textproduct: Marquette

KEY MESSAGES

- Light rain/snow mix presses east this evening followed by scattered lake effect rain/snow for the NW wind snowbelts through Sunday morning.

- Lake effect snow and wind may impact the Thanksgiving holiday weekend. Travelers and interested parties should continue to monitor the forecast as details become more clear over the coming week.

- There is a 50-60% chance for Gale Force and 20% chance for Storm Force winds/light freezing spray on Lake Superior during the middle of next week.

DISCUSSION

Issued at 244 PM EST Sat Nov 22 2025

Early afternoon satellite imagery and RAP analysis reveals a mid- level trough swinging through western Ontario extending south into the Upper Great Lakes region. Closer to home, breezy south winds have picked up as the pressure gradient has tightened ahead of a weak sfc low. Mid to low level warm air advection has been the primary forcing mechanism for a swatch of precip now moving through the western UP. With antecedent dry air in place, not expecting much more than light rain/snow showers as this progresses eastward through the evening, mainly over the northern and eastern UP. Tonight and into the morning hours of Sunday, the surface trough and cold front dive SE into the Lower Lakes, veering winds to the NW and ushering in 850mb temps between -5 to -7C. With an average Lake Superior water sfc temp of ~+7C, this delta-T will be just enough to kick off lake effect precipitation across the NW wind snowbelts. However, model soundings are rather unimpressive, with meager lake induced eq heights, and varying degrees of drying within the DGZ/sub- cloud layer. Opting to leave in chance PoPs in the Keweenaw and east, moreso the east, for low impact and non-accumulating (or light) lake effect snow/rain/graupel showers are expected. With the longer fetch across the eastern lake, lake effect may linger longer in the east through daybreak tomorrow. Lake effect tapers off tomorrow as a ridge begins to build over the Great Lakes once again, allowing for quiet weather into Monday. This period will feature the warmest temperatures of the week; look for highs in the 40s to and perhaps closer to 50 for some Sunday, and well into the 40s and lower 50s Monday.

More impactful weather returns during the mid to late week as two troughs, one ejecting northeast from the southern Plains and another from the Northern Rockies, phase in the Great Lakes Tuesday into Wednesday. This synoptic evolution will support a deepening surface low pressure in the vicinity of the Upper Great Lakes that moves northeast into Quebec Wednesday night through Friday. The position of this sfc feature and its exact track will have important implications for surface sensible weather such as strong winds, synoptically driven snowfall, and lake effect snow following its passage, including where the heaviest snowfall axis occurs. The general idea presented in all guidance packages though suggests that synoptic rain will spread into the region Monday night and Tuesday and then transition over to lake effect snow showers in the Tuesday night to Wednesday timeframe. The recent suite of 12z ensembles and their deterministic counterparts have come into better agreement on the timing and evolution of the sfc low track, suggesting an overall flatter upper level trough and a slower departure. Both the Euro ENS and GEFS low-center locations suggest a ~990-1000mb sfc low developing overhead the vicinity of Lake Superior or northern lower MI by 12z Wednesday, the Euro a bit more progressive and east. With the deterministic low track in both global models (especially the GFS) being nearly right over the lake, the heaviest synoptic forcing for snow may be largely displaced to our northwest, suggesting that lake effect snow on the backside of the departing low will be the main travel hazard heading Wednesday afternoon into Thanksgiving and the following weekend. Ensemble probabilities for 24hr snow totals >3" begin to ramp up 50-75% into Thursday over the northwest wind lake effect snow belts, especially in the west half where deformation/banding may occur in conjunction with lake effect/enhanced precip. Probs for total snow >6" for the NW LES belts increase above 75% through the weekend as cold NW flow persists with the departing system. Another concern will be blowing lake effect snow as NBM probs of NW gusts >40 mph increase above 50% Wednesday with a low (<20%) chance for NW gusts >50 mph.

As we continue to monitor forecast trends through the coming days, Thanksgiving travelers should maintain awareness of the forecast should confidence in travel hazards increase.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 619 PM EST Sat Nov 22 2025

MVFR conditions are expected through the night at the TAF sites as low clouds spread into the area behind a cold front that was moving through the U.P this evening. Winds will also become gusty (25-30kt) at CMX. Northwest flow will keep lake effect clouds streaming into the area but somewhat drier air should help limit cloud cover towards morning, especially at IWD. Currently have the MVFR cloud deck scattering out at CMX and SAW Sunday morning, however there is quite a bit of uncertainly and it is possible (30-50% chance) the MVFR conditions linger into the early afternoon hours. By late afternoon probabilities for MVFR are negligible as onshore flow decreases with winds turning southwesterly.

MARINE

Issued at 244 PM EST Sat Nov 22 2025

Breezy southerly winds 20-30 kts are ongoing as a surface trough extends across western Lake Superior. Tonight and through tomorrow morning, the trough pushes east and winds veer NWerly behind the surface cold front. Model soundings and ensemble probabilities favor gales to 35 kts, with a few gales to 40 not out of the question, from roughly midnight through 10AM EST. Have hoisted a Gale Warning for portions of the central and eastern lake through this timeframe. Significant wave heights build 7-12 ft east of the Keweenaw with the heights waves closer to the eastern UP shoreline. NW gusts to 25 kts hang on in the east half through tomorrow afternoon before lessening below 15-20 kts lake wide and backing S-SW Monday.

Next week, a system is expected to move through the Great Lakes. There's still a number of questions about how this event will evolve, including whether or not the surface low will deepen over the region and how quickly it will move through the region. What is certain though, is that the airmass moving in behind the system will be notably colder, which increases the likelihood of gales in the Tuesday night through Thursday night window. At this point, Storm Force Winds and pockets of light freezing spray cannot be ruled out. Given the clustering differences among the EC, Canadian, and GFS ensemble membership, there's varying degrees of potential outcomes at this point. Given this, the latest Gale probabilities near 50% and Storms near 25% make sense. As we move into next week, some of this should improve and a clarity on anticipated conditions should materialize.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... None. Lake Superior... Gale Warning from midnight tonight to 10 AM EST Sunday for LSZ249>251-266-267.

Gale Warning from midnight tonight to 7 AM EST Sunday for LSZ265.

Lake Michigan... None.