textproduct: Marquette

KEY MESSAGES

- Widespread fog becoming dense at times this morning, especially for the central and eastern U.P. as well as in the Keweenaw.

- Mostly dry weather through Saturday, then low chances (10-40%) for light rain return late weekend.

- A period of cooler weather is expected for at least early next week as colder air pushes south across the region.

DISCUSSION

Issued at 309 AM EDT Thu Oct 22 2026

Early morning GOES WV imagery places Upper MI in the wake of a southeast progressing trough over southern Ontario and the Lower Great Lakes with a ridge building over the Midwest. Split flow further upstream features a deep trough off the coast of CA alongside broader troughing over the coast of British Columbia. High pressure becomes centered over the UP and northeastern Ontario by sunrise, supporting calm conditions. Subsidence and low level moisture under this radiative cooling setting has already yielded areas of fog development across the UP and out over eastern Lake Superior. As temperatures settle into the mid 30s to mid 40s, further fog expansion is expected through early this morning. This fog could be dense at times lowering visibility down to 1/4 mile, so commuters should leave extra time to reach their destination this morning. Fog then slowly lifts to low clouds mid morning, lingering into the late morning (early afternoon in the east/Keweenaw). Where clearing occurs earlier, temps warm into the 60s to low 70s while mid 50s to mid 60s are expected elsewhere.

The high pressure center moves east tonight to Quebec, but ridging remains overhead. Expect calm conditions in the south-central with light southerly flow overall. This alongside onshore flow off Lake Michigan should support additional fog in the central and eastern UP tonight. Lows will be in the upper 30s to upper 40s, coolest east.

The upper level ridge becomes centered overhead on Friday as sfc high pressure to the east strengthens. This results in an uptick in the southerly flow, warming temps into the 60s to mid 70s, warmest in the west and where downslope flow assists. Partly cloudy skies are expected with some CAMs suggesting isolated light rain showers courtesy of the weak WAA and isentropic ascent. Kept measurable precip mention out of the forecast, but on the low chance anything does resolve (5-14% chance), measurable precip beyond 0.01 inches and impacts are not expected.

The ridging remains overhead through most of Saturday as the western troughing moves east, splitting further into a trough over the southwestern CONUS and a deeper trough over the Canadian Prairie. This develops a sfc low over eastern MT on Friday which lifts northeast to northern Manitoba by the end of Saturday. This keeps well above normal temps (+10-25F) in the 60s to mid 70s, warmest west and in downslope flow. Also expect breezy south winds gusting up to 20-30 mph. The low continues northeast over Hudson Bay through Sunday as the upper level ridge flattens overhead. This sends a cold front through the area late Saturday night through Sunday and brings back shower chances (20-40%). Significant rainfall is not expected at this time, probabilities of just 0.1 inches in 24 hours is only 10-25%.

High pressure passes east over Ontario and the Great lakes Monday and Tuesday favoring dry weather until late Tuesday/Wednesday when higher PoPs return. That said, with colder 850mb temps moving overhead early next week, delta-Ts maybe sufficient for isolated rain showers. Troughing from the west and a resulting sfc low pressure mid next week present better (although still low) chances for precip, but ensemble guidance quickly diverges on track and timing leaving low forecast confidence. The forecast reflects mostly slight chance PoPs (14-24%). Otherwise, temps return near normal in the wake of the cold front on Sunday peaking in the mid 40s to low 50s on Monday. Temps Monday night settle into the 20s to mid 30s, coldest interior west. A slow warming trend then persists the rest of next week.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 705 AM EDT Thu Oct 22 2026

Dense fog continues to bring airport minimum conditions to SAW and CMX this morning while IWD is VFR. The IWD conditions will persist through today and tonight. CMX and SAW on the other hand will see improvement through the morning, though there is some spread in the models in exactly what time conditions improve. VFR conditions are then favored throughout the afternoon hours (75+% chance), but models are trending towards the return of FG overnight. Have elected to introduce IFR conditions tonight at SAW/CMX, but in the 35-65% likelihood that FG does form, it will probably be dense.

MARINE

Issued at 334 AM EDT Thu Oct 22 2026

Winds remain 20 kts or less through early Friday night on Lake Superior and through Saturday morning on northern Lake Michigan and the northern Bay of Green Bay courtesy of high pressure. Areas of dense fog have developed over Lake Superior. This will continue to impact south-central waters west of Grand Marais to the eastern side of the Keweenaw through late morning. Further expansion this morning on the west side of the Keweenaw Peninsula is anticipated, which may result in lingering visibility impacts through early this afternoon over the western waters. Meanwhile, the eastern fog is expected to clear out by early this afternoon.

A stronger low pressure tracking from Montana on Friday to Hudson Bay for Sunday increases southerly flow for Saturday. 15-25 kt winds are expected on northern Lake Michigan with stronger 20-30 kt winds over Lake Superior. Due to the warm southerly flow creating a more stable airmass over the lakes, gales are not expected on Lake Michigan and probabilities remain low for Lake Superior (20-40%). A cold front on Sunday veers winds westerly around 10-20 kts, then high pressure returns keeping winds below 20 kts through Tuesday.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Dense Fog Advisory until 10 AM EDT this morning for MIZ001-003- 005>007-013-014-085.

Lake Superior... Dense Fog Advisory until 2 PM EDT this afternoon for LSZ242>250-264>266.

Lake Michigan... Dense Fog Advisory until 2 PM EDT this afternoon for LMZ221- 248-250.