textproduct: Marquette

KEY MESSAGES

- Widespread fog is expected tonight. Some of the fog could be dense, especially for the central and eastern U.P.

- Mostly dry weather expected through Saturday.

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

DISCUSSION

Issued at 246 PM EDT Wed Oct 21 2026

This afternoon a frontal boundary was pushing from west to east across the U.P. with GOES visible satellite imagery showing widespread cloud cover accompanying the front and NEXRAD radar indicating a narrow band of showers along the leading edge. These showers were very light and little in the way of measurable rainfall was occurring as they passed through the central and eastern U.P. Surface observations showed northerly wind along the north shore of Lake Superior along a rather ill defined cold front. Temperatures had warmed into the 50s and 60s with much of the western U.P. under sunny skies while clouds associated with the front were moving through the eastern U.P. Winds were light from the southwest except they had turned northwest over the Keweenaw. In the upper levels model height analysis and satellite water vapor imagery showed ridging starting to amplify over the Northern Plains ahead of a cutoff low moving towards California.

By this evening winds will shift northeasterly over the U.P. as a weak cold front drops south across the area. Residual low level moisture that was advected into the region today along with moisture from the Great Lakes will combine with weak, mainly upslope flow and radiational cooling to develop widespread fog over the U.P. tonight. There is the potential that the fog could be dense, especially over the eastern half of the U.P. Commuters should leave extra time to reach their destination tomorrow morning as the fog is likely to linger into the mid-morning hours. Thereafter the fog will lift but low clouds will linger over the northern half of the U.P. into the early afternoon with continued flow off of the Great Lakes and a strong subsidence inversion, limiting mixing. Outside of the clouds temperatures will warm into the upper 60s (western U.P.) while area near Lake Superior will only reach the upper 50s (still several degrees above average).

The amplifying ridge will shift into the Great Lakes region for the end of this week as the main energy from the western low moves northeast to Saskatchewan and phases with the main jet stream. The ridge then flattens our with zonal flow redeveloping along the US/Canadian border on Sunday as the low pushes east to the Hudson Bay. Expect warm weather through the weekend, especially on Saturday as temperatures reach into the low to mid 70s over the western U.P. Cooler, 50s to low 60s, can be expected Sunday as a cold front sweeps across the U.P. There continues to be uncertainty with how much moisture will be available with the front and probabilities for >0.10" of rainfall remain low, ~25%. There is the potential for showers to linger into Monday and Tuesday with some guidance showing the frontal boundary stalling across the region. Confidence is high that we will see much cooler temperatures for Monday and Tuesday with NBM probabilities for highs of <50F around 75-95%. The deterministic guidance has highs in the mid to upper 40s Monday and Tuesday, which, believe it or not, is right around average for late October.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 709 PM EDT Wed Oct 21 2026

Behind the weak cold front this evening, expect FG to develop across the terminals late tonight from east to west generally-speaking. However, IWD may avoid the FG tonight as the temperatures are more likely going to fail to reach the dewpoint; nevertheless, I wouldn't be surprised if some MIFG formed by the sensor given it's proximity to a nearby creek. The FG across the area could very well become Dense (1/4 mile or less), potentially closing some of the terminals in the early morning hours on Thursday. However, the FG should lift by the late morning hours as high pressure rebounds across the area; expect weak flow driven mainly by the Great Lakes and SKC conditions by Thursday afternoon.

MARINE

Issued at 246 PM EDT Wed Oct 21 2026

Winds the remainder of the work week hold around or below 20 kts on both Lake Superior and northern Lake Michigan courtesy of high pressure. A stronger low pressure tracking to the north of Lake Superior this weekend and an associated cold front bring back a period of southerly 20-30 kt winds on Saturday, veering west for Sunday in the wake of the cold front. Due to the warm southerly flow creating a more stable airmass over the lakes, gale probabilities remain low (~20-40% chance on Lake Superior and less than 10% on Lake Michigan). Winds turn northerly for Sunday night into early next week but are expected to remain 20kt or less.

MQT WATCHES/WARNINGS/ADVISORIES

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