textproduct: Marquette

KEY MESSAGES

- A quick round of showers and storms moves through Friday night into early Saturday morning.

- The potential for active weather returns early next week as a Colorado Low moves towards the region.

DISCUSSION

Issued at 319 PM EDT Thu Sep 10 2026

Afternoon GOES satellite imagery reveals mostly sunny skies across the northern Great Lakes and Upper Midwest aside from diurnal cu locally seen in the interior UP. With ridging aloft holding through tonight, clear skies should allow temps to fall into the low 50s and upper 40s for much of the interior while the lakeshores remain in the 50s. A breakdown of the ridge aloft to more zonal flow and mid- level troughing shapes up across the central CONUS tomorrow morning, developing a surface low in the northern Plains and increasing the region pressure gradient across the Great Lakes. Southerly return flow will make more another warm summer day with highs near 80 (a bit cooler near northern Lake Michigan). A cold front finally reaches the western UP late tomorrow night, pressing into the eastern 2/3rds by Saturday morning. Showers and a few thunderstorms are expected along the frontal boundary, but with waning instability, no strong to severe storms are anticipated. HREF QPF probs for only a 0.10" are nothing to write home about, only peaking at 50-70% in a stretch from Ironwood to Houghton. Eastward, light rain amounts a tenth of an inch or less is expected with showers dissipating past the central UP. Modest pressure rises and cold air advection will make for a windy but dry day on Saturday. Cant rule out some scattered lake effect rain showers or at least clouds on Sunday as 850 mb temps fall below 5C (0-2C if you're the Canadian or GFS) while the lake average surface temp sits at ~17C.

Looking into early next week, ensembles continue to hone in on a deepening trough over the Rockies ejecting a Colorado Low in the vicinity of the Great Lakes. There remains considerable disagreement between each ensemble and their individual ensemble members regarding the track and strength of the surface low pressure. Given a broad feature placement north and west of the UP, considerable moisture (PWATS near 1.75-2", the 95-99th percentile of climatology), if the best QPF axis winds up in our neck of the woods then meaningful rainfall could be expected. The NBM suggests a 60- 80% chance for QPF >0.5" by Tuesday morning, however, this may be high biased as individual ensembles and the LREF barely scrape 20- 40%.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 126 PM EDT Thu Sep 10 2026

VFR conditions are expected through the TAF period. High pressure over the Great Lakes will shift east tonight as a surface trough approaches from the plains. This will bring a shift in the winds to the south tonight along with increasing wind speeds by morning. Daytime heating will begin to mix down some of the stronger winds Friday by mid-morning, with gusts to around 25kt expected.

MARINE

Issued at 319 PM EDT Thu Sep 10 2026

Lake Superior: Winds <15 kts tonight begin to ramp up early Friday morning as a pair of surface low pressure systems influence the region through the day. Gusts 20-30 kts will be common lake wide much of the day and into Saturday. A few isolated gales to 35 kts may be seen in the open waters of the east-central lake and where funneling occurs close to Isle Royale. Additionally, a showers and thunderstorms are likely in the western half of the lake early Saturday along the system's cold front. Winds then turn westerly behind this front Saturday morning. Modest pressure rises and cold air advection will keep gusty winds around for another day, reaching to near gales in and around the Keweenaw (40-60% chance) in the afternoon. NW winds linger through Sunday, gusting 20-25 kts in the east half. More active marine weather returns early next week in the Monday-Tuesday timeframe as operation models hone in on a deepening low pressure system that works north of the lake. Ensemble probabilities for southerly and western gales associated with this system are reaching 60-80%, however, there remains uncertainty regarding the gust potential of southerly gales given the warm lake temps and low level stability. Also, the track of this system, which is not fully agreed upon, will ultimately inform pressure falls/rises and cold air advection necessary for gusts 40-45 kts.

Northern Green Bay and northwestern Lake Michigan: Breezy N to NWerlies near 15 kts fall off tonight before increasing again tomorrow morning as the area is influence by low pressure systems to the north and southwest. S to SW gusts 20-30 kts will become common tomorrow afternoon and linger through Saturday afternoon. Behind a cold front, gusts diminish between 10-15 kts, remaining out of the NW through Sunday. Active marine weather returns early next week with the passage of a potentially strong low pressure system to the north. This, in turn, will increase winds to near or above gales in the Monday-Tuesday timeframe.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Beach Hazards Statement until 5 PM EDT this afternoon for MIZ006.

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