textproduct: Marquette

KEY MESSAGES

- A low pressure system tracking north of the area through midweek brings widespread wetting rain to the UP tonight into Tuesday.

- Breezy southerly winds develop tonight into Tuesday, with frequent gusts of 15-25 mph expected. There is a 60-70% chance for gusts of 35+ mph near Lake Superior through Tuesday evening.

- Winds shift westerly Tuesday night into Wednesday, with frequent gusts of 20 to 30 mph expected. There is a 30-60% chance for gusts up to 40 mph near Lake Superior and 70-90% chance for gusts up to 45 mph in the Keweenaw on Wednesday.

- A Gale Warning for southerly winds up to 35 knots is in effect for portions of east-central Lake Superior on Tuesday. A Gale Watch has been issued for westerly winds of 40-45 knots across the entire lake on Wednesday.

DISCUSSION

Issued at 310 PM EDT Mon Sep 7 2026

Afternoon RAP analysis continues to depict broad upper level ridging extending from the central CONUS into southern Manitoba and northwest Ontario, however there is some evidence of an impending pattern change as a deep upper level trough begins to lift out of the Pacific Northwest. Closer to home, a disturbance moving over the top of the ridge is spreading mid and high level clouds over Lake Superior, with even a few weak radar echos noted near Isle Royale today. Otherwise, lingering surface high pressure is promoting another pleasant day with light winds and sunny skies across most of the UP, with temperatures again rising into the upper 70s to low 80s as of mid afternoon. Strong mixing has allowed dewpoints to fall into the upper 40s to low 50s across the west, supporting RH values dipping near or below 30% in a few locations. Despite that, do not expect any major fire weather concerns with winds mostly remaining below 15 mph this afternoon and RH quickly recovering tonight.

More active weather is on tap for the next couple of days as the central CONUS ridge is progressively flattened out by the deep Pac NW trough lifting into the Canadian Prairie provinces. This is inducing surface cyclogenesis in the lee of the northern Rockies today, with the resultant strong low then forecast to track to the southern shores of Hudson Bay by Wednesday morning and driving a series of fronts across the UP tonight through early Wednesday.

A warm front will push into the western UP late tonight accompanied by deep moisture as PWATs climb to 1.75-2.00", bringing a round of showers and thunderstorms to the area through Tuesday. Expect most of the area to receive a wetting rainfall from this system as the NBM continues to depict a 65% or greater chance to receive at least a quarter inch for all but the far southcentral UP (closer to 50%) through Tuesday night. The western UP from the Keweenaw to the Porcupines still shows a roughly 40-60% chance to receive an inch or more of rain on Tuesday, but those probabilities quickly drop off to 15-30% over the central and eastern UP. SPC continues to highlight a Day 2 marginal risk for severe weather over the western half of the UP given MUCAPE of 500+ J/kg and bulk shear values increasing above 40 kt. That said, we remain rather pessimistic on overall strong/severe potential for Tuesday as the most favorable instability will not materialize until well after the best forcing has departed with the warm front. Additionally, model soundings continue to depict a strong capping inversion which will further inhibit any convective development. Any lingering shower and thunderstorm activity should depart the eastern UP behind the trailing cold front by Wednesday morning.

Shifting gears to the expected breezy conditions through the middle of the week, southerly winds increase to 15-25 mph across a wide swath of the area tonight into Tuesday with the arrival of the warm front. The strongest gusts in this southerly warm advection regime will be in the areas favored by southerly downslope flow, particularly from the Huron Mountains eastward along the Lake Superior shoreline. These areas show a 60-70% chance for wind gusts of 35+ mph through Tuesday evening per latest HREF and NBM guidance. Winds shift westerly and strengthen further on Wednesday, aided by cold air advection and pressure rises behind the cold front. Expect widespread gusts of 20-30 mph through the day, with NBM probabilities now increasing to 30-60% for gusts to 40 mph near Lake Superior. A Wind Advisory for the Keweenaw continues to look like a strong consideration as the NBM probability for gusts of 45+ mph has increased to 70-90%. Meanwhile, will also have to watch areas to the east as there is a 25-40% probability for 45 mph gusts along the shoreline from east of Marquette to Whitefish Point.

Expect calmer weather to return to the region by Thursday as high pressure temporarily builds back over the UP behind the departing system, with highs on Thursday closer to seasonal norms in the mid 60s to low 70s. However, the overall pattern remains unsettled as another trough has the potential to bring additional rounds of precipitation and breezy conditions into the weekend.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1152 PM EDT Mon Sep 7 2026

VFR will be the predominant flight category for the duration of the TAF period outside of any rain or thunderstorms. However, periods of MVFR/IFR will be possible in any showers and thunderstorms that overspread the TAF sites early this morning from west to east. Rain is still expected to enter the western sites between Tue 6-12Z, eventually reaching SAW between Tue 12-15Z. In addition, southerly winds will become strong after Tue 12Z with gust of 25 to 30 kts.

MARINE

Issued at 310 PM EDT Mon Sep 7 2026

Lake Superior: Continued influence of surface high pressure is keeping winds mainly to 15 kt or less across the lake today, but changes are imminent as a strong system lifts north of the lake and drives a series of fronts through the region tonight through Wednesday. Southerly winds will increase to 20-30 kt across much of the lake on Tuesday with the arrival of a warm front. The probability for gales has leveled off at around 50-60% on Tuesday across east-central portions of Lake Superior. Opted to upgrade to a Gale Warning for the waters between Marquette and Grand Marais as the bulk of guidance still suggests the possibility of frequent gusts to around 35 kt through Tuesday evening. Small craft headlines are in place for the remaining nearshore zones as wave heights build to 2-5 ft over the western half of the lake and 4-7 ft over the eastern half on Tuesday, with 20-30 kt southerly winds shifting southwesterly through Tuesday night. Winds shift westerly behind a trailing cold front early Wednesday, bringing the likelihood of high end gales aided by cold air advection and strong pressure rises. Have hoisted a Gale Watch for the entire lake on Wednesday, with 40- 45 kt winds expected in the west through Wednesday evening and in the east through early Thursday morning. Wave heights continue to build to 6-10 ft in the west and 8-13 ft in the east on Wednesday. Winds briefly settle back below 20 kt under high pressure on Thursday, but another system traveling north of the lake brings additional strong wind potential Friday into the weekend. Confidence in specific details for late in the week is low at this time.

Northern Green Bay and northwestern Lake Michigan: Southerly winds remain 15 kt or less through tonight under the lingering influence of surface high pressure. An arriving warm front associated with a strong system passing well to the north will increase southerly winds to 20-30 kt and wave heights to 2-4 ft on Tuesday, with Small Craft Advisories remaining in place through early Wednesday morning. Another round of small craft headlines is likely on Wednesday as winds turn westerly and continue to gust to 20-30 kt behind a trailing cold front. The return of high pressure brings calmer conditions for Thursday, with additional rounds of stronger winds possible Friday into the weekend. Confidence in specific details for late in the week is low at this time.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... None. Lake Superior... Gale Watch from Wednesday morning through Wednesday afternoon for LSZ162.

Gale Watch from Wednesday morning through Wednesday evening for LSZ240>244-263-264.

Gale Watch from Wednesday morning through late Wednesday night for LSZ245>248-265.

Gale Warning from noon to 8 PM EDT Tuesday for LSZ249-250-266.

Gale Watch from Wednesday afternoon through late Wednesday night for LSZ249>251-266-267.

Lake Michigan... None.