094
FXUS63 KMQT 250237
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
937 PM EST Sun Nov 24 2024

.KEY MESSAGES...

- Light to moderate snow spreads northward into the UP after
  midnight, continuing through Monday evening. Some rain will
  mix in with snow closer to the Lake Michigan shorelines.

- Snow accumulations of 3 to 6 inches expected for much of the
  interior UP through this evening, with lower totals along the
  Great Lakes shorelines.

- A Winter Weather Advisory has been issued for late tonight
  through Monday evening. Slippery travel conditions are
  possible for the Monday morning commute.

- Temperatures will become below normal for this time of year
  by late this week.

&&

.UPDATE...
Issued at 936 PM EST Sun Nov 24 2024

Persistent onshore flow and steep low-level lapse rates/weak
instability continues to result in lake effect snow showers over
Marquette County this evening. Models are struggling to depict this
activity, with moisture likely a bit deeper than models are
indicating. Although just a dusting is expected before the main
system arrives later tonight, temps are getting cold enough for it
to stick to untreated roadways, so some locally slippery conditions
are possible.

Otherwise, the leading edge of the synoptic-scale precip has made it
into Menominee County, where temps are warm enough for rain. Made
slight adjustments to PoPs but overall the forecast remains on
track. Did make a few headline adjustments: 1) extended advisory for
western/central UP through 00Z Tue (7 pm EST Mon), and 2) issued
advisory for Alger, northern Schoolcraft, and Luce, from 09Z tonight
through 06Z Tue (4 am tonight through 1 am Tue EST). That should
cover the synoptic system, but lake effect will continue for the NW
snow belts, so some headlines may need to be extended.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 304 PM EST Sun Nov 24 2024

Weak ridging extending southward from surface high pressure over
Ontario and Manitoba is turning winds easterly this afternoon, with
lingering spotty lake effect snow showers over the north-central UP
shifting westward in response. With limited moisture aloft as
inversion heights continue to lower, it is not out of the question
that we see some freezing drizzle mixing in with these before we dry
out completely, but impacts will be limited. Otherwise, much of the
UP remains under a blanket of low stratus, with some breaks in the
cloud cover across the west and south-central. This is helping to
limited temperatures to the lower to mid 30s across most of the UP.

Meanwhile, water vapor imagery and RAP analyses reveal midlevel
shortwave action over the Canadian Prairies and the Rockies. These
two features phase this evening and swing into the Upper Midwest,
with a surface low closing off and heading towards southern Lake
Michigan by early Monday morning. Resulting isentropic ascent will
kick off a round of precipitation across central WI late tonight
that will work northward into the UP. Simulated reflectivity
continues to favor onset time more towards 06Z in the southern UP as
midlevels moisten up, with precipitation continuing to spread
northeast through sunrise. Ensembles show a widespread 0.10-0.20in
of QPF across the western and central UP from 06-12Z, with higher
totals near a quarter-inch closer to the WI border. Soundings
generally favor a wet snowfall, though warmer (if still below-
freezing) profiles, especially in the south-central UP, would
indicate a better potential for some sleet to mix in. Some NAM
profiles do continue to show a weak above-freezing warm nose aloft,
so some freezing rain would not be out of the question. However, will
note that the more northerly NAM track (which brings warmer air into
the UP) remains an outlier among the guidance. With SLRs up to 8-
10:1 across most of the UP, and below 5:1 closer to Lake Michigan, a
slushy 1-2in of snowfall is expected across the western UP by
sunrise Monday, with higher amounts up to 3in possible. East of M-
95, expect to wake up to an inch or less of snow. With more snowfall
on the way after 12Z Monday (discussion continues below), a Winter
Weather Advisory has been issued for the western half of the UP.

&&

.LONG TERM /MONDAY THROUGH SUNDAY/...
Issued at 416 PM EST Sun Nov 24 2024

The work week starts off with snow over much of the UP with a wintry
mix of rain and snow (possibly including sleet in Menominee and
Delta counties) hugging the shores of Lake MI Monday morning. This
stratiform precip continues lifting north into the afternoon hours
as the sfc low over southern Lake MI moves northeast toward the
thumb of Lower MI. SLRs are likely to hold around or below 10:1 with
the system snow as sfc temps begin to warm back up. The highest snow
ratios are expected in the north and west due to close proximity
with the colder airmass accompanying the mid level trough. Some lake
enhancement off northern Lake MI is also possible Monday morning,
given the southeast winds aloft and 850 mb temps around -1C to -2C
over the warm waters of 10-12C. This lake enhancement is being
picked up by the 11/24 12Z NSSL/HRRR and 18Z HRRR, but weakly noted
in the last few RAP model runs with a lower magnitude. They place a
small corridor of up to around 4-6" of snow over Menominee and into
the lakeshores of Delta county through ~18-20Z Monday. This
enhancement has some bust potential given the placement of the sfc
low and the circulations aloft, but will monitor it with upcoming
forecast packages. Around 0.2 to 0.4" of additional QPF associated
with the synoptic precip is likely during the day on Monday.

