textproduct: Marquette

KEY MESSAGES

- Moderate to heavy lake effect snowfall and areas of blowing snow continue over the northwest wind snow belts today through tonight. See the latest Winter Weather Advisories for additional information.

- Gales and heavy freezing spray are expected on Lake Superior into early Sunday.

- Below normal temperatures continue this weekend before a warm up above freezing next week.

DISCUSSION

Issued at 326 AM EST Sat Dec 13 2025

As a 1004mb low over northern Ontario this morning continues to weaken with time as it travels into northern Quebec this evening, lake effect snow showers over the northwest wind snow belts continue across the U.P., with snowfall rates getting up to 1/2 inch per hour over the west and 1 inch per hour over the east in the strongest bands/highest elevation areas. With some of the coldest Arctic air overhead so far this Winter season, mixing of stronger winds aloft down to the sfc will allow for areas of blowing snow to develop, particulary along the lakeshore and higher elevation areas of the northwest wind snow belts; thinking things could be particularly hazardous/dangerous along M-26 atop the Spine of the Keweenaw and along the lakeshore in the west and M-28 west of Munising today into tonight due to the sand-like nature of the snow crystals greatly reducing visibilities in the areas of blowing snow and in the heavier snow bands; wouldn't be surprised to see lower than quarter mile visibilities at times over these spots. While several inches are expected over the eastern northwest wind snow belts today and tonight, with a couple of isolated spots potentially seeing up to a foot or more, was more on the fence on extending the Winter Weather Advisory over the western U.P. today through this evening as I'm not confident that we will achieve snowfall amounts that traditionally warrant one (only up to around a 30% chance of 6 inches or more). However, when considering that the snowflakes will be more sand-like given the frigid Arctic air (temperatures are looking to be too cold to have much dendritic growth, instead relying more on sector- plating processes) and that this type of snow is more likely to cause blowing/drifting problems, especially as it pertains to visibility reductions, decided that this additional hazard over the western U.P. warranted the extension of the current Winter Weather Advisory over Ontonagon, northern Houghton, and Keweenaw counties, as well as including Gogebic County too to 1 AM EST tonight. In addition to the Winter Weather Advisories, wind chills down to -31F are being seen across the interior west early this morning. These anomalously cold apparent temperatures have warranted the continuation of the Cold Weather Advisory over Iron and Gogebic counties until 9 AM CST this morning.

As ridging builds in on Sunday, expect the lake effect snow to dwindle and leave the area, with the last of it leaving the east in the evening hours. Beyond this weekend, expect a pattern shift as the past few weeks of below normal temperatures gives way to above normal temperatures. After another Clipper looks to move through late Sunday night through Monday across the Upper Great Lakes (bringing light snowfall back to the north and east), the rex block over the Pacific Coast breaks down. This will allow for above freezing temperatures to return across the U.P. for the first time in weeks; with winds picking up from the southwest throughout the day as a deepening Clipper moves through the Canadian Prairies through northern Ontario, we could see some of the south to southwest wind downslope areas get into the lower 40s on Tuesday. While the cold front of the Clipper could bring light LES back over northwest wind snow belts Tuesday night, not much, if any measurable snowfall, is expected to replace any snow we lose during the daylight hours. Given that most of the snowfall we've received this year has been lake enhanced/effect and not wet/synoptic, I'm curious as to how much of the snow pack we will lose. What may help us, though, is that we will have modified air in the lowest levels due to the loss of snowpack further south of us; I'm very confident that the warm Gulf air will do far more damage to the snowpack that's south of us (such as in IL/WI). Thus, the melting further south may help the lowest levels be cooler and reduce any melting we see up here on Tuesday.

The next period in the extended worth noting is the middle of next week. As of now, medium range guidance is highlighting an anomalously strong Clipper low deepening down to around 981mb as it approaches the Upper Great Lakes around Thursday. As of the time of this writing, solutions have generally trended cooler, even though things are looking to be less windy (temperature advection is not looking to be as strong ie. 12C temperature difference now in 6 hours instead of 15C as previously predicted). Will continue to keep an eye on this system, as some impactful winter weather and winds could be realized if this plays out right. Beyond this, the Clipper action and more normal-ish temperatures look to continue to the end of the week.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 623 AM EST Sat Dec 13 2025

Lake effect snow showers will continue to impact KIWD and KCMX in this TAF period. Both sites will see LIFR conditions due to the showers and blowing snow from strong winds. The combination of the two may result in airport mimimums at times for KCMX. KSAW can expect VFR this morning, but conditions fall to MVFR this afternoon. By evening, snow showers may move into the KSAW area, but there continues to be uncertainty.

MARINE

Issued at 354 AM EST Sat Dec 13 2025

Anomalously cold Arctic air behind a weakening low moving from northern Ontario into northern Quebec today will allow strong northwesterly winds aloft to mix down to the sfc, with some gale force gusts up to 35 knots expected from time to time today to keep moderate to heavy freezing spray going across the open waters. As the winds veer more northerly tonight, expect an increase in the winds slightly over the north central and eastern lake this evening before ridging moving in on Sunday calms things down and brings an end to the freezing spray by Sunday afternoon; winds are expected to calm down to 20 knots or less by late Sunday afternoon as well, although with a Clipper looking to move through late Sunday night into Monday across the lake, hi-res models are showing winds increasing from the southwest over the western half of the lake late in the day on Sunday through Sunday night to gales up to 35 knots (potentially even to 40+ knots if the latest HRRR is to be believed). As the Clipper moves through the lake Monday morning, expect the winds to slacken behind the low, although west to eventually northwesterly winds of 20 to 25 knots look to continue over the eastern half of the lake until Monday evening. Ahead of and immediately behind the low, some moderate freezing spray could be seen.

As a deepening Clipper low traverses through Canadian Prairies and northern Ontario Tuesday, expect the winds to pick up from the southwest with time, with gales up to 40 knots possible Tuesday evening (30% chance according to the NBM). After another ridge slackens the winds across the lake to 20 knots or less by Wednesday afternoon, an anomalously vigorous and deepening Clipper low moving over or at least close by looks to potentially bring high-end gales across the lake on Thursday (40% chance of 45+ knot gales according to the latest NBM). This Clipper could also bring moderate to heavy freezing spray back across the lake; continue to monitor the forecast to see the latest changes on the track of this strong system.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Winter Weather Advisory until 1 AM EST /midnight CST/ Sunday for MIZ001>003-009.

Winter Weather Advisory until 7 AM EST Sunday for MIZ006-007- 085.

Cold Weather Advisory until 9 AM CST this morning for MIZ009- 010.

Lake Superior... Heavy Freezing Spray Warning until 1 AM EST /midnight CST/ Sunday for LSZ162.

Heavy Freezing Spray Warning until 7 AM EST /6 AM CST/ Sunday for LSZ240>245-248>251-263>267.

Gale Warning until 7 AM EST Sunday for LSZ244>246-248>251- 264>267.

Lake Michigan... None.