textproduct: Marquette

KEY MESSAGES

- Potential (20-50% chance) for showers and storms today through Wednesday afternoon. Severe storms are not expected.

- Temperatures are expected to be seasonably warm to slightly above average through Wednesday, before cooling to slightly below average through the weekend.

- Dry weather Thursday and Friday ahead of the next chances for more widespread rain this weekend (around 45% chances).

DISCUSSION

Issued at 253 AM EDT Tue Aug 11 2026

Early morning RAP analysis shows broad northwesterly flow aloft as sprawling ridging over the southern half of the CONUS is only partially depressed by a closed low over Hudson Bay. Minor ripples in the flow reflect mesoscale disturbances embedded within the northwest flow, and while the most impactful disturbances will remain south of the UP, some small troughs in the vicinity will erode the presence of ridging aloft/surface high pressure that would otherwise have too much subsidence for any precipitation to occur. CAMs show little agreement in the details of showers and potential thunder today (which is to be expected in weakly forced, nebulous patterns such as this), but lake breezes may serve as a focal point for showers and a few thunderstorms today. With weak, unidirectional flow, the shear pattern will not be supportive of severe weather, though the HREF SBCAPE solutions offer a wide spread as to how buoyant updrafts may become. While the ensemble minimum for SBCAPE is genuinely 0, the ensemble mean is around 500 J/kg with ensemble maximums in the 1000+ J/kg territory, so some thunder remains possible (maybe 1 or two strong thunderstorms cannot be ruled out). As to what probability exists for those storms to occur, that will be a moving target through the day. For now, HREF chances of a shower capable of producing a tenth of an inch of rain within 25km of any point in the interior UP is between 30-60% with chances of a thunderstorm capable of producing modeled radar reflectivity exceeding 40 dBZ is around 15%.

Clarity on the weather pattern is not really provided on Wednesday either as the 500mb pattern remains much the same as today, so a general repeat of today is expected. All eyes turn upstream to a trough that will be over the Seattle/Vancouver area by Wednesday 18Z. This trough will provide the best mechanism to progress the weather pattern, though it will first kick ridging from over the Rockies and Plains to be over the Midwest and Great Lakes late this week. This will lead to rising surface pressure and dry conditions for virtually all of the UP Thursday and Friday.

The aforementioned kicking trough arrives over the UP Saturday. Unfortunately, spread in the track and depth of this trough passage is high as at the same time as the trough arrives, ridging builds over the Southeast, allowing for ensembles to have a spread of solutions regarding how this trough fares against either a weaker or stronger Southeast ridge. Current LREF chances of a wetting rain (around a tenth of an inch/24hr) is around 45% by Sunday afternoon. Thunderstorms are uncertain as well, though the LREF mean SBCAPE by 00Z Sunday being around 15 J/kg is not an encouraging sign for those looking forward to a rumble of thunder. While there is understandable spread on the pattern that follows, it is generally expected that by Sunday evening and through Monday night, ridging resumes in the wake of the trough, with next Tuesday looking to resume the ongoing pattern of weak precip signals in persistent NWerly flow.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 127 AM EDT Tue Aug 11 2026

VFR conditions expected at Upper Michigan terminals through Tuesday evening under surface high pressure. May see some patchy fog develop in a few locations tonight, but probability is too low to include in the TAFs. Scattered showers and thunderstorms are possible Tuesday afternoon, especially over the central UP. Included a PROB30 for SHRA at KSAW after 18z Tue.

MARINE

Issued at 253 AM EDT Tue Aug 11 2026

Winds will be less than 20 kt throughout the week this week as high pressure dominates. An isolated thunderstorm cannot be ruled out (up to 35%) over the Bay of Green Bay and Lake Michigan waters this afternoon through Wednesday afternoon. Gusty conditions return to Lake Superior Saturday afternoon with an approaching disturbance, but confidence is low in the timing, location, and intensity of such gusts.

MQT WATCHES/WARNINGS/ADVISORIES

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