textproduct: Marquette

KEY MESSAGES

- A Beach Hazard Statement is in effect through this evening for the shoreline of Alger County due to strong winds and high waves creating dangerous rip currents and swimming conditions.

- Fog is possible (~20% chance) across much of the central and eastern UP tonight.

- The next chances for widespread showers and thunderstorms arrives in the west on Tuesday, spreading east overnight and Wednesday before ending for most late Wednesday.

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

DISCUSSION

Issued at 226 PM EDT Mon Aug 24 2026

Early afternoon GOES-East imagery shows mostly clear skies over the UP except for a few fair weather cu along the western UP highlands and sine low clouds along the shores of eastern Lake Superior where moisture and forcing is still marginally present associated with a RAP-analyzed 1007mb low over the Ontario/Quebec line. A 1018 mb surface high extends from western Lake Superior to Illinois which is providing the clear skies elsewhere and allowing temperatures to climb back into the mid 60s after an autumn-feeling morning. With efficient radiational warming expected today, expect highs to reach into the 70s except immediately along the Lake Superior shoreline along the east half, where continued brisk northwesterlies are leading to Lake Superior-cooled air to be advected onshore. These winds are also driving wave heights of 3-6 feet from 1-5 miles from shore along Alger and Luce County shorelines today, which will drive a high risk of dangerous rip currents. Therefore, the Beach Hazards Statement will continue through this evening, though the swim risk drops significantly tonight as the high pressure fully establishes itself over the UP and wind speeds similarly decrease. Another mostly clear night tonight will allow temperatures to fall to their dew points for many interior locations, with the HREF giving pockets of 20-40% chances of fog formation especially in the east. Temperatures should be too high for frost, though a few interior locations may fall into the upper 30s.

By 12Z Tuesday, the upper air pattern consists of a massive ridge over the south-central to southwestern CONUS flanked by a pair of deep troughs, one over Quebec and off the Pacific Northwest coast respectively. Additionally, a trough will be over southern Manitoba and will pivot around the ridge into the Great Lakes region for the midweek period, bringing a period of active weather. With the CAMs now beginning to cover this time period, the consensus on the arrival time of showers in the west with the prefrontal isentropic ascent has accelerated, with the HREF mean arrival time of precip now showing shortly after noon Tuesday at IWD and around 22Z for the US41/141 corridor. Moist southerly flow ahead of the cold front will allow for dew points to climb into the low 60s and for PWATs to grow to 1.25-1.5 inches in the west, which is above the 85th percentile of climatology for this time of year. This will promote an unstable airmass with HREF mean SBCAPE values in the west ballooning to around 750 J/kg by 23Z Tuesday. However, shear is relatively unimpressive as soundings show flow is sub-30 kt below 525mb, though the low level hodographs do show good curvature. Therefore, will expect mostly sub-severe thunderstorms as buoyancy is sufficient with weak forcing and not enough shear to keep storms organized enough.

Overnight into early Wednesday, showers and thunderstorms overspread the UP. If storms can maintain elevated from the boundary layer, the Euro ensemble projects they will have 500-750 J/kg of MUCAPE to work with, though shear remains subpar with weak flow aloft, so overnight thunderstorms are not expected to be severe. Diurnal destabilization will reinvigorate storms during the afternoon Wednesday as Euro mean MUCAPE will climb to near 1000 J/kg for much of the east half. Even if storms remain sub-severe for most, a good soaking rain is expected as LREF probabilities of over a half inch of rain are 40- 60% for most.

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. Over the last 24 hours, confidence has increased in high pressure settling over the Great Lakes Friday into the weekend, leading to dry weather. 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 /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 152 PM EDT Mon Aug 24 2026

VFR conditions prevail at all TAF sites under clear skies. Breezy northerlies at CMX and SAW persist through the afternoon, but will fall off below 15 kts by the evening. Under mostly clear skies and decoupling, areas of fog are possible across the UP, however, confidence is low regarding visibility impacts at any one terminal, so have opted to leave mention out of this TAF cycle.

MARINE

Issued at 226 PM EDT Mon Aug 24 2026

Wind gusts linger around 20 kt this afternoon before falling below 20 kt through Tuesday afternoon with high pressure settling over the region. Southerly to southeasterly wind gusts of around 25 kt pick up Tuesday night ahead of an approaching cold front, with winds turning northwesterly behind the front by Thursday morning. Winds quickly relax below 20 kt Thursday night into Friday as uncertainty in the forecast grows into the weekend. Along the midweek cold front will be 20-40% chances of thunderstorms. Ongoing waves of 3-6 ft fall below 3 ft this evening before increasing again to 4-7 ft in the southeast part of the lake Thursday morning through Thursday night.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Beach Hazards Statement until 8 PM EDT this evening for MIZ006.

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