textproduct: Marquette

KEY MESSAGES

- Showers and thunderstorms pass over the UP today through Thursday AM, with the highest rain totals expected in the south half. There is a Slight Risk (category 2 out of 4) 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.

UPDATE

Issued at 245 AM EDT Wed Jul 8 2026

The going forecast remains on track this morning. Similar to last night, MRMS reflectivity mosaic shows a rather robust line of thunderstorms draped across MN, but the nearest detected lightning is still nearly 100 miles WSW of Ironwood at 06Z, so impacts to the UP prior to 12Z are looking minimal. RAP analysis shows mostly zonal flow from Quebec to the Dakotas at the base of a deep closed low over Hudson Bay. A subtle shortwave over the western Dakotas will pivot through this zonal flow and be the forcing supporting not only the ongoing disturbed weather upstream, but also showers and thunderstorms today through Thursday morning.

The biggest chance in the 00Z HREF for today's rainfall is the southward shift of the heaviest axis of total QPF by about a tier of counties. The zone with mean QPF accumulation over 0.5 inches is now limited to the MI/WI state line and the counties bordering Lake Michigan, with Menominee County and western Delta County seeing the highest chances at over an inch of rain at 40-60%. This has resulted in the WPC Slight Risk for Excessive Rainfall shifting to just covering the south-central UP. Also covering the south-central UP is a Marginal Risk of severe weather as instability has trended upwards somewhat with HREF mean SBCAPE climbing to 750-1000 J/kg in the south-central with 30-40 kt of mean 0-6km shear and around 100 m2s2 of 0-3km SRH. As the surface trough struggles to depart from the Upper Great Lakes, some light rain showers may (~30% chance) over the south-central and Lake Michigan-adjacent communities into Thursday morning.

A quieter pattern then settles in for the late week and beyond as robust ridging sets up over the central CONUS (500mb heights above the 99th percentile of climatology over the Northern Plains by Sunday). This puts the UP in northwesterly flow aloft, which will initially keep temperatures close to normal, but as the upper ridge gets closer to the UP by early next week, the high heights lead to warmer temperatures, with the NBM deterministic even calling for 90s for the typical warm spots on Monday. Precipitation forecasts are too widely spread to divert from the NBM with this forecast package.

DISCUSSION

Issued at 401 PM EDT Tue Jul 7 2026 Amended at 245 AM EDT Wed Jul 8 2026

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 today and into Thursday. As flow becomes strongly zonal, this embedded wave brings vorticity maxes overspreading the CWA throughout today. 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 today, 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 today 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 /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 121 AM EDT Wed Jul 8 2026

VFR conditions for most of tonight begin to deteriorate into the pre- dawn hours as a batch of showers, possibly with some thunder, approach the area. This will cause the flight category at all terminals to drop to MVFR, first closer to 10Z at IWD and then from 12-15Z at CMX and SAW. Ceilings lower further to IFR mid to late morning. Rain showers taper off at IWD and CMX Wednesday afternoon with a gradual improvement to VFR, but additional showers and storms will be possible at SAW into the evening. MVFR restrictions linger at SAW the rest of the forecast period. 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 Amended at 245 AM EDT Wed Jul 8 2026

Light winds prevail on Lake Superior and the Bay of Green Bay through the period. Periods of rain and thunderstorms will be over the lake 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.