textproduct: Marquette

KEY MESSAGES

- Dry weather expected through much of the workweek.

- Warmer than normal temperatures persist through the end of October.

DISCUSSION

Issued at 210 AM EDT Tue Oct 20 2026

Early morning GOES WV imagery and RAP analysis show the 500 mb zonal flow spanning much of the northern tier of the CONUS. Upstream, a deep trough is noted along the Pacific Coast. At the surface, high pressure holds over Ontario and the Great Lakes. This sets up more favorable conditions for radiative cooling than last night, yielding temps in the upper 20s to mid 30s away from the lakeshores. Tds suggest that lows will be a few degrees colder with interior areas reaching into the mid to upper 20s yet this morning.

High pressure and zonal flow dominate the remainder of the work week with continued unseasonably warm afternoon temps in the upper 50s to 60s (10-15 F above normal). Lows will be near to slightly warmer than normal (~5 F above normal) courtesy of partly cloudy to mostly clear nights allowing for better radiative cooling processes to offset the positive height anomalies and warmer airmass overhead.

A shortwave tracks to the north on Wednesday with an associated weak sfc low moving over Hudson Bay. This sends a weak cold front through the area, but likely only results in increased cloud cover or brief periods of sprinkles as model soundings indicate lackluster and quick passing moisture. Probability of measurable precip: <15%.

The better, albeit still low, chances for precip (15-25%) hold off until late weekend. The aforementioned deep trough along the Pacific Coast forms a closed low and spins relatively in place through mid week before moving eastward on Thursday. The now deep trough splits, with the northern stream pivoting northeast to the Canadian Prairie by Saturday. This broader troughing pattern then shifts east over Canada through early next week when discrepancies arise in the resulting sfc pattern. Two main solutions are present. The first scenario: a deeper more progressive sfc low closer to the UP. The second scenario: not quite as strong of a low with a slower and further north track. Both scenarios set up unseasonably warm temps from southerly flow (10-20F above normal), but details on winds are murky. Cluster analysis reveals the progressive and gustier solution is primarily favored by the GEFS (70%), but does have ~20% of the EPS members. This solution could lead to elevated fire weather conditions, particularly on Sunday when post-frontal westerly winds and subsidence combine for drier and gusty conditions. Widespread, appreciable rainfall is not expected.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 704 AM EDT Tue Oct 20 2026

Expect mostly light southerly winds only briefly exceeding 10 kt at SAW (or gusting above 15 kt at CMX) this evening/tonight. The highest chances of FG formation are at SAW, where a few models are forecasting dense FG, but as winds are a little too high for traditional radiation fog formation, model confidence in FG formation has fallen from above 30 percent to below 20 percent, so no deviation from VFR is noted in this TAF issuance.

MARINE

Issued at 210 AM EDT Tue Oct 20 2026

High pressure will dominates the forecast through Friday with winds mainly below 20 kts on both Lake Superior and northern Lake Michigan. An exception to this is south becoming southwest winds gusting up to 25 kts tonight ahead of a cold front on Lake Superior, mainly along and east of the Keweenaw. A stronger low pressure system tracking to the north of Lake Superior this weekend alongside its stronger cold front bring back a longer period of southerly 20- 30 kt winds late Friday through Saturday, veering west for Sunday in the wake of the cold front. 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.