textproduct: Gaylord

KEY MESSAGES

- Widespread rain tonight/Saturday as a cool-season cyclone passes south of the Great Lakes. Heavy rain threat parts of eastern Upper/northeast Lower this evening.

- Drying out from north to south Sunday (though could be a slower process than we would like).

- Rain chances return Wednesday.

DISCUSSION

Issued at 316 PM EDT Fri Jul 31 2026

Pattern Synopsis/Forecast: Broad upper ridge encompasses roughly the southern half of the CONUS...save for a long wave trough that runs along the east coast. A short wave trough coming over the top of the ridge and into the Midwest today will be a feature of interest heading into the weekend...a couple of smaller PV anomalies also coming over the top of the ridge across Idaho/Montana. Low amplitude westerly flow across much of Canada...emanating from a long wave trough off the British Columbia coast. Anticyclonic upper level flow across the Great Lakes today with broadly difluent flow ahead of the Midwest short wave trough; also ahead of this trough is a narrow axis of deep layer moisture (precipitable water at or above 2.00 inches spanning the Mississippi Valley). Mid level deformation zone extends from eastern North Dakota/northern Minnesota/northwest Ontario. At the surface...1006mb low along the Iowa/Minnesota border with a warm front extending southeast across Iowa and along the Mississippi River. Cold front was north of Lake Superior into northern Minnesota. Broad high pressure across the Ohio Valley and mid Atlantic region with several high centers including a 1016m high bubble over southern Lower Michigan.

Cold advection into the backside of the upper Midwest short wave trough suggests a continued digging and strengthening over the next 24 hours...approaching a -3 sigma 500mb height anomaly across the mid Mississippi Valley. This trough will slowly meander across the Ohio Valley this weekend...what happens beyond that is uncertain. Will this system track into the mid Atlantic Monday...will it hang on longer (slower is usually the better way to go)...or does the trough split and a piece gets left behind to drift into the southeast states early next week? Questions about the evolution of this feature may not have much impact on the upper Lakes...provided we can get some height rises/surface high pressure into the region by Tuesday and the "piece gets left behind to drift into the southeast states" idea mentioned above gets slingshotted back in our direction instead. Regardless...the trend should be toward more unsettle weather by midweek...as the trough currently over the northeast Pacific moves inland and takes up residence across central Canada. This should send height falls and a cold front into the Great Lakes around Wednesday.

Primary Forecast Concerns:

Widespread rain tonight/Saturday as a cool-season cyclone passes south of the Great Lakes. Heavy rain threat parts of eastern Upper/northeast Lower this evening: Upstream system over southern Minnesota much more reminiscent of something we will be more familiar with in a couple of months rather than something we typically see in late July. But it is there...with a nice deformation precipitation shield across southern Minnesota/northern Wisconsin...and a warm frontal rain band spreading northeast across southern Wisconsin. Meanwhile...at the onset this afternoon things are just starting to bubble up on the cloud front...with the Lake Huron breeze having kicked in north of Thunder Bay. Across eastern Upper an uncapped MLCAPE 1000+J/kg... with lake breeze convection underway from Marquette to the Soo. Combination of afternoon convection...eastward extension of precipitation band across northern Wisconsin/western Upper...and the main precipitation shield wrapping around the upper midwest cyclone will be the impetus for rain across northern Michigan tonight and Saturday. Given high precipitable water...K indices above 35...and light cloud layer flow there is concern for slow moving heavy downpours through midnight across eastern Upper and parts of northeast Lower and may carry an explicit heavy rain wording to cover this. A lot of moisture around Saturday but not a lot of forcing...though southern portions of the forecast area will still be close to the main deformation zone.

Drying out from north to south Sunday (though could be a slower process than we would like): Rain chances should start to come to an end across eastern Upper and parts of northwest Lower Saturday night...but will continue into Sunday for about the southeast third of the forecast area. Slow moving deformation zones can be stubborn in clearing out...so later forecasts may trend toward hanging onto some rain chances over (at least) northeast Lower for a bit longer. But expecting things to dry out all areas by Monday.

Rain chances return Wednesday: Height falls and a resultant cold front looks to cross the upper Lakes Tuesday night/Wednesday which will bring the next chance for showers and thunderstorms. Outlook beyond Wednesday is a bit more uncertain...but removed a lot of spotty slight chance PoPs for Thursday/Friday for the time being.&&

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 746 PM EDT Fri Jul 31 2026

Showers and a few storms will increasingly prevail tonight into Saturday. Vsbys and especially cigs will tend to lower with time. MVFR develops everywhere overnight into Saturday, and IFR should develop at CIU. Light winds.

APX WATCHES/WARNINGS/ADVISORIES

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