textproduct: Detroit/Pontiac

KEY MESSAGES

- Periodic chances for showers and thunderstorms continue through much of the week, with the highest coverage favored across northern areas.

- Very warm and humid conditions are expected Monday through Wednesday, though daily peak temperatures will depend on cloud cover and precipitation.

DTW THRESHOLD PROBABILITIES

* Low in thunderstorms tonight.

PREV DISCUSSION

Issued at 307 PM EDT Sun Aug 30 2026

DISCUSSION...

A moist airmass is in place over Lower Michigan, as both 12z DTX/APX RAOBS came in with a 5 C dew pt at 700 MB. Waves of isentropic ascent have been supportive of widespread showers. Fortunately, instability is limited, and rainfall amounts have been manageable, generally in the range of a quarter of an inch (south) to one inch (north).

An upper level ridge/heat dome over the central Plains will drift northeast, reaching southern Illinois by Monday evening. The extension of the ridge axis over the northern Mississippi River Valley will subsequently move overhead into the central Great Lakes on Monday as well. High temperatures will be dependent on how well the warm front and tonight's expected showers and thunderstorms clear southeast Michigan Monday morning. The north half of the CWA is favored location, as local probabilistic guidance suggests pops aoa 70 percent north of M-46.

With 850 MB temps progged to rise into the 20-21 C range Monday- Wednesday, max temp potential is certainly aoa 90. However, much like today, any thick cloud cover and shower/thunder activity during the day could short-circuit max temps. In addition, the outgoing NBM surface dew pts appear to be too high (widespread lower 70s), so advertised heat indices appear too high as well.

The upper-level ridge is already flattened on Tuesday over Lower Michigan, with westerly flow in place as 500 MB low tracks through northern Ontario. At least moderate instability building up in a weakly capped environment suggests that there will be some diurnal activity, especially with any enhanced low level convergence/lake breeze/marine influence. Sufficient bulk shear to support a chance of severe storms, if in fact storms do go up.

A slight drying out of the deeper moisture in place as we head into Wednesday could support the warmest maxes of the week, per the NBM. Still, confidence is not high, as height falls arrive by Wednesday evening/night and a potentially active baroclinic/frontal zone develops over southern Lower Michigan into Thursday.

MARINE...

Several days of unsettled weather as a primary low pressure system over central Canada and secondary low over the northern Plains send a series of fronts across the region. Periodic showers and thunderstorms will accompany the fronts while the slightly cooler air over the waters brings chances of waterspouts with the storms over the lakes. Winds will largely be from the south today with max gusts around 20 knots. Winds turn more southeasterly on Monday while remaining mostly below 20 knots before turning westerly on Tuesday.

HYDROLOGY...

Renewed shower development and possible thunderstorms are expected tonight into Monday morning, mainly north of the I-69 corridor. With today's heaviest rainfall falling along M-46 priming the ground, even a low chance scenario of rainfall totals exceed 1 inch late tonight into Monday morning could cause localized minor flooding of roads, poor-drainage areas and rises in local rivers. The chance for additional showers and thunderstorms lingers Monday into Tuesday. Any isolated to scattered storms on Tuesday could become intense and produce torrential rainfall, leading to localized flooding in poor drainage areas as well.

DTX WATCHES/WARNINGS/ADVISORIES

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