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