textproduct: Marquette

KEY MESSAGES

- Cooler today with scattered rain showers in the east half.

- Dangerous swimming conditions persist along the Alger County shoreline today.

- Chilly tonight with frost in the interior west. Frost Advisory in effect for Gogebic, Iron, and Baraga counties.

- Widespread rain moves into the UP from west to east late Monday into Monday night, ending Tuesday morning. Rainfall amounts of an inch or greater range from 40 to 70% across the U.P.

- A Gale Watch has been issued for southerly gales followed by westerly gales over the Upper Great Lakes Monday evening through Tuesday.

DISCUSSION

Issued at 221 AM EDT Sun Sep 13 2026

Satellite imagery hints at a subtle shortwave beginning to roll through the Lake Superior early this morning, allowing lake enhanced rain showers to develop over mainly the eastern half of the U.P. by the late morning hours. That being said, some sprinkles could be see for a few hours over the Keweenaw and north central even as high pressure starts to build back into the region by the afternoon hours. With PWATs around 0.50 to 0.75 inches today and delta-Ts getting into the upper teens, we could see some spots in the east get a tenth of an inch or two before the rain ceases late this afternoon. However, with the gusty winds being WNW today, expect most of the lake enhanced rain showers to fall east of Munising and north of M-28. The gusty winds will create dangerous swimming conditions along Alger County and potentially even in Marquette County near the Alger County border (i.e. the Shot Point area); thus a Beach Hazard Statement has been issued for Alger County today. Elsewhere across Upper Michigan today, expect pretty dry weather as temperatures will be cooler than yesterday (highs in the 60s, mostly the lower half). As high pressure builds in tonight, expect the clear skies and antecedent cooler air aloft to allow temperatures to drop into the 30s across much of the interior area, with the interior west looking to dip into the 20s. This will allow for frost to develop over the interior west tonight, potentially damaging unprotected plants and crops. Around normal temperatures with highs in the upper 60s returns to the area on Monday as a warm front approaches the U.P. from the southwest.

Our next real rain chance comes with the warm front that occludes over us late Monday through Monday night. While strong atmospheric shear, helicity, and a LLJ are lining up over the area late Monday into Monday night, with CAPE being about 0 J/kg, no severe weather is expected over the U.P. with this system; the threat is further south in Wisconsin. That being said, while the energy within the atmosphere is lacking for severe convection, with PWATs reaching up to 2.00 inches in spots (highest along the WI border) and with abundant synoptic-scale forcing available, some heavy rainfall could be seen across the area Monday evening to Tuesday morning; the mean NBM has generally a soaking (1 inch) rainfall event across the entire U.P. late Monday through Tuesday morning, with the probabilities for an inch or more of rainfall at any spot in the U.P. ranging from 40% to 70%. Hopefully, this system rainfall will lead to drought improvement across the area as severe to even extreme drought in the far west holds across portions of the U.P. still. Outside of the rainfall, expect windy conditions with the occluding front's passing and behind it; expect to see southerly winds of 25 to 35 mph Monday night with the occluding front followed by westerly wind gusts of 40 to 50 mph along the Lake Superior shoreline behind it on Tuesday (a Wind Advisory may be needed for the Keweenaw Peninsula in the future if the forecast holds).

Expect flattening ridging to move back into the area for the mid- week as near normal temperatures and dry conditions dominate. We could see some more patchy frost over the interior west on Tuesday night, but uncertainty on that is still high at this time given that it's 3 days out and the incoming rainfall late Monday. We may also see rainfall one more time late next week, but given the high pressure ridge projected over the Southeastern U.S., there are some doubts on if any shortwave activity will move over the U.P. or not. Regardless, expect near normal temperatures to continue through the end of the week.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 713 AM EDT Sun Sep 13 2026

VFR conditions prevail through the forecast period with just some high cloud cover over the area so far. A weak disturbance moving through, and chilly air over the lake, may touch off some lake enhanced rain showers, but confidence is too low to include in the TAF. Cigs may lower to FL035-060 during this time but are expected to stay VFR. West-northwest winds become gusty again this afternoon, gusting to 25 kt at KIWD and KSAW and 30 kt at KCMX. Winds will diminish below 10 kt Sunday evening, and though skies largely clear out, dry air is limiting the potential for fog development early Monday.

MARINE

Issued at 221 AM EDT Sun Sep 13 2026

Lake Superior: WNW winds of 20 to 30 knots this morning dwindle to 20 to 25 knots by the mid-morning hours, before reinvigorating to around 30 knots with some gale force gusts up to 35 knots being seen along the southern shore and Keweenaw through the afternoon hours. With high pressure ridging building back in by this afternoon, expect the winds to weaken back down to 20 knots or less again tonight and to remain that way until Monday afternoon. As a warm front approaches the area on Monday, expect the winds to increase from the southeast and south ahead of it later in the day, with southerly gales of 35 to potentially even 45 knots being seen across most of the lake Monday night as the warm front starts to occlude with the cold front. While some rumbles of thunder may be heard with the passage of the occluding front, no severe weather is expected. Behind the front, expect the winds to veer westerly, increasing to gales of 40 to 45 knots once again across the entire lake on Tuesday; some storm force gust up to 50 knots could be seen near the Keweenaw Peninsula, the latest available LREF at the time of this writing (12z from Sept. 12th) shows up to around a 20% chance of this occurring. As a flattening high pressure ridge begins to move into the area for the middle of the week, expect the winds to weaken back down to 20 knots or less by late Tuesday night, remaining that way until potentially next weekend.

Northern Green Bay and northwestern Lake Michigan: Winds of generally 15 knots or less increase to WNW winds of 15 to 25 knots this afternoon before dying back down to 15 knots or less again late tonight. The lighter winds remain until an approaching warm front on Monday increases winds from the south during the afternoon hours. As the front occludes Monday night, expect the southerly winds to become maximized to gales of 35 to 40 knots. In addition to the gale potential, some rumbles of thunder could be heard during the overnight hours. However, no severe weather is expected. While cold air advection does work into the area on Tuesday, with the better CAA over Lake Superior, expect the winds to slowly dwindle with time as they veer, eventually becoming 15 knots or less again Tuesday night as flattening high pressure ridging builds into the Upper Great Lakes. Expect the winds to remain light through the middle of the week and potentially even into next weekend.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Frost Advisory from 2 AM EDT /1 AM CDT/ to 9 AM EDT /8 AM CDT/ Monday for MIZ004-009-010.

Beach Hazards Statement through this evening for MIZ006.

Lake Superior... Gale Watch from late Monday night through Tuesday afternoon for LSZ162.

Gale Watch from Monday evening through Tuesday evening for LSZ240>251-263>267.

Lake Michigan... Gale Watch from Monday evening through Tuesday morning for LMZ221-248-250.