textproduct: Marquette

KEY MESSAGES

- Temperatures approaching freezing Friday morning likely will result in frost away from the Great Lakes. Frost Advisories are in effect tonight into Friday morning.

- Elevated fire weather conditions are possible (40-60% chance) Friday afternoon as winds gusts increase to 20-25 mph with humidities falling into the 20s and highs in the upper 50s and 60s.

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

DISCUSSION

Issued at 312 PM EDT Thu May 21 2026

High pressure over the Upper Great Lakes gradually builds into Quebec/New England through this weekend, but holds ridging over the CWA into Saturday. This continues dry weather for most through Friday night. The colder than normal airmass will continue to impact the UP through tonight, limiting highs today in the 50s to low 60s, warmest west. Lows tonight will not be quite as cold as last night due to less optimal placement under the high pressure, a slight increase in low level moisture from last night, and light southeast winds instead of calm ideal conditions. That said, lows are expected in the 30s, coldest east. There is a 10-30% chance for low lying areas, particularly in the east, to dip into the upper 20s. Opted to hoist a Frost Advisory from 12 to 8 am EDT (11 pm to 7 am CDT) for all except the far western counties/Keweenaw. Friday brings borderline to possibly elevated fire weather conditions (40-60% chance, highest southwestern UP). Afternoon highs will be warmer, peaking in the upper 50s and 60s. Mixing brings RH down into the 20s with winds gusting up to 20-25 mph in the afternoon-early evening hours.

Attention then turns to the troughing pivoting from the Plains, moving over the Upper Midwest/Great Lakes late Friday night and Saturday. The broader trough is composed of two main waves. The more rigorous one over the Northern Plains remains MN westward and the weaker trough emanating from the Southern Plains remains southeast, tracking over the Lower Great Lakes. These features both bring weak low pressure systems with them, but the best lift remains outside the CWA. Isentropic ascent and minimal PVA scraping the west and southeastern edges of the UP will squeeze out a few hundreths of QPF into Saturday night. Probabilities for at least 0.25 inches of rain have fallen to 10-15% across the CWA except the far western spine of the UP where 20-40% remains given its proximity to the more vigorous trough.

A trailing shortwave trough on Sunday yields a 15-30% chance for showers and weak thunderstorms with a few hundred J/kg of MUCAPE available, likely less than 500 J/kg (60-75% chance), and bulk shear struggling to reach 25-30 kts. Instability increases (~50% chance for up to 1000 J/kg of MUCAPE) alongside better bulk shear up to ~30 kts supporting 15-30% chance of showers and storms in the afternoon on Memorial Day with a transient shortwave. Around 15% PoPs on Tuesday are a result of a clipper system to the north, but shear drops off to 25 kts or less as instability continues to grow. Then high pressure develops, favoring dry weather into the latter part of next week. Expect highs to warm back into the 70s to mid 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 124 PM EDT Thu May 21 2026

High pressure over the region is leading to P6SM and SKC conditions, with VFR forecast to prevail throughout the period. While winds will remain light with sustained winds only rarely exceeding 5 kt, wind directions may change significantly especially in the vicinity of the lake breeze. SE winds pick up later in the forecast period, gusting to around 15-20kts at SAW beginning early Friday afternoon.

MARINE

Issued at 312 PM EDT Thu May 21 2026

Easterly winds mainly hold 20 kts or less through Friday morning with high pressure overhead. This high pressure shifts northeast from Lake Superior through Saturday while a low pressure over the Central Plains lifts north over MN and another low pressure lifts from the Southern Plains to the Lower Great Lakes. These features straddle Upper Michigan and Lake Superior with troughing Saturday night and Sunday as they continue toward Canada. Easterly winds increase to 20-30 kts by Friday evening lakewide. Winds settle to 20 kts or less over the west half by Saturday morning, but east half winds remain elevated between 15-30 kts Friday night through Saturday. Winds fall off Saturday night as the low pressures dissipate, likely remaining below 20 kts through much of next week as high pressure returns to the Great Lakes.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Frost Advisory from midnight EDT /11 PM CDT/ tonight to 8 AM EDT /7 AM CDT/ Friday for MIZ004>007-010>014-085.

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