textproduct: Marquette

KEY MESSAGES

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

- The weather pattern through the week and into next weekend is defined by periodic Clipper low pressure systems, which will not be strong enough to deliver accumulating snow on their own, but the proceeding lake effect snow will bring the potential for 4"/day snowfall rates (50% chance) especially in the NW wind lake effect snow belts, beginning Wednesday.

DISCUSSION

Issued at 456 AM EST Tue Dec 2 2025

Early morning observations in Marquette County feature some light snow showers, but nothing accumulating. Further west, ship obs, IWD, and CMX have reported snowfall this morning, and lining up KDLH radar returns of a SW-flow LES band with CAM modeled reflectivity (as the Keweenaw has no low level radar coverage) shows that dominant band brushing mainland Keweenaw County through this morning before lifting north. Will keep the Winter Weather Advisory as-is, given there is not much evidence that the previous forecast is much different than what the given observations show. 00Z HREF LPMM plots show that if the LES band does reside over approximately the Eagle River vicinity, 6 inches of snowfall is possible, though more likely outcomes are an additional 1 to 3 inches. Still, this could make for a challenging morning commute along US-41 and M-26 in Keweenaw County, so drivers beware of rapidly changing road conditions and visibility.

As the LES band lifts offshore, expect a quiet day across the UP today, with high temperatures in the 20s despite increasing southwesterly flow, which usually brings warmer air to the region. 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. The first such clipper arrives tonight into Wednesday. The HREF shows the synoptic snowfall from this event being not terribly impressive with mean 6-hourly snowfall rates of 1"/6hr or less widespread. However, as winds become northwesterly behind the cold front, lake enhancement (850mb temps falling into the -20s C over a Lake Superior still around 5 C) and orographic enhancement do highlight the spine of the Keweenaw as likely to see 2-4 inches of snowfall by Wednesday evening. Some blowing and drifting snow is also possible as the cold advection behind the front allows wind gusts of near 35 mph to mix down to the surface Wednesday. The other area of concern will be the east-half NW wind LES belts, as long-lake fetch with the aforementioned supportive thermodynamics (and a not-yet frozen Lake Nipigon in support as well) will provide the ingredients for moderate snowfall. At this time, still anticipating around 4"/day rates in the east by Thursday morning. With the next 12Z HREF, expect some more clarity as to whether further advisories are needed, though potential for Winter Storm Warnings (8+ inches) is low (10% or less).

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 Thursday evening. 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 -10 (50-80% chance interior west).

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 641 AM EST Tue Dec 2 2025

MVFR conditions will continue into the morning hours due to a stubborn cloud deck that has been in the region for the last day. It is starting to erode and should give way to VFR conditions by late this morning or early afternoon. A clipper low will push into the area late tonight bringing MVFR and IFR conditions back into the area, especially over the west at IWD and CMX. Winds will shift northwesterly tonight behind a cold front with gusts to around 20kt.

MARINE

Issued at 456 AM EST Tue Dec 2 2025

Wind gusts of near 25 kt this morning ramp up to near 30 kt especially between the Keweenaw Peninsula and Isle Royale ahead of a cold front. As the cold front passes Wednesday, chances of gale force gusts increase to around 50 percent over central Lake Superior, though the timing is too uncertain to commit to a headline at this time. Wind gusts fall down to near 25 kt for Thursday morning before wind gusts ramp up once again ahead of the next disturbance, arriving Thursday evening and ramping up wind gusts to near gales in the far west (50% chance of exceedance) and around 30% chances of gales further east. This pattern of weak clipper lows followed by periodic chances of low end gales will continue into the weekend. Each gale or near-gale looks to bring 8-11 ft waves, and the coolest airmass of the season residing over the lake will introduce some moderate to heavy freezing spray threats at times.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Winter Weather Advisory until 10 AM EST this morning for MIZ001.

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