textproduct: Detroit/Pontiac

KEY MESSAGES

- A Severe Thunderstorm Watch remains in effect for parts of Southeast MI this afternoon and early evening.

- An Air Quality Alert is in effect north of I-69 today due to wildfire smoke returning from the north this afternoon. A statewide Air Quality Alert has been issued for Sunday.

- Benign weather Sunday and Monday before the next round of showers and thunderstorms arrives Monday night into Tuesday.

DTW THRESHOLD PROBABILITIES

* Low in ceilings aob 5000 feet Sunday.

PREV DISCUSSION

Issued at 338 PM EDT Sat Jul 18 2026

DISCUSSION...

Today's cold front has reached northern Metro Detroit and will continue to advance southward before exiting the area by early evening. The bulk of deep convection along the front so far this afternoon has been east of I-75 where deeper moisture and better frontal convergence appear to have set up. A Severe Thunderstorm Watch remains in effect for areas south of the front as we continue to monitor additional development. Wind gusts of 45 to 65 mph will be the primary threat. Based on current trends, suspect we will be able to end the watch locally before the current 8pm expiration time. Behind the front, breezy northwest wind has pulled down some of the northern Great Lakes wildfire smoke plume. This will take residence through the evening into tonight. Current visibility and AQI observations indicate a lower concentration of PM2.5 than was seen earlier this week.

Weak mid-level height rises allow high pressure to build into the Great Lakes on Sunday, with northeast flow through much of the day bringing in a dry air mass with seasonable temps. One or more additional bands of wildfire smoke will likely work across the area but available models generally show a decreasing trend in concentration with time. The high passes into the Mid-Atlantic on Monday with southwest return flow bringing rising thicknesses and slightly higher temps. Another dry day is forecast as deeper moisture will hold farther upstream until Monday evening. A shortwave ushers in a plume of deeper moisture along the surface warm front Monday night and brings the next round of showers and thunderstorms. Severe prospects are uncertain given the mainly nocturnal timing, but some pockets of heavy rain will be possible. The cold front will lag behind, likely passing through during the day Tuesday. This leaves the door open for some additional convection Tuesday but chances may be hampered by the activity Monday night and Tuesday morning.

The upper air pattern shows an amplified trough tracking across northern Ontario and the Great Lakes Tuesday into Wednesday. 850mb temps are modeled to fall to the single digits C by Wednesday, which favors cooler highs in the 70s. Deep cyclonic flow and passing shortwaves aloft bring potential for showers. Northwest flow remains pervasive over the region into the late week as a strong ridge dominates the western CONUS - this keeps seasonable temperatures and lower humidity around locally.

MARINE...

Cold front settles south of the region this evening. A brief period of gusty post-frontal northwest winds will exist through early tonight, with an accompanying increase in wave action along the nearshore waters. This will maintain a period of small craft conditions lasting into tonight. Benign weather conditions with lighter winds will then exist Sunday as high pressure builds across the area. Unsettled conditions may develop again by late Monday and Monday night, as a strong low pressure system tracks across Ontario. Gusty winds ahead of the attendant front may lead to small craft advisory conditions Monday, particularly across Saginaw Bay. Potential for showers and thunderstorms will increase during this time.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Beach Hazards Statement until 10 PM EDT this evening for MIZ049.

Lake Huron...Small Craft Advisory until midnight EDT tonight for LHZ421-422.

Small Craft Advisory until 4 AM EDT Sunday for LHZ441>443.

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