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.

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 /18Z TAFS THROUGH 18Z MONDAY/

Issued at 124 PM EDT Sun Jul 26 2026

VFR conditions prevail at all sites with the only elevated clouds at 16Z being some high cirrus south of IWD and some elevated wildfire smoke causing a milky white sky but otherwise not reducing visibility in a meaningful way. The main threat to aviation in this forecast is thunderstorm chances today into tonight. TSRA will move near and/or into the UP this afternoon and/or evening from the west and northwest, with some storms capable of producing damaging winds and quarter-sized hail. There is an enhanced risk (~30%) of this severe weather impacting IWD and a slight risk (15-30%) of occurrence at CMX/IWD, with the window of highest risk for each beginning at 19-20Z at all sites and lasting until around 01Z at CMX/IWD and until around 03Z at SAW, with lesser risks (around 5- 15%) in the preceding and proceeding hours. Outside of the immediate vicinity of thunderstorms,the only threats to vis and ceilings will be overnight with the potential for a marine fog layer to sweep over the Keweenaw Peninsula late tonight, with chances of visibility reductions to MVFR or below at 30-40% along with some chances of light rain showers.

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.