textproduct: Marquette

KEY MESSAGES

- Above-normal highs Thursday and Friday wrap up the work week.

- Precipitation (30-80%) and thunderstorm (up to 30%) chances arrive Friday afternoon and evening, with localized heavier rainfall. Severe weather is not expected.

DISCUSSION

Issued at 346 PM EDT Wed Aug 5 2026

Today, visible satellite and RAP analysis show high pressure building into the region behind yesterday's trough, now sitting over Lake Michigan and Michigan's lower peninsula. Temperatures are reaching into the high 70s across the UP, except for some coastal locations with light onshore winds and subsequently lower temperatures in the high 60s and low 70s. While today's highs are expected to remain very near climatology, anticipate slightly above normal highs in the low- to mid-80s for tomorrow and Friday. This will be due a shot of warm low-level air detaching itself from Four Corners high and riding southwesterly flow to Upper Midwest ahead of an embedded shortwave. In addition, weak ridging & anticyclonic flow will lead to southerly winds over the UP, resulting in downsloping on Lake Superior shorelines. Thus, expect the highest temperatures to be found along the Lake Superior shoreline for the next two days.

At a larger scale, GOES water vapor imagery shows that the mid-level Canadian low has set up in conjunction with a Four Corners high, leading to SW'ly geostrophic flow over the region. As weak ridging today yields to a relatively tight pressure gradient on Thursday morning ahead of an embedded shortwave, land areas may see periods of higher-than-normal wind speeds. Friday looks be the day of highest winds, with widespread southerly gusts at 20-25 mph during the afternoon ahead of a cold front.

Friday's embedded shortwave brings with it notable precipitation and thunderstorm chances in the afternoon and evening. For moisture, the EPS and GEFS have 1-1.5" of PWAT while the CMCE has over 1.5". The NBM runs from 24 hours previous have upped the 6-hr (18Z-00Z Friday) mean QPF totals from 0.02"-0.13 to 0.02"-0.40". The NBM 90th percentile distributions remain around 0.50", and localized maximums sit upwards of 1". High PWATs, the trend in recent model runs, and high-end totals lend confidence to the possibility of localized higher rainfall during the afternoon and evening hours. For severe potential, the ingredients are in place but largely lacking in magnitude. While good model agreement exists that the UP will be under RR entrance region of an upper level jet Friday afternoon, the speed of this jet is lackluster and positioning yields only speed shear. NBM mean MUCAPE for Friday at 00Z shows just upwards of 1000 J/kg with 30 knots of 0-500mb shear. Clear skies ahead of this may increase daytime heating and lead to better convection chances later in the day, but as of now, the CWA is categorized in SPC's Day 3 General Thunderstorms group.

For the weekend, given the slow-moving Canadian low to the north, SW'ly mid-level flow veers to zonal. Subsequent shortwaves bring periods of some low chances of precipitation and thunderstorms Saturday through Monday, and temperatures should be close to seasonable.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 136 PM EDT Wed Aug 5 2026

Wind shifts will be the main focus as westerlies shift to the south tonight. However, with winds only in the 5 to 10 kt frame, impacts will be minimal. The outlier will be a slight uptick in gusts to 20 kts at IWD tomorrow morning. Otherwise, VFR will be the prevailing flight category. Cannot rule out a period of fog again at IWD tomorrow morning, but will not mention until confidence increases.

MARINE

Issued at 346 PM EDT Wed Aug 5 2026

For Lake Superior, light winds begin to pick up from the south throughout the night tonight, veering to SW'ly and reaching gusts of 15-20 knots over the open lake by mid-morning Thursday. This pressure gradient flow remains from the southwest and peaks during the early morning hours on Friday ahead of the cold front, with gusts to 30 knots over the open water mostly between 02 and 08Z. With frontal passage Friday afternoon/evening, rain and thunderstorms are likely and winds shift westerly and gusts decrease to 15 knots. Winds remain westerly up to 20 knots through Saturday evening, and up to 15 knots on Sunday. Waves build to 3.5 feet on the open lake on Thursday afternoon, then peak near 5 feet Friday morning before diminishing throughout the day. After this, waves remain below 2.5 feet through Sunday.

For the Bay of Green Bay and northern Lake Michigan, southerly flow will pick up to 15 knots for a brief period Thursday evening. Friday evening ahead of the frontal passage, winds pick up to 20-25 knots for several hours, accompanied by rain and thunderstorm chances. After this, winds remain light (<10 knots) through the weekend. Waves are less than 1.5 feet the entire period, except for overnight on Friday when they approach 3 feet in northern Lake Michigan and 2 feet in the northern part of Bay of Green Bay.

MQT WATCHES/WARNINGS/ADVISORIES

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