textproduct: Detroit/Pontiac

KEY MESSAGES

- Scattered showers and thunderstorms move into the Tri Cities today, expanding across the rest of SE Michigan tonight.

- An unsettled pattern continues Thursday into the weekend with periods of showers and thunderstorms likely.

- Temperatures remain seasonable through the weekend.

DTW THRESHOLD PROBABILITIES

* Low for ceilings below 5kft this evening, moderate tonight into Thursday.

PREV DISCUSSION

Issued at 324 PM EDT Wed Aug 5 2026

DISCUSSION...

Deformation stretches from Hudson Bay low pressure into the southern Plains, observed as a continuous band of cloud cover and line of convection that bisects mid Michigan. This boundary will very slowly drift into SE Michigan this evening and overnight, and has already started to generate low-topped showers over SW Lower MI and a line of convection across northern lower MI. So far have seen limited evidence of deep convective growth, effectively limiting severe chances this evening. The dry airmass is even more prevalent southeast of the cloud shield, which currently spans from Sturgis- Howell-Bad Axe and is a good delineation for rain potential this evening. While the cloud shield is expected to expand east into the Detroit Metro region overnight, rain chances hold off until overnight-early Thursday morning given the dry column in place (PW ~1.6" at MBS versus ~0.6" at DTW). Even then, duration of rain chances will mainly be tied to a glancing bout of moisture advection as a wave travels from Iowa to northern Michigan early Thursday morning. Thus highest PoPs exist in the Tri Cities and Thumb.

Higher confidence cloud cover keeps overnight lows several degrees above normal--in the mid to upper 60s, which is close to afternoon dewpoints across the Tri Cities and Thumb regions. MOS guidance is highlighting a brief window for fog around daybreak, mainly across the north where rainfall has saturated soils.

The surface trough lingers just to our west Thursday, keeping a weak convergence zone in tact before fully washing out Friday. This brings slightly cooler air into the region both due to the leftover post-frontal airmass and dynamic cooling, with highs forecast to be in the low 80s Thursday and mid 80s Friday. Thermodynamic profiles are right on the cusp of being unstable both days, but may struggle to break the cap as mid-level dry air surges in behind the departing wave. The best opportunities for convection both days will thus come if one of the many perturbations in the wave train slides through during the peak heating cycle. This provides the best support for mid-level moisture/cooling as well as a more organized wind field for updraft sustenance. Not out of the question for a stronger cell to produce gusty winds, but this is an outlier scenario in the model distribution. Periods of dry weather are expected to emerge between episodes of rain, and may even see some pockets of sunshine.

Longwave troughing stays entrenched across eastern CONUS through the weekend, transitioning to a zonal pattern aloft by early next week as the Atlantic high dislodges. Continued influence of the high through the weekend maintains a gulf moisture connection, keeping conditions unsettled as the wave train also persists. This supports a continued pattern of oscillating wet and dry periods into the weekend, while convective influence makes it difficult to pinpoint timing. Models at the moment are targeting late morning-early evening timing on Saturday for a frontal passage, which would be the most focused period of ascent this weekend. High temperatures stay seasonable in the mid 80s through the weekend as well.

MARINE...

A slow moving cold front will bring rain showers and a low chance for some isolated thunderstorms across the Great Lakes through tomorrow. For today, activity will primarily be focused across Lake Huron and the Saginaw Bay, with increasing rain chances expanding farther south into tomorrow as the front progresses. Winds generally remain light, shifting northwest or west after the passage of the front. High pressure builds in in the wake of the front, with a second cold front moving through Friday to Saturday. This will bring additional chances for showers and thunderstorms leading into and through the weekend.

DTX WATCHES/WARNINGS/ADVISORIES

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