187
FXUS63 KMQT 052304
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
604 PM EST Wed Feb 5 2025

.KEY MESSAGES...

- Two system snowfalls during this forecast cycle, the first tonight
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 35% with
either event. Slippery travel conditions will occur with the
snowfall.

- Strong west winds expected over northwest Upper MI (Keweenaw in
particular) Thursday afternoon and evening. Probability of peak
gusts in excess of 58mph is 40-70%. The strong, gusty winds and
developing lake effect snow showers will lead to frequent whiteout
conditions in blowing snow and falling snow. Blizzard conditions
possible for several hours.

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

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 604 PM EST Wed Feb 5 2025

Under sfc high pressure ridging, conditions will remain dry and
partly cloudy probably through this evening. Temps early this
afternoon are on their way to rebounding into the lower to mid 20s
after chilly, and in some cases sub-zero, overnight lows.

Later tonight, attention turns to a couple shortwaves set to track
through the Great Lakes region. The first wave now moving through
the Central Plains and mid-Mississippi Valley region will pass
across the southern Great Lakes tonight, slightly preceding the
other stronger shortwave now over the Northern Rockies which will
track e into the Upper Great Lakes late tonight/early Thursday. The
southern wave will capture much of the moisture return from the
Gulf, particularly since it precedes the northern wave. This will
work to hold down snowfall amounts across Upper MI even though the
northern wave is stronger and ends up with a deepening sfc low
response. Developing waa/isentropic ascent will result in -sn
spreading across western Upper MI later this evening and reaching
eastern Upper MI overnight. The 280-290k sfcs show, at best 6 hrs of
ascent late tonight with available mixing ratios ~2g/kg, suggestive
of ~1-2in of system snow tonight into early Thursday mainly for west
and central portions of the U.P. DGZ is in a narrow layer high up at
about 13-15kft with only modest lift in the layer, so expect SLRs on
the lower side, ranging from 10-15 to 1. Look for min temps dipping
into the 10 to 15 F range over the interior this evening under
partly cloudy skies before rising into the upper teens lower 20s
later tonight under increasing clouds and increasing boundary layer
winds.

&&

.LONG TERM /THURSDAY THROUGH WEDNESDAY/...
Issued at 604 PM EST Wed Feb 5 2025

An active weather pattern will be ahead for the region as a 500mb
cutoff low over the Pacific Northwest breaks down and ejects a
number of shortwave troughs over the Upper Great Lakes through the
next week in addition to shortwaves rotating around a longwave
trough centered over Hudson Bay. These features will ultimately
result in two synoptic system snowfalls for the UP, one tonight
through Thursday and the other Saturday, with other shortwaves
providing synoptic support for lake effect snowfall. Building
ridging over Alaska by Sunday will set up broad troughing over the
Canadian Prairie and Northern Great Plains for the first half of
next week. The amplified pattern for early next week will provide a
supply of cold air to sustain LES in the wake of the weekend system
as well as below normal temperatures into the middle of February.

System snowfall will be widespread across the UP by Thursday
morning. Throughout the morning, the surface trough associated with
the deepening ~993mb low passing through northern Ontario will fully
push through the UP. As winds veer to the west, the GFS suggests
850mb cold advection locally in excess of -20C/12hr as well as
pressure gradient in excess of 8mb from Copper Harbor to Ironwood
will kick up intense winds in addition to rapidly developing lake
effect snowfall. Euro ensemble probability of peak gusts of 58mph or
higher ranges from 40-70% across the Keweenaw. In addition to the
Keweenaw, expect gusts to 50-55mph near the lakeshore down into
Ontonagon County and lakeside east of Munising as well. Elsewhere,
expect gusts to 30-40mph. A secondary 500mb shortwave quickly
following the main wave will aid a deepening moisture profile in the
PM along with some lifting of inversion from ~6kft to ~8kft,
supporting widespread LES development in the W wind snowbands. While
HREF and Euro ensemble visibility shows a wide range of solutions,
the combination of strong winds following a couple inches of snow
and widespread LES leads to high enough confidence to upgrade the
Winter Storm Watches  to Blizzard Warnings. While the winds will be
a bit less over the southern tier of counties within the Blizzard
Warnings relative to the Keweenaw Peninsula, higher snowfall totals
expected should compensate to provide similar blizzard conditions.
Near storm-force wind gusts along the lakeshores east of Munising
will lead to localized whiteout at locations such as Grand Marais,
though lesser confidence of the duration of widespread low
visibility conditions will lead to a Winter Weather Advisory being
issued for the proceeding LES.

