textproduct: Detroit/Pontiac

KEY MESSAGES

- Scattered showers and storms again today as low pressure drifts south of the state. Bulk of activity expected south of I-69.

- Locally heavy rainfall is the primary threat from these storms though an isolated damaging wind gust can't be ruled out.

- Seasonably average heat and humidity to start the new work week with highs in the lower to mid 80s Monday-Tuesday.

DTW THRESHOLD PROBABILITIES

* Medium for thunderstorms this afternoon and evening. * High in ceilings aob 5000 feet this afternoon through tonight.

PREV DISCUSSION

Issued at 845 AM EDT Sun Jul 5 2026

UPDATE...

A forecast update was issued to reflect current meso scale trends with respect the widespread rainfall now impacting the southern portions of the forecast area. A slow moving mid level short over the Mi/Oh border is associated with a compact mid level deformation area along and just northwest of the mid level wave. The forced ascent within very high moisture (precipitable water values around 1.9 inches within the short wave) and weak elevated instability has produced locally intense rainfall rates within the compact deformation axis. While hi res solutions have been struggling to fully resolve this wave and axis of heavy rain, current observational trends suggest a good portion of the southern half of metro Detroit/Ann Arbor areas and points south may be impacted by this through the rest of the morning, with some indications of periods of ascent and mid level convergence persisting into the evening.

Given the timeline, short fused flood advisories and warnings will be the avenue to address any flooding concerns today.

PREV DISCUSSION... Issued at 308 AM EDT Sun Jul 5 2026

DISCUSSION...

Developing scattered showers over southern MI mark the arrival of height falls tied to a mid-level shortwave pushing into northern OH. The resident humid, unstable airmass doesn't require much in the way of forcing leading to blossoming coverage through the rest of the morning as a N/NW flank deformation coalesces over southern SE MI. The stalled frontal boundary bisecting the region sags south over the Metro Detroit area this afternoon providing a surface convergence axis to become the focal point convective initiation. Main concern with this feature is the potential for locally heavy rainfall and flooding- both from training as the parent wave is slow to pivot across OH maintaining deformation across southern SE MI for most of the afternoon-evening, as well as slow individual storm motion as column winds are aob 15kts through 500mb. The storm environment itself is also very favorable for heavy rainfall rates with PWATs around 1.8" and warm cloud layers around 13kft promoting efficient rain processes. While the lack of column wind/shear precludes much in the way of storm organization, still can't rule out a localized downburst as the strongest cells eventually collapse.

Shortwave trough is slow to fully peel away from the southern Great Lakes tonight as the now fully closed mid-upper circulation essentially crawls across the Ohio/Tennessee Valleys. Result is lingering light shower chances through most of the night, mainly along/south of M-59. Drier conditions look to become established by Monday morning as the system slides just enough east to shift showers over Ontario/northern Ohio with weak surface high pressure building in from the northern Great Lakes. Seasonably average temperatures accompany this high with highs in the lower to mid 80s.

Above average temperatures look to make return midweek as low amplitude Plain's ridging is folded/squeezed into the Great Lakes- Ohio Valley in response to an upper trough ejecting out of the northern Rockies. With the ridge progged to flatten as this occurs, the core of the associated hotter airmass is favored to hold southwest of the region towards the Mississippi with SE MI instead residing on its fringe. As such, this would limit the chance at seeing highs in the 90s Wednesday with temps topping out in the upper 80s. Trough eventually crosses the Great Lakes Thursday offering the next shot for the area to see rain.

MARINE...

Northeast flow holds through the day in the wake of a cold front. Winds generally remain light given a weaker pressure gradient outside of the Saginaw Bay, where the favorable fetch brings localized strong winds that range between 20 to 25 knots. As a result, a Small Craft Advisories will be in effect through the day. Some additional shower and thunderstorm chances will also remain possible through the day today under the warm and humid airmass. High pressure builds in tomorrow through Tuesday which will promote dry weather along with continued light flow.

HYDROLOGY...

A weak area of low pressure reaches the Ohio Valley today sparking additional scattered showers and storms, particularity south of I- 69. A stalled frontal boundary currently near M-59 is expected to become a focal point for storm development this afternoon over/around the Metro Detroit area. Environment is favorable for heavy rain with rainfall rates in excess of 1"/hr, with rates near 2"/hr in the most robust storms. Additionally slow storm motion and potential for training along the boundary could lead to areas of localized storm totals in excess of 3 inches. If this occurs there is increased potential for flash flooding especially in urban, low- lying, and flood prone areas.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422.

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