textproduct: Marquette

KEY MESSAGES

- A disturbance moving south of the region tonight and Tuesday to bring chances of thunderstorms to the southern UP, around an inch of wet snow to the northern UP, and a wintry mix (including up to a tenth of an inch of ice) for the central UP.

- Another system arrives late Wednesday, bringing the potential for accumulations of snow and/or ice through Friday morning, though exact values are uncertain.

- Chances of a Colorado Low passing through the area late Friday through the weekend are increasing, potentially bringing a third round of a mix of precipitation types.

- Daily high temperatures near/above freezing and chances of rainfall will cause snowfall and runoff to gradually raise river levels this week.

DISCUSSION

Issued at 344 PM EDT Mon Mar 30 2026

Afternoon GOES-East Day Cloud Phase imagery shows scattered fair weather clouds over the UP, verified by most METARs in the region reporting CLR conditions under 12kft. These higher clouds are a sign of the disturbed weather upstream, but for today, they will act to keep high temperatures from climbing as much as they did yesterday. NBM high temperatures climb to the 40s for most, save for the immediate Lake Superior shores hanging out in the 30s and the MI/WI state line breaking into the low to mid 50s. This will continue to erode the snowpack slowly, which NOHRSC still analyzes at around a foot of SWE for much of the UP, except for up to 2 feet in the Keweenaw Peninsula and the far west and far south. The latter couple locations are showing some vulnerability in the snowpack, with the southern tip of Menominee County, some areas in the Porcupine Mountains, and urban areas around Ironwood, Crystal Falls, and Iron Mountain showing very little snowpack. Snowmelt (and rainfall runoff from snowpacks) is going to garner quite a bit of attention over the next month or so with some reports of small streams and rivers already beginning to rise.

Tonight, the 500mb trough that is over the Canadian Rockies this afternoon will continue to ride the US/Canada border, reaching the Northwest Angle by Tuesday afternoon. Ahead of this upper trough, a surface trough between 1000-1005 mb will advance south of the UP throughout tonight and Tuesday. As would be expected from prominent 850mb warm advection in late March, soundings show a prominent warm nose that lingers through much of the overnight period into Tuesday until the 850mb trough pivots through and cooler northwesterlies prevail. This warm nose will cause a wintry mix of precipitation to occur, and given that the 925 mb layer will also be above freezing for much of the first half of the event, there will be supportive conditions for some freezing rain to occur. There is some disagreement in the models as to exactly how much freezing rain will occur, with the HREF not showing much accumulation at all, though the GEFS/GEPS show nearly a 75% chance that the US-41 corridor west of Marquette to see a tenth of an inch of precipitation. Some of that difference may be in the amount of precipitation altogether, with a consensus blend of models having a much higher coverage of precipitation in general relative to the hi-res models, which suggest a dry slot with individual cells that drop higher amounts of precipitation. This package represents a solution somewhere in between those two forecasting philosophies. Elsewhere, the LREF suggests a 30% or greater chance of an inch or greater of wet snow accumulation for the Keweenaw Peninsula and 15+% chances for the Lake Superior shores by 00Z Wednesday. Further south, the CAMs have struggled to coalesce around a solution for Menominee County and the Lake Michigan shores, which continue to have modeled ingredients for severe thunderstorms (including up to 1000 J/kg of elevated CAPE coincident with 400+ m2/s2 of 0-3km SRH), yet nebulous forcing may leave these ingredients unassembled. Still, on the chance that elevated thunderstorms are able to initiate overnight, the SPC gives around 5% chances of 1+" hail and/or damaging wind gusts within 25 miles of the Lake Michigan shores. As far as winter headlines are concerned, will elect to punt to the mid shift given the discrepancy in precip coverage/impacts between the CAMs and global ensembles, though soundings do show a shallow saturated layer forming, which could support freezing drizzle that is not covered by either suite of models and could necessitate a reactionary SPS.

