textproduct: Marquette

KEY MESSAGES

- A quick round of showers moves through late tonight through Saturday. Most of the central UP is slated to remain dry.

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

DISCUSSION

Issued at 256 PM EDT Fri Sep 11 2026

Afternoon GOES satellite imagery reveals mostly clear skies across the UP save for some convective debris in the far western lake and Keweenaw. Out that way, better low to mid level moisture and WAA has been able to kick off scattered thunderstorms that may skirt around Isle Royale this afternoon but not impact the mainland UP. Otherwise, gusty SW winds have been able to lift temperatures into the 70s to low 80s as of ~1:30 PM EDT. Later tonight, troughing that extends from from the Hudson Bay down to the northern Plains lifts north and works east across the UP, bringing in a round of showers and maybe some thunder to the far western UP closer to midnight along a surface cold front. Cant rule out a few WAA driven showers in the far west between ~9p to midnight local but the main line will be approaching into the overnight hours to early morning of Saturday. With the lack of synoptic support and loss of any diurnal instability, and plenty of dry air to fight against, CAMs suggest this line of precipitation falling apart as it reaches the central portion of the UP by Saturday sunrise, thus opting to leave NBM PoPs at only 15-30% chance. CAMs then suggest a short window of potential redevelopment in the east half by Saturday afternoon. Overall, not looking good for precipitation amounts should showers hold together as this morning's 12z HREF suggests a 30-60% chance for QPF >0.10" confined to isolated pockets in the far west and Keweenaw, a 0% chance in the central third, and a 10-30% in the east.

Behind the cold front, 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. Breezy westerlies will be the rule with gusts 25-35 mph common in the Keweenaw. 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. Interestingly, the 12z deterministic RRFS and REFS ensemble depicts more widespread lake effect rain coverage with a banded structure pointing into Munising that may be able to provide upwards of a quarter inch of rain, however, with a lot of dry air noted in area soundings, and global model bufkit lake-induced parcels only reaching 6-8k ft (CAMs likely overdoing it), I am remaining skeptical on rainfall amounts for now.

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 /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 107 AM EDT Sat Sep 12 2026

A southwesterly LLJ will bring LLWS concerns to the terminals overnight, with model soundings depicting winds of around 45 kt at FL020 exiting KSAW after daybreak Saturday. A cold front entering western Lake Superior will bring scattered showers and potentially a few embedded thunderstorms across Upper Michigan through early this morning, prompting the use of PROB30 groups in the TAFs. Intermittent MVFR ceilings will be possible in any stronger showers moving over the terminals. Any lingering showers exit to the east 12- 15z Sat, leaving VFR conditions behind the front with gusty west- northwest winds to 20-25 at at KIWD and KSAW and as high as 30 kt at KCMX. Winds diminish below 10 kt after 00z Sun.

MARINE

Issued at 256 PM EDT Fri Sep 11 2026

Lake Superior:

Gusty southerly winds 20-30 kts have been observed for much of the UP and nearshore waters through this afternoon and will persist this evening. A cold front front moves through the UP overnight, turning winds westerly through early Saturday. Modest pressure rises and cold air advection will keep gusty winds 25-30 kts around for another day, with isolated gales to 35 kts 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 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. Historically, southerly wind regimes in the late summer and early fall tend to be vastly overdone by the NBM and CAM wind gust (which is really a high wind gust potential) in the Great Lakes, so adjustments have been made to keep peak gusts 35-40 kts.

Northern Green Bay and northwestern Lake Michigan:

Gusty SW winds 20-30 kts are commonly found this afternoon and will persist this evening. A cold front moves through tomorrow morning turning winds more westerly with gusts diminishing between 10-15 kts Saturday evening and 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.