textproduct: Marquette

KEY MESSAGES

- Widespread showers and thunderstorms arrives over the west half today, spreading east overnight and Wednesday before ending for most late Wednesday.

- Expect dangerous waves and rip currents over the Lake Michigan beaches of Schoolcraft County on Wednesday.

- Generally seasonable temperatures are expected through the rest of this week.

DISCUSSION

Issued at 239 PM EDT Tue Aug 25 2026

Early afternoon radar mosaic and satellite imagery shows mostly clear skies in the eastern two thirds of the UP with an area of showers in Ontonagon County as well as the MN Arrowhead, northwest Wisconsin, and northwest Ontario. Thus far, lightning activity has been limited to the Thunder Bay to Isle Royale region and west. These showers and thunderstorms have initiated in the pre-frontal, isentropic ascent regime ahead of a RAP-analyzed 1008mb low over the Ontario/Manitoba line and associated cold front draped south of it. Aloft, vertically stacked troughing is present mainly in southern Manitoba, with the trough pivoting around a significant southwestern CONUS ridge. CAMs have trended lower with the availability of instability with the HREF now showing peak MUCAPE values around 500 J/kg until Wednesday afternoon. While low level hodographs are well-curved, deep shear (especially speed shear) is particularly lacking). Given that the strongest forcing will be passing over the UP with only modest shear or instability (despite good moisture presence with PWATs climbing to 1.25-1.5 inches, well above the climatological norm), severe weather is unlikely through tonight (and if it does, it would occur in the far west where the SPC gives 5% chances of severe wind and hail).

The cold front properly pushes through the UP throughout Wednesday. Diurnal destabilization occurs in the east ahead of the front with around 1000 J/kg of SBCAPE for much of the east half by 18Z. This will lead to a redevelopment of showers and thunderstorms which could be particularly strong-to-severe in the far east. Shear is similar to today with good low level curvature but otherwise very little speed shear, so the severe threat remains marginal. The pre- frontal long-duration and gusty south to southwest winds will drive waves in excess of 4 ft within 5 miles of the Schoolcraft County shoreline, which will increase the risk of dangerous rip currents. A Beach Hazards Statement may become necessary in the next couple of forecast packages. By the time synoptic precipitation ends in the east, chances of 1 inch or more of accumulated rainfall are around 40-60% for the east and 15-35% chance for the west, though there is also a 20-40% chance that some western locations may see less than a tenth of an inch of rain, which would certainly not help the increasing drought conditions in that part of the state.

Lingering northerly flow behind the shortwave will allow temperatures aloft to fall to similar temperatures that caused light lake effect rain showers yesterday, so some PoPs will linger into Thursday. While the models differ in the details, the global deterministic suite has come into increasing agreement that the ridge aloft will shift to the southeast CONUS and bring with it a more potent trough through the Great Lakes in the early portions of next week, which could bring unsettled weather to the UP as soon as late Saturday and Sunday.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 753 PM EDT Tue Aug 25 2026

Showers and thunderstorms will impact the terminals over the next several hours bringing MVFR/IFR conditions at times; outside of the showers and storms conditions will be VFR. Thereafter showers and thunderstorms will continue to be possible but timing/placement remains uncertain due to the scattered nature of the precipitation. Handled the remainder of the period with PROB30s.

The low levels are expected to saturate late tonight into the early morning hours bringing MVFR cigs to IWD, IFR at SAW, and LIFR at CMX. Should showers impact SAW cigs could fall to LIFR at times. During the morning hours surface heating and mixing will help lift the cloud base but cigs will likely only improve to MVFR at CMX and SAW.

MARINE

Issued at 239 PM EDT Tue Aug 25 2026

Ahead of a low pressure that will pass north of Lake Superior over the next couple days, southeast wind gusts increase to around 20 kt tonight. The front veers the winds to the northwest by Wednesday, keeping gusty conditions for the east half of the lake into Thursday. Due to the long-duration southwesterly long-lake winds, waves will peak in northern Lake Michigan at 3-5 ft. The shifting wind directions will keep waves under 4 ft until late Wednesday night, when the northwest flow behind the front will drive waves of 3-5 ft for the south half of eastern Lake Superior through Thursday evening. Winds below 20 kt and waves below 3 ft will be in the forecast from then until Saturday evening when the next disturbance arrives, though uncertainty in the timing and details remains high as models are spread out in handling that disturbance.

MQT WATCHES/WARNINGS/ADVISORIES

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