textproduct: Marquette

KEY MESSAGES

- Scattered showers and thunderstorms are expected this afternoon and evening. Severe weather is not expected, but heavy rainfall and minor flooding is possible with isolated rainfall amounts over 2"+ over a short period of time.

-Isolated to scattered showers linger into Saturday, mainly over the eastern two thirds of Upper Michigan.

- Temperatures fall back into the 70s to low 80s for the weekend, coolest near Lake Superior. Lower dewpoints will result in a more comfortable airmass on Sunday and Monday.

- The chance for showers and thunderstorms returns on Tuesday as a cold front approaches the area.

DISCUSSION

Issued at 247 PM EDT Fri Jul 31 2026

Early this afternoon upper air analysis and GOES-R water vapor imagery showed relatively zonal flow over the north-central U.S. with a shortwave trough closing off over MN/WI. While the strongest large scale ascent remained south of the U.P., closer to the low pressure. Clouds were spreading northeast across the area along deep moisture, with PWATs running around 1.8" (close to the 97th percentile of climo). Rain showers had been ongoing much of the day over the western U.P. along and south of a deformation axis, especially closer to the WI/MI border. Over the central and east the clouds were progressively thinner, allowing for surface heating and destabilization, with temps ranging from the low 70s west to the low 80s east. SPC RAP analysis showed 1000-2000 J/kg surface based cape over the central and eastern U.P., along and ahead of a lake breeze pushing south off of Lake Superior. A few thunderstorms were already forming in this area.

Low pressure will continue to slowly move from northern IA/southern MN to near Lake Erie through the weekend. Deep moisture and instability (~500-1500 J/kg) will remain over the area through this evening (PWATs of around 1.8" and surface dewpoints up to 70F). This will combine with an advancing Lake Superior lake breeze this afternoon to trigger thunderstorm development over the central and eastern U.P., especially over the interior along and ahead of the boundary. Elevated instability along with a notable deformation zone will also trigger showers, and possibly a rumble of thunder, on the cool side of the lake breeze boundary (Lake Superior lakeshore areas). 0-6km shear is practically non-existant, less than 10kt as the flow through the layer is very weak. This will result in slow shower/storm motion through the evening. Any showers and thunderstorms that form will be capable of very heavy rainfall rates, with HREF guidance PMM showing areas of over 2" QPF and isolated amounts to 4". Given the deep warm and moist layer and slow storm motions isolated heavy rainfall of 2+" seems reasonable. However, trying to pin down to any single location is difficult. The best chance for the more extreme rainfall rates will be ahead of the lake breeze boundary. Given the expected isolated nature of the heaviest rainfall feel a flood watch is not warranted but will continue messaging through other channels.

Showers and thunderstorms should shift to the eastern U.P. by late tonight and diminish in (rain rate) intensity. Patchy fog may develop overnight as the low levels cool along with weak flow and ample moisture. Expect a winds shift to the north slightly after daybreak. This will help clear out the fog except it may continue in the north wind upslope areas (highlands of Marquette County and the Keweenaw) and along Lake Superior should fog form over the lake tonight. Temperatures will be cooler, highs in the upper 60s north to 70s south. Locations along Lake Superior could see temperatures fall into the low to mid 60s in the late afternoon as cooler air continues to push south behind a secondary cold front. Showers will be possible as well in the east, closer to the low pressure. Additional light showers or perhaps a period of drizzle can be expected over the north-central, especially Marquette County.

Notably drier air can be expected for Sunday into Monday with dewpoints in the 50s, resulting in more comfortable conditions. Temperatures will be in the 70s on Sunday and upper 70s to low 80s on Monday (close to seasonal averages).

On Tuesday humidity will begin increasing ahead of an approaching cold front. Showers and thunderstorms may accompany the front on Tuesday but the risk for organized convection remains uncertain at this point in time, with global models showing lower instability and shear. It will fall back into the 70s for Wednesday behind the front with a rebound again on Thursday along with a slight chance for thunderstorms.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 734 PM EDT Fri Jul 31 2026

With SHRA draped primarily south of CMX, MVFR to VFR conditions are observed at 23Z. Several TSRA were observed at NWS MQT (15 NW of SAW), but lightning within the VC of SAW has been rare. Thus, will keep TS mention in a TEMPO group at SAW for now as chances of thunder fall from above 30% to near 20% after sunset this evening. Eventually, SHRA will give way to chances of FG formation overnight, with chances of at least MVFR conditions at all sites at 40-60% with chances of LIFR conditions at around 20-30%. Will give TEMPO groups of borderline MVFR/IFR vis with this issuance, though close attention will be paid to the 00Z hi-res model guidance to see if confidence increases or decreases in overnight FG. Conditions improve at CMX/IWD tomorrow with northerly winds, though SAW is up to 40% likely to see some lingering -SHRA and MVFR conditions through the day with the upsloping north to northeast winds.

MARINE

Issued at 247 PM EDT Fri Jul 31 2026

The lake will remain under a weak pressure gradient through early next week resulting in mainly light winds, 20kt or less. Thunderstorms will be possible through this evening but no severe storms are expected. Areas of fog may develop late tonight and linger into Saturday morning. Showers and thunderstorm are expected again on Tuesday but there remains uncertainty as to the the coverage and strength of the storms.

MQT WATCHES/WARNINGS/ADVISORIES

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