textproduct: Marquette

KEY MESSAGES

- Expect the warmest temperatures of the week today, with highs in the 30s to lower 40s (warmest along the Lake Superior shoreline).

- Windy conditions are expected late Tuesday into Tuesday night, especially in the Keweenaw where there is a 70% chance for wind gusts exceeding 45 mph. See the latest Wind Advisory for additional details.

- Multiple gale events could be seen across Lake Superior this week into this weekend, with the current one going until Wednesday morning. A Storm Force Wind and Heavy Freezing Spray event could be seen Thursday.

- The strong winds across the Great Lakes this week could create times of minor lakeshore flooding and beach erosion. See any pertinent Lakeshore Flood Advisories for more info.

- A strong Clipper low could bring high winds, a flash freeze, and/or several inches of snowfall across the area Thursday into Thursday night. Continue to monitor the forecast as impacts could change depending on subtle shifts in the strength and track of the low.

DISCUSSION

Issued at 336 AM EST Tue Dec 16 2025

As low-level GOES Water Vapor imagery shows a shortwave low moving through northern Ontario this morning, expect increasing warm air advection across our area to strengthen the inversion above the boundary layer overhead throughout the rest of the morning hours. Thus, while 850mb temperatures are expected to approach 10C by this afternoon, we can expect temperatures at the sfc to initially struggle to warm above freezing until later today as we slowly shift from a warm air advection regime to a cold air one. However, once the inversion weakens this afternoon across the area, expect temperatures to rise into the mid to upper 30s across the U.P., with increasing south/southwesterly winds throughout the day today bringing high temperatures into the lower 40s in the downslopes by Lake Superior. While gusts of 30 to 40+ mph could be seen during the afternoon hours as mixing improves into the boundary layer with time, once the cold front of the low begins to move into the region late today through tonight, expect impressive mixing to bring wind gusts of 45+ mph to the Keweenaw and along the Lake Superior shoreline from time to time; with about a 70% confidence in winds of 45+ mph occurring over the Keweenaw this evening into tonight, decided to hoist up a Wind Advisory for the Copper Country as some isolated power outages could be realized given the strong winds. In addition, the strong winds will kick up high waves on Lake Superior, which could bring minor lakeshore flooding and beach erosion to the shoreline, particularly along the north shore of Keweenaw County and Alger and Luce counties north of Munising; minor lakeshore flooding is also expected along the Lake Michigan beaches of southern Schoolcraft County this afternoon into this evening as no/very little ice has formed along the lakeshore (unlike the Bays de Noc, although the high waves hitting the ice may break up some of the developing ice sheet). As the cold front works to bring latent heat release from Lake Superior tonight into Wednesday morning, we could see some upslope/weak lake effect drizzle/freezing drizzle/snow showers develop over the northwest wind snow belts tonight, eventually becoming pure lake effect pre-dawn Wednesday morning from west to east. While subtle, there is a small flash freezing threat for late tonight as temperatures rapidly cool. However, with precipitation amounts ahead of the freezing being near null, thinking we will see only some patches of black ice develop by areas of snowpack. Overall, expect impacts to be nothing more than a nuisance; only a tenth or two of snow and at most a glaze of ice is expected accumulation-wise.

Attention then turns towards the 'main event' of the forecast package: the strong Clipper low moving through the Northern Plains into the Upper Great Lakes Wednesday night through Thursday. As ridging kills the last of the lake effect snow over the eastern U.P. Wednesday morning, expect warm air advection to return to our area once again Wednesday afternoon as the low starts its journey towards our neck-of-the-woods. This will allow temperatures to get to as high as the lower 30s across much of the area late Wednesday afternoon before and just after the sun sets. While most guidance has the better warm frontogenesis north of the U.P. Wednesday night into Thursday, if the dry layer between 700 and 850mb is able to be overcome, we could see a wintry mix of rain/drizzle, freezing rain/freezing drizzle, sleet, and/or snow over us; if, however, it doesn't but the NAM suite is correct, we could see more freezing drizzle over us, bringing a few hundreths of an inch of ice across portions of the area. The best chances for precipitation happening are across the northern tier near Lake Superior. In addition, strengthening southerly flow will allow winds to get up to 30 to 40 mph, highest in the downslopes by Lake Superior and along the Lake Michigan shoreline Wednesday night into Thursday morning; these strong southerly winds are looking to bring lakeshore flooding concerns back over southern Schoolcraft once again early Thursday morning, and additional ice break-up could be realized over the Bays de Noc. Over the past several hours, the 00z deterministic guidance among the different model suites have nudged the track of the sfc low further south than previously anticipated. What does this mean? First, this reduces the chances and threat for flash freezing over the U.P., especially over the western half. The latest GFS and NAM model soundings show either nothing or a light wintry mix becoming light snowfall Thursday morning over the west half of the U.P. ahead of the comma-head of the low bringing the wrap-around Arctic air over our area (rain still expected over the eastern U.P. still though). In addition, the temperatures don't look to fall as fast throughout the day Thursday, with the rapid drop looking to occur more in the Thursday night timeframe instead as the low doesn't appear to be as vertically-stacked as it did a couple of days ago; this can be explained due to guidance picking up on a shortwave disturbance lifting from the Mid-Mississippi Valley and phasing with the Clipper on Thursday. Overall, we may see more snowfall than previously anticipated over the western half of the U.P. Thursday and a diminished flash freezing threat. Nevertheless, flash freezing is still a real possibility, especially over at least the eastern half of the U.P. Thursday into Thursday night as rain showers over there progressively give way to snow in the evening. With the Arctic air wrapped moving through late Thursday through Thursday night, expect more isolated power outages and potentially even a few downed powerlines (aided by the moisture added on Thursday) as north/north- northwesterly winds potentially get up to 45+ mph along the Keweenaw and Lake Superior shoreline. With the low not looking to be as organized, the forecasted winds over Lake Superior are weaker in comparison to yesterday. That being said, high winds and waves are still expected over the lake, with at least minor lakeshore flooding possible over Keweenaw County and east of Big Bay/Marquette. The strong winds could also potentially create blowing snow concerns across the north/north-northwest wind snow belts Thursday night into Friday morning as most of the atmospheric profile cools into the DGZ, allowing for fluffy dendrites to be broken up and pushed around by the strong winds; this could create Winter Weather Advisory or even Winter Storm Warning conditions due to sharply reduced visibility within the areas of blowing snow (mainly along the Lake Superior shoreline). Snowfall amounts also range widely at this time; the 25th percentile for snowfall amounts Thursday and Thursday night show between 1 and 3 inches in the north/north-northwest wind snow belts, whereas the 75th shows potentially several inches of snowfall. Regardless, the most is expected over the Keweenaw Peninsula. Overall, the forecast for this event still remains rather fluid; just a slight change in the track or dynamics of the low could significantly alter the impacts we receive from this system. Be sure to keep your eyes peeled to the forecast as the system approaches and more hi-resolution modeling systems become available.

