textproduct: Marquette

KEY MESSAGES

- Scattered showers and thunderstorms return on today, with another round likely Friday afternoon and evening. Uncertainty remains regarding precise timing and rainfall amounts in storms. Additional chances for showers and thunderstorms linger into Saturday.

- A return to hotter and drier weather is favored as high pressure returns from Sunday into next week.

DISCUSSION

Issued at 435 AM EDT Thu Jun 4 2026

Latest RAP analysis depicts a stacked low pressure system over southern Manitoba early this morning with a surface cold front extending south into Minnesota. This system will continue eastward into Ontario later this morning with CAMs continuing to depict cold frontal showers moving into the far western U.P. after daybreak. Do not expect much in the way of thunderstorm activity with this initial round of showers as instability will be rather meager through this morning, however thunder chances will increase later in the day as daytime heating yields MUCAPE values of 500-1000 J/kg this afternoon into this evening. Have doubts about the potential for any strong to severe storms as effective shear values will only manage around 20 kt or less today, and SPC has indeed removed the U.P. from the Day 1 marginal risk. Still, thunderstorms will be capable of producing locally heavy downpours as a plume of Gulf moisture sends PWAT values to around 1.5 inches by later this afternoon. That said, there remains low confidence on precipitation amounts today as CAMs continue to show significant differences with regards to placement and intensity of showers and thunderstorms. As such, HREF probs to receive a wetting rain of a tenth of an inch in any one location are still only around 50% and remain almost entirely west of the US- 41/141/2 corridor (Crystal Falls, L'Anse/Baraga, Houghton/Hancock). Meanwhile, will also have to keep an eye on fire weather concerns in parts of the eastern U.P. today where showers are not likely to arrive until later this evening. Could see some areas from eastern Alger County eastward flirt with RH values near or below 30% this afternoon with south winds gusting to 15-25 mph. Opted not to issue an SPS given the relatively localized and marginal nature of the threat, but conditions will bear watching if dewpoints are able to mix out a little more effectively and conditions become drier than expected.

The low will only make slow progress eastward along the northern shore of Lake Superior through Friday, keeping rain shower and thunderstorm chances in the forecast. The best chances for thunder will be in the interior west to southern UP, especially east of the US-41/141/2 corridor where it is less likely that the previous day's storms will have worked over the atmosphere. LREF mean SBCAPE grows to around 500 J/kg with little to no CIN with 20-30 kt of deep layer shear. Another SPC Marginal Risk day appears warranted. One big difference in the forecast on Friday is the precipitation potential, as some training signal in the showers is seen. LREF chances of over a quarter inch of rain on Friday ranges from around 25% in the north to 75% in the south, which will be a welcome reprieve from the dry soils and vegetation.

Saturday morning, showers and thunderstorms depart to the east, with the exception of up to 30% chances (NBM) of the south seeing some diurnal afternoon showers/thunder in the afternoon. Ridging then sets up, leading to a dry Sunday. Models diverge on the details of the forecast into next week, but the general pattern is ridging over eastern North America and troughing over the west, setting up a warm and moist flow pattern that will allow NBM high temperatures to climb to the 90s in the west half and keep daily 15-30% shower and thunderstorm chances in the forecast.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 748 AM EDT Thu Jun 4 2026

Weak low pressure system moving into Upper Great Lakes will bring scattered showers and thunderstorms today, beginning this morning at KIWD and spreading east to KSAW this evening. Expect VFR conditions to prevail at the sites through at least 06z Fri, handling -TSRA potential with PROB30 groups after 18z at KIWD and KCMX and after 00z at KSAW. Conditions eventually trend downward towards MVFR at all sites 06-12z Fri as another round of precipitation moves into the area. Winds primarily out of the south-southwest today, gusting to 15-20 kt at times this afternoon, then becoming lighter tonight.

MARINE

Issued at 435 AM EDT Thu Jun 4 2026

Gusty southerly winds will produce low end Small Craft Advisory criteria for the northern Lake Michigan zones including the northern Bay of Green Bay this afternoon and evening. Otherwise, winds will be mostly light throughout the period. Besides a brief period of wind gusts near 20 kt in the west in response to a LLJ, the next chances for widespread 20+ kt gusts will be Monday as the gradient tightens with various low pressure elements in the western US and a building high to the east of the lake.

MQT WATCHES/WARNINGS/ADVISORIES

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