textproduct: Detroit/Pontiac

KEY MESSAGES

- Dry and seasonable conditions persist through Tuesday.

- A low chance of showers and thunderstorms starting late afternoon Tuesday across the Saginaw valley and thumb, with a greater potential for showers with isolated thunderstorms for all of southeast Michigan Tuesday night.

- A few lingering showers possible early Wednesday, then turning drier again with temperatures slightly below normal for the end of the week.

DISCUSSION

Drier and slightly cooler post-frontal environment will continue to settle across Southeast Michigan through the overnight period as a diffuse bubble of high pressure builds under weak zonal flow aloft. Any lingering lower stratus will rapidly scour out during the evening hours as greater drying takes hold. With lighter northerly to variable winds at the surface and clearing skies, efficient radiational cooling will allow overnight lows to drop into the upper 50s across the northern Thumb and rural corridors, while urban areas around Metro Detroit hover in the lower 60s. Shallow patchy fog cannot be ruled out in localized low-lying areas, though low surface dewpoint depressions should limit widespread visibility impacts.

Tuesday starts off with dry conditions and ample sunshine as high pressure lingers over the Great Lakes. Light surface winds will turn southerly to southwesterly around 10 to 15 mph by afternoon, initiating weak return flow moisture advection. High temperatures will reach seasonable averages in the lower to mid-80s. Dew points will gradually creep back up into the lower 60s ahead of the next incoming disturbance. An upper-level wave traversing northern Ontario will drag a mid-level trough and accompanying surface cold front into Northern Lower Michigan late in the day, expanding across Southeast Michigan toward 00z. As forcing increases along the frontal boundary, scattered showers and embedded thunderstorms will push in from the northwest through the overnight period. Modest elevated instability will build ahead of the front. While severe organized convection is not favored due to marginal thermodynamic support, isolated stronger storms with brief downpours and gusty winds remain possible. Overall coverage diminishes from north to south late Tuesday night into Wednesday morning. A smaller window may emerge Wednesday afternoon for shower production, mainly in the thumb, as a secondary front slides through as more notable height falls commence late in the day.

Broader mid level troughing to govern conditions to finish the work week. This occurs atop another sprawling area of high pressure. This ensures dry and stable conditions both Thursday and Friday. Resident thermal profile marked by 850 mb temperatures of 10-12C. This will keep boundary layer temperatures seasonable to slightly below late- August normals. Stronger mid level wave digging into the mean trough will offer the next opportunity for unsettled conditions Friday night into the upcoming weekend.

MARINE

Diffuse region of high pressure now established over the Great Lakes will support light winds for the remainder of the day. As this high pressure system washes out east of the region, this will allow southwest flow to become established for most locations tomorrow. Winds generally remain light with this transition to southwest flow, but localized stronger gusts around 20 knots will be possible through the Saginaw Bay given the more favorable fetch.

More active weather returns tomorrow afternoon through tomorrow evening with the passage of a cold front. Showers and thunderstorms will be likely with the passage of the front as winds veer from southwest to northwest in the wake of the front. A slight uptick in winds are expected along and behind the front as cooler conditions filter in. Wind gust of 20 to 25 knots will be likely with the frontal passage.

PREV DISCUSSION

Issued at 216 PM EDT Mon Aug 17 2026

AVIATION...

Mixed afternoon ceilings across the terminals as surface high pressure resides beneath weak troughing aloft. The lowest cloud deck (sub-2 kft) should finish scouring out early this afternoon, while a second layer settles above 3.5 kft, augmented by moisture off Lake Huron. Winds should continue to weaken before losing the northernly component, after high pressure slides into the lower Ohio Valley. Skies turn mostly clear overnight while dewpoints steadily decline. Winds eventually trend near calm, so brief fog cannot be ruled out, but confidence is too low for any TAF mention at this time. Expect dewpoint depressions to remain large enough to avoid MVFR visibility reductions. Winds turn southwesterly ahead of an inbound cold front, with a mix of partial low and high cloud cover.

D21/DTW Convection...No thunderstorms are anticipated today or tonight.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5000 feet after 19Z.

DTX WATCHES/WARNINGS/ADVISORIES

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