textproduct: Marquette

KEY MESSAGES

- High temperatures will be around 10 degrees above average through midweek with highs in the upper 60s to mid 70s.

- A storm system tracking through Ontario will bring rain chances back into the U.P. Tuesday night through early Thursday, followed by cooler, more seasonable temperatures.

DISCUSSION

Issued at 221 AM EDT Mon Sep 28 2026

Early morning GOES satellite imagery reveals a ridge extending into the western Great Lakes reflecting a ~1020 mb sfc high planted atop the state of Minnesota. Residual moisture in the wake of a departing shortwave has manifested into patchy dense fog and or stratus as noted by area ASOS obs in N WI and the western UP. Fog is expected to lift through sunrise. Aforementioned sfc high meanders across the UP today through Tuesday, holding dry and seasonably warm weather in place with highs pushing the upper 60s to the low and mid 70s south. Patchy dense fog may be possible again tonight.

Headed into the mid-week, west-southwest flow will overspread the region as troughing moves into central Canada and the northern plains. Meanwhile, the trough over the Pacific Northwest will cut off over the four-corners region and track into the southern Plains. This will bring increasing Pacific and Gulf moisture transport northeast into the U.P. with PWATs reaching up to 1.75" (95-99th percentile of climo) Tuesday night through Wednesday. With dewpoints pushing 60F on Wednesday it will feel a bit humid for fall. There will be multiple opportunities for precipitation Tuesday night through Wednesday night as warm, moist air advection increases along with a 40-45kt low level jet providing a focus for large scale ascent. Then a cold front will push through the area by Thursday morning with additional showers preceding it and cooler, drier air behind it. As far as rainfall totals ending early Thursday, there still remains some uncertainty. The latest global ensembles have trended the greatest QPF axis a hair south, highlighting a barely 50% chance for QPF >0.5" in the far southern UP (largely Menominee Co). Meanwhile the NBM and and LREF still favor a 50-70% chance for QPF >0.5" across much of the central and southern half of the UP. This is likely an influence of the Canadian ensemble, the obvious outlier, who favors the greatest QPF axis further north across essentially the entire UP. With deep moisture would expect that some locations will overachieve with localized heavy downpours. Regardless, any rain is welcome as drought conditions have expanded across the UP recently. Month-to-date percent of normal precipitation analysis reveals the entire UP in a deficit between 10-50% of normal, worst in the eastern half from Alger Co to Drummond Island. Luckily, no significant warm-ups or fire weather watch out patterns present themselves in the forecast, unlike the warm and dry early Octobers of 2024 and 2025.

Expect cooler, more seasonable temperatures to finish out the week and into next weekend with highs in the low 60s. Wouldn't rule out lake effect rain showers, especially over the eastern U.P. on Thursday night into Friday morning as a passing shortwave brings the potential for deeper inversion heights and colder 850mb temps. The GEFS is the most aggressive among the ensembles with a mean of 0C at 850mb while the LREF (EC/GEFS/CMC) mean sits around 3C with 0C falling into the 10th percentile. With lake temperatures sitting around 13-16C would expect a high potential for lake effect cloudiness and a few light showers even with the warmer, mean solution.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 120 AM EDT Mon Sep 28 2026

With weak high pressure overhead through the duration of the 6Z TAF period, the primary impact once again is fog. Low clouds clear from west to east, yielding favorable radiative cooling conditions at IWD/CMX through early this morning. Winds turning northerly behind a boundary will support upslope flow at CMX, supporting the fog development, and bring a brief period of MVFR CIGS at SAW early Monday morning. Fog deteriorates VIS down to IFR/LIFR at CMX and VLIFR at IWD. There remains a 30-50% chance for VLIFR at CMX. VFR conditions return by mid-morning persist into Monday evening. Fog looks to redevelop Monday night, with a 50% chance for IFR conditions at SAW and CMX after 03z Tue.

MARINE

Issued at 221 AM EDT Mon Sep 28 2026

Lake Superior: Light winds dominate through Monday before ramping up out of the south on Tuesday. Gusty southerlies 25-30 kts in the eastern lake persist through much of Wednesday before briefly falling between 15-20 kts late Wednesday into early Thursday. A cold front is then expected to sweep across the lake early Thursday morning. Modest cold air advection and strong pressure rises behind the frontal passage will contribute to westerly gales between 35-40 kts much of Thursday before falling below 25 kts into Friday.

Northern Green Bay and northwestern Lake Michigan: Light winds dominate through Monday before ramping up from the south Tuesday, lasting through Wednesday. Elevated winds 15-20 kts are expected before reaching 25-30 kts Wednesday. A cold front sweep winds to the west early Thursday, but remain between 15-20 kts.

MQT WATCHES/WARNINGS/ADVISORIES

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