textproduct: Marquette

KEY MESSAGES

- A pair of systems bring chances for showers today and Monday. There is a slight chance (20%) for thunderstorms across the south- central and eastern UP this afternoon. Otherwise, minimal impacts expected through Monday.

- Benign weather with cooler than normal temperatures expected through much of next week and beyond.

DISCUSSION

Issued at 344 AM EDT Sun May 3 2026

The upper level pattern remains dominated by large scale troughing centered near James Bay this morning, with an embedded shortwave noted on GOES water vapor imagery dropping into northwest Ontario. A weak clipper system is passing through the Upper Great Lakes this morning, bringing light rain showers to the UP, although little if any precipitation has been reported across the area as of 3 AM EDT Sunday. This batch of showers will continue eastward through later this morning, producing anywhere from a few hundredths to a tenth of an inch of rain before exiting the area. Warm advection will help to push highs into the 50s across most of the area today with some 60s near the WI border, also helping to keep minimum RH values a bit higher than yesterday though still likely dipping into the 30s in the interior west this afternoon.

The most notable change in the short term forecast is the introduction of a slight chance of thunderstorms to the south- central and eastern UP along a weak cold front this afternoon, as several CAMS are trying to develop a line of storms from roughly northern Menominee County to eastern Alger County and tracking southeast towards Lake Michigan later this afternoon. With the aforementioned shortwave diving southeast across Lake Superior during peak heating along with effective shear values around 40 kt, any potential thunderstorms would have at least a few things going for them, however this would also tend to be countered by a relative lack of moisture and meager instability on the order of 200-400 J/kg SBCAPE per latest HREF guidance. Nonetheless, have expanded PoPs back across the eastern half of the UP this afternoon and added a slight chance of thunderstorms to account for this possibility.

Further minor ripples in the 500mb flow and decreasing 500mb heights will resume weak shower activity over the UP for Monday as surface low pressure passes through northern Ontario. Expect similar QPF totals and (lack of) impacts on Monday, with minimal impact on the improving hydro situation as remaining flood headlines have now ended. It will be a gustier day, with NBM wind gusts up to 25-30 kt by midday Monday.

Once shower chances end Monday night, a period of dry weather ensues, with only minor diurnal rain chances (up to 30%) Thursday and beyond. Fire weather will be the focus of the weather impacts during the midweek period as NBM RHs fall to around the 30 percent mark during the afternoon hours of Tuesday and beyond, and NBM wind gusts are around 15 kt (or 15-20 mph) during those times. Sustained cool northerly flow will keep temperatures below normal, with highs generally in the mid-50s or below and lows in the 20s for the interior and around freezing at the shores of the Great Lakes.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 738 AM EDT Sun May 3 2026

VFR conditions prevail across Upper Michigan today as scattered rain showers depart to the east with a passing system. Winds shift westerly at the terminals this afternoon behind a cold front, increasing to around 10 kt with gusts to 20 kt. A few thunderstorms may form along the front over the eastern U.P. this afternoon, but those should remain well east of the terminals. Winds shift back southerly tonight as another system passes to the north, bringing LLWS to KIWD and KCMX after 06z Mon.

MARINE

Issued at 344 AM EDT Sun May 3 2026

A stagnant weather pattern defined by stubborn troughing over the James Bay region and stubborn ridging near the East and West Coast will lead to few chances for gusty winds and high waves. In fact, the one forecasted period of wind gusts exceeding 20 kt begins tonight and lasts through Tuesday afternoon in response to a surface low cutting through northern Ontario. This will initially lead to southwesterly winds gusting to near 25 kt late today through early Monday then becoming westerly to northwesterly late Monday through mid Tuesday following the passage of another cold front. Waves look to build to 4-6 ft Monday morning through Tuesday evening as a result. Chances of gales with this system have increased to around 30 percent.

MQT WATCHES/WARNINGS/ADVISORIES

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