textproduct: Detroit/Pontiac

KEY MESSAGES

- Intervals of showers will persist overnight and early Sunday. Potential exists for heavy rainfall to develop at times.

- Dry weather returns on Monday, but it may become unsettled again for parts of next week with chances of showers. Temperatures will be close to average for early August.

DTW THRESHOLD PROBABILITIES

* Medium to high for ceiling 5000 ft or less overnight and Sunday.

* Low for thunderstorms Sunday morning.

PREV DISCUSSION

Issued at 319 PM EDT Sat Aug 1 2026

DISCUSSION...

A west-east axis of showers and embedded thunderstorms has begun to develop this afternoon along an broad axis of surface convergence as deeper moisture lifts north. This area is currently along/near the M- 59 corridor and expected to slowly lift north towards the I-69 corridor through this evening. This mornings raob from DTX showed PWATs above the 90th percentile for this time of year and a narrow pocket of elevated instability between 1-6km. Latest RAP analysis also shows this area generally uncapped, thus this pocket of instability is likely now surface based. While instability is not all too impressive, the warm, moist environment remains favorable for higher rainfall rates with any thunderstorm activity. Rainfall this afternoon and into tonight will be highly variable and dependent on where slow moving thunderstorm activity tracks.

Afternoon surface and satellite analysis show both the surface and upper-level low across central Illinois. With the low already having occluded across the Midwest and the upper-level wave becoming cutoff, it will be very slow to move east over the next 24-36 hours. Another wave of energy is progged to dig south across the region tonight and through Sunday, helping move the system along to the east. With these two waves of energy approaching the area through Sunday, there remain uncertainties in how the potential for heavy rain and training convection evolve. There will be multiple rounds of large-scale ascent that move through the region, which will favor a few windows of convection that look to remain loosely organized. Thus, it remains very difficult to pinpoint where any axis of training convection could set up and bring possible urban flooding concerns, so have opted to hold off on a Flood Watch. Expect at least 0.5-1 inch of rain late tonight through Sunday. Locally higher totals if we get into a training scenario with embedded thunderstorms.

Early next week, high pressure moves in behind the departing system and we should have a few drier days with seasonable temperatures in the lower 80s. With warm air advection moving back into the region ahead of another system tracking east across the upper great lakes and central Canada, we should see a gradual warming trend through mid to late week.

MARINE...

Northeast flow picks up across the central Great Lakes tonight and especially Sunday afternoon as a low pressure system over the lower Ohio Valley lifts northeastward. Strongest flow will channel across Saginaw Bay leading to Small Craft Advisory conditions. Similar concerns for the rest of the Lake Huron nearshore, but will reconsider an extension with the evening update. Chances for rain and thunderstorms continue through the remainder of the weekend as the low and its associated frontal features approach. Isolated storms could produce locally strong winds and elevated waves today through Sunday. High pressure influence becomes entrenched across the region Monday offering drier weather and weaker winds, with headline-free conditions.

HYDROLOGY...

Scattered to numerous showers with embedded thunderstorms are forecast this afternoon into Sunday. Heavy rainfall rates are still possible, especially with any thunderstorm activity. Localized rainfall totals may exceed 2 inch where persistent training convective activity develops. This may lead to isolated flooding concerns this weekend, particularly in urban areas.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory from 8 AM to 10 PM EDT Sunday for LHZ421-422.

Small Craft Advisory from noon Sunday to 4 AM EDT Monday for LHZ441>443.

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