Area Forecast Discussion

KEY MESSAGES

- Spotty, light rain showers continue to graze the southern UP through this evening. Rain totals below 0.10in are expected.

- Light lake-enhanced showers will be possible (30-50%) especially along the terrain of the western and north-central UP Sunday. Gusty northeast winds will cause potentially hazardous swimming conditions and rip current risks along Lake Superior.

- Dry pattern with high pressure sets up through much of next week. Below-average temperatures expected through Wednesday (including morning frost potential), giving way to above-normal temperatures late week.

DISCUSSION

Issued at 306 PM EDT Sat Sep 19 2026

Early afternoon RAP analysis and water vapor imagery reveal midlevel ridging moving towards the central Mississippi valley, with midlevel lows closing off over southern Idaho, Florida, and Hudson Bay. A shortwave trough is swinging southeast of the latter feature into Ontario. At the surface, broad low pressure is stretched out from Kansas northeastward into IA, with resulting WAA into WI touching off light rain showers particularly over the southern portions of the state. Still, some light rain showers have been able to make it into the south-central UP. These could drop a couple hundredths of an inch of rain mainly over Menominee and Delta county through the rest of the afternoon, but significant impacts are not expected apart from persistent cloudiness across the UP. In spite of the cloud cover, temperatures across the area are climbing comfortably into the mid 60s for most, with some spots even flirting with the upper 60s.

Tonight, a cold front associated with the Ontario trough drops southeastward over Lake Superior and into the UP. This may bring some spotty rain showers to the western and central UP, but they will have to contend with dry midlevel air...and will note that most of the CAMs show these dying out soon upon reaching our shores. Into the daytime hours, a surge of cooler air aloft will cause marginally-supportive thermodynamic profiles for some lake-enhanced or lake-effect rainfall, with CAMs showing the orographic forcing of the western and north-central UP being enough to force weak precipitation. Thus, will maintain chance pops and another couple hundreds of QPF. This will also come with some gustier NE winds, with gusts of 20+ MPH forecast especially along the Lake Superior shores. This in turn cranks wave heights up to 6 ft within 5 miles of the Lake Superior shoreline, which will drastically increase the risk of hazardous rip currents and challenging swimming conditions for those trying to squeeze in a late-September Sunday beach day at Lake Superior beaches.

In the wake of the weekend disturbances, the western CONUS trough will shift over the Dakotas by Sunday, weakening slightly. At the same time, ridging to the north of the trough amplifies, causing split flow. This results in dominant surface high pressure establishing over northern Ontario and Quebec through much of next week, likely bringing an extended period of dry weather to the UP. The latest NBM keeps us dry even through next weekend as ensembles flip-flop on whether ridging will persist over the region. Upstream ridging aloft results in cooler continental flow aloft, and being on the south/southwest periphery of a surface high results in cool easterly to northeasterly flow at the surface off of the Canadian Shield. This brings cool conditions for the beginning of the week with a gradual warming trend as the week goes on. For instance, the NBM even calls for up to 50% chances of sub-freezing temperatures for Tuesday morning, though the LREF chances are significantly lower. By the end of the week, NBM highs are widespread 70+. The CPC 6-10 and 8-14 day outlooks both show 50+% chances for the UP to be in above average temperatures for the end of September and a slight favoring of below normal precipitation (30-40% chance).

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 151 PM EDT Sat Sep 19 2026

Afternoon visible satellite imagery reveals dense cloud cover over the southern half of the UP on the periphery of a system passing south across WI and IL today. This is resulting in MVFR cigs at KIWD and KSAW, with VFR farther north at KCMX. Expect VFR cigs to return across the UP this evening as the system continues to move off to the east away from the region. MVFR cigs return to all sites late tonight after 06z Sun as a weak cold front approaches from the north. Do not expect any precipitation to accompany this feature, but winds will increase out of the north-northeast to around 10 kt with gusts to 15-20 kt near the end of the period.

MARINE

Issued at 306 PM EDT Sat Sep 19 2026

This afternoon and evening, weak low pressure to the south and departing high pressure to the northeast will keep wind gusts largely below 20 kt. A stronger high building to the north on Sunday in addition to gusty winds mixing down in the wake of a Hudson Bay cold front looks to bring 20-30 kt northeast gusts to most of Lake Superior. Waves across Lake Superior (especially in the south and the west) build to 4-6 ft. Northeast wind gusts to 20-25 kt will develop over Lake Michigan by Sunday afternoon as well, with wave heights building to 2-3ft. Winds slowly fall back to near or below 20kts Sunday night. For the beginning of next week, high pressure building over Northern Ontario opposing low pressure over the Lower Mississippi Valley will drive some gradient wind gusts to around 20 kt out of the east before model spread and forecast uncertainty increases late in the week.

MQT WATCHES / WARNINGS / ADVISORIES

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