textproduct: Detroit/Pontiac

KEY MESSAGES

- A statewide Air Quality Alert is in effect through Monday as additional wildfire smoke filters across Michigan.

- The next round of showers and thunderstorms arrives Monday night into Tuesday that poses a Marginal Risk for severe weather.

DTW THRESHOLD PROBABILITIES

* None.

PREV DISCUSSION

Issued at 332 PM EDT Sun Jul 19 2026

DISCUSSION...

Stretch of dry and stable conditions to finish the weekend period maintained by existing high pressure. High remains anchored locally through tonight, affording a window of meaningful radiational cooling as a weak pressure gradient and clear sky capitalizes on a slight reduction in moisture quality. This will yield overnight lows in the mid-50s across some rural zones and lower 60s within the Detroit urban heat island. Air quality will remain a concern into tonight as the Canadian wildfire smoke plume trapped beneath the strengthening near-surface subsidence inversion continues to oscillate across the lower peninsula. HRRR-Smoke profiles suggest localized visibility restrictions in haze/smoke through early Monday morning.

Dry and seasonable conditions exist into Monday. High pressure slips off to the Mid-Atlantic coast, affording a modest window of low level warm air advection as flow emerges from the south. This will support highs generally in the lower 80s. Potential does exist for a remnant convectively induced/enhanced vort max to eject out of the upper midwest and track into the lower peninsula late afternoon/ evening. Little evidence to suggest anything more than some increase in high based cloud should this scenario materialize, given the lack of both greater moisture quality or instability at this stage.

Attention then turns to the implications of greater height falls expected to expand across the great lakes Monday night and Tuesday. Convective initiation and expansion likely west of lake Mi by Mon evening as increasing large scale ascent supplements ongoing deeper moisture transport within the greatest instability reservoir. While some degree of nocturnal moisture advection will occur given the magnitude and trajectory of 850 mb flow, there remains some question as to depth and scale of this process. This subsequently casts greater uncertainty as to prospective convective coverage and vigor as ongoing activity spills downstream and into an inherently less receptive early morning window /after 06z/. Forecast continues to highlight a high likelihood of showers with embedded thunderstorms, carrying an isolated risk for strong wind gusts should a more supportive low level environment manifest despite the overnight timing. The parent shortwave and trailing cold front will move across Lower Michigan during the day Tuesday. Substantial cloud cover and ongoing morning shower activity will hamper destabilization, but trailing forcing along the cold front will keep a chance of scattered showers and thunderstorms in the forecast through Tuesday afternoon.

A deep upper-level closed low establishes over northern Ontario Wednesday, maintaining broad cyclonic flow over the Great Lakes. A solid period of cold advection by July standards will drop 850 mb temperatures into the single digits by afternoon. A steep lapse rate environment should offer a generous stratocu field, while lending to a lower end potential for diurnal shower production mainly across the thumb. Highs firmly below average in the low to mid 70s. The region remains tucked within the eastern edge of the dominant western US ridge, keeping dry but cooler northwest flow in place to finish the work week. Surface high pressure builds back over the Ohio Valley, suppressing convective chances and offering high insolation potential. Temperature remain at or just below average this period.

MARINE...

High pressure commands control of the central Great Lakes today supporting dry conditions and prevailing winds below headline criteria. Unsettled conditions build in late Monday and Monday night, as a strong low pressure system tracks across central/southern Ontario. Gusty winds ahead of the attendant front may lead to a period of Small Craft Advisory conditions, particularly across Saginaw Bay, where southwesterly flow could channel more efficiently. A Small Craft Advisory will likely be issued with the evening forecast update. Potential for showers and thunderstorms then increases across the waterways as the front moves through supporting periods of locally higher winds and waves. Wet weather could persist into Tuesday before high pressure from Alberta/Manitoba builds in by Tuesday evening with a drying effect. Strong gradient flow arises Tuesday afternoon with an energetic northwesterly low-level jet favoring low-end potential for gales across the Huron basin. Favorable dynamics remain in-place through Wednesday.

DTX WATCHES/WARNINGS/ADVISORIES

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