textproduct: Detroit/Pontiac

KEY MESSAGES

- Warming trend through the middle of the week with increased humidity.

- Next chance for showers and thunderstorms arrive late Wednesday. An isolated strong storm possible Wednesday evening.

- Lingering chances for scattered showers/storms Thursday afternoon.

DISCUSSION

Cyclonic influence from the closed low circulation over Ontario has supported an expansion of stratocu across the most of the northern half of SE MI this afternoon. This cloud quickly fades late this evening as troughing finally dislodges east allowing northern Ohio Valley high pressure to fully build over southern lower MI tonight. Cooler night is again in store albeit a couple degrees warmer than last night (more mid 50s than the lower 50s yesterday). High pressure drifts east over the course of Tuesday maintaining a pleasant day with partly cloudy skies and highs back around 80.

Next shortwave drops out of the Canadian Prairie into the northern Great Lakes Tuesday night. Locally, this results in a developing warm front lifting through the area early Wednesday morning. Organizing low level southwest winds result in slow moisture transport over the course of Wednesday as dewpoints climb from the upper 50s in the AM to the mid 60s by evening. Given the gradual arrival of moisture and the main theta-e plume tied along the approaching cold frontal slope, expectation is the majority of the day will stay dry. Possible exception is the Tri-Cities/northern Thumb who reside closer to the mid-level trough base that will be sinking through northern lower MI potentially offering a few passing afternoon showers. Instead, main window for showers/storms for the entire area is looking to between ~23-06Z coinciding with both the arrival of the cold front/preceding pooling of theta-e as well as the mid/upper trough digging south through the state. In terms of severe potential, set-up remains marginal. Late evening arrival is on the backedge of the diurnal cycle allowing for at least several hundred J/kg of MLCAPE being place; however column wind fields aren't particularly robust, largely unidirectional 20-30kt flow yielding shear values between 25-30kts. Given this setup, the current Day 3 Marginal Risk from SPC appears warranted for an isolated strong/borderline severe cell.

While the cold front clears the region by Thursday morning, trailing airmass is essentially the same as dewpoints remain in the mid 60s with highs in the lower 80s. Lapse rates steepen by afternoon as upper troughing settles over the central Great Lakes sparking chances scattered showers/thunderstorms. Passage of a secondary cold front Thursday night should finally shunt the bulk of humidity south returning dewpoints to upper 50s/60.

MARINE

High pressure will begin to settle in across the Great Lake regions tonight and will center over the region by tomorrow afternoon. This will work to decrease wind speeds tonight, leading to light winds by tomorrow. Wind direction will pivot south to southwest ahead of an upper-level disturbance and cold front on Wednesday which will bring some elevated winds ahead of the front. Wind gusts around 20 to 25 knots will be increasingly likely with the southwest flow along with rain showers and some isolated thunderstorms. Wind direction to veer to the west-northwest in the wake of the front on Thursday as high pressure builds in. This will support light winds to end the week.

PREV DISCUSSION

Issued at 104 PM EDT Mon Aug 24 2026

AVIATION...

Low pressure remains stalled over eastern Canada, sustaining cyclonic flow across NE CONUS with surface winds from the NW locally. We are just on the edge of the wrap-around moisture plume, which has afforded a brief window of MVFR to low VFR for the Thumb and Saginaw Valley. MBS is just being clipped by the thicker cloud cover. Expecting diurnal cu to flare up at other terminals through the rest of the afternoon, but cigs are likely to stay above 3.0 kft agl. Breezy NW flow (peak gusts of 25 to isolated 30 knots) gradually subsides by early evening before backing to the west Tuesday morning. Weak signal for radiation fog begins early Tuesday morning, mainly toward the Saginaw Valley where dewpoint temperatures are slightly higher this afternoon. High cloud presence may hinder radiative cooling in otherwise favorable conditions.

D21/DTW Convection... No thunderstorms forecast today or tonight. Brief intervals of ceilings 5000 feet or less will be possible through roughly 21z with low confidence in radiative fog development Tuesday morning.

DTW THRESHOLD PROBABILITIES...

* Moderate for ceiling 5000 feet or less through early this evening.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Beach Hazards Statement until 8 PM EDT this evening for MIZ049.

Lake Huron...Small Craft Advisory until 8 PM EDT this evening for LHZ421-441>443.

Small Craft Advisory until 4 PM EDT this afternoon for LHZ422.

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