textproduct: Marquette

KEY MESSAGES

- A Beach Hazard Statement is in effect today for the shorelines of Marquette and Alger Counties due to strong winds and high waves creating dangerous rip currents and swimming conditions.

- Spotty light lake effect rain showers/sprinkles are possible over the east half through this evening.

- The next chances for widespread showers and thunderstorms arrives in the west Tuesday PM, spreading east overnight and ending for most late Wednesday.

- Seasonable temperatures are expected through the week with the exception of slightly below normal temperatures today and tonight. Some patchy frost is possible in the typical cold spots and elevated surfaces in the interior west tonight.

DISCUSSION

Issued at 228 PM EDT Sun Aug 23 2026

Late morning GOES-East Day Cloud Phase RGB imagery and KMQT radar reflectivity show a few bands of isolated to scattered light rain showers this morning over mainly the central UP with bands of clouds across the rest of the UP. Temperatures at 850mb of around 5 C are above a Lake Superior that ranges from 12 C to 20 C, which ranges from "good enough for lake effect clouds" to "good enough for lake effect showers", reflecting the variable effects of lake effect that is ongoing this morning. Impacts will be low to none as the showers are not particularly intense, but it may keep temperatures from breaking out of the 60s today for all except for the south-central and Isle Royale which will see less clouds today. The brisk northwesterly flow today will continue, and the wind-driven waves of 5-7 ft east of Marquette from 1-5 miles out from the shores will drive a high risk of dangerous swim conditions including rip currents.

RAP analysis shows a 1004mb low pressure over the Ontario/Quebec line with broad 1018-1020mb high pressure stretching from far northwestern Ontario to Missouri. The low is vertically stacked with deep 500mb troughing extending over much of eastern North America, opposed by a 500mb ridge spanning from the Four Corners region to the Canadian Prairie. While the trough will not be moving much tonight, the ridge axis will pivot from the Canadian Prairie towards the Manitoba/Ontario line, which will advance the high pressure towards the UP and clear out skies for most after 00Z. As the high brings relaxing winds, efficient radiational cooling will allow temperatures to plummet in the interior west tonight, with a few interior western locations reaching the mid 30s (wouldn't be surprised if Alberta Ford Center or other traditional cold spots dipped to freezing). This will result in some patches of frost (especially on elevated surfaces or low spots where cold air pools), however, with the prior August heat still hanging on in the soil temperatures, widespread frost is not forecast, so an advisory will not be sent this shift. However, some caution should still be taken for those in the interior west with sensitive vegetation. Also, with temperatures falling overnight, a few patches of fog cannot be ruled out in areas sheltered from the wind in the west (around 20% chance).

As high pressure establishes itself over the region, dry weather and seasonable temperatures are expected Monday into Tuesday. Meanwhile, a 500mb trough currently over eastern Washington and southeast British Columbia will complete its journey around the northern periphery of the western CONUS ridge, arriving around the Northwest Angle Tuesday afternoon. This will drive significant PVA and also support a surface low of 1005-1010mb arriving near western Lake Superior by 00Z Wednesday. Moisture advects into the region ahead of the cold front and PWATs climb to 1-1.25 inches. Directional wind shear will certainly be present as southerly to southwesterly low level flow is contrasted with the westerly to northwesterly flow aloft, though speed shear is somewhat lacking as LREF 500mb winds by 00Z Wednesday around the interior west are only around 25 kt. Instability is likely going to be sufficient for thunderstorms as Euro ensemble MUCAPE is 40-60% likely to exceed 750 J/kg for the far western UP by 00Z Wed. Instability probabilities fall off overnight, but by 18Z Wed, mean MUCAPE values for the east half are widespread over 1000 J/kg, though uncertainty in the available forcing by Wednesday afternoon to realize such an uncertain airmass (and paltry shear profiles to organize buoyant updrafts) casts doubt on the severe weather potential, though unorganized thunderstorms with plenty of available moisture can still bring notable rainfall, with the LREF probability of 0.5+ inches of rain by 06Z Thursday widespread 40-70%.

With 850mb temperatures around 60% likely to fall to around 8 C, some lingering light lake effect showers (or at least, cloud cover) is possible for Thursday into Friday. Models diverge on solutions beyond then as different members of different ensemble suites handle the persistent Four Corners ridge and troughs over Hudson Bay and southwestern Canada differently, but at least some period of ridging seems reasonable to bring dry weather to the UP to kick off the weekend before the next ridge-riding shortwave arrives.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 207 PM EDT Sun Aug 23 2026

Mainly VFR conditions are anticipated at all three sites for the period, with the exception of visibility restrictions at IWD prior to dawn and MVFR ceilings at SAW this afternoon due to to lake enhanced clouds and showers. At KIWD, LAMP LIFR ceilings and visibility probabilities run around 15% for the pre-dawn period; given very low winds and a moist atmosphere, included BR in TEMPO group for this site. At KCMX, gusty northerlies lay down a bit overnight. At KSAW, expecting ceilings to bounce between VFR and MVFR this afternoon as showers are generated from onshore northerly flow; these should clear out as diurnal heating increases throughout the day.

MARINE

Issued at 228 PM EDT Sun Aug 23 2026

Northwest wind gusts continue especially over the east half of Lake Superior at 25-30 kt into tonight, with European ensemble probabilities of gales at 15 percent or less. Wind gusts linger around 20-25 kt early Monday before falling below 20 kt Monday afternoon through Tuesday afternoon with high pressure settling over the region. Southerly to southeasterly wind gusts of around 25 kt pick up Tuesday night ahead of an approaching cold front, with winds turning northwesterly behind the front by Thursday morning, including a few gale force gusts to 35 kt possible (20-40% chance particularly south of Stannard Rock). Winds quickly relax below 20 kt Thursday night into Friday as uncertainty in the forecast grows into the weekend. Along the midweek cold front will be 20-40% chances of thunderstorms. Ongoing waves of 4-7 ft fall below 3 ft Monday afternoon before increasing again to 4-7 ft in the southeast part of the lake Thursday morning through Thursday night.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Beach Hazards Statement until 10 PM EDT this evening for MIZ005-006.

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