textproduct: Marquette

KEY MESSAGES

- Scattered showers and thunderstorms move eastward with a cold front over central and eastern Upper Michigan through this evening.

- Additional scattered showers and thunderstorms are possible across mainly central Upper Michigan tomorrow with minimal rainfall totals.

- Seasonable temperatures are expected through next week with the exception of slightly below normal temperatures Sunday and Sunday night.

DISCUSSION

Issued at 319 PM EDT Fri Aug 21 2026

Afternoon RAP analysis indicates the weak sfc low has made it over central Lake Superior, opening up into a trough which extends northward into northern Ontario. Sfc obs place the cold front just past the far western UP with temps in the upper 60s to mid 70s ahead of it. Tds in the low to mid 60s support SBCAPE in the 500-1500 J/kg range, but lapse rates are unimpressive. Bulk shear is also below 25 kts, so strong to severe storms are not expected. Latest radar mosaic has showers along this boundary with Day Cloud Phase RGB satellite imagery showing glaciation and GLM/ground networks indicating lightning activity is just starting. These are expected to progress eastward through this evening before diurnal instability decreases and lingering convection falls apart. PWATs of ~1.3 inches indicate some isolated higher amounts up to 0.5 to 1 inch are possible (30-50% chance, highest central UP), but most likely accumulations will be less than 0.25 inches.

In the wake of this front, isolated showers and a few rumbles of thunder are possible (15-30% chance) with a shortwave and limited elevated instability tonight. Lows settle into the upper 40s to low 60s, coldest interior west. Additional scattered showers and weak storms are possible on Saturday as another cold front and shortwave drop southeast overhead. That said, CAMs are even less impressed with this round. Outside the south-central where some spots could reach up to 0.25 inches, accumulations remain below 0.1 inches. Highs will be in the upper 60s to mid 70s.

Temps continue to decrease this weekend, bottoming out Sunday as a mid level trough deepens over the Great Lakes. CAA lowers 850 mb temps to between 3-6C, yielding highs in the 60s to low 70s and lows in the 40s to mid 50s. Some interior spots likely will dip back into the upper 30s Sunday night. Northerly winds are expected to gust up to 20 mph on Saturday and between 20-30 mph on Sunday, highest east...particularly near Lake Superior. High pressure moving in from the west keeps weather dry through Monday, likely through most of Tuesday as well before the next mid level trough moves through the region. This brings back shower and storm chances for Tuesday night and Wednesday, then dry weather is favored the rest of the work week.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 727 PM EDT Fri Aug 21 2026

Weak low pressure continues to bring a few areas of showers over the central UP this evening. Low stratus trailing the showers was bringing MVFR cigs to CMX but conditions should improve to VFR over the next hour as satellite shows a well defined clearing line approaching the Keweenaw Peninsula. A few showers will impact KSAW with MVFR conditions over the next hour and a period of MVFR cigs through late this evening as the low stratus moves through. For late tonight through Saturday afternoon expect mainly VFR conditions. Isolated showers and perhaps a thunderstorm are expected over the western and central U.P. on Saturday afternoon but with the isolated nature there is too much uncertainty to included in the TAF at this time.

MARINE

Issued at 348 PM EDT Fri Aug 21 2026

Lake Superior - Northwest winds behind a cold front increase on Saturday to 20-30 kts over the east half of the lake by late afternoon, strongest near the south-central shores. Gusts approach 20 kts over the west. As winds become more northerly Saturday night behind a second cold front, central lake superior winds increase to 15-25 kts; the stronger winds to 30 kts over the east persist. This holds into Sunday morning before winds gradually simmer down from west to east into Sunday night. This builds significant waves of 3-7 ft over the southeastern waters this weekend. Probabilities for gales to 35 kts are only between 15-25%, highest south of Stannard Rock and along the Marquette/Alger County shores. Winds otherwise remain below 20 kts through Tuesday before the next system brings back winds up to 20-25 kts Tuesday night into Wednesday morning.

Northern Bay of Green Bay and northern Lake Michigan - Southerly winds of 15-25 kts ahead of the cold front this afternoon drop off into this evening, becoming northwest for Saturday. Scattered thunderstorms are expected this evening, but severe storms are not expected. Winds increase to 20-30 kts this weekend as a colder airmass descends over the Great Lakes. Winds fall back below 20 kts Sunday night, remaining below 20 kts through much of next week.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Beach Hazards Statement until 10 PM EDT this evening for MIZ014.

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