textproduct: Marquette

KEY MESSAGES

- A major winter storm will impact the UP Sunday evening through Monday, with the worst conditions Sunday night into Monday morning. Heavy snow and high winds are likely to result in very difficult to impossible travel conditions, with blizzard conditions resulting in near-zero visibility at times. Strong winds and heavy snow have the potential to result in power outages.

- The heaviest snow is expected in the counties bordering Lake Superior, where there is a 60-80% chance of exceeding a foot of snow, locally up to two feet. Wind gusts of 40-60 mph are expected near the lakeshore and Keweenaw, with 30-40 mph expected inland.

- From Iron through Delta Counties, there is a 40-80% chance of exceeding 8 inches of snow, locally up to 15 inches.

- Light freezing rain cannot be ruled out tonight into Sunday morning for central and eastern areas, with only a light glaze expected at most (30% chance).

- Gale and Storm Watches are in effect Sunday night into Monday night. There is a 50-80% probability of storm force winds over the central and eastern lake, with gusts as high as 60 kt possible.

DISCUSSION

Issued at 400 AM EST Sat Dec 27 2025

Early morning water vapor and RAP analysis shows flat ridging over the Upper Midwest with dry air at mid/upper levels. Boundary layer is moist with low clouds and some fog/mist, which should continue through the night. Light echoes on MQT 88D over the central/eastern UP have been observed to be flurries so far, although model soundings show potential for freezing drizzle as well. It's thought that even if that does occur, it's not likely to raise additional impacts over that being seen from surfaces refreezing from earlier melting, so no headlines/messaging are planned at the moment.

Today into tonight, the main feature of this forecast, a vigorous shortwave trough now evident over the Pac NW, continues to shift eastward into the northern Rockies, possibly developing a closed low in southern SK late in the period. Midlevel ridging builds a bit in advance over the Great Lakes, while a surface low emerges onto the Plains. Southeasterly low-level flow increases locally ahead of this feature, which will result in another seasonably mild day, although it's not likely that any breaks of sun occur as we remain stuck beneath a deepening low-level inversion. Forcing for ascent is weak to nonexistent until later in the day, when it's possible that an impulse embedded in the midlevel SW flow forces an area of showers late in the day into tonight. With temps hovering around freezing, some of this could be in the form of freezing rain and sleet overnight, although given marginal surface wetbulb temps near freezing, not enough confidence to message impacts with any certainty at this time. Somewhat better threat for light fzra exists over the east late tonight into Sunday morning, but still not enough confidence for any headlines.

A vort max is expected to dive south across the Rockies Saturday night into Sunday, rounding the base of the trough and resulting in a second closed low developing from WI into lower MI. This puts upper MI squarely in the crosshairs for upper level diffluence, with poleward exit region dynamics in play as well. These strong dynamics are expected to result in the rapid development of a surface low along the preexisting baroclinic zone, with very impressive deepening rates near 24 mb in 24 hours progged from 12Z Sun through 12Z Mon by many of the 00Z deterministic models (1000 mb to ~mid 970s). The 00Z GEFS/EPS means even approach this benchmark of a meteorological bomb, so while there is some concern in the deterministic models over-deepening the storm, the support from the ensembles increases confidence. These values are near the climatological minimum of MSLP in both the NAEFS and EPS. In terms of raw values, WPC's minimum MSLP database shows all time December mins around 970 around the path of the low, so while it may not be record setting, its climatological context puts it toward the stronger end of winter storms for this area. The exact path of the storm is still somewhat in question, with a Chicago to northern Lake Huron track favored, but still some strong western outliers going from Chicago to near Beaver Island. Of note is that the AI ensembles are generally a bit weaker and further east. An eastward/weaker solution would result in totals/winds being on the lower end of the ranges, and vice versa.

Any way you slice it, confidence is high in a major winter storm for the UP Sunday evening into Monday, with the worst conditions expected Sunday night into Monday morning in terms of heavy snowfall and winds. EFI/SoT for snow is exceeding 0.95/2 now, with wind gusts 0.9/1. The worst conditions are expected to be from the Keweenaw into Marquette, Alger and Luce Counties where lake and orographic enhancement will play a role, and winds in the Keweenaw and along the lakeshore are expected to gust 40-60 mph given the 45-55 kt 925 mb jet advertised by some of the deterministic models. Blizzard conditions resulting in near-zero visibility are a strong possibility, and Blizzard Warnings may be needed here soon. Probabilities of exceeding a foot of snow are up to 60-80% here, and even 30-50% of exceeding 18" for the higher elevations in the north- central and eastern UP. Travel will become very difficult to impossible. Due to the strong dynamics, heavy snow is still expected in the interior and Lake Michigan counties as well, though amounts will be a little lower. Given the strong winds gusting to 30-40 mph, it's even possible we see localized blizzard conditions here, even though it's not climatologically favorable.

As the storm pulls away, snow tapers off from west to east Monday afternoon into Monday night. There are indications that a quick- hitting clipper moves back in on Tuesday, which would result in a bit more light snow, but perhaps more importantly, heralds a reinforcing shot of Arctic air for the New Year holiday. LREF mean shows 850 mb temps in the low -20s (C), which is around the 10 percentile. This would result in wind chills well below zero for the New Year's Holiday, along with northwest flow lake effect snow.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 738 AM EST Sat Dec 27 2025

Conditions will waver a bit between MVFR and IFR this morning at all TAF sites with ample low level moisture still trapped under a low level inversion. And, they will only get worse later today when a disturbance in the midlevel flow triggers light precipitation, mainly in the form of rain initially, then possibly some freezing rain/sleet by late evening. So, anticipate IFR/LIFR to become prevailing flight categories late this afternoon through tonight. In addition, southerly wind gusts up to 20 kts could accompany the afternoon precipitation.

MARINE

Issued at 411 AM EST Sat Dec 27 2025

South to southeast flow increases today up to 30 kt east of the Keweenaw, with the probability of gales 20-40 kt. A gale warning is not expected.

High-impact marine weather is set to occur Sunday night into Monday night as an unusually strong low pressure quickly strengthens over the western Great Lakes and moves into Quebec. Gales are expected with a moderate to high (50-80%) probability of storms out of the north to northwest over the central/eastern lake, up to 60 knots possible. Risk of significant waves exceeding 20 feet from the experimental National Blend of Models is 50-80 percent east of Marquette toward Pictured Rocks, possibly up to 28 feet, with 12-20 feet elsewhere. Heavy freezing spray and limited visibility in heavy snow is also expected.

Gales end from west to east Monday night, but a reinforcing shot of Arctic air across the lake is expected to result in northwesterly gales and heavy freezing spray at times Tuesday night to the end of next week, especially over the central and eastern lake.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Winter Storm Watch from Sunday evening through Monday evening for MIZ001-003>007-010>014-084-085.

Winter Storm Watch from Sunday afternoon through Monday afternoon for MIZ002-009.

Lake Superior... Gale Watch from Sunday evening through Monday evening for LSZ162-240-241.

Storm Watch from Sunday evening through Monday evening for LSZ242>244-263-264.

Storm Watch from Sunday evening through late Monday night for LSZ245>251-265>267.

Lake Michigan... Storm Watch from late Sunday night through late Monday night for LMZ221-250.

Gale Watch from late Sunday night through late Monday night for LMZ248.