textproduct: Detroit/Pontiac

KEY MESSAGES

- Periods of showers with potential for a few embedded thunderstorms until late tonight.

- Additional showers and storms possible Saturday with isolated strong to severe storms possible, capable of producing marginally damaging wind and large hail.

- Heat builds next week with reoccurring periods of thunderstorms.

DTW THRESHOLD PROBABILITIES

* Moderate in thunderstorms tonight and early Saturday morning.

* Moderate for ceiling 5000 ft or less tonight and Saturday.

PREV DISCUSSION

Issued at 845 PM EDT Fri Jun 5 2026

UPDATE...

Deep layer moisture advection in advance of a mid level short wave has led to widespread showers across most of Se Mi this evening. The forcing outpaced the instability and as a result there has not been much thunder with these showers. This wave will exit east of the forecast area late this evening. Subtle subsidence in its wake will drastically reduce the coverage of these showers, if not end them completely.

Attention then turns to a deeper wave now diving across nrn Minnesota and Wisconsin, forecast to advance into Lower Mi late tonight into Saturday. Elevated instability is forecast to advect into Se Mi during the night within strengthening deep layer west- southwest flow. There is some concern, especially in light of recent HRRR runs, that this influx of instability overnight will allow either the convection across Wisconsin to accelerate into srn Michigan or will support the development of additional convective clusters across srn Mi. This will be enough to warrant a continuation of at least chance pops during the overnight. The degree of upscale convective growth, if any, across srn Mi late tonight will also heavily determine whether there will be enough instability to sustain convective chances through Saturday. In short, a more robust convective response tonight will lower the chances for convection on Saturday as instability may be exhausted and convective induced short waves may allow for some meso scale subsidence to take hold. A forecast update was issued for evening convective trends. With still some uncertainty as to how convection will evolve overnight and Saturday morning, no major updates were made to pops at this time.

PREV DISCUSSION... Issued at 317 PM EDT Fri Jun 5 2026

DISCUSSION...

After an 8+ day stretch of rain-free weather, showers are lifting across Southeast Michigan. Confluent low-level winds have transported Gulf moisture up through The Plains and into Lower Michigan, while ThetaE advection has been even more aggressive within the mid-levels. This has raised PWATs from less than 0.50 inches this morning to over an inch, and PWATs should exceed 1.50 inches by this evening. Expectation for convective evolution is that showers should largely be void of thunder through the rest of today given lackluster instability. Latest SPC Mesoanalysis Viewer shows an axis of +500 J/kg SBCAPE extending across central Lower, but the ongoing convective showers are rooted eastward, along the gradient. Some uncertainty remains as to how quickly this activity moves east through the rest of the forecast area this evening, before losing a surface-based mixing connection. Should evening convection deepen to produce thunder, the severe threat would be low. Inverted-V soundings with DCAPE in excess of 750 J/kg support an isolated gusty wind threat along the unmodified lead edge, limited by displacement from the instability reservoir. Weak mid-level cooling after dark should offer a bit of elevated nocturnal instability for a few rumbles of thunder prior to midnight. Rising dewpoints lead to a warmer night, with lows only cooling into the mid-upper 60s.

Showers should generally be dissipating early Saturday morning as the lead shortwave moves east of the area, but the lull gives way to another opportunity for convection late Saturday morning and midday. Coverage of thunder carries a high degree of uncertainty, even as the track of a secondary mid-level trough digs cleanly through Lower Michigan. Distinct increase in instability is probable Saturday as dewpoints rise into the upper 60s with positive buoyancy lifting above 1000 J/kg, paired with EBS of 25-35 knots. Ascent will be boosted by an inbound could front draped across the Great Lakes. Main convective threats should be water-loaded microbursts/winds and possibly some stray larger hailstones. Convection dissipates quickly in the wake of the front Saturday evening as stabilization settles in. Surface high pressure over the northern Great Lakes leads to veering northerly flow and minor surface-layer cooling/drying on Sunday. Geopotential heights rise overhead Sunday while a cut-off low lifts northward from the eastern Plains, into the Upper Midwest. Precipitation with this wave should remain just west of the region, ensuring a dry Sunday forecast, locally.

The main two concerns for next week week will be Tuesday convection and then heat the rest of the week. A Pacific longwave trough nudges the orphaned cyclonic wave into Lower Michigan while anomalous moisture transport spills in from the southwest. This supports a high-CAPE low-shear convective environment. With dewpoints approaching 70F, strong to severe storms may arise Tuesday. By mid- week, a 590+ dam 500 mb ridge will extend from Baja California to Ontario which would allow for highs in the 90s. Given persistent humidity, potential exists for heat indices to approach 100F, which would raise concern for heat headlines.

MARINE...

Warm southerly winds topping out around 20 knots this afternoon are advecting moisture, with showers moving through the central Great Lakes. A surface low tracking through the central Great Lakes this evening will bring a renewed round of numerous showers and a few thunderstorms to the region, persisting into the night. Light, mostly westerly winds on Saturday. A weak cold front will sink southward late in the day, serving as the focal point for scattered, potentially marginally severe thunderstorms, with the highest probability over Lake St. Clair and Lake Erie. Very light northeast flow and dry conditions will follow for Saturday night and Sunday. Warm and humid weather returns early next week, bringing showers and thunderstorms on Tuesday. An upper level ridge will become reestablished for the mid week period, resulting in mainly light winds and and hot temperatures through the end of the work week.

DTX WATCHES/WARNINGS/ADVISORIES

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