textproduct: Marquette

KEY MESSAGES

- Temperatures falling back into the lower to mid 30s tonight will lead to a potential for frost formation again. A Frost Advisory is in effect late tonight into early Wednesday morning.

- Dry weather persists at least into the early weekend with high pressure over the area. Below-average temperatures through tomorrow gives way to above-normal temperatures late week.

DISCUSSION

Issued at 223 PM EDT Tue Sep 22 2026

Afternoon RAP analysis has steep midlevel ridging over the north- central CONUS and into central Canada, with surface high pressure of 1034mb centered over the Ontario/Quebec border. This is helping to suppress a shortwave well to our south, over northern IL, with sunny skies over most of the UP. Visible satellite does show some fair weather cumulus development over Menominee county,but this should diminish heading into the evening hours. Temperatures, meanwhile, are climbing into the upper 50s to lower 60s area-wide so far, and should peak in the lower to mid 60s for most today. Dewpoints are mixing out quite nicely, already into the upper 30s and lower 40s across portions of the interior UP. This would support some pockets where RH drops as low as 35-40% this afternoon, but light winds help to mitigate fire weather concerns.

Temperatures plummet into the 30s across the interior of the UP again tonight, coldest over the interior-west, with clear skies and light winds. Model soundings show a very dry airmass, but will note a brief period where lower-level moisture profiles show some saturation, which could support frost development and even some patchy fog. Have opted to issue another Frost Advisory late tonight into early Wednesday morning.

Dry, sunny, and quiet weather persists Thursday and Friday, alongside a slight increase in temperatures as the surface high shifts eastward and we come under mainly southerly flow. Expect highs in the mid and upper 60s Thursday, followed by warmer temperatures possibly near 70 Friday afternoon. Model soundings still support a dewpoint drop during the afternoon hours, but will note that more midlevel moisture is apparent compared to previous days. So, minimum RH should still remain above 40% for both days. Looking ahead into the weekend, latest deterministic and ensemble guidance shows the midlevel ridge axis sliding eastward into Quebec, with deeper troughing moving from the Pacific Northwest towards the prairie provinces. In between, a shortwave ejecting out of the Plains may scrape the western UP with some rain showers late Saturday into Sunday, while most of the UP likely remains dry for the remainder of the forecast period.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 724 AM EDT Tue Sep 22 2026

VFR conditions prevail throughout the forecast as high pressure to the north and northeast of the region suppresses chances of fog formation below 15%. Winds will be light and variable during overnight periods, increasing to 5-10 kt during the afternoon hours out of the northeast to southeast before decreasing again in the evening.

MARINE

Issued at 223 PM EDT Tue Sep 22 2026

For Lake Superior: East-northeast winds are on the increase again this afternoon, with gusts increasing to around 15-20kts in the western arm as well the east-central portions of the lake. Winds gradually lay down again after sunset, and then pick up again out of the east for those same spots Wednesday afternoon and evening. Correspondingly, wave heights increase to 1-2ft as winds increase during the afternoon and evening hours. Wednesday night into Thursday, winds turn over to the south to southeast, and with gusts to around 15-20kts for most of the lake overnight into early Thursday (with waves to 2-3 feet). These elevated winds become more isolated to the east-central portions of the lake into Thursday afternoon, then winds fall back below 10kts across the entire lake Friday. Southerly wind gusts up to 20kts develop again Saturday ahead of a shortwave, then winds fall back into Sunday.

For the Bay of Green Bay and Northern Lake Michigan: Easterly winds are gusting to around 15-20kts this afternoon, then gusts to 20-25 kts become more common this evening. Winds lay down slightly (gusts to 15 knots) for a brief period Wednesday morning before increasing again in similar fashion for Wednesday afternoon and night. Winds shift over to the E/SE Thursday and Friday, falling below 15kts. Waves increase from 2-3 feet in Lake Michigan this afternoon to near 4 feet this evening before subsiding to 2-3 feet Wednesday morning.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Frost Advisory from 2 AM EDT /1 AM CDT/ to 9 AM EDT /8 AM CDT/ Wednesday for MIZ002-004>007-009>011-013-014-084-085.

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