textproduct: Marquette

KEY MESSAGES

- Cooler than normal temperatures today through the rest of the work week.

- Up to 35% chance of frost impacting the early portion of the growing season Friday AM.

UPDATE

Issued at 254 AM EDT Tue May 19 2026

The going forecast remains on track this morning as the prior day's downward trend in the thunderstorm forecast for the early morning hours this morning proved correct with KMQT radar returns showing a broken line of showers with scattered thunder, mostly clustered in Baraga County and along the state line adjacent to Iron County as of 6Z. Elsewhere, fog is observed ahead of the cold front as moisture- rich easterly and southeasterly flow upslopes from Lake Michigan and upslopes towards the higher terrain of the west half. As the front mixes the boundary layer and winds shift to be out of the northwest, some low stratus and slight chances (mainly 15-30%) of lingering showers is forecast but fog is not expected to persist, so the Dense Fog Advisories will be allowed to gradually expire from west to east as originally intended.

Otherwise, the main impactful weather will be the remnant gusty conditions and choppy waters creating conditions hazardous to small craft today and the potential for frost for the morning of the 22nd with the resumption of frost/freeze headlines as agricultural growing season approaches. Despite high pressure dominating the local weather pattern for the work week, cold advection in the wake of the passing trough results in 850mb temperatures being in the 25th percentile or lower relative to the climatology of 850mb temps for this time of year, translating to surface temperatures that are up to 5-10 degrees below normal. The LREF shows up to 35% chances of Friday morning's low falling to 36 or lower, with the NBM deterministic low around that temperature for much of the interior UP.

DISCUSSION

Issued at 331 PM EDT Mon May 18 2026 Amended at 254 AM EDT Tue May 19 2026

Quiet and benign weather follows the ongoing passage of a cold front for most of the remainder of the week.

Isolated to scattered showers linger into today, however instability will likely be elevated and only briefly uncapped in the east/south-central for a few hours at best. Thunder is in the forecast, but strong to severe storms are not expected. Highs in the east half today will be in the upper 50s to upper 60s, lower in the northwestern UP where mid 40s to mid 50s are expected.

From there, the low departs to the northeast and high pressure over the Plains replaces it. This maintains over the Great Lakes through most of the work week yielding dry weather until the weekend. Lingering troughing aloft keeps colder northwest flow through Wednesday, resulting in temps between 5-15 degrees below normal; highs in the 40s and 50s and lows in the 30s. A warming pattern is then expected toward next weekend as mid level ridging slowly builds over the southeast and extends up into the Great Lakes. Another trough over the Rockies on Friday looks to move toward the Upper Great Lakes during the weekend, bringing back precip to the UP. Instability with this is lacking, so impactful strong to severe storms are not anticipated.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 702 AM EDT Tue May 19 2026

In the wake of a cold front, damp conditions are leading to LIFR conditions at SAW and MVFR conditions at CMX as of 11Z, though CMX did spend much of the overnight period at airport minimums. While chances of further precipitation after 12Z are 20-40%, the atmosphere dries out after noon and conditions improve to at least MVFR at all sites, though lingering ceilings will prevent a clearing to VFR until overnight tonight at the soonest. With the front past IWD/CMX, northwest winds will continue throughout the period, with SAW still observing southerly winds until the front fully passes this morning.

MARINE

Issued at 331 PM EDT Mon May 18 2026 Amended at 254 AM EDT Tue May 19 2026

A low pressure moves northeast over Upper Michigan and Lake Superior today. This tightens the pressure gradient and increases northeast winds over the west and north- central portions of the lake to 20-30 kts early this morning. As the low moves overhead, winds become northwest and strongest winds shift from the west half to the east as colder air moves in. Probabilities of gales to 35 kts are 25% or less, highest in the east this afternoon. Showers and storms are expected with this system into this morning, however severe storms are no longer expected. This rainfall will prolong fog over the east into this morning. High pressure returns winds to 20 kts or less by Wednesday afternoon, winds likely maintain light into the weekend.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... None. Lake Superior... Dense Fog Advisory until 11 AM EDT this morning for LSZ244- 264>266.

Dense Fog Advisory until 8 AM EDT this morning for LSZ245>251.

Dense Fog Advisory until 2 PM EDT this afternoon for LSZ267.

Lake Michigan... Dense Fog Advisory until 1 PM EDT this afternoon for LMZ221- 248-250.