textproduct: Detroit/Pontiac

KEY MESSAGES

- Scattered shower and thunderstorm chances this morning into early evening mainly along/south of I-69. Torrential rainfall and minor localized flooding possible with any storm.

- Additional scattered shower chances mainly north of I-69, particularly in the Thumb, this evening-early tonight as a cold front crosses.

- Dry, seasonably average conditions for the early week period.

- Shower and storm chances return Tuesday night into Wednesday with the arrival of the next cold front.

DTW THRESHOLD PROBABILITIES

* High for ceiling 5000 feet or less today, medium this evening, low overnight.

* Low for thunderstorms today.

PREV DISCUSSION

Issued at 316 AM EDT Sun Aug 16 2026

DISCUSSION...

Ongoing convection across northern IL/IN is tied to the arrival of a central Plains shortwave that will slide along MI's southern border over the rest of the morning/early afternoon. While the majority of convection is again expected south of the state where the stalled frontal boundary resides, reinforcing moisture and modest mid-level ascent supports scattered AM shower chances over the southern half of SE MI. Thunder chances during the morning activity will be quite limited due to the lack of available instability (MUCAPE <500J/kg). This gradually changes by afternoon however as ongoing moisture advection pushes surface dewpoints into the the lower 70s allowing diurnal heating to generate MLCAPE between 1000-1500J/kg. Increasing instability combined with the modest synoptic support from the passing shortwave supports scattered convective showers and thunderstorms through the afternoon, mainly along/south of I-69 given the location of the wave. Severe storms are unlikely as weak column winds keep shear sub-30kts in addition to abysmal mid-level lapse aob 6 C/km. PWATs in excess of 2" and warm cloud layers near 15kft however do offer the threat of torrential rainfall. That said, the progressive nature of any convection plus the dry summer thus far should keep flooding more localized to the typical floodprone urban/low lying areas. Storm chances wane by early evening in the south as the shortwave departs east; though the arrival of a cold front dropping out of northern MI shifts scattered shower chances towards the northern half of SE MI, particularly the Thumb, this evening-early tonight. Late arrival in the diurnal window likely keeps thunder more isolated.

Passage of the aforementioned tonight ushers in a more seasonably average airmass as dewpoints and 850mb temps return to around 60F and lower teens C, respectively. As such, pleasant early week in store with highs in the lower to mid 80s Monday-Tuesday and sunnier skies.

Broad Hudson Bay upper trough sends another cold front into the Great Lakes midweek. Currently, frontal timing and associated preceding showers favored to work across SE MI late Tuesday night- Wednesday. Cooler air follows to close out the work week with 850mb temps hovering around 10C keeping highs slightly below normal by the latter part of August standards.

MARINE...

As low pressure tracks north of the area it will push a cold front through the central great lakes region later today and tonight. Ahead of the front, south winds prevail for much of the day around 10 to 20 knots. Behind the cold front, northwest winds fill in and increase across Lake Huron, and eventually down through Lake St. Clair and the Michigan waters of Lake Erie late tonight. The strongest winds are expected across Lake Huron, especially the Open Waters with 20-25 knot winds expected late Sunday evening into early Monday morning. Thus, will need to keep an eye on the wave forecast and the potential for Small Craft Advisories for nearshore waters across the tip of the Thumb of Michigan. Showers and thunderstorms will be possible as this system moves through today through tonight. The best chance for thunderstorms will be along the cold front later this evening.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None.