to generate lake
effect snow over the NW wind snow belts, but the extremely cold air
mass will result in poor snow growth and fine snow which will limit
overall accumulation. At the same time, the fine snow will get blown
around more causing the potential for whiteout conditions within the
snow bands. A winter weather advisory remains in effect for Alger,
Luce and northern Schoolcraft through Monday where a longer NW
fetch across Lake Superior should bring 4 to 7 inches of
additional accumulation and perhaps locally higher amounts near
10 inches over eastern Alger and northern Luce counties where
strong low-level convergence will set up due to enhanced lake-
induced troughing from land breezes.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 458 AM EST Sun Jan 19 2025

By 12Z Monday, 500mb ridging will have shifted over British
Columbia and Northwest Territories, continuing an extremely
efficient surge of frigid Arctic air in the form of an
anomalously deep trough centered over the Upper Great Lakes,
with the GEFS showing a -30 dam 500mb height anomaly over the UP
by 12Z Monday, good enough for below the 2.5th percentile of
the NAEFS climatology. The HREF mean 850mb temperature will be
around the -30C mark Monday (slightly warmer values over the
eastern UP, slightly cooler over western Lake Superior). This
will translate into surface high temperatures 50+% likely to
remain below 0F on Monday. Similar if not slightly cooler high
temperatures are expected Tuesday as 850mb temperatures will not
change much according to the LREF mean. Low temperatures will
take a tumble, especially over the interior west, with the NBM
calling for -22F for the interior west Tuesday morning and
various MOS guidance calling for as low as -27F near Watersmeet.
The surrounding mornings will see lows in the negative double
digits in the interior west and negative single digits
elsewhere, still cold, but Tuesday morning will be the coldest.
With dominant surface pressure features far from the UP (a train
of 1040-1050mb shortwave highs over the Plains, 960s mb low
over Newfoundland and Labrador), persistent WNW to NW winds
gusting to around 20 mph are expected. While those winds are not
unusual for this time of year, the combination with the frigid
air temperatures will provide some of the most hazardous wind
chills since at least Feb. 2021, if not Jan. 2019. At the LREF-
mean wind chill of -44F in the Ironwood area Tuesday morning,
frostbite can take place in 10 minutes, half an hour or less for
much of the UP that is expected to see -20F or lower wind
chills through Wednesday morning. Additionally, such cold air
moving over particularly shallow snowpacks (or in the case of
the southern UP, no snow pack) could drive a deep frost depth,
which would increase the threat of damage to pipes/etc that are
not buried particularly deeply, though frost depth forecasting
is challenging, so to what depth would be considered "safe" is
uncertain. One important note with this hazardous wind chill is
that for multiple days, the daytime wind chill values will still
be in the negative teens to negative 20s, so no reprieve is
expected when the sun comes up, putting some vulnerable
populations even further at risk as it becomes much more
difficult to just "ride it out". Impacts to people, pets, pipes,
and plants are expected, so take precautions if any of the
above apply. Due to continued high confidence in wind chills as
low as -45 in the interior west by Tuesday morning, Extreme Cold
Warnings will be issued with this forecast package in addition
to the ongoing Cold Weather Advisories.

Of course, with such frigid temperatures aloft and a wide-open Lake
Superior (only 3-4% ice cover per GLERL and most of it in Black Bay,
Nipigon Bay, the bays north of Sault Ste Marie, and the Apostle
Islands region), lake effect snow will be present. Such frigid
airmasses will support tiny crystals as even the boundary layer will
be colder than the DGZ, bringing expected QPF to near 10:1. QPF
values are not expected to be extreme with such a cold airmass not
being able to hold much water content, as the HREF mean only shows
about 0.07"-0.12"/24-hr QPF rates. Slightly better QPF rates might
locally be realized over the east where CAMs show a remnant "surface
inverted trough"-like feature that is expected to bring better
convergence for the bands. This results in snowfall rates of around
1"/6 hr broadly along the spine of the Keweenaw and 2-3"/6hr rates
over the eastern Lake Superior shores. As such, a Winter Weather
Advisory continues for a portion of the eastern UP through Monday.
Extensions in time and expansions to the west may become necessary
if a BLSN threat is realized with such a dry snow with tiny
particles that are extremely efficient at reducing visibility. The
Euro ensemble is calling for 70+% chance of sub-quarter mile
visibility through Monday and into Tuesday for the Keweenaw with
lesser vis restrictions expected elsewhere.

