textproduct: Marquette

KEY MESSAGES

- Patchy dense fog is possible (50-75% chance) across the interior UP early this morning and again tonight.

- Additional showers and storms are possible today and early this week.

- Above normal temperatures and higher humidity is expected this week into early September.

DISCUSSION

Issued at 248 AM EDT Sun Aug 30 2026

Rain showers have mostly dwindled away and have become relegated to the southern half of the U.P. early this morning as the first shortwave has now passed through the area. While not much precipitation has been seen over the past 24 hours, enough has fallen to potentially produce areas of fog across the land before dawn this morning. However, a 'wrench' in the fog prediction is the upper-level cloud cover overhead; this cloud cover will actually limit fog development as it will weaken the inversion just above the sfc. Regardless, some spots could get down to quarter mile or less visibilities. Should this occur, then an SPS or Dense Fog Advisory could be forthcoming. As the sun rises, expect the fog to slowly dwindle away, with the U.P. becoming fog-free by the mid to late morning hours.

A second shortwave looks to move through the Upper Midwest today, with maybe some showers and weak thunderstorms moving through the area today. However, with the shortwave moving through south of the area (i.e. Wisconsin and central Lake MI), rain chances seem fairly limited, ranging from around 10% in the Keweenaw and in Luce County all the way up to 30/35% in the interior west and south central. Behind this shortwave, additional fog could form across the region tonight.

Things become more interesting during the overnight hours as a warm front 24-hours ago looking to come during the day on Monday is now slated to arrive earlier, potentially bringing heavy rain showers and thunderstorms back across the U.P. during the overnight hours. Because the warm front now looks to be coming in during the overnight hours, expect the severe weather threat to now be very low if not next to zero as instability will be limited to above the sfc inversion and the mid-levels. That being said, won't completely rule out a stronger thunderstorm or two where some sub-severe/non- damaging hail and gusty winds could be seen. In addition, some spots may actually see a wetting to even soaking rainfall from this round of convection, as the latest HREF shows a 30 to 85% chance for at least a quarter inch of rainfall with the passage of the warm front tonight through Monday; there is even up to a 60% chance for some portions of the interior west to see over an inch of rain (including Ironwood). The rainfall would also bring an end to the fog threat overnight, although fog could reform before dawn Monday morning once the rain showers and storms cease across any particular area. That being said, as the warm front continues NE late tonight through Monday, CAMs show the line of convection along the warm front breaking up and weakening with time during the early morning hours on Monday. While a second round of convection may occur via a secondary shortwave moving through behind the warm front Monday afternoon, expect this round of precipitation to be rather quick, if it even moves through at all. Thus, not as much rainfall is expected over the more NE areas of the U.P. late tonight through Monday, and flash flooding is not expected given the very dry ground.

Expect rain chances to in general decrease for the remainder of the forecast period as high pressure ridging builds back over the central CONUS and into the Great Lakes region. That being said, the latest runs of the medium range guidance do suggest that a shortwave rotating on the southern end of the ridging could move through the Upper Great Lakes this Wednesday. If the track of the shortwave is close enough to the U.P., some additional (much-needed) showers and thunderstorms could be seen across the area. Otherwise, expect mainly dry weather, although the above normal temperatures and humid conditions seen today look to continue into early September as Gulf air continues to be funneled into the region.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 701 AM EDT Sun Aug 30 2026

Expect fairly poor flying conditions over the next 24 hours compared to normal as low-level cloud cover stubbornly holds on today, before an incoming warm front brings additional SHRA and TSRA tonight (mainly over IWD and SAW). Ahead of and even behind this warm front, expect FG to develop over the terminals, dropping all of the TAF sites to LIFR or lower near the end of the period; the SHRA and TSRA may bring some vis relief from the FG as they move through, but expect lower cigs down to LIFR regardless; don't be surprised to see FG return behind the rainfall tonight. While we will eventually see an improvement to MVFR by this afternoon over SAW and CMX and potentially even VFR at IWD, expect the improvement to those conditions to take several hours (between now and this afternoon). And, once the sun sets, expect the conditions to deteriorate rapidly once more. Expect the winds to build from the E/SE with time today as the warm front approaches. The sustained winds lighten up a little but continue as they slowly veer throughout the overnight hours.

MARINE

Issued at 248 AM EDT Sun Aug 30 2026

Lake Superior: Light winds of 20 kts or less increase to NE winds of 20 to 30 kts over the western lake by this afternoon as a warm front approaches. As the showers and storms associated with the front start to move in tonight from the SW, expect the winds to dwindle over the western lake while increasing from the SE to 20 to 25 kts over the eastern half of the lake on Monday. Some stronger storms with gusty winds up to 34 kts and marginally severe hail up to dime sized could be seen over the far west this evening, but expect the shower and storm coverage as well as the marginal marine severe threat to diminish with time tonight into Monday. Expect light winds of 20 kts or less to return to Lake Superior Monday night. However, SW winds of 20 to 25 kts could return between Isle Royale and the Keweenaw on Tuesday before becoming 20 kts or less again Tuesday evening. The light winds remain until potentially late on Thursday when NE winds of 20 to 25 kts possibly return to the western arm.

Northern Green Bay and northwestern Lake Michigan: Light winds of 15 kts or less this morning look to continue until Monday. Meanwhile, some showers and storms could be seen today through tonight, with some potentially marginally marine severe weather possible tonight (gusty winds up to 34 kts and hail up to dime sized). We could see some S'rly winds of 15 to 20 kts over the area on Monday before winds return to 15 kts or less Monday evening. The light winds continue through the rest of the week, although some more showers and storms could return on Wednesday.

MQT WATCHES/WARNINGS/ADVISORIES

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