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 tonight and Friday.

* Low in visibilities below 1/2 mile tonight and Friday morning.

PREV DISCUSSION

Issued at 355 PM EDT Thu Jul 16 2026

DISCUSSION...

Afternoon GOES West and recently restored GOES East satellite imagery show the expansive plume of forest fire smoke extending from the MN/Ontario border, over the Great Lakes, and into the mid Atlantic states. The plume is fortified by stable high pressure similarly aligned which is only allowing incremental visibility improvement as a proxy for density/concentration. Boundary layer mixing is clearly also limited by the cooling effect of the smoke on daytime heating that is limiting temperatures to the lower and mid 80s most locations. Nocturnal surface layer stabilization after sunset combines with just a slow eastward drift of high pressure to maintain similar smoke density tonight and Friday morning.

The next low pressure system, organizing in the northern Plains tonight, moves into the upper Midwest Friday. It offers an opportunity for smoke improvement over Lower Mi but not until Friday night as the surface warm front approaches from the mid MS/OH valleys. Until then, HREF and REFS mean QPF projects convection along and west of the warm front Friday afternoon which matches up well with hi-res versions of the NAM and RAP. This timing has sub- severe thunderstorms moving from the west toward SE Mi with isolated to scattered coverage late in the day and Friday evening. The warm front then moves SW to NE to help displace the smokey air mass into Ontario late Friday night.

The warm front moves into Ontario as low pressure reaches just north of the Straits by Saturday morning. There is good model agreement on this solution which places nocturnal/elevated convection mainly over the northern Great Lakes and northern Ontario Friday night, and places SE Mi in the warm sector of the system through Saturday morning. The trailing cold front is strongly supported for this time of year by the parent mid level short wave tracking over the northern Great Lakes, enough to maintain a band of showers and thunderstorms along the front Friday night and Saturday morning as the front moves through northern Lower Mi. REFS mean surface based CAPE is in the 1000-2000 J/kg range as the front enters central and SE Mi during the morning rising to around 2500 J/kg Saturday afternoon. The broad instability axis combines with the southern fringe of faster flow aloft to set up a respectable storm environment. Model forecasts of 0-6 km bulk shear averaging 30 knots presents an opportunity for organized thunderstorms Saturday afternoon until the front exits into Ontario and Ohio Saturday evening. SPC maintains a Marginal Risk for severe storms in SE Mi in the Day 3 update and this looks solid.

Passage of the cold front Saturday evening ushers in dry weather with cooler and less humid conditions Sunday into early next week. Extended range global models project a prolonged period of mid level trough development from Hudson Bay into southern Ontario. Low pressure systems track through this long wave pattern and reinforce cooler air across Lower Mi during the early to mid week period. This results in temperatures closer to, or even below normal, with lower potential for thunderstorms.

MARINE...

Dense smoke due to Canadian wildfires persists across the entire central Great Lakes today and into tomorrow. This supports the continuation of a Dense Smoke Advisory until 4 AM Friday for visibilities AOB 1 NM. Additional extensions in time may still be needed. Weak high pressure influence over the central Great Lakes maintains light north-northwest winds through this afternoon, although speeds may approach 20 knots 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 more active weather with periods of showers and thunderstorms arriving later in the day. 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 associated with a secondary, and more robust, low pressure system passing through The Straits on Saturday. High pressure builds back into the region late Saturday and Sunday supporting drier conditions.

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.