textproduct: Marquette

KEY MESSAGES

- Benign, sunny weather continues through Friday with highs near seasonal norms. There is a slight chance of showers and thunderstorms both Saturday and Sunday, but no severe weather is expected.

- A warming trend is forecast as high temperatures increase daily through early next week. Highs near or above 90 are becoming more likely from Sunday through Tuesday.

DISCUSSION

Issued at 349 PM EDT Thu Jul 9 2026

GOES visible satellite reveals mostly clear skies across Upper Michigan this afternoon, save for some pesky low stratus and fog hanging on over parts of Lake Superior and some fairweather cumulus popping up over the higher terrain of the western UP. RAP analysis shows surface high pressure beginning to build in over Lake Superior as it extends southward from Hudson Bay and northern Ontario. This will promote dry and pleasant summer conditions through Friday as high temperatures increase into the upper 70s to mid 80s across the area for Friday afternoon. Will likely see some patchy fog develop again tonight, especially in the vicinity of Lake Superior, but do not expect coverage to be as extensive as last night as the lower levels of the atmosphere trend a bit drier.

Temperatures continue to gradually increase through the weekend as expansive upper level ridging builds from the Intermountain West into the central CONUS, sending highs solidly into the 80s across the UP on Saturday afternoon and pushing 90 degrees for at least the interior areas by Sunday. Will retain a slight chance of showers and thunderstorms both Saturday and Sunday as a few weak disturbances transit the periphery of the upper ridge this weekend, but with MUCAPE only around 500 J/kg and relatively meager shear would not anticipate any strong to severe thunderstorms.

Heat remains the primary forecast concern early next week as 500 mb heights rise above 590 dam, near or above the climatological max for mid July per multiple ensemble suites, while 850 mb temps climb to 25-27 C or higher. This will likely result in widespread readings in the 90s across the UP for Monday and Tuesday, with the NBM depicting a greater than 75% chance to exceed 90 away from the immediate shorelines and even the often low-biased LREF showing a 60-75% chance in these locations. Humidity will not be as high as in the late June heat wave as low level trajectories will have more of a westerly component, but dewpoints into the 60s will still support potential 100 degree heat indexes in some interior locations per the NBM. This coupled with high overnight low temps in the 60s to perhaps even 70 degrees will correspond to a major HeatRisk across much of the UP for Monday and Tuesday. There remains uncertainty as to the duration of the heat later into the week as medium range guidance continues to hint at a strong upper trough flattening out the ridge as it moves into the vicinity of Hudson Bay Tuesday into Wednesday of next week, increasing shower and thunderstorm chances again across the area as we head into the middle of next week.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 216 PM EDT Thu Jul 9 2026

Dense fog has cleared out from all three sites, leaving VFR conditions at SAW, CMX, and IWD for the rest of today and into tonight. Winds are light and northerly during daytime hours, going calm or very light and variable around 00Z. Chances for fog redevelopment in the early Friday morning hours are nonzero; LAMP probabilities of LIFR visibility are less than 25% at all three sites and highest at CMX and SAW. Calm winds tonight will aid fog development, as will radiational cooling. LAMP probabilities for LIFR visibility are of similar magnitude to those of IFR or MVFR at all three sites 05Z-12Z, indicating that if fog does form, it could very well be dense.

MARINE

Issued at 349 PM EDT Thu Jul 9 2026

Surface high pressure building over the lake from the north will maintain light winds of 15 kt or less into the weekend. Patches of dense fog will likely linger over parts of the lake, especially the eastern half, through at least Friday morning. There is some indication that the pressure gradient will tighten across the lake early next week as string high pressure resides over the Lower Great Lakes while a strong low approaches from the northwest. This will likely result in 25-30 kt southwesterly winds over the western half of the lake during the first half of next week, with the NBM showing a 15-25% chance for a few gale force gusts Monday into Tuesday.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... None. Lake Superior... Dense Fog Advisory until 8 AM EDT Friday for LSZ248-250-251- 265>267.

Lake Michigan... None.