textproduct: Detroit/Pontiac

KEY MESSAGES

- A statewide Air Quality Alert is in effect through today with lingering wildfire smoke across Michigan.

- Thunderstorms tonight will pose an isolated risk for severe weather.

- Mostly dry with temperatures at or just below average during the mid-late week period.

DISCUSSION

High pressure will drifts off the Mid-Atlantic Coast today leading to increasing southwest return flow. Influence from this high pressure will bring dry and around average temperatures this afternoon. Highs today should land in the low 80s for most the area. There remains haze/smoke from wildfires hanging around to the west and parts of the state today that will pivot back through the area as winds become southwesterly. Some improvements to the air quality are expected compared to the last several days, but concentrations still may be in the Unhealthy for Sensitive Groups AQI range per EGLE. Thus, an Air Quality Alert remains in place through today.

Prospects for showers and thunderstorms increase tonight as a potent Canadian shortwave and cold front swing across the region. Models do point to a vort max that will round the western CONUS ridge ahead of this wave early this evening, but lack of instability and moisture availability should keep the area mostly dry until later tonight. Hires models depict blossoming convection occuring west of Lake Michigan that arrives as a broken line into southeast Michigan. There is some uncertainty in regards to timing with convection first arriving between 04-06Z across the Saginaw Valley and spreading southeastward to the Detroit Metro region in the 10-12Z window. The greater uncertainty remains the available instability in the 06-12Z window as convection is expected to arrive with the greater synoptic support outpacing the instability. This would lean towards a weakening of any more organized convection as it moves into southeast Michigan. Though, moisture quality is expected to improve with PWATs to near 2.00 inches along with increasing deep layer shear and steepening mid- level lapse rates. This at least supports high PoPs for showers with embedded thunderstorms that will pose an isolated severe weather risk. Convective Outlook continues to carry a Marginal Risk for all of southeast Michigan with a small portion of Slight Risk across far northwest portions of the CWA. Damaging wind gusts and brief heavy downpours are the main threats.

System's cold front will be trailing behind the lead wave of thunderstorms in the morning and push through during the day. Destabilization will be questionable post morning thunderstorms. If frontal timing lags enough, additional thunderstorms will be possible that may pose an isolated severe risk. Favored area would be far southeast portions of the CWA (roughly along and south of a Port Huron to Adrian line).

Passage of the front will bring a noticeable drop in temperatures for Wednesday with 850mb temperatures falling to below 10C resulting in daytime high temperatures in the low to mid 70s. Surface high pressure should keep conditions mostly dry mid-week even with broad cyclonic flow aloft from the eastern Canadian closed mid-upper low. The only exception may be across the Thumb where a few showers early Wednesday may be possible as a shortwave drops across the north central Great Lakes. Michigan will remain under a dry and cooler northwest flow into the late week period while residing between the east Canadian trough and the western CONUS ridge. This brings temperatures roughly around average to close out the work week while limiting convective chances.

MARINE

High pressure influence wanes across the central Great Lakes today with dry initial conditions. Unsettled weather builds in this evening and overnight, as a strong low pressure system tracks across central/southern Ontario. Gusty winds ahead of the attendant front will lead to a period of Small Craft Advisory conditions, particularly across Saginaw Bay, where southwesterly flow channels more efficiently. A Small Craft Advisory has been issued for The Bay with additional Small Craft Advisories extending across the rest of the nearshore zones with time, as flow veers westerly, then northwesterly. Potential exists for showers and thunderstorms to overspread the waterways as the front moves through, supporting periods of locally higher winds and waves. Showery/stormy conditions could persist on Tuesday before high pressure from Alberta/Manitoba builds in by Tuesday evening, producing a drying effect. Tighter gradient flow arises Tuesday afternoon with an energetic northwesterly low-level jet favoring non-zero potential for a period of gusts to gales for portions of the Huron basin through Wednesday.

PREV DISCUSSION

Issued at 1141 PM EDT Sun Jul 19 2026

AVIATION...

Light winds and clear skies will last into early-mid Monday morning with high pressure overhead. Light south-southwest winds will develop by Monday afternoon as the high pressure system drifts east of the area. An influx of instability will arrive late Mon evening/Monday night in advance of a mid level trough. This will warrant a chance of thunderstorms in the TAFs.

D21/DTW Convection...No thunderstorms are forecast through Monday evening. The chances for thunderstorms increase during the early morning hours Tuesday.

DTW THRESHOLD PROBABILITIES...

* Low in thunderstorms late Monday night.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory from 2 PM this afternoon to 4 PM EDT Wednesday for LHZ421-422.

Small Craft Advisory from 4 AM Tuesday to 10 PM EDT Wednesday for LHZ441>443.

Lake St Clair...Small Craft Advisory from 4 AM to 10 PM EDT Tuesday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 4 AM to 10 PM EDT Tuesday for LEZ444.