High pressure sliding to the south and east of the UP by Wednesday
will shift the boundary layer wind pattern to be more southwesterly,
providing a 1-2 combination of shifting lake effect bands offshore
and advecting warmer southern air over the UP, giving some reprieve
to the hazardous conditions ahead to end the weekend and begin the
work week. Granted, chances of high temperatures reaching the
"normal" mark (around 20) for this time of year are below 30% before
Friday, but after 48-72 hours of subzero temperatures, Wednesday`s
highs in the 11-16 degree range might just feel tropical. Ensembles
are increasing in confidence in a shortwave pivoting from the Juneau
vicinity Monday afternoon to the Dakotas by Wednesday morning, with
the GEFS showing a cluster of weakening clipper surface lows late
Wednesday into Thursday over the UP. While synoptic precipitation is
possible with that potential system, blocking from various synoptic
systems far to the south and east will block moisture transport from
effectively reaching the UP, limiting QPF potential. Regardless of
exact solution, the LREF shows 925mb flow becoming 85% likely to be
within 30 degrees of NWerly by late Thursday into Friday with
greater than 75% chances of 850mb temperatures supportive of an LES
pattern, a return to cooler (but not frigid) temperatures and LES is
expected to end the work week. Moving into next weekend, some early
indications in the ensembles show another potential clipper low
around Saturday morning, but uncertainty is understandably high. The
general pattern remains largely unchanged from prior expectations
with continued cool air aloft supporting favorable conditions for
post-clipper LES.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 628 AM EST Sun Jan 19 2025

IFR conditions in lake effect snow and blowing snow will
persist at CMX through the period. IFR conditions in lake effect
snow will persist at IWD today before improvement to generally
MVFR conditions tonight. At SAW, lake effect clouds and
scattered showers will cause VFR conditions to trend toward MVFR
later this morning into the afternoon, although expect
improvement back to VFR tonight.

&&

.MARINE...
Issued at 458 AM EST Sun Jan 19 2025

With large-scale surface pressure features far away from Lake
Superior, northwest winds gusting to around 25 kt will be the norm
through Tuesday. Frigid arctic air will cause periods of heavy
freezing spray throughout the weekend and early portion of next
week. High pressure sliding to the south and east will cause winds
to become more southwesterly Wednesday, remaining around 25 kt,
though warming temperatures and a change in wind direction reducing
wave heights should reduce the freezing spray to light-to-moderate.
Beyond then, gales will depend on whether or not a clipper low
materializes in the mid-to-late week period and again over the
weekend, in which case gales to 35 knots become possible, but
probabilities at this time are only around 20-30%.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Cold Weather Advisory until 1 PM EST Tuesday for MIZ001-003.

  Cold Weather Advisory from 10 PM EST /9 PM CST/ this evening
     to 10 PM EST /9 PM CST/ Monday for MIZ002-004-005-007-011-
     084.

  Extreme Cold Warning from 10 PM EST /9 PM CST/ Monday to 1 PM
     EST /noon CST/ Tuesday for MIZ002-004-005-011-084.

  Winter Weather Advisory until 7 PM EST Monday for MIZ006-007-
     085.

  Cold Weather Advisory from 10 PM EST /9 PM CST/ this evening
     to 1 PM EST /noon CST/ Tuesday for MIZ006-012>014-085.

  Cold Weather Advisory until 4 AM CST Monday for MIZ009-010.

  Extreme Cold Warning from 4 AM Monday to noon CST Tuesday for
     MIZ009-010.

Lake Superior...
  Heavy Freezing Spray Warning until 7 PM EST /6 PM CST/ Tuesday
     for LSZ162-240>251-263>267.

Lake Michigan...
None.

&&

$$

SHORT TERM...Voss
LONG TERM...GS
AVIATION...Voss
MARINE...GS