textproduct: Marquette

KEY MESSAGES

- Confidence is increasing in an impactful winter weather event Wednesday into Thanksgiving. Chances of 6 inches or more of snow are 40-70 percent over the western UP by Thanksgiving.

- Wind gusts of 25-35 mph are expected Wednesday, with some gusts to 40 mph over the Keweenaw. The combination of wind and moderate to heavy snowfall could make holiday travel difficult.

- Gales up to 45 kt are expected (70-90%) on Lake Superior Wednesday and Thursday with 20-30% chances for Storm-force gusts. Wave heights of 8-12 ft are expected, with some spots near the tip of the Keweenaw and between Marquette and Grand Marais seeing up to 16 ft waves.

DISCUSSION

Issued at 405 PM EST Sun Nov 23 2025

GOES-East visible satellite imagery shows lingering cloud cover in the east associated with the most recent shortwave diminishing this afternoon. The central UP has mostly clear skies, though along the MI/WI state line, high clouds are streaming in as some moisture aloft is slightly disturbed by minor impulses in the flow. RAP analysis shows that the upper air pattern consists of a closed low over the Four Corners region, northwesterly flow over much of the central CONUS, and troughing lingering over the Ontario/Quebec line. Highs today have been in the 40s today, and the high- to mid-level cloud cover tonight will keep low temperatures from falling too much below freezing tonight. A weak surface trough shown on RAP analysis over the Dakotas currently will progress over the region tomorrow, though enough dry air is present at the surface that chances of precipitation are 14 percent or less during the daytime hours. Warm, southwesterly flow in the lower levels will allow temperatures to climb warmer on Monday than today, though the aforementioned cloud cover will temper that warmth somewhat, with highs not expected to be widespread over 50 degrees F.

Attention then turns upstream as a northern stream shortwave interacts with the trough associated with the aforementioned Four Corners closed low as they move over the Upper Midwest. Confidence is increasing that however the troughing aloft resolves, a 1000-1005 mb low will be moving over the UP by Tuesday night. Ahead of that low, weak warm advection and isentropic ascent will allow for showers to form and lift into the UP Monday night. NAEFS IVT plots show near 90th percentile vapor transport associated with a Gulf connection which will help moisten the lower layers. While a few snowflakes may mix in over the high elevations at times, this will primarily fall as rain, and not particularly heavy rain at that, as LREF mean daily QPF prior to Wednesday is only around a third to two thirds of an inch. The bigger story is going to be when the low deepens as it approaches, wrapping in cooler air and bringing the more likely precip type to be snowfall just as the strongest dynamic and mesoscale forcing moves over the western UP. The snow forecast is going to be a bit touchy as there is some uncertainty in the timing of when the rain/snow transition occurs and sounding show that even after a transition to snow, a lot of the early forcing occurs warmer than the DGZ prior to Wednesday afternoon. The EFI for snowfall over the western UP Wednesday is around 0.8, which means that the more likely solutions for impactful snowfall is high but not extreme. However, the Shift of Tails is near 2, which means that if the "worst case scenario" occurs, significant snowfall accumulation could occur. In other words, it is a somewhat "boom or bust" forecast at this time. The LREF suggests 40-70 percent chances of 6-8 inches of snowfall accumulation over the western UP by the end of the day Wednesday. Additionally, a strengthening low pressure passing in close proximity to the UP is a prime setup for gusty winds, which in conjunction with the potential for 0.5"-1"/hr snowfall rates could make travel quite hazardous as blowing and drifting snow will be possible as snow transitions from wet synoptic snow to fluffy, lake enhanced to lake effect snow late Wednesday into Thanksgiving. Ultimately, for those with late travel plans for the Thanksgiving holiday, close monitoring of the forecast will be necessary.

A transition to pure lake effect snow showers is expected as the 5-6 C waters of Lake Superior contrast with 850mb temperatures falling into the negative teens C. Inversion heights on Thanksgiving may be as high as 10 kft, though the depth of the moist layer may be a little uncertain as there is some indication of dry air at the top of the inversion. The showers will primarily fall in the NW wind lake effect snow belts, though that is also uncertain as the deterministic models show slight variations in the progression of the surface low that could result in some variance in the surface wind pattern. Eventually, ridging will begin to encroach on the area late in the week into the weekend, shifting the lake effect bands, introducing dry air, and reducing the forcing available. There is some early indication in the ensembles that another system could transit the Great Lakes late in the weekend, but given the complex setup, confidence is very low.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 1219 AM EST Mon Nov 24 2025

VFR conditions are expected through most of the TAF period. A strong low level jet will develop late tonight resulting in LLWS at all the terminals until Monday morning when it weakens and mixing allows for stronger surface winds. Wind will become light late during the late afternoon. Clouds will begin to increase late in the TAF period (after 02Z) as a storm system approaches the area, with MVFR possible (30% chance) at SAW.

MARINE

Issued at 405 PM EST Sun Nov 23 2025

As high pressure passes south of the Great Lakes, wind gusts quickly fall below 20 kt this evening, with wave heights falling below 4 ft tonight. A dry trough passing over the lake will briefly kick up wind gusts of 20-25 kt over Lake Superior Monday with a few gusts in the eastern third up to 30 kt (~50%). This will force waves in the eastern third of the lake up to 3-5 ft. Winds and waves then relax once again overnight Monday into Tuesday.

Attention then turns to a merger of upper-level systems resulting in a deepening surface low pressure passing over the Michigan UP late Tuesday and over eastern Lake Superior Wednesday. Ahead of the low, northeasterly wind gusts increase to 25-30 kt Tuesday night, then to high-end gales to 45-48 kt by Wednesday morning. Chances of storm- force gusts to 50 kt are 20-30 percent by Wednesday evening. Winds will remain at least 50 percent likely to exceed gale force until overnight Thursday into Friday before falling to 20-25 kt Friday and below 20 kt overnight into Saturday. During the high-end gale, wave heights will increase to 8-12 ft lakewide, with the areas near the shores of the top of the Keweenaw and between Marquette and Grand Marais increasing to 12-16 ft.

MQT WATCHES/WARNINGS/ADVISORIES

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