textproduct: Marquette

KEY MESSAGES

- Showers continue and/or redevelop this afternoon and evening, becoming most widespread over the southern half of the UP. A couple of stronger storms resulting in gusty winds and locally heavy rainfall cannot be ruled out over the south-central UP.

- Temperatures will remain closer to normal through the mid-week, and start to increase by the weekend. Highs around 90 are becoming more likely Sunday into early next week.

DISCUSSION

Issued at 117 PM EDT Wed Jul 8 2026

Early afternoon water vapor imagery and RAP analysis show quasi- zonal flow over the upper Great Lakes with a good deal of coincident moisture, sampled by 12Z KMPX RAOB with a 1.71 in PWAT. Upstream vorticity maxima are located over SW Ontario and the western Dakotas. Subtle NE/SW oriented low-level wind shift boundary is located roughly from western Marquette County through central Gogebic County. It is upon this boundary that we will have to watch for convective redevelopment this afternoon. With weak midlevel lapse rates, any instability will have to be generated from diurnal heating, which is a question mark given the extensive cloud cover across the region. There are some breaks in the cloud cover, and SBCAPE around the WI border region could approach 1000 J/kg should these breaks continue. With strong effective bulk shear around 40 kt, some more organized convection cannot be ruled out from mid- afternoon into the evening, especially for Dickinson, Menominee, and Delta Counties, where strong wind gusts would be the main threat. Given the moist atmosphere and tendency for the low-level boundary to be parallel to the cloud- layer winds, some locally heavy rainfall will also be possible, exemplified by the 12Z HREF LPMM showing values in excess of 2" in 6 hours (representing possible local max amounts).

Upstream vorticity maxima continue to push through tonight, allowing the low-level boundary and deeper moisture to settle south of the area. While showers and a few storms could linger over Menominee County for the first part of the night, high pressure building from the north will result in dry weather elsewhere with patchy fog possible. Synoptic-scale subsidence is favored for Thu/Fri with seasonable temps.

This weekend into early next week, anomalous midlevel anticyclone over the Four Corners region will build into the northern Plains by early next week. Impressive 500 mb heights approaching 600 dam are modeled by early next week over the northern Plains, +2 to +3 sigma as we approach the hottest time of the year. 850 mb temps in the low to possibly mid-20s (C) are similarly impressive. The upshot is growing confidence in a period of highs approaching or exceeding 90F Sunday through Tuesday. It does appear that humidity will be less of an additive factor to the apparent temps than the previous heat spell at the end of June/early July, as low-level trajectories will have more of a westerly/downsloping component off the high plains. Given the lack of deep-layer moisture and positioning downstream of the apex of the ridge, convective potential is fairly low until probably Tuesday, when there are indications of a possible backdoor front/ridge rider.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 725 PM EDT Wed Jul 8 2026

While skies have largely cleared out at IWD and CMX, expect a deterioration to MVFR and then IFR from around 04-07Z, as fog develops over the region. At SAW, ceilings continue to drop to IFR at times, but IFR really settles in over the next few hours with fog development. LIFR visiblity eventually becomes possible at SAW as well as CMX after 06Z. IFR/LIFR lingers through the rest of the night, then after sunrise, IWD and CMX quickly lift to MVFR and then VFR. Restrictions may linger longer at SAW, but VFR returns by late morning.

MARINE

Issued at 117 PM EDT Wed Jul 8 2026

High pressure building over the lake in the wake of a weak frontal boundary will maintain light winds through at least Saturday. Rain showers may lead to areas of fog through at least Thursday morning. A thunderstorm or two cannot be ruled out this evening, especially closer to the shoreline, but overall potential is low.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... None. Lake Superior... Dense Fog Advisory until 8 AM EDT /7 AM CDT/ Thursday for LSZ162-263>267.

Lake Michigan... None.