textproduct: Marquette

KEY MESSAGES

- Strong to severe storms are possible this afternoon and evening. Those with outdoor plans should remain weather aware, have multiple ways to receive a warning, and have a plan should one be issued.

- Another round of strong to severe storms is possible tomorrow (Monday), however, uncertainty remains regarding spatial extent and specific timing.

- Generally quieter weather in store after Monday into the middle of this week.

UPDATE

Issued at 756 PM EDT Sun Jul 26 2026

Thus far, convection has been able to hold off over the UP, likely courtesy of dry lower levels and capping in place. However, we continue to monitor upstream convection around Thunder Bay and in the Arrowhead. CAMS that are catching this (particularly the latest HRRR) bring this activity into the area around 03-06Z; in particular, the northern batch of convection would impact the Keweenaw, northern and central Lake Superior, and eventually the eastern UP while the Arrowhead batch grazes the UP/WI border. Storms over northern MN so far have remained sub-severe, while stronger storms moving off of Thunder Bay and out over northern Lake Superior have shown a better potential for hail and gusty winds. By the time convection really looks to reach the UP, model soundings and the HREF still shows up to 1500j/kg over the area as well as 30-40kts of bulk shear. So, our thunderstorm threat remains worth monitoring, if pushed back a ways. In the meantime, with this latest forecast update, have largely removed PoPs from the UP before midnight.

DISCUSSION

Issued at 124 PM EDT Sun Jul 26 2026

Early afternoon GOES satellite imagery reveals the Upper Great Lakes on the northern fringes of a "Ring of Fire" upper level ridge. Subtle shortwaves rotating around the top of the ridge will be the focal point for rounds of strong to severe thunderstorms expected today through parts of Monday before building surface high pressure returns "quieter" weather to the region into the midweek.

Northwest flow aloft will carry a mid-level impulse into the region this afternoon/evening, driving strong to severe thunderstorms from MN into Superior/UP and initiating additional storms. Increased ascent ahead of a midlevel impulse will help erode a strong cap currently atop the UP. Be the time the cap erodes, a fairly volatile environment will be supportive of strong to severe thunderstorms. CAM ensembles suggest healthy mucape upwards of 1500-2500 j/kg with bulk shear values pushing 45-55 kts. Low level soundings across the interior central and west show fairly dry low levels and high LCLs with rather straight line hodographs between 1-6 km, pointing to more of a hail/wind threat. Still, 0-1 km SRH pushes 50-150 m2/s2 at times, so if an isolated supercell can tap into ample surface based instability, cant rule out an isolated tornado. Latest RAP analysis suggests between 1000-1500 DCAPE already in place across the west half, thus air parcels will have plenty of downward momentum to create potentially damaging winds, especially if isolated supercells can merge and grow upscale into more linear segments. The main issue is timing out convection. CAMs are still struggling on the spatial extent and specific timing of storms this afternoon/evening, but the bulk of CAM members suggest activity reaching the western UP/lake between 5-7 pm edt carrying southeast through midnight. This morning SPC has introduced a wind/hail driven Enhanced Risk (level 3 of 5) for severe weather across all of WI, including parts of our border counties. Elsewhere, a Slight Risk (level 2 of 5) remains for most of the UP. Needless to say, those with outdoor plans should remain weather aware tonight. Have a way to receive a warning and a plan should one be issued!

Another round of strong to severe storms is possible tomorrow as a deeper shortwave dives through the Great Lakes. SPC continues to place most of the UP in a Slight Risk (level 2 of 5), though there remains a fair amount of uncertainty with this round as well, and it may have some contingency on how storm behavior occurs tonight. CAM guidance is not as excited about severe weather parameters, nor does it have any handle on timing/spatial coverage of precipitation.

Behind the Clipper low on Monday, expect quieter weather across the region as geopotential heights rise over the central CONUS into Canada. With a semi-omega block appearance forming over the central CONUS, we could see a few weak Canadian shortwaves move across the area (mainly the first weekend of August). However, medium-range runs are showing mid-level heights increasing locally over the Upper Midwest and Great Lakes for the middle of the week, thinking we will more likely than not remain dry until potentially next weekend.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 756 PM EDT Sun Jul 26 2026

VFR prevails this evening at all terminals, with thunderstorm activity holding off over the UP so far. However, later tonight, storms over northern MN and Ontario may finally be able to reach the UP. Storms stand the best chance at reaching IWD after 03Z, though some activity may be nearing CMX closer to 03Z if it can survive the trek across Lake Superior. This is more uncertain, and so has been left out of the TAF. Otherwise, spotty showers and storms may finally develop around CMX and SAW by 11Z and linger through the morning. Any storms that develop tonight into early Monday could be on the stronger side, with hail and gusty winds. Some patchy fog will also be possible tonight, mainly at CMX, potentially dropping ceilings and visibility down to MVFR/IFR. This lifts after sunrise. After a brief break in shower/storm activity, additional convection will be possible at IWD and SAW into Monday afternoon.

MARINE

Issued at 124 PM EDT Sun Jul 26 2026

Winds <15-20 kts dominate through the early parts of this week. The main marine hazards will be in the form of thunderstorms capable of producing severe winds and hail (>50 kts and >1" in diameter). A round of strong to severe thunderstorms is possible this afternoon and evening. There remains uncertainty regarding specific timing and spatial coverage of storms, however, the west and central lake may be in the greatest risk. A secondary round of thunderstorms may redevelop tomorrow (monday), but uncertainty continues again on timing and coverage. Otherwise, transient marine fog is likely, especially where thunderstorms occur.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... None. Lake Superior... Dense Fog Advisory until 8 PM EDT /7 PM CDT/ this evening for LSZ162-243-244-251-263-264-266-267.

Lake Michigan... None.