textproduct: Detroit/Pontiac

KEY MESSAGES

- Pockets of light rain toward the Tri Cities this evening become scattered to numerous showers and thunderstorms late tonight and Sunday morning. Additional rounds of showers and thunderstorms continue Sunday afternoon into Monday. - Severe storm intensity is not expected, however there is a chance for locally heavy rainfall mainly along and north of I-69 from late tonight through early Monday.

- The weather pattern supports warmer temperatures and increased humidity during the early to mid portion of next week, however with high temperatures strongly dependent on coverage and duration of lingering showers and thunderstorms.

DTW THRESHOLD PROBABILITIES

* Low in thunderstorms Sunday.

PREV DISCUSSION

Issued at 358 PM EDT Sat Aug 29 2026

DISCUSSION...

Another pleasant late August day under quickly thickening high clouds is in progress for SE Mi as high pressure centered on the Atlantic coast extends back into the Great Lakes. The high pressure air mass has carried temperatures on the mild side with low humidity over the last few days. This begins to change tonight as a broad area of low pressure developing across the Plains increasingly becomes the forecast concentration for the Great Lakes Sunday through the early week period.

First up is the MCS decaying nearby upstream this afternoon and the potential for remnants surviving into Lower Mi this evening, followed by a new round of nocturnal convection later tonight. Afternoon satellite and radar trends offer convincing evidence of MCS dissipation, but also of a robust MCV produced as a result. This wave is captured well by the range of deterministic models and is projected to move into the area with a chance of carrying remnants this far east or producing new scattered showers overhead this evening. Model depictions of the mid level theta-e ridge indicate slightly improved potential toward the Tri Cities and northern Thumb followed by a period of subsidence trailing the MCV heading into the post midnight hours. The Tri Cities and Thumb, down toward the I-69 corridor, is also the area favored for another round of showers/storms that move in from the Midwest late tonight and Sunday morning. This is convection forced by the low level jet more nearby to the west compared to this morning, from WI into western Lower Mi, which then follows the 850 mb theta-e ridge inbound ahead of the system warm front into central and SE Mi. The convective signal is convincing in both HREF/REFS ensemble mean QPF and in that from deterministic runs as well due to the involvement of the larger scale low pressure system. NBM rain probabilities are much improved in this model cycle offering chance POPs this evening trending to likely/numerous late tonight and categorical/widespread Sunday morning north of metro Detroit. No concerns for severe intensity given the considerable west to east instability gradient, however there is a low chance of localized heavy rainfall in the west to east alignment of convective development and downstream propagation.

The same is true for Sunday as low pressure moves toward the SD/IA/MN border and the warm front extends eastward into southern Lower Mi by Sunday afternoon. The position of the warm front maintains cloudy conditions all areas and showers again having greater coverage with northward extent from metro Detroit toward the Tri Cities and northern Thumb. HREF and REFS mean SB and MU CAPE are below 500 J/kg while mean PW approaches 2 inches through peak heating, limiting convective potential to an additional chance for locally heavy rain (see Hydro below) Sunday afternoon and Sunday night.

There was a slight edge toward model solutions moving the warm front into the northern Great Lakes for a lengthy period of time Monday afternoon and Tuesday, allowing a new round of heat and humidity to build into the region. Trends in today's model cycle are less favorable for full development of a warm sector into SE Mi during this time. Instead, model solutions suggest a flatter mid/upper level ridge and faster westerly flow aloft over the Great Lakes leading to quick progression of surface low pressure and arrival of the trailing cold front. This scenario both shortens the residence time of any potential heat and humidity while increasing the chance for clouds and additional showers/storms as the front stalls until perhaps Wednesday.

MARINE...

High pressure has drifted eastward over much of the eastern seaboard today as we now look west as the developing low pressure system and associated fronts that will slowly move into the area. Leading warm front will lift toward Lake Michigan today with increasing clouds and rain chances tonight through Sunday. In addition, a cold front will be drifting southward toward the northern Great Lakes adding to the forcing which will drive precipitation chances. Winds will largely be from the south today and Sunday with max gusts around 20 knots. Winds turn more southeasterly on Monday while remaining mostly below 20 knots before turning westerly on Tuesday.

HYDROLOGY...

Forecast confidence is increasing on an active pattern of showers and thunderstorms developing across central and southern Lower Michigan from late tonight through the early week. The system incorporates deep Gulf moisture into clusters of thunderstorms that generally have greater coverage along and north of the I-69 corridor where rainfall totals are expected to average 0.5 to 1 inch from Sunday morning through Monday morning. There is a chance for locally higher totals where thunderstorms occur repeatedly over a shorter time period, however these location and time details are unclear at this point in the forecast. This general pattern raises the chance for localized flooding of roads and poor drainage areas from early Sunday through early Monday. The chance for additional showers and thunderstorms also lingers later Monday into Tuesday.

DTX WATCHES/WARNINGS/ADVISORIES

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