116
FXUS63 KMQT 012040
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
340 PM EST Mon Dec 1 2025

.KEY MESSAGES...

- Winter Weather Advisory for moderate to possibly heavy lake
  effect snowfall in Keweenaw County tonight into Tuesday
  morning. Uncertainty remains high in the exact placement of
  the dominant band with a high boom/bust scenario.

- Periods of light to moderate lake effect snowfall is expected
  through the week as a cooler than normal airmass resides over
  the region.

- The next chance of widespread light snowfall comes with a
  fast-hitting Clipper Low Tuesday night into Wednesday.

&&

.DISCUSSION...
Issued at 323 PM EST Mon Dec 1 2025

Afternoon GOES water vapor imagery and RAP analysis show the weak
ridge and surface high pressure over the Lower Great Lakes/Ohio
River Valley drifting east. Temps in the upper teens to mid 20s will
begin their descent as colder air filters in.

A shortwave and weak surface trough press in from the northwest this
evening. Best forcing remains south of the CWA, but flurries and a
few stray light snow showers may graze Lake Michigan shores and
southern Luce County. Accumulations in those areas will be limited
to a few tenths of a inch. The primary concern during this period
into Tuesday will be the LES over Lake Superior. The latest SPC
mesoanalysis indicates -14C to -16C 850mb temps over Lake Superior,
which is currently sitting at an average temp of just above 6C
slightly warmer near the western lakeshores. With delta-Ts of 20-
22C, inversion heights of 5-6 kft, strong low level convergence, and
plenty of moisture available into the DGZ, moderate to heavy LES is
anticipated with the dominant band setting up. The limited view on
the radar mosaic paired with visible satellite show this is well
underway over the west half of the lake. The tricky part of the
forecast will be where this dominant band sets up. With tonights
cold temps in the single digits to teens, a land breeze component
could keep this snowband further off shore and limit snowfall totals
to 1-2". But, if the surface trough is strong enough to shift the
band further south, higher amounts reaching into the 6-12" range
could be realized. Experimental REFS/NBM probabilistic data indicate
40-60% chances for greater than 4" of snow, focused north and west
of US-41. This is also where the same guidance points to moderate to
heavy snowfall rates up to 1"/HR which would reduce visibility.
Given the high boom/bust potential of the forecast and the likely
hazards given the southerly track, opted to hoist a Winter Weather
Advisory for 7 PM EST this evening to 10 AM EST Tuesday. Upgrades to
a warning may be necessary given the boom potential so stay tuned
for forecast updates. Impacts to the morning commute are possible on
Tuesday.

In the wake of this initial wave, southwest flow strengthens again
Tuesday morning in advance of the next system lifting any LES north
away from the UP. Highs will be in the 20s. Dry weather by the
afternoon will be brief, as the next round of widespread snow arrives
Tuesday night.

There remains pretty decent model agreement in an Alberta Clipper
Tuesday night into Wednesday. Even with the subtle differences
between ensemble suites on how far north this low will track,
amounts will not be impressive regardless. Widespread amounts of a
dusting to 1" are the likely solution (60% chance) with higher
amounts to 2-3" over the northwest wind snow belts, primarily
influenced by the lake influence. Strong pressure rises and the cold
airmass of -23C to -25C descending over the region Wednesday into
Wednesday night with the mid level trough will result in a period of
LES and windy conditions. Northwest winds of 20-35 mph are expected
near Lake Superior and in the Keweenaw with widespread 15-25 mph
elsewhere Wednesday into Thursday. Temps on Wednesday will again
lift into the 20s early, but tank to the single digits for most save
for low teens by eastern Lake Superior by Thursday morning. Highs on
Thursday only rise into the teens to low 20s. Expect wind chills
below 0 by Thursday morning across the UP. In terms of trailing LES
over the northwest wind snow belts, NBM probabilities for at least
4"/24HR are ~30% in the Keweenaw/North Central with a 50-75% chance
over the east.

Meanwhile high pressure builds in from the northwest, gradually
working against available moisture Wednesday through Thursday. This
also shifts winds out of the southwest on Thursday, lifting any
lingering LES to the north. This dry period once again does not last
long as the next clipper system arrives Thursday night. That said,
there still is a fair amount of spread on timing/track of this
latter system. What is more certain is LES associated with the
continued colder than normal airmass that accompanies it. An active
pattern including potential additional systems early next week and
periods of LES keep PoPs in the forecast.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1212 PM EST Mon Dec 1 2025

Given the trend in MVFR cigs holding on longer than anticipated,
keeping things that way through the rest of the daytime today as
winds from the SW continue through the period. However, as IWD has
improved to VFR as of the 17z observation, have them VFR until this
evening. Could see a Bayfield Bomber lake effect snowband move over
CMX tonight; if so, periods of even +SN are possible (low/10% or
less chance). However, most guidance keeps the band north of the
terminal and either in Keweenaw County or Lake Superior.
Nevertheless, could see some drifting at CMX that could reduce vis
down to even IFR at times tonight. Expect clearing late in the
period to bring VFR conditions back over the terminals Tuesday
morning, although lake effect cloud cover may keep cigs MVFR over
CMX Tuesday.

&&

.MARINE...
Issued at 340 PM EST Mon Dec 1 2025

A low pressure trough descends southeast over the lake this evening
shifts winds over the north half of the lake out of the northwest,
settling to around 20 kts or less tonight. Meanwhile, west-southwest
winds across the rest of the lake hold around 15-25 kts. Moderate to
heavy lake effect snow bands across the long axes of the lake will
reduce visibility to less than 1 NM at times overnight into Tuesday.
Significant wave heights settle below 4 ft by Thursday morning.

The pressure gradient tightens with a Clipper Low Tuesday night into
Wednesday. Southwest winds increase once again to 20-30 kts by
Tuesday night, veering northwest Wednesday morning behind the cold
front and maintaining between 20-30 kts into Thursday. This system
brings the best shot at gales to 35 kts during the forecast period
(40-60% Wednesday into Wednesday night, highest chances east) as a
cold airmass descends overhead accompanied by strong pressure rises.
If confidence increases, a Gale Watch would be warranted on the next
forecast package. Significant wave heights build to 6-12 ft, highest
southeast. The elevated winds/waves and cold airmass support light
to moderate freezing spray across the lake, and likely some heavy
freezing spray over the north central waters (~60% chance).

Northwest winds fall back down to 20-30 kt for Thursday, but may
increase again out of the southwest to 35 kts Thursday night into
Friday ahead of the next clipper system. That said, there remains
plenty of uncertainty regarding the exact timing and track of the
late week system.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory from 7 PM this evening to 10 AM EST
     Tuesday for MIZ001.

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

&&

$$

DISCUSSION...77
AVIATION...TAP
MARINE...77