textproduct: Marquette

KEY MESSAGES

- A Winter Weather Advisory is in effect for 3-7 inches of snowfall in the eastern UP associated with NW wind lake effect snow bands.

- Gale Warnings are in effect for much of Lake Superior for northwest winds up to 40 knots today and tonight. Additional gale potential (30-50% chance) exists Thursday evening into Friday. Both rounds will be accompanied by moderate to heavy freezing spray and waves of 8+ ft.

- Colder than normal temperatures continue through the forecast. Expect wind chills in the single digits above and below zero Wednesday into Thursday.

DISCUSSION

Issued at 454 AM EST Wed Dec 3 2025

Early morning KMQT radar returns show widespread light to moderate snow showers across Upper Michigan, with some breaks in the western UP in particular. Observations show that the winds have as of 09Z shifted to be out of the northwest behind the front in the western third while southwesterly winds prevail ahead of the front in the east and central. Aloft, few longwave features are noted at 500mb over North America, with the dominant feature being a Hudson Bay closed low with a few shortwaves embedded within the peripheral flow. Elsewhere, a Rex Block is set up off the Pacific Coast, with the closed low being off the coast of Los Angeles and the Baja California, while the ridging is off the Pacific Northwest and British Columbia coast. As this blocking pattern is in no hurry to progress (especially as the number of longwave features downstream is low), the weather pattern over Upper Michigan will be dictated by the aforementioned embedded shortwaves within the Hudson Low and any shortwaves embedded in the northwesterly flow proceeding through the Canadian Rockies. Either shortwave mechanism is primed to deliver clipper-type low pressure systems, though given the diminutive size of the parent troughing features, these clippers will not be particularly strong. However, the cyclonic surface flow and shot of cool air over the warm Great Lakes that come with each clipper will mean that the more impactful weather this forecast period will be the post-system LES.

For today, CAMs show snowfall quickly becoming banded in nature, aligning with the typical NW wind LES bands. 850mb temps falling into the -20s C over a Lake Superior still around 5 C will mean that the thermodynamic support for the bands will be healthy. Soundings for the Munising area show inversion heights growing to around 7.5 kft, though given just how cold the lower levels are, the DGZ is somewhat shallow at around 2 kft and the bottom of the DGZ is not fully saturated. The HREF gives chances of snowfall rates exceeding 0.5"/hr at only around 30% in the east today. Given the mixture of supportive and not-so-supportive forecast elements, have elected to go with a Winter Weather Advisory for the east, with snowfall totals expected to be in the 3-7 inch range for the NW wind LES belts. An isolated report of 8+" cannot be ruled out (30%), but reports that high will be the exception, and not the rule. Besides the precipitation, wind will also complicate matters, with the cold advection behind the low helping wind gusts of 35+ mph mix down to the surface, especially near the lakeshores. In conjunction with the falling snow, the wind will cause some lower visibility at times and snowdrifts over some roads, which could make travel difficult in some spots at some times. By Thursday afternoon, local surface ridging will help shift winds to be out of the SW to SSW, fully shifting LES bands offshore, though not before the coolest high temperatures of the season are forecast, with NBM highs on Thursday only in the low teens in the interior west.

While high temperatures in the teens and 20s persist throughout this week and into the weekend, not much change in Lake Superior's temperature is expected until some clearing skies can allow for more efficient cooling. With persistent cool NW flow aloft over the warm lake for the foreseeable future, expect some flavor of LES to persist between rounds of clippers, the following of which, the NBM brings increased PoPs with late Thursday night into Friday morning. Again, given the weaker nature of these systems, the lake effect may be the more noteworthy mechanism for delivering accumulating snowfall, and with persistent background NW flow, expect the NW wind snow belts to be the hardest hit this week and into the weekend. Overnight lows in the single digits to occasionally subzero in the interior west will bring some of the coolest temperatures of the season, with Thursday morning being the most likely to have wind chills below -15 (50-80% chance from Iron River to Ironwood, 30% rest of the interior).

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 623 AM EST Wed Dec 3 2025

MVFR conditions will be dominant for much of the TAF period. A cold front will push through the U.P this morning with gusty northwesterly winds to 20-30kt behind the front. Lake effect clouds and snow showers will result in MVFR conditions at IWD and CMX through the taf period. Snow showers will increase in intensity and coverage this evening which could bring periodic IFR conditions to CMX and IWD. SAW will start out VFR but drop to MVFR after the frontal passage this morning. VFR conditions return to SAW this evening.

MARINE

Issued at 454 AM EST Wed Dec 3 2025

Gale Watches have been upgraded to Warnings for today as the post- cold front winds will gust to 35-40 kt out of the northwest today and tonight, driving waves of 8-12 ft across the lake (locally up to 15 ft north of Grand Marais, MI). As a weak ridge moves over the lake Thursday, wind gusts fall to near 25 kt, backing to the west, then southwest. Ahead of the next clipper low, gales to 35 kt are once again expected across Lake Superior associated with the pre- front southwesterlies. Winds slowly decrease Friday to near 20 kt out of the west. Into the weekend and beyond, expect the pattern of periodic weak clipper low pressure systems to continue with cooler than normal temperatures. Because of the occasionally frigid temperatures, moderate heavy freezing spray can be expected with the periods of strongest wind, with heavy freezing spray forecast tonight, even as some of the Gale Warnings end.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Winter Weather Advisory until 7 AM EST Thursday for MIZ006-007- 085.

Lake Superior... Gale Warning from 4 PM EST /3 PM CST/ this afternoon to 1 AM EST /midnight CST/ Thursday for LSZ241-242-263.

Gale Warning until 7 AM EST Thursday for LSZ243>251-264>267.

Heavy Freezing Spray Warning from 7 PM this evening to 7 AM EST Thursday for LSZ244-263-264-266.

Lake Michigan... Gale Watch from Thursday evening through Friday morning for LMZ221-248-250.