textproduct: Marquette

KEY MESSAGES

- Areas of dense fog this morning in eastern Upper Michigan.

- Mostly dry weather expected through Saturday.

- Overall warmer than normal temperatures persist through the end of October. However, a period of cooler weather is possible early next week.

DISCUSSION

Issued at 331 AM EDT Wed Oct 21 2026

Early morning GOES WV imagery and RAP analysis show zonal flow aloft with a trough upstream over Manitoba and a closed low over Pacific off the coast of CA. High pressure ridging extends overhead at the surface, keeping skies mostly clear and winds calm. Increasing cloud cover over the west will limit further cooling this morning, but the interior central should settle a few degrees yet. Cool and calm conditions alongside weak southerly flow off Lake MI and ample low level moisture has resulted in patchy fog in the central UP with more widespread fog coverage in Delta, Alger, and Schoolcraft Counties. Opted to hoist a SPS for areas of low visibility down to 1/4 mile at times, holding off on any Dense Fog Advisory due to the somewhat transient nature of the eastern fog noted on nighttime microphysics. Lows ahead of sunrise are expected in the mid 30s to upper 40s, coldest interior central.

The trough over Manitoba tracks east over northern Ontario and the UP today, sending a weak cold front across the area. Better forcing remains north of the CWA, but a low (15-25%) chance of showers is briefly present, passing from west to east. Measurable precip, if any will likely be sparse and limited to a few hundreths at best. The more likely scenario is a brief period of sprinkles under cloudy skies as winds shift northerly. Otherwise temps warm 10-20F above normal into the 60s, save for upper 50s in the Keweenaw.

Through the remainder of the week, the deep trough off the coast of CA lifts northeast through the intermountain west to Saskatchewan, phasing with the upper level jet. This amplifies downstream ridging building into the Great Lakes. As a result, the well above normal (+10-20F) temps continue into the weekend with widespread 60s to even low 70s in the west! With the drier airmass in place, tonight and Thursday night will only be slightly above normal in the 30s to low 40s. Increasing low level southerly flow into the weekend keeps lows in the 40s to low 50s. Low level moisture and a strengthening subsidence inversion could result in more widespread fog and low clouds developing tonight, lingering into much of the morning hours before lifting in the afternoon with diurnal heating and strengthening southerly flow.

As a low pressure tracks north of the area this weekend, southerly flow will strengthen resulting in breezy conditions Saturday, followed light westerly winds behind the cold front Sunday. While the air isn't much colder behind the initial front it will be notably drier which could result in borderline elevated fire weather conditions on Sunday. While showers will accompany the front, they are expected to remain rather hit-and-miss and appreciable rainfall is not expected.

Early next week ensembles are trending towards a period of cooler weather that could lead to at least some lake effect precipitation and high temperatures closer to or below seasonal averages. The NBM has a 40-75% chance for much of the UP to remain below 50F Monday and Tuesday, decreasing to 20-60% on Wednesday.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 114 PM EDT Wed Oct 21 2026

A cold front will push through the U.P. early this afternoon with winds shifting to the northeast by late afternoon though they will remain light. A few showers will accompany the front but did not include in the TAF as they will likely be exiting SAW by the start of the TAF period.

Tonight moisture from the Great Lakes, weak flow and strong radiational cooling will result in widespread fog development, especially over the central and eastern U.P. SAW will fall to LIFR overnight, with IFR at CMX and MVFR at IWD. After sunrise fog will begin to lift but weak flow off Lake Superior will keep improvement limited to MVFR at SAW due to low cigs.

MARINE

Issued at 348 AM EDT Wed Oct 21 2026

Winds the remainder of the work week hold around or below 20 kts on both Lake Superior and northern Lake Michigan courtesy of high pressure. A stronger low pressure tracking to the north of Lake Superior this weekend and an associated cold front bring back a period of southerly 20-30 kt winds on Saturday, veering west for Sunday in the wake of the cold front. Due to the warm southerly flow creating a more stable airmass over the lakes, gale probabilities remain low (~20-40% chance on Lake Superior and less than 10% on Lake Michigan).

MQT WATCHES/WARNINGS/ADVISORIES

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