The 11/24 12Z HREF probabilities of at least 4" of snow through 18Z
Monday (10:1 SLR) are between 40-80% over the west and 20-50% over
the east. Also with the latest GFS/ECMWF/Canadian ensembles, there
is ~50-80% chance for at least 3" or more over the west; about a 10-
20% increase from previous ensemble runs. Given the QPF and SLRs,
the forecast total is between 2-4" of wet snow with potential for
localized totals up to 6". This would create some slippery roadways
affecting the Monday morning commute; hazardous conditions may
continue into the afternoon and evening hours with a transition over
to LES. Opted to hoist a Winter Weather Advisory for travel impacts
as well as wet snow accumulations Marquette and Dickinson counties
westward. Eastern counties may be added and/or advisories may be
extended in future forecast packages.

As we move to Monday evening, the sfc low will be tracking through
Lower MI and the mid level trough will begin swinging through the
Upper Great Lakes. This will begin to usher in a much colder airmass
that continues through the extended forecast period. Northwest flow
brings 850mb temps down to around -8C by Tuesday morning with as low
as -12C possible over the far western waters of Lake Superior. Given
the anomalously warm Lake Superior sfc temps ~8C, this will be more
than sufficient for LES. This pattern of west-northwest to northwest
LES is expected to continue over the CWA through the rest of the
forecast with 850mb temps gradually lowering to -12C to -14C across
the region by next weekend. A period of weaker LES is likely
Wednesday and Thursday as weak ridging moves through the Upper
Midwest. LES then should be re-invigorated moving into next
weekend/early the following week as broad troughing over the Great
Lakes sends multiple shortwaves down through the region. This snowy
pattern should result in several inches of snowfall over the course
of the extended forecast, impacting holiday travel plans into early
December. Otherwise, temps trend to below normal by late this week.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 708 PM EST Sun Nov 24 2024

VFR/MVFR conditions continue through the evening with light lake
effect snow showers at SAW, however, deteriorating cigs/vis are
expected at all TAF sites overnight into Monday morning as low
pressure moving through Lower Michigan overspreads wet snow across
the UP. Snow will spread north overnight, beginning at IWD first
around 06z, then at CMX and SAW closer to 09z. IFR conditions are
expected to begin (>80% chance) shortly after snowfall arrives.
Confidence is also high (>80%) that visibilities at all sites will
fall through the early morning, lessening to 3/4SM around ~15z and
persisting through the rest of the day. Winds will be light, gusting
to near 10 knots out of the east/northeast.

&&

.MARINE...
Issued at 416 PM EST Sun Nov 24 2024

East winds up to 20-25 kts over the far western third of the lake
diminish this evening. Meanwhile, northeast winds over the east half
of the lake veer east for tonight as a Colorado low pressure system
approaches from the southwest. Winds then remain 20 kts and less
tonight through most of the day Monday as the Colorado low begins
moving over the Great Lakes, phasing with another low coming from
the northwest. As the newly phased low moves through Lower MI Monday
afternoon into Monday night, winds do gradually back north. Winds
then re-invigorate up to 20-30 kts Monday night through Tuesday
evening behind a cold front. A few gale force gusts up to 35 kts are
possible on Tuesday, but only a low chance (25% or less) is noted on
internal probabilistic guidance between Marquette, Stannard Rock,
and Grand Marais. Overall, strongest winds are expected over the
southern half of the lake. Expect the winds to gradually weaken
Tuesday night as weak ridging moves through the Upper Midwest, with
winds becoming 20 kts or less again by Wednesday morning. However, a
shortwave dropping down from Canada on Friday brings additional
potential for winds to increase into the 20-30 kt range.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory from 1 AM EST /midnight CST/ to 7 PM
     EST /6 PM CST/ Monday for MIZ001>005-009>011-084.

  Winter Weather Advisory from 4 AM Monday to 1 AM EST Tuesday
     for MIZ006-007-085.

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

&&

$$

UPDATE...Thompson
SHORT TERM...LC
LONG TERM...Jablonski
AVIATION...BW
MARINE...Jablonski