textproduct: Marquette

KEY MESSAGES

- Winter Storm Watches are in effect for much of the UP as a deepening low pressure tracks across the UP Tuesday and Wednesday with an eventual transition to lake effect snowfall. Chances of 12 inches or more of snow are over 90 percent across the western UP by Thanksgiving.

- Wind gusts of 25-35 mph are expected Wednesday, with some gusts to 45 mph or more possible over the Keweenaw. The combination of wind and moderate to heavy snowfall could make Thanksgiving holiday travel very difficult to near impossible at times.

- Gales up to 45 kt are expected (70-90%) on Lake Superior Tuesday night through Thursday, with near 50% chances for Storm-force gusts. Wave heights of 12-18 ft are expected, with some spots near Stannard Rock and between Marquette and Grand Marais seeing up to 18-20 ft waves.

DISCUSSION

Issued at 409 PM EST Mon Nov 24 2025

GOES-East Day Cloud Phase imagery shows some high to mid level clouds over the southern tier of the UP, with a few fair-weather cu over the far eastern UP. The high clouds are streaming in ahead of a 500mb trough over the Central and Southern Plains, though with that trough weakening and being more positively tilted as time goes on, precipitation associated with that trough beginning tonight will be low-impact. HREF mean accumulated precipitation by noon tomorrow is only around a quarter of an inch over the south-central, down to a tenth of an inch or less for the north half. With the cloud cover and precipitation, low temperatures tonight are less than 10 percent likely to fall below freezing.

Attention then turns to an upstream digging trough that is currently over Montana and is expected to deepen and become negatively tilted as it progresses through the Upper Midwest Tuesday through Wednesday. This is a prime setup for strong dynamic forcing for precipitation, and the ensembles are converging on a surface solution that brings a mid 990s mb low pressure over the central UP by 12Z Wednesday and to the lower 990s to upper 980s mb over the eastern UP by 18Z Wednesday. Dynamic cooling within the profile is allowing for the CAMs to show precip types becoming 40-50% likely to be snowfall in the west as soon as early afternoon Tuesday, though accumulation will be difficult as rain mixing in as well as warm air and ground temperatures inhibiting accumulation early. However, by Wednesday as cool air wraps in behind the low pressure, the western UP will see snow ratios climbing from below 10:1 early in the morning to over 15:1 by the afternoon. This cold advection will also help mix 30-40 mph wind gusts from aloft down to the surface in the wake of the low. HREF joint probabilities of wind gusts over 35 mph and snow rates sufficient to drop visibility below a quarter of a mile are 40-70% from Copper Harbor to Ironwood, indicating growing potential for blizzard conditions. 850mb temperatures falling into the negative teens C over Lake Superior water temperatures around 5 C will allow for lake enhancement of the synoptic precipitation eventually becoming lake effect, and the western UP will also get a orographic boost as winds will be perpendicular to the terrain of the Copper Country. As lake effect ramps up behind the low later Wednesday into Thursday and rain turns to snow across the east, snow totals will begin to ramp up over the eastern UP as well, with snow totals increasing in the LREF to over 8 inches along the Lake Superior shores from Marquette to at least Alger County if not into Luce County. Winter Storm Watches have been expanded into Iron and Marquette County for the synoptic precipitation and watches have also been hoisted for the eastern UP for primarily post-system lake effect snowfall. At this point, sources of uncertainty are primarily in the snow ratios, mesoscale enhancements or dry slots, and how well the gusty winds aloft can mix to the surface. However, with the chances of 1"/hr snowfall rates in the west increasing to 70+ percent on Wednesday sustained over a long period of the day, confidence is high that the pre-Thanksgiving travel period will become hazardous over the western UP.

Given the supportive thermodynamics, lake effect snowfall is expected to linger at least over the eastern UP through Thanksgiving and towards the weekend, though with the complexity of the shortwaves interacting prior to Thanksgiving, spread is high on how well ridging will be able to move in and bring cessation of showers as well as whether any further clipper shortwaves will be able to impact the UP.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1245 AM EST Tue Nov 25 2025

MVFR conditions will develop overnight at SAW as a winter storm approaches the region. Expect MVFR conditions at CMX and IWD by morning. Conditions will fall to IFR through the morning hours as showers, fog and low clouds overspread the area. By Tuesday late afternoon LIFR conditions will develop as rain intensity increases and snow begins to mix in at CMX and IWD. VLIFR conditions are expected toward the end (or just after the end) of the TAF period with heavy snow developing in the west and upslope fog develops around SAW.

MARINE

Issued at 409 PM EST Mon Nov 24 2025

As high pressure passes southeast of the Great Lakes, wind gusts will remain below 20 kt tonight. 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 have increased to near 50 percent by Wednesday evening. Should probabilities of storm-force winds remain elevated and are supported by hi-res model guidance tonight, Storm Warnings may be necessary, though Gale Watches will remain for this package. 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 8-16 ft lakewide, with the areas from Stannard Rock to Munising Bay seeing potential for 18-20 ft waves.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Winter Storm Watch from this evening through Thursday morning for MIZ001>004-009-084.

Winter Storm Watch from late tonight through Thursday morning for MIZ005-010.

Winter Storm Watch from Wednesday afternoon through Thursday evening for MIZ006-007-013-014-085.

Lake Superior... Gale Watch from this evening through Thursday morning for LSZ162-240>242-263.

Gale Watch from this evening through Thursday evening for LSZ243-244-264.

Gale Watch from late tonight through Thursday evening for LSZ245>248-265.

Gale Watch from Wednesday morning through late Thursday night for LSZ249-250.

Gale Watch from Wednesday afternoon through late Thursday night for LSZ251-267.

Gale Watch from late tonight through late Thursday night for LSZ266.

Lake Michigan... Gale Watch from Wednesday afternoon through Thursday afternoon for LMZ221-248-250.