textproduct: Detroit/Pontiac

KEY MESSAGES

- Low chance for a shower tonight south of Detroit and Ann Arbor.

- Temperatures return to near normal this weekend with dry weather.

- Very hot and humid conditions are expected next week as heat indices will exceed 100F, especially Tues into the late week period. Potential exists for thunderstorms later in the week.

DISCUSSION

Lingering lower tropospheric troughing under weak forcing conditions has resulted in persistent lower clouds across much of Southeast Lower Michigan this Friday. Temperature recovery has been lacking - with 70F being a challenge for many locations.

While low clouds are thinning, they are being replaced by mid and high level cloud cover from an area of disturbed weather over the Ohio and mid-Mississippi Valleys. Meaningful shower coverage is occurring across much of that region this afternoon - with an extension northward toward Southern Lake Michigan along an inverted trough structure. This feature will roll east and have a minor influence near the Ohio border, where a few showers are possible tonight. Additionally, weak confluence under east/northeast flow conditions within the broad trough looks to be sufficient to support low cloud development over Lake Huron - inundating much of the Thumb region tonight - with a departure Saturday morning as cloud edge heating erodes the cloud field quickly.

An upper-level jet streak positioned over the Great Lakes today will squeeze east of the region by late tonight into Saturday. Entrance region dynamics associated with the jet will be adequate enough to support additional lower-level height falls and favorable cyclonic flow conditions across the Ohio Valley. A ribbon of low to mid- level deformation forcing will accompany this system on Saturday - skirting just south of the region - but offering some cloud presence from Detroit and areas farther south. Regardless, there will be greater influence from the high late June sun to encourage warming back to around 80F away from the big cool water.

A major flow regime transition remains on the docket for next week. A significant longwave compression episode - starting with a cyclonic wave break along the West Coast on Sunday - will induce dramatic downstream ridge amplification over the eastern half of the country. The shortening of the planetary-scale wavelength will boost height amplification - cascading into a strong deep subsidence event and establishment of a formidable heat dome. The entire global ensemble suite is trending toward a slower evolution of the ridge complex - thus suggesting a prolonging the heat effects through the entire week.

Upstream convective activity is anticipated Sunday along the northern periphery of the emerging heat dome. A few residual showers may wander in from the northwest late Sunday into early Monday - before mid-level stabilization via subsidence takes full form. Once it does, guidance projections of 700-mb temps >12C are common late Monday through Thursday - with meager signs of loosening grip until Friday. Highs will climb to near 90F on Monday then into the mid/upper 90s Tuesday through Friday. Furthermore, dewpoints will be around 70F, given the moisture availability via transport and evapotranspiration. This will limit the capacity to cool dramatically at night - with lows expected only to settle into the low-mid 70s. Net result will be daytime heat index values well over 100F for the balance of the week.

The trend is toward the geopotential ridge axis staying planted over the Upper Great Lakes through nearly the entire week - with only showing signs of broad softening on Friday - rather than migrating east like earlier cycles depicted. This configuration limits convective chances across the immediate region, and likely will until the subsidence forcing begins to relent Friday.

MARINE

High pressure will hold over the region through the weekend resulting in light winds and favorable marine conditions. A warm front will lift north through the region on Monday opening the door for very warm air to move into the region for next week. There will also be a chance of showers and thunderstorms for northern Lake Huron Monday as the front lifts north.

PREV DISCUSSION

Issued at 142 PM EDT Fri Jun 26 2026

AVIATION...

Lake moisture plume is maintaining some degree of lower VFR clouds and pockets of MVFR ceilings across southeast Michigan under mid and high clouds streaming overhead. A southeast wind near the southern lakes should affect metro terminal wind direction this afternoon while northern terminals hold out of E-NE. Conditions are expected to remain mostly VFR into tonight under a light E-NE wind. An Ohio Valley system will send an overcast mid cloud with potential for spotty light showers across later today into tonight. Will keep mention out of TAFs given low expected coverage if any. If enough clearing can occur tonight, some patchy radiation fog may develop. Confidence too low to mention in TAFs at this time as best potential for clearing would be east of the terminal corridor as a more easterly direction sets up across the lakes.

D21/DTW Convection... No thunderstorms forecast through Saturday.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5000 ft this afternoon and tonight.

DTX WATCHES/WARNINGS/ADVISORIES

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