As the low and associated forcing departs to the east, precip winds down Tuesday into Wednesday. Some 15-30 percent PoPs have been left in for upslope/marginal lake effect snow showers as 850mb temperatures fall to around -10 C, though accumulations should be minimal. The coolest day of this forecast period will be Wednesday with the cool northwesterlies to northerly to northeasterly flow keeps high temperatures sub-freezing for the Keweenaw and counties east along the Lake Superior shores.

Relief from precipitation is brief. By Wednesday night, a negatively tilted trough proceeds from the Rockies into the Central Plains. This will support a ~1000mb surface low tracking from the KC/Omaha around 12Z Thursday to the Bay of Green Bay around 06Z Friday, with +/- 200mi in each cardinal direction for ensemble spread. This will drive an active period of weather from Wednesday night with ascent ahead of the low to Friday morning's system-trailing precipitation. While some spread in the ensembles is understandable in the details, there are a few different aspects of threatening weather in play. Once again, thunderstorms are possible over the Lake Michigan- bordering counties, with Euro ensemble MUCAPE probabilities of exceeding 100 J/kg of up to 40% Thursday evening. Soundings show the potential for another warm nose to set up with the warm advection ahead of the low, which translates to the GEFS/GEPS to show widespread 30-40% chances of ice accumulation exceeding 0.1" by Friday morning (and up to 30% chances of 0.25" for the counties along Lake Michigan). However, if a more southerly track of the low occurs (or the warm advection is on the lower end of forecast), a more snowy solution is on the table, with the LREF showing 30-60% chances of 6+" of snowfall by Friday morning. However, there is up to a 20 percent chance of less than an inch of snow, so there are a wide range of scenarios for this system, worth monitoring especially as the parent trough enters the US radiosonde network tomorrow. Frankly, it is amazing to have the good enough model agreement that we have now given the parent trough is currently roughly halfway between Hawaii and San Jose, CA.

Speaking of upstream systems, a 500mb closed low that started today in the Bering Sea is expected to continue pivoting from the Gulf of Alaska to the Pacific Northwest through the first half of the week. As it passes through the Rockies late in the week, a CO Low is expected to form in some flavor, though ensemble spread is high at this point in the track and intensity of such a feature. The ceiling of how impactful this system could be is high, with the 90th percentile of the LREF showing potential for up to 8 inches of snowfall Saturday, though the floor is low, 10th percentile snow totals are literally 0. Impactful ice is a similar story, though chances of over a tenth of an inch of ice are only around 25%. Thunderstorms also cannot be ruled out entirely, as Euro ensemble probabilities of 100+ J/kg of MUCAPE is around 30% for the far south Saturday afternoon.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 736 PM EDT Mon Mar 30 2026

VFR conditions are expected through the evening hours before deteriorating overnight as a disturbance passes through the region. For CMX cigs will fall to MVFR late tonight with IFR developing during the morning hours as -sn spreads across the Keweenaw. Further south precip will not be as widespread though IFR cigs will develop by morning at SAW and IWD. Limited the mention of precip and vsby reduction to prob30s as confidence is not very high. Should precipitation occur expect a rasn mix at IWD and -fzra or fzdz at SAW.

MARINE

Issued at 344 PM EDT Mon Mar 30 2026

An active period of weather is ongoing as northeasterlies are in excess of 25 kt over far western Lake Superior, with localized effects of funneling winds causing some gale force gusts to 35 kt around the Apostle Islands and around the Twin Harbors nearshores this evening. Northeasterly gusts around 25 kt spread across the lake tonight before falling below 20 kt late Tuesday. Widespread waves of 5-7 ft are expected by Tuesday morning before falling below 4 ft Tuesday night. A quiet period is expected on the lake until Wednesday night, where easterly to northeasterly wind gusts increase to around 25 kt ahead of an approaching low pressure. Thursday, these winds increase to gales, lasting until Thursday night, where winds back northerly around 25 kt for Friday. Active winds continue through the weekend, where another low pressure is expected to pass through the region at some point, driving around 25%+ percent chances of gales as it passes. Periods of light to moderate freezing spray are also expected periodically this week as cool northerly flow interacts with building wave heights.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... None. Lake Superior... None. Lake Michigan... None.