textproduct: Detroit/Pontiac

KEY MESSAGES

- Sunny and cooler with low humidity today.

- A chance of showers and thunderstorms returns Tuesday. The best chance of storms is late afternoon and evening south of I-69.

- A chance of showers lingers Wednesday before becoming more numerous Wednesday night and Thursday.

- Dry weather with temperatures around normal Friday into next weekend.

DTW THRESHOLD PROBABILITIES

* None

PREV DISCUSSION

Issued at 357 AM EDT Mon Sep 14 2026

DISCUSSION...

The center of expansive surface high pressure drifts across central Lower Mi to dominate conditions today. It has already delivered a cool and dry air mass to the region as evidenced by temperature observations dropping into the upper 40s outside of Detroit and away from the shorelines. Also impressive is temperature guidance that struggles to break 70 this afternoon despite full sun, although we are getting closer to the equinox.

High clouds are on the increase this evening which signal a quick transition to the next low pressure system. It is projected to move out of the Rockies and along the Canadian border today and occlude across NW Ontario tonight. This track sets up the low level jet and plume of moisture transport from the central Plains into the northern Great Lakes which then settles into central Lower Mi by sunrise Tuesday. Behavior of regional and hi-res deterministic models reflects a tendency for erosion of the precipitation pattern by dry air lingering out ahead of the system. There is also some breakup caused by the moisture axis outrunning the upper jet and mid level short wave, both of which are positioned well to the north across northern Ontario and the northern Great Lakes. Mostly chance or scattered POP guidance in the NBM looks good in this regard until flaring up later Tuesday afternoon. Daytime heating is projected to boost convection by then, mainly across metro Detroit to the Ohio border, as the cold front crosses the area into Tuesday evening. The SPC Day 2 outlook grazes Lenawee and Monroe counties in a Marginal Risk for severe intensity.

The surface cold front makes it south of the IN/OH border by Wednesday morning where it stalls and wavers across central IN/OH through Wednesday night and Thursday. This keeps a chance of showers in the forecast for SE Mi, mainly south of I-69 as elevated portions of the frontal zone are activated by southward expanding upper level jet. The 00Z models maintain a consensus on a more coherent mid level short wave and surface low pressure reflection along the stationary front late Wednesday night and Thursday. ML/AI runs of the GFS and ECMWF help narrow down areas closer to the Ohio border for the highest POPs and QPF, and in general agreement with the WPC Marginal outlook for excessive rainfall.

We get a break in showers/storms by Friday in the subsidence wake of the passing short wave. Building surface high pressure drives the frontal zone well down into the Ohio valley where it takes most of Saturday to begin a northward return. Global/extended range models bring the next low pressure system back into the upper Midwest Saturday and through Lower Mi Sunday.

MARINE...

NW wind dropped off rapidly with the approach of broad surface high pressure since midnight. The high moves across Lower Mi and Lake Huron today on pace for a rapid transition of conditions ahead of the next low pressure system. This system gains strength while tracking across the Canadian Prairies tonight and Tuesday, and eventually reaches the Hudson Bay region by Tuesday night/Wednesday. Southerly flow out ahead of the system will increase across the north half of Lake Huron with gusts now expected to reach gale force toward sunrise Tuesday and continuing through mid afternoon. Concern for warm air falling short of gales is balanced by model soundings that do indicate a well mixed boundary layer within the inbound warmer air mass, and this makes the wind profile capable of tapping into higher gusts aloft. The Gale Watch is upgraded to a Warning in this forecast update with the same effective time of 4 AM tonight through 4 PM Tuesday. It was also decided to include zone LH361 as gusts reach offshore of Presque Isle and extend northward across the Canadian border. A band of showers and thunderstorms also accompanies this gale event until pushed to the south and east by a cold front Tuesday night.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Gale Warning from 4 AM to 4 PM EDT Tuesday for LHZ361>363.

Small Craft Advisory from midnight tonight to 4 PM EDT Tuesday for LHZ421-422-441.

Small Craft Advisory from 2 AM to 4 PM EDT Tuesday for LHZ442-443.

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