textproduct: Marquette

KEY MESSAGES

- Cooler than normal temperatures through Friday. Widespread frost expected tonight. Areas of frost possible Thursday night (30-50% chance).

- Dry weather through Friday is followed up by light rain this weekend.

DISCUSSION

Issued at 323 PM EDT Wed May 20 2026

High pressure has moved in over the UP today and will continue to reside over the Great Lakes into the weekend. This keeps dry weather going through Friday. Low level CAA has limited warming today with current obs showing a range of 40s and 50s, warmest south-central. A few colder spots in the 30s are noted near Lake Superior. This cooler than normal airmass will reside overhead into the weekend, keeping highs in the 50s and 60s Thursday through Saturday. Coldest lows are expected tonight with dry air in place, subsidence and clear skies favoring radiative cooling processes. Opted to hoist a a Frost Advisory for most of the CWA tonight into Thursday morning. Went with a Freeze Warning for for Luce County where widespread temps remain below 32F the longest. Lows Thursday night will be slightly warmer than tonight in the 30s; additional Frost Advisories may be needed into Friday morning. The other thing to monitor is fire weather conditions. Mixing on Thursday and Friday suggest RH in the interior dipping into the 20s. That said temps are marginal both days and wind gusts only reach 20 mph on Friday, so borderline elevated fire weather conditions are the high-end solution.

Attention then turns to the troughing over the Plains on Friday. This collection of waves pivots northeast Friday, moving overhead on Saturday. At the surface a weak low moves from the Southern Plains into the Lower MI vicinity while a secondary low moves from the Central Plains to MN/IA before dissipating. Better ascent straddles the UP, but some light showers are likely. NBM probabilities of 0.25 inches of rain in 24 hours are 25-50%, highest near Lake MI, south- central, and along the western Spine of the UP.

Next week brings a warming trend as a strong mid level ridge builds over the Great Lakes. A trailing shortwave on Sunday leaves 15-25% PoPs in the forecast before favoring drier weather high pressure returns to the Great Lakes on Monday. Expect highs to warm back into the 70s and 80s for most early next week, cooler 60s by the lakeshores. Lows rise into the mid 40s to 50s. Forecast confidence quickly falls off by late next week as models struggle to resolve a closed low that develops over the west CONUS.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 659 PM EDT Wed May 20 2026

With high pressure passing through the Upper Great Lakes, VFR conditions and light winds continue over the U.P. tonight through Thursday.

MARINE

Issued at 323 PM EDT Wed May 20 2026

High pressure keeps winds variable below 20 kts through Friday morning. A low pressure system lifting into the Great Lakes on Saturday increases easterly winds between 15-25 kts late on Friday, continuing through much of Saturday. Winds settle below 20 kts Saturday night, once again remaining light and variable below 20 kts into next week as high pressure returns to the Great Lakes.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Frost Advisory from 11 PM EDT /10 PM CDT/ this evening to 9 AM EDT /8 AM CDT/ Thursday for MIZ001>006-009>014-084-085.

Freeze Warning from 11 PM this evening to 9 AM EDT Thursday for MIZ007.

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