textproduct: Detroit/Pontiac

KEY MESSAGES

- Dry conditions with near normal temperatures are expected today.

- 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 Sunday, with a more organized severe weather threat arriving Monday. Damaging winds are the primary hazard both days.

DTW THRESHOLD PROBABILITIES

* None.

PREV DISCUSSION

Issued at 338 AM EDT Sat Jul 25 2026

DISCUSSION...

The 00z.KDTX RAOB sampled a very dry airmass last night, with PWAT of 0.61" falling in the 10th percentile of daily sounding climatology. The dry column is still in place this morning, with mostly clear conditions observed via satellite across Lower Michigan. Intervals of cloud anchored to a shortwave over the Upper Midwest will begin to work across Lower Michigan around mid-day, although not expecting any precipitation given how dry the resident airmass is. The wave combined with a shift to southwest flow signals the pattern shift on tap for Sunday-Monday, with just one more day of seasonable temperatures in the mid-80s before warm and humid conditions arrive.

Main drivers of this pattern shift are the amplifying ridge sprawled over western CONUS and a strong low over Hudson Bay. Placement of these features puts the Great Lakes within the enhanced belt of NW flow aloft and in the path of multiple embedded shortwaves over the next couple of days. Arc of instability advects into SE Michigan late tonight-Sunday coincident with the arrival of left exit region dynamics, triggering shower/isolated thunderstorm chances as early as Sunday morning across the Saginaw Valley/Thumb. The instability plume then presumably expands into all of SE Michigan during the day Sunday, with models signaling possible peak heating redevelopment followed by MCS potential overnight-Monday morning. The enhanced NW flow (35-45 knots at 500mb) will be supportive of organized convection, but with low confidence in timing and coverage. SPC SWODY2 Marginal Risk reflects the uncertainty in both scenarios, where several models suggest a capping inversion is in place during the afternoon and/or send the nocturnal MCS activity to our south/west toward the instability bullseye. For any thunderstorms that do overcome these barriers, main concerns will be damaging wind and heavy rainfall.

The more organized severe weather potential still looks to be latter half of Monday with the arrival of the surface low and cold front. This is going to depend largely on how convection unfolds throughout the day, and how much instability is available to be engaged by the stronger forcing. Still looking at a lot of model variability for Monday, including thunderstorm coverage, timing of the frontal passage, etc. which makes it difficult to glean any meaningful details from the global/regional models beyond a broad severe weather threat. All modes of severe weather are possible including heavy rain, although damaging wind is again the primary threat. The latest SWODY3 puts all of Lower Michigan in a Slight Risk of severe weather.

The other aspect of this airmass is the heat and humidity, in which temperatures both Sunday and Monday climb toward 90 degrees. This pushes heat indices into the low-mid 90s each afternoon, supported by a humid airmass with dewpoints in the 70s. More seasonable temperatures then return mid-week behind the frontal passage, with drier weather also anticipated.

MARINE...

Influence of high pressure wanes over the course of today as it moves more along the Atlantic coast and as low pressure organizes over the Plains states and central Canada. Light southerly wind between the systems pulls warmer air and greater instability into the central Great Lakes leading to increasing thunderstorm activity by Sunday, including the chance for a strong to severe storm Sunday night. The primary low pressure system then tracks across the northern Great Lakes during Monday. Thunderstorm activity continues to increase coverage and intensity with this system, especially along the trailing cold front that brings a chance of strong to severe thunderstorms as it moves through the region. Outside of storms, wind and waves are low until the northerly wind shift post front late Monday night into Tuesday when speed has 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.