W to WNW flow LES will diminish during Fri under moderating/drying
air mass and approaching sfc high pres ridge. Over the weekend,
attention turns to the remnant of the mid-level low that was off of
the Pacific NW coast. That wave reaches the Great Lakes Sat night.
Ensembles continue to be show a tight cluster of low tracks from
Missouri Saturday to Pennsylvania/West Virginia by 06Z Sunday. The
UP will be on the northern end of that precip shield, supporting
another round of widespread near-advisory criteria snowfall. The
highest snowfall will be the vicinity of Menominee, where the Euro
ensemble shoes a mean of around 3.5 inches of snowfall, though the
90th percentile is as high as 6 inches with a slightly more
northerly storm track and stronger forcing. However, a weaker and
further south track might only bring 1-2 inches of snow for
Menominee with even lesser snow further north. Regardless of exact
solution, ensembles are near-certain in 850mb temperatures
plummeting well into the negative double digits following the
system, so generally westerly to northwesterly LES is expected to
follow. Cold air aloft will translate to cooler surface
temperatures, especially in the overnights next week in weaker cloud
coverage away from LES bands. Current NBM lows are around -10F
Wednesday and Thursday morning for the interior west with wind
chills approaching -20. The surface pressure pattern is less certain
for next week, so if a tighter pressure gradient is realized, cold
weather products could become necessary again, though the LREF
currently only has up to 30% chances of reaching -25F wind chills
next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 529 PM EST Wed Feb 5 2025

VFR conditions will continue into the overnight, before light snow
moves in. When it does, conditions will fall to IFR first at IWD and
last at CMX. VLIFR conditions will happen in the heavier snow and
blowing snow at CMX Thu morning with gusts up to 40 knots.

&&

.MARINE...
Issued at 431 PM EST Wed Feb 5 2025

Southeast to south gusts build to 20 kt this evening and to 25-30 kt
overnight tonight ahead of a deepening low passing north of Lake
Superior. As the low passes Thursday, cold advection and rapid
pressure changes will force westerly wind gusts to gales to 45 kt in
the morning and storms to 50 kt in the afternoon. The gusty winds
will be relatively short-lived, with only an 8-hour window of storms
expected and WNW winds falling below gales by Friday morning. W to
NW winds will gradually decrease to near 25 kt by Friday evening and
below 20 kt by early Saturday morning. A low pressure passing south
of the Great Lakes this weekend will bring gusts back up to 20-25 kt
out of the W to NW Sunday and Monday, with the pattern into next
week supporting similar wind gusts dependent on the exact track of
any minor disturbances that track through the Upper Great Lakes in
that time period. Heavy freezing spray is expected Thursday and
Friday as well as waves of 14-17 feet, with locally up to 21 feet
possible late Thursday night over the eastern end of Lake Superior.
Waves fall below 8 ft late Friday.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Blizzard Warning from 11 AM Thursday to 1 AM EST Friday for
     MIZ001>003.

  Blizzard Warning from 1 PM Thursday to 1 AM EST Friday for
     MIZ004-084.

  Winter Weather Advisory from 1 PM Thursday to 7 AM EST Friday
     for MIZ006-007-085.

Lake Superior...
  Gale Warning from 7 AM EST /6 AM CST/ Thursday to 1 AM EST
     /midnight CST/ Friday for LSZ162.

  Heavy Freezing Spray Warning from 7 AM EST /6 AM CST/ Thursday
     to 7 AM EST /6 AM CST/ Friday for LSZ162.

  Storm Warning from 7 AM EST /6 AM CST/ Thursday to 4 AM EST /3
     AM CST/ Friday for LSZ240>242-263.

  Heavy Freezing Spray Warning from 10 AM EST /9 AM CST/
     Thursday to 1 PM EST /noon CST/ Friday for LSZ240>242-263.

  Storm Warning from 10 AM Thursday to 7 AM EST Friday for
     LSZ243>251-264>267.

  Heavy Freezing Spray Warning from 1 PM Thursday to 7 PM EST
     Friday for LSZ243>251-264>267.

Lake Michigan...
  Gale Warning from 10 AM to 10 PM EST Thursday for LMZ221.

  Gale Warning from 10 AM Thursday to 4 AM EST Friday for LMZ248-
     250.

&&

$$

SHORT TERM...Voss
LONG TERM...GS
AVIATION...07
MARINE...GS