textproduct: Marquette

KEY MESSAGES

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

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

DISCUSSION

Issued at 238 AM EDT Fri Sep 11 2026

Early this morning, RAP analysis has the midlevel ridge axis shifting over the Great Lakes at this time, with the surface high centered over the Lower Peninsula. Meanwhile, a shortwave is moving into Manitoba and another into eastern Wyoming. With ridging over the area, nighttime microphysics is showing mostly clear skies over the UP, though some stray cirrus has been able to move in at times amid the developing SW flow ahead of the Plains trough. Temperatures are falling back nicely into the lower 50s so far, apart from the far west, where temperatures range in the upper 50s to lower 60s. We should expect lows in the mid to upper 40s across most of the UP and the lower to mid 50s in the far west.

As we head into the daytime hours, expect the midlevel ridge to break down, with flow aloft turning more zonal. The Wyoming shortwave moves eastward, with a surface low eventually closing off over the Plains. This looks to get "scooped" up in the broader midlevel troughing that will be developing over the Plains late in the day. Southerly return flow on the backside of the ridge will make for another warm summer day with highs near 80 (a bit cooler in the mid 70s near northern Lake Michigan). A cold front finally reaches the western UP late tonight, 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. Expect an otherwise cooler day, as temperatures climb from lows generally in the upper 50s to highs in the 70s for most. Sunday, we can't rule out some scattered lake effect rain showers or at least clouds 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 >1.0" by Tuesday morning, however, this may be high biased as individual ensembles and the LREF barely scrape 20- 40%.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 101 AM EDT Fri Sep 11 2026

VFR conditions will prevail for the duration of the TAF period as high pressure over the Great Lakes shifts east early this morning while a surface trough approaches from the Plains. This will bring a shift in the winds to the south with increasing wind speeds this morning. Southwesterly winds will gust to 25 kts by mid-morning. Did introduce PROB30 for thunderstorms late in TAF period at IWD as a cold front approaches the western portions of Upper Michigan.

MARINE

Issued at 238 AM EDT Fri Sep 11 2026

Lake Superior: SSW winds are on the increase early this morning as a pair of surface low pressure systems are leading to a tightening pressure gradient over the Great Lakes. Gusts of 20-30 kts will be common lake wide by daybreak, lingering 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 late tonight into 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: SW winds are on the increase early this morning as a pair of surface low pressure systems are leading to a tightening pressure gradient over the Great Lakes. Gusts 20-30 kts will become common by the afternoon and linger through Saturday afternoon. Behind a cold front, gusts diminish between 10-15 kts Saturday evening, 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... None. Lake Superior... None. Lake Michigan... None.