textproduct: Marquette

KEY MESSAGES

- Temperatures remain above normal through Thursday. Widespread 80s are expected on Wednesday, approaching 90 in the far west.

- Slight risk of strong to severe thunderstorms Wednesday evening across Upper Michigan. Primary hazards are large hail and damaging winds.

- Marginal risk of strong to severe storms Thursday afternoon and evening in the south and east.

DISCUSSION

Issued at 347 PM EDT Tue Jun 9 2026

Afternoon RAP analysis and GOES water vapor imagery indicate the shortwave has made it to eastern Upper MI and northern Lower MI with a trailing weak surface trough over Lower MI. Shower coverage has significantly diminished and lingering low chances (20-40%) for light rain showers over the east continue to fall off into this evening as the two features depart to the northeast. Additional accumulations remain below 0.1 inch. The associated cloud cover has prevented significant warming in the east compared to the interior west which has already warmed into the 70s. Highs this afternoon peak in the 70s to mid 80s west and mid 60s to mid 70s in the east and Keweenaw County. The lull in shower activity persists tonight as calm conditions set up. Temps settle into the 50s to low 60s. Fog development is anticipated tonight, potentially becoming dense at times down to 1/4 mile (25-50% chance) in the east and central.

Wednesday into Wednesday night bring multiple chances for showers and storms as a closed low develops over the Canadian Prairie and Northern Plains. A warm front lifts toward the UP Wednesday morning alongside an approaching weakening LLJ from the west. MUCAPE of up to 1000-2000 j/kg, mid level lapse rates of 7-7.5C/km and shear between 25-30 kts will be supportive for convection. Severe weather is not expected with this round as forcing weakens and elevated instability/shear diminish with storm progression into the drier and capped airmass in our CWA. This ill-defined line progresses in from the west around 12Z Wednesday, dissipating over the remaining morning hours. Strong WAA brings temps into the upper 70s and 80s with a few spots in the far west reaching near 90. Gulf moisture primes the environment noted by PWATs between 1.75 to 2.00 inches (at or above the the NAEFS 99th climatological percentile) and Tds rising into the mid to upper 60s. Steep lapse rates, elevated instability, and 25-35 kts of shear once again set the stage for convection. Better lift from the upper level jet and a cold front moving in from the west leave severe potential on the table with this round, captured by SPC in their Day 2 Outlook: slight risk for the entire CWA. In addition, because of the anomalously high PWATs and warm rain processes up to around 13 kft, there still remains a Marginal Risk for excessive rainfall during this same time period. The main window of concern is 23Z Wednesday to 6Z Thursday, but forecast confidence is low. CAMs are struggling to come to agreement on placement of storms due to prior convection. Shower and storm chances quickly fall off from west to east into Thursday morning as a drier airmass moves in. Otherwise temps only settle into the upper 50s to mid 60s Wednesday night.

Thursday will be hot but less muggy than Wednesday. The NBM shows above 90% probability of high temperatures above 80F in the the majority of the eastern UP and 60-70% in the west. Chances of dewpoints above 60F remain above 50% until 13Z, when anomalously very high moisture exits the region eastward.

The ECMWF EFI for CAPE-shear shows low EFI but a SoT>0 for the southern tip of Menominee County and the eastern UP between 0Z Thursday and 0Z Saturday. This aligns with the areas highlighted in SPC's Day 3 Outlook, and indicates most ensemble members are finding solutions near climatology, but a small number of members are presenting more extreme solutions. Potential for severe weather can't be ruled out, but confidence is low. The potential of activity during this period will be driven by a strong upper-level jet streak moving over the region supporting broad lift and consequent shear, and relatively high PWATs aloft (1-1.5"), which could support heavy rainfall. Uncertainty stems from the preexisting environment left behind from the Wednesday storms, timing in the movement of the jet streak over the region, the track and timing of a relatively small surface Colorado Low fusing with the much deeper Hudson Bay low. However, NBM SBCAPE remains well below 500 J/kg Thursday afternoon through Friday morning, and any diurnally-driven higher amounts may not coincide with higher shear.

As far as rainfall goes, NBM shows 24-hour rainfall probabilities >0.5" of 50-70% across most of the eastern UP ending at 12Z on Friday. Slivers of probabilities >40% for >1" during the same time frame clip our CWA from the southeast, so higher amounts should not be ruled out.

Looking ahead to the weekend, the Hudson Bay low stalls out as it propagates slowly southeastward toward Quebec, sending multiple impulses toward the Upper Great Lakes as it does so. While high and low temperatures approach climatological normal this weekend, these shortwaves lead to rounds of showers with perhaps a rumble of thunder until late Monday, when the low moves east toward the Atlantic.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 145 PM EDT Tue Jun 9 2026

Any lingering rain showers this afternoon should stay east of TAF sites. However, MVFR conditions will linger at SAW through the evening due to abundant low level moisture. Tonight, expect FG to return to terminals, potentially bringing CMX and SAW to airport mins. Expect the winds to be light and lake-breeze influenced with an easterly component today and tonight.

MARINE

Issued at 347 PM EDT Tue Jun 9 2026

Widespread, dense fog persists this afternoon over Lakes Michigan and Superior due to antecedent rainfall, low dewpoint depressions (<5F) in the marine layer, and light winds <10 kt. Expect this fog to remain throughout the day and to intensify/expand tonight to include all offshore and nearshore zones. The potential for severe thunderstorms with rain begins tomorrow late morning over Lake Superior, with the main round of storms occurring in the evening and overnight hours. The most intense storms will hit western Lake Superior and the Bay of Green Bay earlier in the evening, though eastern Lake Superior could see thunder and rainfall in the second half of the night. Along with these storms, expect sustained southeasterly flow up to 20 kts backing to southerly until the cold front passes in the early hours of Thursday morning, after which point flow will become westerly and diminish somewhat throughout Thursday. During this period of active weather, significant wave heights could build to 2-5 ft in localized offshore areas in Lake Superior.

On Friday, a deep layer low-level jet sends sustained southwesterly flow of 20 kts over Lake Superior (<10 kt in the Bay of Green Bay) with gusts up to 30 kt in western Superior Friday afternoon and and into Friday night. During this time of steady flow, significant wave heights build to up to 5-7 ft in western Lake Superior on Friday night. Through the weekend, marine surface conditions remain benign, with sustained winds mostly <15 kt, gusts <20 kt, and waves diminishing to 2 ft by the end of Sunday. On the Bay of Green Bay, sustained winds are <10 kt, gusts <15 kt, and waves <2ft through the weekend.

As multiple impulses associated with the Hudson Bay low pass through the region this weekend, Lake Superior and the northern part of the Bay of Green Bay may see occasional showers and a rumble of thunder.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... None. Lake Superior... Dense Fog Advisory until 11 AM EDT /10 AM CDT/ Wednesday for LSZ162-240>250-263>266.

Dense Fog Advisory from 8 PM this evening to 11 AM EDT Wednesday for LSZ251.

Dense Fog Advisory until 11 AM EDT Wednesday for LSZ267.

Lake Michigan... Dense Fog Advisory from 1 AM to 11 AM EDT Wednesday for LMZ221- 248-250.