textproduct: Detroit/Pontiac

KEY MESSAGES

- Temperatures on the cool side of average today, then a gradual warming trend carries through the late week.

- Aside from a low chance of light rain mainly south of I-94 this morning, dry conditions are expected into early next week.

DTW THRESHOLD PROBABILITIES

* High in ceilings aob 5000 feet this morning. Medium this afternoon.

PREV DISCUSSION

Issued at 351 AM EDT Wed Sep 23 2026

DISCUSSION...

Weak flow aloft associated with a transient rex configuration passes over the Great Lakes today, with ensemble MSLP output indicating a +2 sigma ridge centering over southern Ontario and Quebec. Low-level easterly wind holds thermal troughing over SE MI with 850mb temp stagnant in the single digits Celsius. A weak cutoff low passing through the Ohio Valley is causing moisture to retrograde east to west across the southern forecast area, bringing mostly cloudy skies at least through the morning hours before drier air starts to work back in. Scattered light showers remain possible mainly south of I- 94 where mid-level deformation coincides with low-level convergence downwind of Lake Erie. TDTW radar data shows these shallow showers moving into the Luna Pier vicinity already. Given the cloud cover, highs in the mid 60s are expected for much of the area. Farther north toward the Saginaw Valley and interior Thumb, mostly sunny skies should prevail today and boost temps slightly toward 70 degrees.

Longwave ridge cresting over eastern Canada allows the resident surface high to hold in place through the end of the week. Persistent wind direction from the east maintains a cooler pattern, though a warming trend is likely as increasing insolation provides some modification to the air mass each day. The surface high is forecast to expand more into the Great Lakes by Friday and Saturday as greater subsidence spreads overhead in response to a coastal low tracking up the eastern seaboard. This allows each day to become less breezy as the gradient subsides. Dew points holding in the 40s/50s and mostly clear skies will favor crisp nights with lows in the 40s outside of the urban heat island. Split flow aloft looks to dominate the late weekend and early week, favoring continued dry and benign conditions as high pressure remains parked overhead.

MARINE...

Easterly gradient winds persist over the central Great Lakes today as a strong/expansive 30.70 inHg high pressure system centers over Quebec. This sustains elevated on-shore waves for most of the waterways, therefore, a Small Craft Advisory remains in effect for all nearshore waters until 10 PM. Diurnal afternoon gusts should hold below 30 knots as split flow emerges in the low-levels. Still monitoring a Rex Block with the closed low positioned over the northern portion of the Ohio Valley, offering a low-end chance for a few light showers over western Lake Erie during the first half of the day. Wind speeds gradually decline into Thursday as the pattern unlocks, and deep-layer split flow returns aloft, after the surface pressure gradient relaxes. Wave heights should recover accordingly, precluding the need for any extensions to the ongoing Small Craft Advisories. Mainly dry and headline-free into the weekend with weak flow.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422- 441>443.

Lake St Clair...Small Craft Advisory until 10 PM EDT this evening for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT this evening for LEZ444.