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KEY MESSAGES

- Shower/thunderstorm chances through Monday along with the threat for severe storms.

- Bit cooler/breezy for Tuesday/Elevated swim risk and cold upwelling possible.

- Dry during the midweek period.

DISCUSSION

Issued at 304 AM EDT Sun Jul 26 2026

Pattern Synopsis/Forecast: Basic ridge west/trough east pattern across North America early this Sunday morning...beneath a high latitude Rex block in the vicinity of Baffin Island...and south of a strong +AO/polar vortex. Long wave trough/-PNA off the west coast of North America...and a strong (598dam/nearly +3 sigma) 500mb high south of the Aleutians (WPO is off the charts negative phase). North American ridging is centered over the Four Corners states...while eastern trough axis crossed Michigan earlier Saturday and is over the lower Lakes and along the Ontario/Quebec border. Short wave trough is climbing up the backside of the western ridge into British Columbia/Alberta... attached to an elongated latent PV anomaly that comes over the top of the ridge and into the upper Great Lakes. Flow around the ridge is also dragging a lot of wildfire smoke from the Pacific Northwest and western Canada into the Midwest/Great Lakes. Elevated mixed layer spreading east from the Rockies and into the upper Midwest. Strong low level warm advection also spreading east across the Midwest and into the Great Lakes with 0000Z 850mb temperatures of 20C crossing the Mississippi River. At the surface... Great Lakes sandwiched between a cold front across Northern Ontario...and a warm front snaking its way southeast from North Dakota/Minnesota...across the Ohio Valley and eventually off the coast of the Carolinas. Surface dew points well into the 70s on the warm side of that frontal boundary. Great Lakes will remain in between the upper high over the southwest and southern Plains...and an upper low over Hudson Bay with prevailing northwest flow. Short wave trough will ripple southeast across Michigan later Monday/Monday night...reinforcing the mean trough downstream (and possibly splitting it into two pieces). This whole process just looks to slow things down... especially if a closed low develops in the southern branch across the mid Atlantic/ New England. As it is the northern branch becomes blocked (going from a high latitude Rex block to a high latitude omega block across the North Atlantic). May see some height rises into the upper Lakes beyond midweek but that evolution is definitely tied to southern branch troughing downstream.

Cold front north of Lake Superior doesn't look like it will make much progress into Michigan today...with a broad/disorganized area of low pressure across the Midwest/upper Lakes by Monday morning. Short wave trough for later Monday will drag a surface reflection across Michigan Monday night...and some cooler/gusty north winds Tuesday in its wake. High pressure will try to muscle into the region Wednesday...how successful that will be will depend on how stubborn the southern branch upper wave is. End of the work week could see another short wave trough digging across the Great Lakes.

Primary Forecast Concerns:

Shower/thunderstorm chances through Monday along with the threat for severe storms: Have been watching some wannabe showers trying to pop across eastern Lake Superior/eastern Upper most of the night as a passing short wave trough works on a low level theta-e ridge and associated moisture convergence. Haven't seen much south of M-68 and water vapor imagery suggesting subsidence is already spreading into northwest Lower. So will keep some PoPs across parts of eastern Upper and northeast Lower to start the day along/ahead of the passing short wave trough. Will hold off on northwest Lower for now given water vapor presentation unless trends suggest otherwise. Morning clouds should scatter out with time...allowing temperatures (through a smoky haze aloft) to warm into the 80s. Some surface based instability expected to develop though there will likely be some inhibition as well depending on how much dew points may mix out (think most areas will stay at or above 60...maybe some upper 50s across interior northern Lower). Best chance for development this afternoon is probably along the Lake Superior lake breeze in Chippewa County... and along the northeast Lower shoreline as well.

The main show for convective potential will arrive tonight...all depending on how thunderstorms develop across northern Minnesota/ Wisconsin along the edge of the EML (saturation thickness considerations suggest an initiation corridor from the Boundary Waters and Minnesota Arrowhead southeast into northern Wisconsin/far western Upper. Storms that develop should propagate southeast... thus the greatest threat for severe storms should be across northwest Lower around and after midnight...with upstream convection likely transitioning from supercells to a squall line/wind damage threat by the time it reaches Lake Michigan. Will just have to see how much inertia this activity will have by then...and/or starts to take a harder dive toward southwest Lower.

As for Monday's forecast...hard to get a good feel for that at this point. Much will depend on the evolution of tonight's activity... and potential for new showers/thunderstorms developing for most of Monday ahead of surface wave expected to move into Lower Michigan later in the day (which is my suspicion). For now will simply run with widespread PoPs for Monday...may be a bit more cautious with high temperatures as cloud cover could be a spoiler. Still solidly in the SPC slight risk for Monday.

Bit cooler and breezy for Tuesday/Elevated swim risk and cold upwelling possible: Tighter gradient and some cold advection will make for a breezy day Tuesday with gusts 20-25+mph expected from the north. Elevated swim risk for northern Lower beaches in play for Tuesday... and currents driven by northerly flow Ekman spiral may result in cold water upwelling along the northwest Lower shoreline (hope you enjoyed swim season while it lasted). Temperatures should be back in the 70s for the most part.

Dry during the midweek period: High pressure nudging in from the north expected to keep things dry Wednesday and Thursday...with rain chances returning to the forecast Friday.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 612 AM EDT Sun Jul 26 2026

Lowered CIGs across parts of northern Michigan will persist over the next few hours, but are eventually expected to lift to VFR this morning -- leaving VFR conditions in place through this evening for most areas. Low chances for thunderstorm development this evening to move into TAF sites, but confidence is too low to include in the TAFs at this time. Otherwise, mainly light winds around 5-10 kts out of the west-northwest are expected today and will allow lake breeze formation to push inland from Lake Huron this afternoon.

APX WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...None.