textproduct: Marquette

KEY MESSAGES

- The threat for flooding continues due to snowmelt and potential rainfall. A Flood Watch is in effect for everywhere except the far western UP through Saturday morning.

- Southerly gales up to 40 knots are expected over east-central Lake Superior this afternoon into this evening.

- Showers and thunderstorms are expected with a cold front late this afternoon into this evening. Widespread totals of 0.25 to 0.50 inches are expected.

- Some stronger storms capable of producing hail and strong wind gusts are possible late this afternoon into early this evening over mainly the far western U.P and close to the MI/WI state line. - Becoming much cooler this weekend, which will slow snowmelt.

- West to northwest gales up to 35 knots are possible late tonight through Saturday. A Gale Watch is in effect for most of the lake save for the far west.

DISCUSSION

Issued at 228 PM EDT Fri Apr 17 2026

The main forecast concerns over the next 24 hours is continuing river rises along with the potential for additional rainfall from thunderstorms. A few strong to severe thunderstorms are possible in the western, greatest risk close to the MI/WI state line, this afternoon and evening.

Early this afternoon water vapor imagery and model high analysis showed an upper level low over southern Manitoba approaching the Upper Great Lakes. Scattered showers and thunderstorms were forming along a front stretching north to south though Minnesota. A few thunderstorms had also developed this morning over east-central MN and were now over northwest WI, tracking to the northeast. Widespread cloud cover was limiting the surface heating ahead of these storms. Cloud cover will prove challenging for the forecast regarding the development of strong to severe thunderstorms that could impact the western U.P. HREF joint probabilities for surface based CAPE > 500mb and shear > 30kt are high in the far western U.P. but nil everywhere else. This is likely due to somewhat cooler flow off Lake Michigan keeping the rest of the U.P. under a capping inversion. The better instability and helicity will reside south of the WI/MI state line where the threat for severe thunderstorms greatly increases and dewpoints rise above 60F. SPC has a slight risk over the far western U.P. and close to the MI/WI stateline with severe thunderstorm watches over NW WI. HREF updraft helicity tracks and probabilities have shifted south into NW WI as well with the latest run, where probabilities exceed 80%. Probs drop off rapidly to the north and east.

The overall expectation is that thunderstorms will develop with the potential for a strong to severe thunderstorm, with marginally severe hail and strong winds being the main threat in the far west. As storms track eastward they will become elevated and run into less instability, limiting the severe potential. Storm motion will be along the boundary so expecting any storms to quickly grow upscale into a linear system.

Flooding will continue to be a concern with the expected showers and thunderstorms along the cold front tonight. While most locations will see between a quarter and half in of rainfall, any of the heavier storms could produce up to one inch of rainfall in a short time. WPC is highlighting a marginal risk for excessive rainfall in U.P. This will contribute to continued river rises through Saturday. Water levels also remain high over the south central, even though most of the snow is gone any heavy rain could result in flooding or expansion of ongoing flooding of low laying areas, small stream and creeks.

It will turn sharply colder behind the front tonight leading into a cooler weekend. For Saturday light trailing showers behind the cold front will change to the wintery precipitation during the morning. Scattered snow showers are expected into Saturday night with instability driven from strong caa but any accumulations should be limited to under an inch, with most places only seeing a dusting. It will feel chilly after the recent warm days though with highs in the 30s north and 40s south through Sunday. The good news is that this should help slow the snowmelt a bit before we warm up next week.

Expect warmer and drier weather Monday through at least Wednesday with high pressure dominating, bringing highs into the 50s central and east and up into the low 60s west. It will be cooler near the shorelines as the Great Lakes remain fairly frigid.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 723 PM EDT Fri Apr 17 2026

A cold front is crossing the western UP at around 23Z, which is bringing and will continue to bring TSRA, gusty winds, and lowered ceilings/vis (up to 50% chances of temporarily as low as IFR) as it crosses from west to east tonight. Some slow improvement to VFR then follows behind the front, though there is some uncertainty in timing when the ceilings eventually lift and/or scatter out. For Saturday, a persistent approximately 20 percent chance of light SHSN exists, but is not expected to impact the flight category and confidence in the timing is too low to include in the TAFs at this time, though future TAFs may include it via a PROB30 group.

MARINE

Issued at 228 PM EDT Fri Apr 17 2026

Southerly winds will continue late this afternoon ahead of an approaching cold front, with gales at times over the east-central portion of the lake. Winds will shift west-northwest behind the cold front tonight with low end gales expected through the day Saturday into Saturday night. A few stronger thunderstorms could accompany the front over the far western part of the lake through this evening, with hail and gusty winds being the main threats.

Northwest winds continue into Sunday, as high as 30kt over the eastern half of the lake, with lighter winds in the west. Late Sunday night into Monday morning winds become light and shift southerly. Southerly winds will increase Monday night with potential gales (30-50% chance) over the eastern half of the lake as low pressure moves north of the area. Winds then shift northerly behind a cold front on Tuesday and fall below 20kt. Winds turn southerly on Thursday as the next low pressure moves through Canada, with winds to 30kt over the east.

HYDROLOGY

Issued at 228 PM EDT Fri Apr 17 2026

NOHRSC analysis continued to show snowpack remained over the northern half of the U.P. were several inches to over a foot of SWE remained, greatest in the higher terrain. Some of the lower elevations in the north had lost most of the snowpack, close to Lake Superior and from L'Anse to Baraga. Snowmelt will continue through this evening as the warm, moist airmass from the Gulf advects over the U.P. An area of showers and thunderstorms will move through late this afternoon through this evening with generally 0.25-0.50 inches of rainfall expected across most of the area, although there is up to a 40% chance for greater than 1 inch possible in some of the thunderstorms. Colder weather is expected for late tonight through Sunday, which should slow the melt of any remaining snowpack.

Waters remain high in the southern U.P. where recent heavy rains and snowmelt contributed to flooding of low-lying areas and some rivers. Rivers will continue to rise in portions of the northern U.P. due to continued snowmelt and additional rainfall. A Flood Watch remains in effect over the central and eastern U.P. through tonight. Once drier and cooler air moves overhead for this weekend through next week, expect the flood risk to decrease. Therefore, expect the Flood Watch to expire by Saturday morning.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Flood Watch through Saturday morning for MIZ001-003>007- 010>014-084-085.

Lake Superior... Gale Warning from 4 AM EDT /3 AM CDT/ to 11 PM EDT /10 PM CDT/ Saturday for LSZ241>251-263>267.

Gale Warning until 11 PM EDT this evening for LSZ244-245-264- 265.

Gale Warning until midnight EDT tonight for LSZ266.

Lake Michigan... Dense Fog Advisory until 5 AM EDT Saturday for LMZ221-248-250.