textproduct: Detroit/Pontiac

KEY MESSAGES

- Periodic chances for showers and thunderstorms continue through much of the week. Tuesday carries a Marginal Risk for severe weather with Wednesday evening carrying a Marginal to Slight Risk.

- Warm and humid conditions develop through mid-week. Daily peak temperatures will depend on cloud cover and precipitation.

DTW THRESHOLD PROBABILITIES

* Low in thunderstorms this afternoon, tonight and early Tuesday.

PREV DISCUSSION

Issued at 946 AM EDT Mon Aug 31 2026

UPDATE...

Like yesterday morning, have increased pops as tropical moisture (12z DTX sounding indicating 7 C dew pt at 700 MB) has supported a thick canopy of clouds once again with healthy coverage of high based showers as a shortwave tracks through Lower Michigan. Instability continues to be meager, preventing flooding rainfall and limiting coverage of thunderstorms. Made no adjustments to maxes, as forecast is lower than MAV/MET/ECS guidance and certainly the right direction with extensive cloud cover taking much of the day to thin out.

PREV DISCUSSION... Issued at 400 AM EDT Mon Aug 31 2026

DISCUSSION...

An unsettled/active weather pattern is expected to set up over southeast Michigan through this week as we reside on the north end of a flattened mid/upper level ridge. The center of this ridge will be slow moving across the mid Mississippi River Valley and over the OH/TN River valleys over the next several days. Quasi-zonal mid- level flow and southwesterly low level flow will allow for a persistent warm and moist airmass across the region. This will help support near daily shower and thunderstorm chances throughout most of the week as shortwaves waves and frontal/baroclinic zones capitalize on the favorable warm and humid environment.

For today, a warm front will be the focus for scattered showers this morning into the afternoon. There will be a decreasing precipitation trend with time today as the front is drawn northward by the progression of the Midwest low pressure system. Low level jet forcing over the front will kick off the highest coverage of chance PoPs this morning through 18Z this afternoon. Not expecting a severe thunderstorm threat as instability will be limited with poor CAPE depth and MUCAPE values of less than 500 j/kg. The threat of heavy rainfall has decreased to some degree with this additional round of precipitation across the Thumb, especially with the break in precipitation last evening. QPF through 18Z this afternoon offers 0.25-0.50" of rainfall with some model support for up to an inch possible across the portions of the Thumb. Warmer airmass pushing into southeast Michigan today with 850 mb temperatures towards 20C will support highs towards the mid 80s if enough clearing can occur post morning activity.

Better instability will build across the area on Tuesday with a weak cap present. HREF highlights mean surface CAPE values increasing to 2000+ j/kg during the afternoon. Steeper mid-level lapse to around 7C and 0-6km bulk shear values of 30-45 knots will be more than supportive of more organized convection if any activity is able to develop. Hi- res models showing a bit of variety in both timing and overall convective response, so Tuesday still carries a degree of uncertainty with the better forcing mechanism ill-timed with the better diurnal instability. Given the favorable environment, any storm that can develop should be able to mature and be capable of a severe wind and hail threat along with heavy downpours. SPC has maintained a Marginal Risk for severe weather across all of southeast Michigan given the favorable environment.

Wednesday looks like the best chance to be the warmest day of the week if the higher coverage of clouds and precipitation hold further to the north. This could push temperatures in the afternoon to around 90 degrees. As with most of the days this week, any higher coverage of precipitation and clouds will temper NBM forecast highs. Cold front and height falls forecast to arrive late Wednesday afternoon into Thursday bringing additional chances for showers and thunderstorms. Favorable environment for strong to severe thunderstorms will again be in place with MLCAPE values to 2000+ j/kg, steep mid-level lapse rates, and favorable shear that will pose a wind and hail risk.

MARINE...

Several days of unsettled weather as a primary low pressure system over central Canada and secondary low over the northern Plains send a series of fronts across the region. Periodic showers and thunderstorms will accompany the fronts while the slightly cooler air over the waters brings chances of waterspouts with the storms over the lakes. Winds will largely be from the southeast today with max gusts up to 20 knots. Winds turn briefly westerly on Tuesday before turning back to the southwest on Tuesday night.

HYDROLOGY...

Another round of showers and thunderstorms this morning to the early afternoon mainly north of the I-69 corridor, particularly across the Thumb. Average rainfall totals are in the 0.25" to 0.50" range with localized areas up to 1 inch possible this morning until early afternoon. Flooding threat has decreased compared to yesterday, but localized minor flooding of roads and poor-drainage areas will be possible if repeated rounds of heavier downpours occurs. Isolated to scattered severe thunderstorms will be possible on Tuesday and will come with a heavy rainfall threat if any organized storms are able to develop.

DTX WATCHES/WARNINGS/ADVISORIES

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