textproduct: Marquette

KEY MESSAGES

- Lake effect snow is expected to continue into Saturday. The most impactful periods look to be during the overnight and early morning hours, especially Thursday night into Friday.

- A Winter Weather Advisory is in effect for Baraga and Marquette Counties through Noon EST Friday. Snowfall of 3-8" is expected through Friday over the higher terrain of Marquette and Baraga counties with 1-3" elsewhere. There is a 60% chance for snowfall exceeding 10" west of Marquette CR510, 10+ miles north of US-41 and 10+ miles southwest of Big Bay.

- Temperatures rebound to unseasonably warm (upper 40s/low 50s) early next week.

DISCUSSION

Issued at 310 AM EST Thu Nov 12 2026

Early this morning GFS 500mb height analysis showed an elongated upper level low pressure over Quebec and Newfoundland. Shortwaves were rotating around the low with a more well defined shortwave over the Upper Great Lakes. This shortwave was also evident in the GOES-R water vapor imagery, spinning over the U.P. Surface observations showed temperatures had cooled into the low 30s for the inland areas of the western and central U.P. with mid 30s near Lake Superior and the eastern U.P. where relatively warm lake waters were modifying the airmass. Satellite and radar showed snow showers over much of the western and northern half of the U.P. Snow was struggling to stick on concrete surfaces but webcams did show periods of slushy conditions during heavier snow showers over the higher elevations of Marquette and Baraga counties.

The primary forecast concern continues to be the lake effect snow potential through Saturday. A Winter Weather Advisory is in effect through 1200 EDT Friday as the high terrain of Baraga and Marquette Counties is still expected to see 3"-8" of snow throughout the next 2 days.

Through Saturday shortwaves will dive south through the Upper Great Lakes, around the back side of the upper low over Quebec, helping to maintain moisture, cooler temps and lake effect snow showers. 850mb temperatures this morning were in the -6 to -8C range, plenty sufficient for LES given Lake Superior water temperatures are in the 8-10C range.

The main challenges with this forecast continue to be temperatures, snow ratios, precip intensity (QPF) and the resulting accumulations when combining the QPF and snow ratios. While the current forecast of 3-8" above 1000' elevation (or about 400-600+ ft above Lake Superior) is still on the lower end of traditional criteria for a 48 hour span, the wet/slushy nature of the snow (at least initially) and expected occasional moderate-to-heavy rates (0.5-1.0+"/hr) support the first advisory of the 2026-27 winter season. Near the Lake Superior shoreline, warm flow onshore from an above-freezing Lake Superior will result in generally less than an inch of accumulation (including the city of Marquette). The best chance to see any accumulations there would be Thursday night when the 850mb temps fall to near -9C (REFS mean). Impacts to the area roads will be greatest during the overnight hours, though periods of heavier snow during the daylight hours will still be impactful.

For snow ratios and intensity, frictional convergence over the terrain of the western and north central U.P. have largely contributed to the development of snow showers thus far but banding has become more prevalent over the last hour with the passing shortwave trough axis. Expecting this trend to continue as convergent flow develops over the eastern 2/3 of the lake. Thermodynamic profiles have shown an overall lack of moisture in the DGZ (mainly snow pellets / riming was being observed overnight). Low level moisture is expected to deepen as well this morning. CAM (HRRR/ RRFS) simulated reflectivity align with this as they show rather well defined bands forming by mid-morning along with an uptick in intensity. SLRs continue to be overdone in the NBM with 16:1 by Friday including over the Great Lakes. High snow ratios are unlikely given the warmer low levels and warm ground temperatures (mid 40s) ongoing. Similar thermal profiles to last week's high terrain lake effect snowfall yielded between 5:1 and 7:1 SLR. These values seem reasonable for today, then approach 10:1 tonight as cooling continues. A locally developed temperature-to-SLR curve matches up well with this for areas away from the lake. Have largely maintained the SLRs from previous shifts. Notably REFS soundings interior from the Great Lakes do show inversion heights to around 8- 9kft and saturation into the DGZ, which would support periods of above 10:1 SLRs (without the above context of warmer temperatures, etc) in heavier bands.

For temperatures, the NBM continues to forecast much too cold for overnight temperatures as its bias-correction has been trained on recent stretches of cool, clear nights. This results in it having temperatures falling into the mid 20s over the interior and even below freezing at the immediate lakeshore tonight and Friday night. This is unlikely given the strong onshore flow from a warm lake, cloud cover, precipitation processes releasing latent heat, and only marginally cold 850mb temps of -8 to -10C. Overall thinking is that temperatures will remain above freezing near the Lake Superior shoreline and much of the eastern U.P. through Friday night, thus limiting snow accumulations there.

Confidence remains high in achieving a low end advisory scenario, confidence is low with regards to higher end scenarios. While the coarse resolution models (LREF members) are producing a mean QPF of around one third to two thirds of an inch, the hi-res models such as the REFS members are much more aggressive with a mean QPF over the high terrain of Marquette and Baraga counties of over an inch. The 75th percentile of the REFS (a "reasonable high-end solution") paints a bullseye of nearly 1.5" in the high terrain at the Baraga/Marquette County line. Even with lower end SLRs, this would yield warning criteria snowfall of 12-16" or more. REFS probabilities for 12"+ over the advisory period are in the 30-40% range for the highest terrain (well away from any US/MI highways in the McCormick Wilderness area). The area of strongest convergence will determine if these high-end scenarios are able to be realized. If convergent bands can reside over the same location for much of the next couple days, higher snow totals would be realized, but if those bands waver and wobble, the snow would be spread out over a wider area. As typical with lake effect, confidence is low in the placement and residence time of these bands but terrain enhancement favors the high elevations of Marquette and Baraga counties. Current probabilities for moderate snowfall rates (0.5-1.0"/hr) remain around 80% with a 30% chance for heavy snowfall rates (1"+/hr).

LES should diminish Saturday, confined mainly to northern Marquette County and Alger County during the morning hours with a few lingering rain/snow showers into the afternoon, though as is typical with LES events, wouldn't be surprised if LE showers linger longer than guidance suggests. As ridging aloft moves over the Plains, high pressure will keep Sunday through Wednesday mostly dry with temperatures warming into the 40s and eventually back into the upper 40s to lower 50s.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 628 AM EST Thu Nov 12 2026

The 12Z TAF period consists of persistent MVFR CIGs with periods of MVFR/IFR VIS in northerly wind lake effect snow showers captured in many TEMPO and PROB30 groups. Brief periods of LIFR VIS (or lower) and IFR CIGs are possible, but probabilities were too low to include at this time (~25% chance or lower). Most likely period for worst conditions is late this afternoon into the overnight hours. Otherwise expect northerly winds around 10 kts at CMX and SAW with a few gusts up to 20 kts; 5-10 kt winds at IWD.

MARINE

Issued at 310 AM EST Thu Nov 12 2026

Northerly wind of 25-30kt are expected today over the Lake Superior and northern Lake Michigan. Tonight winds fall down to 20-25kt over the west part of Lake Superior but additional minor disturbances aloft will keep gusty northerly winds of 25-30kt over the eastern half of Lake Superior and northern Lake Michigan through Friday evening. This will drive waves of up to 5 ft on Lake Michigan and 4- 8 ft on Lake Superior (highest in the nearshore waters from Au Train Bay to Big Bay). Waves fall below 4 ft Friday afternoon for all except the east half of Lake Superior, with waves falling below 4 ft in the east Saturday afternoon. High pressure will keep winds mostly below 20 kt and waves mostly 2 ft or less through the first half of next week.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Winter Weather Advisory until noon EST Friday for MIZ004-005.

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