textproduct: Marquette

KEY MESSAGES

- Widespread fog over the central and eastern U.P. this morning. The fog will be dense at times.

- Mostly dry weather through Saturday, then low chances (20-40%) for light rain return Saturday night.

- A period of cooler weather is expected early next week as colder air pushes south across the region.

DISCUSSION

Issued at 301 AM EDT Fri Oct 23 2026

Early morning GOES WV imagery and RAP analysis show the upper ridge over the Plains, reaching over the western Great Lakes Basin with troughing over the far western CONUS and British Columbia. The sfc high pressure center is now over southern Quebec, extending ridging overhead. Radiative cooling, light southerly flow increasing low level moisture, and moisture enhancement off Lake Michigan has allowed for another night of fog. Nighttime microphysics clearly shows this over the central and eastern UP as well as in the Keweenaw where upslope flow off Lake Superior is observed. Surface observations indicate this fog is dense and the going forecast is for this to continue expanding through this morning over the central and eastern UP, thus left Dense Fog Advisories as is. Commuters should leave themselves extra time to reach their destinations. Otherwise temps remain in the 40s.

Fog slowly lifts this morning with a diminishing pattern toward northern Lake Michigan. Could see the need for Dense Fog Advisories in the east, particularly the zones near Lake Michigan, to be extended into the early afternoon. The anomalously warm airmass in place, 850 mb temps of 8-10 C, alongside positive height anomalies continue the well above normal temps. The lingering stratus in the east will complicate temp forecasts this afternoon, limiting warming into the mid 50s to low 60s (~10 F above normal). The west will be warmer in the mid 60s to mid 70s (15-25 F above normal). Otherwise dry weather with light southerly winds 5-10 mph with gusts mainly ~15 mph. Unlike the past nights, winds stay light out of the south with gusts in downslope areas around 15-20 mph. Temps settle into the 40s to mid 50s, warmest west where there is a brief low chance for light rain showers (15-20% chance).

Breezy and warm on Saturday. A low pressure tracking over northern Manitoba and Hudson Bay this weekend tightens the pressure gradient and increases winds to 10-20 mph with gusts of 25-35 mph. Strongest winds are expected in areas of south downslope flow, particularly in the eastern Lake Superior shoreline areas. 850 mb temps climb further to 11-13 C, continuing well above normal temps (+10-25 F) with highs in the 60s to mid 70s, warmest west. This combination heightens fire weather concerns, thankfully mostly cloudy skies limit Td mixing and RHs remain above 30%, limiting elevated fire weather conditions.

A cold front sweeps across the UP from west to east Saturday night into Sunday, bringing a chance (20-40%) for rain showers. Accumulations around or below 0.1 inches are expected; probabilities exceeding this amount are only 5-25%. Winds turn west behind the front with cooler near normal temps peaking in the upper 40s to low 60s, coldest northwest and warmest south-central (generally 5-10 F above normal). As drier air presses in, clouds clear and mixing lowers RHs in the west into the 20-30% range. Higher minimum RH in the upper 30s to mid 60s is expected in the Keweenaw and east. Winds look to remain under 15 mph at this time where RH is lowest (only a 10-30% chance for wind gusts exceeding 20 mph coupled with RH below 30%), limiting fire weather concerns. Will continue to monitor this period.

High pressure passes east over Ontario and the Great lakes Monday and Tuesday. Then flow aloft turns zonal, allowing for multiple shortwave troughs to track east next week into the following weekend. Guidance begins to struggle to resolve this pattern already by Tuesday night, but this likely sends a low pressure system just to the northwest of the Great Lakes mid to late next week. The shortwaves, low pressure system, and late week colder airmass yielding sufficient delta-Ts for lake effect precip keeps PoPs in most of the extended forecast. Otherwise, temps return near normal in the wake of the cold front on Sunday peaking in the 40s to low 50s Monday and Tuesday. Temps Monday night settle into the 20s to mid 30s, coldest interior west. Southerly flow returning for Wednesday and Thursday warm temps into the 50s with lows in the 30s and 40s.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 735 AM EDT Fri Oct 23 2026

Areas of VLIFR/LIFR fog continue to plague the eastern half of the UP this morning while IWD and CMX remain fog free. This will continue to be the rule for much of the morning through the early afternoon. Quarter mile fog at SAW will slowly scatter through the late morning, transitioning to IFR/MVFR stratus by the early afternoon, eventually clearing to VFR cigs by 17-18z at the latest. Breezy southerlies pick up this afternoon between 10-15 kts with gusts 15-20 kts possible at SAW. Patchy dense fog may impact SAW tonight again but has been left out of this current TAF issuance.

MARINE

Issued at 324 AM EDT Fri Oct 23 2026

Satellite imagery reveals dense fog across much of western Lake Superior as well as northern Bay of Green Bay and northwestern Lake Michigan. Fog is expected to linger through at least mid morning, but could linger on northern Lake Michigan through early afternoon before lifting to low stratus. An area over northwestern Lake Superior may linger around all day. Thus, current Dense Fog Advisories may need to be extended further today.

Southerly winds mainly remain below 20 kts through this afternoon. Then a low pressure tracking over Manitoba and Hudson Bay this weekend increase southerly winds tonight through Saturday morning to 20-30 kts, strongest over the east half of the lake where there is a 10-30% chance of gales to 35 kts. Given the warm southerly flow creating stronger stability, opted to hold off on any Gale Watch for this marginal event. Similar, but slightly weaker winds of 15-25 kts are expected on Lake Michigan. Significant wave heights over eastern lake superior rise to 3-7 ft with lower 2-4 ft over the west by Saturday night. Northern Lake Michigan waves will be 3-6 ft with waves in the northern Bay of Green Bay mostly 3 ft and less.

A cold front Saturday night through Sunday morning shifts winds westerly. Winds on Lake Michigan fall below 20 kts by Sunday morning. Lake Superior winds briefly slacken overnight before increasing to 15-30 kts on Sunday, strongest near the Keweenaw. Winds fall back below 20 kts by Monday, maintaining light through Tuesday with high pressure passing overhead. Another low pressure system tracking near the Great Lakes brings the next potential for winds exceeding 20 kts on both lakes mid to late next week.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Dense Fog Advisory until 10 AM EDT /9 AM CDT/ this morning for MIZ001-003>007-010>014-084-085.

Lake Superior... Dense Fog Advisory until 11 AM EDT /10 AM CDT/ this morning for LSZ162-263-264.

Dense Fog Advisory until 10 AM EDT /9 AM CDT/ this morning for LSZ240-241.

Lake Michigan... Dense Fog Advisory until 11 AM EDT this morning for LMZ221-248- 250.