textproduct: Marquette

KEY MESSAGES

- A batch of showers and storms moves through the western UP early this morning, potentially redeveloping in the eastern UP this afternoon.

- The potential for active weather returns early next week in the form of widespread rain and gusty winds.

DISCUSSION

Issued at 224 AM EDT Sat Sep 12 2026

Early this morning, water vapor reveals midlevel troughing over the north-central CONUS, extending from a midlevel low over the Canadian Prairie. At the surface, low pressure is tracking through far western Ontario, dragging a cold front through the Great Lakes. Judging by the surface wind shift, this is already reaching western Lake Superior. A line of showers and storms has developed ahead of it, within the right-rear quadrant of the ~40-50kt LLJ, and showers and storms should continue to move through the western UP into the pre-dawn hours. Most of the western UP should see totals of a tenth of an inch or less, but will not rule out some higher amounts closer to 0.20in where thunderstorms can hold together. CAMs continue to show showers falling apart with eastward extent as they contend with a drier airmass. However, convection may re-fire over the far eastern UP as we destabilize ahead of the front, but strong storms are not expected with lackluster CAPE and shear.

Behind the cold front, modest pressure rises and cold air advection will make for an otherwise breezy and cooler day. Expect an otherwise cooler day, as temperatures starting in the upper 50s and lower 60s climb to highs in the lower to mid 70s for most. Breezy westerlies will be the rule with gusts 25-35 mph common in the Keweenaw, and up to 20-25mph elsewhere. Sunday, we can't rule out some scattered lake effect rain showers or at least lake effect cloud cover for the NW wind snowbelt as 850 mb temps fall below 5C (0-2C per NAM or GFS) while the lake average surface temp sits at ~17C. Some of the CAMs are showing somewhat more widespread lake effect rain coverage, and even hints for a banded structure pointing into Munising that may be able to provide upwards of a quarter inch of rain. That said, with a lot of dry air noted in area soundings, and soundings only showing decent mixing to around 6-8kft, these higher-end amounts seem rather ambitious.

Looking into early next week, ensembles continue to hone in on a deepening trough over the Rockies ejecting a deepening surface low from the northern Plains northeast through Ontario Monday PM through Tuesday. Operational deterministic models and their ensemble counterparts are coming into better agreement regarding the track and timing of the surface low pressure feature, but there still remains disagreement between each ensemble and their individual ensemble members. As the trough lifts north of Lake Superior, strong isentropic ascent within the warm sector will be the focal point for shower and thunderstorms development. With considerable northward moisture transport (PWATS near 1.75-2", the 95-99th percentile of climatology), widespread moderate to heavy rain is possible. Across the southern half of the UP, the NBM suggests a 50-75% chance for QPF >1.0" by Tuesday morning, however, this may be high biased as individual ensembles and the LREF barely scrapes 15-30%. Additionally, gusty winds are expected both Monday and Tuesday.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 718 AM EDT Sat Sep 12 2026

We may see cigs become MVFR for a few hours this morning across the terminals, with IWD already reporting MVFR cigs as of 11z. That being said, as CAA continues to move in behind the cold front today, expect VFR conditions to be settled across the area by the early afternoon hours. The CAA will create gusty W/NW winds over the terminals today before lightening up tonight. While some sprinkles/light rain showers could be seen for at most an hour or so this morning, expect SKC or near SKC conditions by this afternoon.

MARINE

Issued at 224 AM EDT Sat Sep 12 2026

Lake Superior:

Winds remain gusty across the lake the rest of tonight and through the daytime Saturday. Wind gusts to 20-30kts persist out of the south so far, though winds shift westerly through the morning and afternoon as a cold front passes through. Some isolated gales to 35 kts are possible (20-40% chance) in the afternoon in and around the Keweenaw. 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 models continue to bring a strong low pressure system 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. Historically, southerly wind regimes in the late summer and early fall tend to be vastly overdone by models in the Great Lakes, so adjustments have been made to keep peak gusts around 35-40 kts. Ridging returns midweek next week, with winds falling back below 20kts in response.

Northern Green Bay and northwestern Lake Michigan: Gusty SW winds 20- 30 kts persist the rest of tonight and into the morning. A cold front moves through later this morning and into the afternoon, turning winds more westerly with gusts diminishing between 10-15 kts by the evening. Winds remain below 20kts through Sunday moring before beginning to increase out of the south late in the day. 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. Ridging returns midweek next week, with winds falling back below 20kts in response.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Beach Hazards Statement through this evening for MIZ014.

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