textproduct: Detroit/Pontiac

KEY MESSAGES

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

- Some scattered showers/thunderstorms are possible Tuesday late afternoon-evening in Saginaw Valley and Thumb. Wider spread showers cross Tuesday night with the arrival of the next cold front.

-Slightly below normal temperatures from midweek into next weekend.

DISCUSSION

Cold front currently residing near Detroit at time of discussion finishes clearing south of the area early this morning with satellite obs showing developing stratus over the northern CWA. Ongoing weak cold advection supports the expansion of this low cloud across the bulk of the region by mid-morning before diurnal heating and improving mixing heights gradually scatter it this afternoon. Cooler airmass (850mb temps 11-12C) in combination with the healthy coverage of AM cloud cover hold highs right around average in the low 80s. Similar day in store for Tuesday albeit a few degrees warmer with sunnier skies to start the day before clouds return late day marking the arrival of another cold frontal boundary sagging through the Great Lakes.

Prefrontal trough centered over northern lower MI looks to slide across northern Lake Huron Tuesday late afternoon-evening with the Saginaw Valley/Thumb sitting near its southern edge. Favorable timing within the diurnal window offers several hundred J/kg of MLCAPE to be in place over the northern portions of the CWA supporting chances for scattered showers/thunderstorms. Wider spread rain chances arrive Tuesday night with the frontal boundary itself. Showers are predominate with isolated thunder given only a few hundred J/kg of elevated instability available. Bulk of activity pushes out of SE MI by the daylight hours Wednesday morning though some lingering pockets of light showers/drizzle are possible through the morning as the elevated portions of the frontal slope are slow to vacate.

Cold frontal passage brings a reinforcing push of cooler air as 850mb temps fall to around 10C. As such, slightly below normal temperatures are favored from Wednesday on with highs in 70s to low 80s and overnight lows in the 50s. Arrival of a respectable mid- level shortwave from the Canadian Prairie amplifies the upper trough over the Great Lakes next weekend maintaining slightly below normal temps as well as offering additional rain chances.

MARINE

High pressure is building into the region in the wake of Sunday's cold front. The winds have become northwesterly while increasing to 15 to 20 knots with gusts to 25 knots across Lake Huron. The increased northwesterly winds will reach Lake St Clair and Lake Erie by morning but gusts should only top out in the 15 to 20 knot range. The winds increase will cause waves to increase to 3 to 5 feet in the nearshore zones of Lake Huron thus a Small Craft Advisory has been issued through this morning. The area of high pressure will persist through most of Tuesday keeping the northerly flow around but at tempered speeds. Next chance of thunderstorms comes late Tuesday with the next cold front.

PREV DISCUSSION

Issued at 1149 PM EDT Sun Aug 16 2026

AVIATION...

925mb cold front is poised to push southward through Southeast Michigan between 06-12z this morning. Low level cold advection will help steepen near surface lapse rates and lead to MVFR stratus over all of the area. Given trends this evening did push the onset of the MVFR cigs back a couple of hours. Cloud is expected to hold into the day on Monday before rising mixing heights cause ceilings to lift low VFR .

D21/DTW Convection...No thunderstorms are anticipated at this time.

DTW THRESHOLD PROBABILITIES...

* High for ceiling below 5000 feet tonight and Monday.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until noon EDT today for LHZ421-441>443.

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