The fluffy lake enhanced snowfall over the north/north-northwest wind snow belts looks to end Friday as sharp high pressure ridging moves back across the region. However, additional shortwave action late this week into early next week looks to bring periods of snowfall and potentially even stronger winds back across Upper Michigan as we approach Christmas.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1228 AM EST Tue Dec 16 2025

Stubborn low cloud cover continues to bring IFR/low end MVFR cigs to KCMX and KSAW this evening. Expect this to eventually clear out 06- 12z and yield prevailing VFR conditions as a strong LLJ with winds of 50+ kt at FL020 introduces low level wind shear to the terminals through the much of the remainder of the TAF period. LLWS will begin to wind down after 00z Wed as surface winds shift westerly and the LLJ departs the region, but winds will remain gusty through the end of the period. An isolated freezing rain shower or two is possible as a warm front crosses the area Tuesday morning, but probabilities are too low to include in the TAF.

MARINE

Issued at 336 AM EST Tue Dec 16 2025

South to southwest winds increase to gales up to 40 knots by early this afternoon as a low moves through northern Ontario today. As the cold front pushes through the lake late today through tonight, expect the winds to slowly veer to the west and eventually northwest tonight as gales continue up to 40 knots, with a few gale force gusts up to 45 knots possible over the eastern open lake (Stannard Rock area). Some areas of freezing spray could return across the lake behind the cold front tonight before the winds die down with incoming high pressure ridging Wednesday morning.

Don't expect the calm winds to last as a strong Clipper low lifting off of the Rockies and through the Northern Plains Wednesday night starts increasing winds from the south Wednesday afternoon and evening. Southerly gales of 35 to 45 knots could be seen Wednesday night across Lake Superior, with the strongest winds expected over the eastern open waters (around 70% chance for gales). As the low moves through either Lake Superior or Upper Michigan on Thursday, expect winds to slacken a bit right around the center of the low, before the Arctic air wrapped around it brings northerly high-end gales to 45 knots to Storm Force gusts to 50 knots back across Lake Superior late Thursday through Thursday evening (50% chance for gales up to 45 knots or greater according to the NBM). In addition, expect heavy freezing spray to return with the Arctic airmass and strong northerly winds through Thursday night. Significant wave heights also look to get to as high as the upper teens in feet, with the highest waves east of the Keweenaw. Due to the these dangerous conditions, avoid traveling on Lake Superior as this occurs.

As sharp ridging returns to the area Friday, expect the winds over Lake Superior to drop back down to 20 knots or less again by Friday afternoon. However, a shortwave moving through the Canadian Prairies Friday night and potentially touching far northern Lake Superior on Saturday could bring southeast to southerly gales up to 40 knots back over the lake Friday night (40% chance for gales, highest over the eastern half). As the low heads towards the St. Lawrence Seaway Saturday, expect the winds to veer to the west behind the low on Saturday as winds of 30 knots to gales up to 40 knots become possible late in the day into Saturday evening (40% chance for gales, highest over east). Freezing spray is possible Friday night and again late Saturday with each of the gale events.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Wind Advisory from 4 PM this afternoon to 4 AM EST Wednesday for MIZ001-003.

Lakeshore Flood Advisory from 11 PM this evening to 4 AM EST Wednesday for MIZ001.

Lakeshore Flood Advisory from 3 AM to 10 AM EST Wednesday for MIZ006-007.

Lakeshore Flood Advisory from 2 PM this afternoon to 11 PM EST this evening for MIZ014.

Lake Superior... Gale Warning from 7 AM EST /6 AM CST/ this morning to 1 AM EST /midnight CST/ Wednesday for LSZ162.

Gale Warning from 4 PM EST /3 PM CST/ this afternoon to 4 AM EST /3 AM CST/ Wednesday for LSZ241-242.

Gale Warning from 1 PM this afternoon to 7 AM EST Wednesday for LSZ243-244.

Gale Warning from 4 PM this afternoon to 7 AM EST Wednesday for LSZ245>248-265.

Gale Warning from 1 AM to 7 AM EST Wednesday for LSZ249.

Gale Warning from 10 AM this morning to 7 AM EST Wednesday for LSZ250-251-266-267.

Gale Warning from 7 AM this morning to 4 AM EST Wednesday for LSZ263.

Gale Warning from 7 AM this morning to 7 AM EST Wednesday for LSZ264.

Lake Michigan... None.