textproduct: Detroit/Pontiac

KEY MESSAGES

- The Air Quality Alert remains in effect today through Friday due to persistence of wildfire smoke causing hazardous air quality.

- Improvement of smoke concentration begins Friday night as wind shifts SW after passage of a warm front.

- Thunderstorm potential increases with scattered coverage Friday and Friday night. Severe intensity is not expected.

- There is a Marginal Risk of severe intensity thunderstorms as coverage becomes numerous Saturday afternoon and evening.

_ Dry weather with cooler temperatures and lower humidity moves in by Sunday.

DTW THRESHOLD PROBABILITIES

* High for ceilings at or below 5000 feet today.

* Moderate for vsbys below 1/2SM early this afternoon, low by late afternoon.

PREV DISCUSSION

Issued at 341 AM EDT Thu Jul 16 2026

DISCUSSION...

Surface air quality observations and reduced METAR visibilities confirm the substantial wildfire smoke plume is fully entrenched across SE MI. Persistent northwest flow with flow trajectories extending to the Ontario wildfires will maintain a steady supply of smoke and provide little opportunity for meaningful improvement per HRRR-smoke model. Persistent smoke cover will introduce considerable uncertainty into the high-temperature forecast given attenuation of shortwave radiation through scattering and absorption leading to suppressed boundary layer growth. As such, have tempered temperature values down relative to statistical guidance, attempting to align where modeled vertically integrated smoke is maximized. But overall there is little precedence and limited guidance for smoke of this density and persistence. Highs have therefore been capped to 90 closer to the MI/OH border and urban metro region and hold in the 80s for locations north. Outside of smoke/haze, dry weather prevails under diffuse high pressure.

Lingering haze/smoke holds into Friday but wind direction will flip to the south as high pressure washes out across the continental northeast. This will attempt to work some of the haze/smoke out of the region but overall gradient flow will be weak so this initially will not be very efficient. This will usher in better moisture and will bring the chance for showers and storms late Friday into Saturday morning along the moisture/theta-e gradient as it initially expands across SW michigan. A low pressure system that will move across southern Ontario/Quebec and associated cold front that in turn pushes across the Great Lakes will then bring likely chances for showers and thunderstorms on Saturday. Projected favorable afternoon or evening alignment of frontal passage could bring the possibility for strong or severe storms noting ensemble mean values of CAPE around 2000 J/kg and bulk shear values around 30 knots. Passage of the front will bring relief from the hotter than normal and humid conditions. Forecasted highs hold in the low to mid 80s in the wake of the front through the midweek period.

MARINE...

Dense smoke due to Canadian wildfires has spread southward across the entire central Great Lakes, in the wake of a backdoor cold front last evening. The Dense Smoke Advisory has been expanded to all waterways until 10 AM but an extension to later times will be likely. High pressure builds back across the central Great Lakes today as north- northwest winds hold this afternoon at or below 20 knots. The higher values should be focused over the northern half of Lake Huron where the pressure gradient is more constricted. Weak low pressures systems emerge over the northern Plains and Mid- Mississippi Valley tonight, eventually converging over the Great Lakes with time on Friday. This leads to a more active period of showers and thunderstorms. Prevailing winds should generally remain below headline criteria through the forecast period, with one exception being marginal Small Craft Advisory gusts over Saginaw Bay and/or The Thumb nearshores Saturday afternoon. This arises within the wake of a cold front from a secondary, and more robust, low pressure system passing through The Straits.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Dense Smoke Advisory until 4 AM EDT Friday for LHZ361>363-421-422- 441>443-462>464.

Lake St Clair...Dense Smoke Advisory until 4 AM EDT Friday for LCZ460.

Michigan waters of Lake Erie...Dense Smoke Advisory until 4 AM EDT Friday for LEZ444.