textproduct: Marquette

KEY MESSAGES

- Scattered showers and thunderstorms may develop this afternoon and evening along the Great Lakes lakes breezes.

- Showers and thunderstorms become widespread Wednesday morning through Thursday morning. There is a Slight Risk (category 2 out of 5) of excessive rainfall and up to a Marginal Risk (Category 1 of 5) of severe weather.

- Temperatures will remain closer to normal through the mid-week, and start to increase by the weekend.

DISCUSSION

Issued at 401 PM EDT Tue Jul 7 2026

GOES water vapor and RAP surface analysis show a weak frontal boundary trailing a stout low centered over the Hudson Bay in Canada. Though this boundary led to some perfunctory convection across the WI border this morning, it has by now passed nearly out of the UP with no initiation. Clearing cloud cover has resulted in warm temperatures above 80 in most locations (in the high 80s in Menominee County) as well as an active cumulus field over the central UP. From radar imagery, a lake breeze initiated from the Lake Superior shoreline at approximately 1:30 pm, and has by now reached KI Sawyer. SPC mesoanalysis currently shows upwards of 1000 J/kg of MUCAPE across most of the CWA and up to 2000 J/kg in spots, as well as 1.1" - 1.3" of PWATs this afternoon. Between the diurnal instability and lake breeze, scattered rain showers and thunderstorms are possible in the central UP this afternoon and evening. Some spots could experience stronger storms and higher accumulations; though the 90th percentile of NBM 6-hour QPF distributions is generally only 0.25", higher amounts can't be ruled out due to adequate buoyancy and plenty of moisture.

The main story is the precipitation potential thanks to the Hudson Bay low shortwave approaching the region, which is expected to bring widespread periods of rain and thunderstorms throughout Wednesday and into Thursday. As flow becomes strongly zonal, this embedded wave brings vorticity maxes overspreading the CWA throughout the day on Wednesday. Models agree that some form of upper level lift, possibly enhanced due to rear-right entrance region positioning, will be present, though the exact placement and timing of the trailing jet streak lobe differ. Embedded within this flow is an east-west equivalent potential temperature boundary at low and mid levels which propagates slowly through the area on Wednesday, pressing from the arrowhead of MN between Tuesday evening and finally exiting southeast on Thursday midday. PWATs during this time frame are anomalously high: NAEFS ESAT table shows PWATs above the 90th percentile (1.5" - 1.75") covering the UP by 12Z on Wednesday and persisting for nearly 24 hours, with locally higher amounts (above 1.75"). Given the moist atmosphere and forcing mechanisms present tomorrow, we are outlooked in the General Thunderstorms, Marginal, and Slight categories by SPC, and in the Marginal and Slight categories by WPC's ERO. However, HREF mean SBCAPE tops out at 500 J/kg only along WI border, and HRRR shear profiles appear weak to modest at best. Thus, with lower potential for severe storms, the main concern is somewhat large rain accumulations throughout Wednesday and into Thursday. NBM shows up to 55% probability of over 1" of rain falling over a 24-hour period between Wednesday and Thursday mornings, and 6-hour distributions show that most rain will fall in the overnight hours on Wednesday evening. Though higher-end totals are below flash flood guidance, training showers and thunderstorms cannot be ruled out as the theta-E boundary aligns with flow aloft. Though flood watches are not issued at this time, this possibility accounts for the WPC's categorization of the UP within a Slight Risk.

The area dries out by midday Thursday as high pressure moves back in behind the Hudson Bay low, and temperatures should be relatively close to climate normal. Friday marks the beginning of a large ridge building over the Great Plains and extending from the Sierra Mtns to the Appalachians. Anticyclonic mid-level flow sends warm toward the Upper Midwest, resulting in very warm temperatures by Sunday

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 732 PM EDT Tue Jul 7 2026

Generally VFR conditions are expected this afternoon and evening across the area. More widespread showers along with isolated thunderstorms will move in late tonight, which will cause the flight category at all terminals to drop to MVFR after 10Z with IFR conditions likely developing at IWD by 12Z and at SAW by 15Z. Rain showers taper off at IWD and CMX Wednesday afternoon, but additional showers and storms will be possible at SAW into the evening. Generally light winds are expected through the TAF period, with the exception of the immediate vicinity of any thunderstorms that develop.

MARINE

Issued at 401 PM EDT Tue Jul 7 2026

Light winds prevail on Lake Superior and the Bay of Green Bay through the period. Periods of rain and thunderstorms commence Tuesday evening through Thursday morning, with most activity expected Wednesday morning through Thursday morning. During this time, winds may be higher near outflow boundaries, though severe storms are not expected. As high pressure builds back in on Thursday, winds lay down through Saturday afternoon. Significant wave heights are expected to be less than 1 ft. Southwesterly flow picks up to 20 knots Sunday and Monday, with gusts to 25 knots and waves to 4 ft.

MQT WATCHES/WARNINGS/ADVISORIES

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