textproduct: Detroit/Pontiac

KEY MESSAGES

- Dry conditions with near normal temperatures are expected through Saturday.

- Heat and humidity build back into the region Sunday-Monday with highs around 90 degrees and heat indices in the low to mid 90s.

- Isolated strong to severe thunderstorms are possible Sunday, with a more organized strong to severe weather threat looking to arrive Monday.

DTW THRESHOLD PROBABILITIES

* None.

PREV DISCUSSION

Issued at 333 AM EDT Fri Jul 24 2026

DISCUSSION...

Longwave troughing pattern holds in place this morning over eastern CONUS, with an embedded shortwave racing across the central Plains. High based cirrus associated with this wave and convective cloud debris clip the southern Great Lakes, but otherwise surface high pressure successfully keeps moisture well to our south to support plenty of sunshine and dry weather. The complementary thermal trough keeps highs a few degrees cooler than normal today--in the low 80s, with a couple degree boost into the mid-80s Saturday.

Dry conditions persist Saturday, but with a pattern shift on its way as winds organize out of the southwest during the day. Aloft, mid- level heights rise modestly in response to ridge amplification over western CONUS and the southern push of a strengthening Hudson Bay low. This draws the theta-e gradient east, folding instability into the Saginaw Valley and Thumb region early Sunday morning which expands south and east through the day. Multiple waves ripple around the ridge Sunday, attempting to engage the destabilizing airmass and generate showers and thunderstorms. Timing of these waves is still uncertain, although the latest 00z/06z guidance favors a round of morning convection and a second round of convection around peak heating. Opted for more bullish PoPs across the Saginaw Valley/Thumb Sunday morning given the strong synoptic support as the left exit region of an ~85 knot jet clips atop the building instability. MUCAPE will still be ramping up though, so only advertising a slight chance of thunder with this activity. Lingering dry air and/or subsidence from prior convection will then be hurdles to overcome Sunday afternoon, both of which could stall the eastward progress of moisture and instability. That said, if deep convection can develop in this environment, storms may become organized given the strong shear profiles (35-40 knots 0-6 km bulk shear). This is supported by the latest SWODY3 Marginal Risk and CSU machine learning probabilities.

Thunderstorm chances continue Sunday night through early next week as SE Michigan remains on the edge of the instability gradient under an active northwesterly jet and wave train. Best opportunity for organized severe weather comes sometime early next week as the low currently off the coast of the Pacific Northwest releases east around the ridge and induces cyclogenesis. Majority of deterministic models and ensemble members bring this wave to the Great Lakes region Monday night, although a smaller subset delays that until Tuesday. The strong synoptic signal in the guidance leans toward organized severe weather potential.

Outside of thunderstorm chances, the upstream ridge sends heat and humidity into SE Michigan beginning Sunday and lasting until the synoptic cold front comes through mid-week. Forecast highs in the upper 80s-low 90s carry low confidence given the thunderstorm potential and cloud debris. Heat indices in the mid-90s will be attainable if a drier outcome materializes.

MARINE...

Winds will be light southerly today as high pressure residing over the Mid Atlantic States stills exerts it influence. A surface trough slowly passing through during the weekend will bring a chance of showers and isolated thunderstorms, though winds are expected to remain light.

The next notable storm system arrives on Monday, as low pressure tracks across the northern Great Lakes. Strong thunderstorms are possible as the cold front works through the Central Great Lakes during the evening hours. Northerly winds behind this system late Monday night into Tuesday have the potential to reach 25 knots over southern Lake Huron.

HYDROLOGY...

Several rounds of showers and thunderstorms are possible Sunday into early next week. An increasingly humid and unstable airmass will lead to rainfall rates over an inch per hour in some thunderstorms. Recent dry weather and low soil saturation will help mitigate widespread flooding concerns, although localized flash flooding of low-lying, urban, and other flood-prone areas remains possible if thunderstorms repeatedly impact the same locations.

DTX WATCHES/WARNINGS/ADVISORIES

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