textproduct: Detroit/Pontiac

KEY MESSAGES

- Extended stretch of seasonably cool conditions will exist into the middle of the week.

- Aside from a low chance of rain early this week near the Ohio border, dry conditions are expected throughout the week.

DTW THRESHOLD PROBABILITIES

* Medium for ceiling at or below 5000 feet tonight. High Tuesday.

PREV DISCUSSION

Issued at 320 PM EDT Mon Sep 21 2026

DISCUSSION...

Broad surface high spread across most of the Great Lakes, Ontario and Quebec will keep a cool easterly flow across the region through the bulk of the week. Mid level split flow pattern will help keep the current conditions stagnate through the week as well. 850mb temps will hover in the mid-upper single digits setting the stage for highs in the 60s all week with low dipping into the 40s. The cool air flowing over the relatively warm waters will open the door for some cloud cover which would largely affect locations west of Lake Erie. With clearer skies across Mid MI, could see a gradient in temps from the low 60s across the south under the blanket of clouds and upper 60s northward with the additional sun.

A mid level low will ride along the southern stream of the split flow through Ohio Tuesday night into Wednesday. This will bring deeper moisture depths back north into southern MI with model soundings showing saturation layers from 2-10kft with some mid level deformation just north of the low with low level convergence south of I94 as well. This is the only period in the week which will support a chance of precip as once the low passes Wednesday, heights begin to rise and surface high pressure settle back southward.

Weak troughing over the east coast will strengthen mid week in part because a mid level wave tracking across northern Ohio phases with it. Moreso the deepening will occur because the overall longwave pattern amplifies in response to the next trough coming ashore the Pacific NW later in the week. This causes the Plains ridge to amplify and shift over the Great Lakes and stalls the downstream upper low over the East Coast. This will all result in a gradual warm up across the region this weekend back into the low 70s with dry conditions continuing.

MARINE...

Modest northeasterly gradient wind field persists over the central Great Lakes through mid week as an expansive 30.40 inHg high pressure system makes little forward progress between Ontario and Quebec. This translates to elevated wave action for most of the waterways, therefore, a Small Craft Advisory remains in effect for all nearshore waters. Afternoon/diurnal contribution to elevated gusts will be most prevalent over Saginaw Bay, briefly exceeding 30 knots late this afternoon and Tuesday afternoon. Additionally, upper level energy intersecting a stalled elevated frontal boundary could offer some sporadic light shower chances over the far southern waterways (i.e. Lake St. Clair and western Erie) this evening and/or Tuesday night. A weak low pressure system should emerge over the northern portion of the Ohio Valley on Wednesday, altering the pressure and moisture fields. This could lead to slightly broader coverage of showers for the south-central Great Lakes on Wednesday while wind speeds gradually start to decline for the latter half of the week. An extension to the Small Craft Advisories may still be needed for a subset of the nearshores.

DTX WATCHES/WARNINGS/ADVISORIES

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

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

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