textproduct: Detroit/Pontiac

KEY MESSAGES

- Mainly dry today with isolated to widely scattered showers possible focused over the Thumb this afternoon-evening.

- Scattered showers are possible Saturday morning. Additional chances Saturday afternoon in addition to isolated thunderstorm chances.

- Broader coverage of showers and thunderstorms possible Sunday evening and overnight, especially south of I-94.

- Cooler than normal temperatures are expected through at least the middle of next week.

DISCUSSION

Healthy diurnal cumulus response today as weak mid-level cold advection has supported steepening lower level lapse rates. Weak resultant instability (<500 J/kg) is focused over the Thumb where coolest air aloft resides offering an isolated to widely scattered shower chance through the evening. Lack of instability precludes thunderstorm chances however a rumble or two of thunder is possible given freezing levels around 7kft.

Shortwave ridging overnight is shunted east by the arrival of a compact wave arriving out of the upper Midwest late tonight-early Saturday morning. Accompanying nocturnal convection is expected to at least partially decay as it arrives over SE MI owing to both unfavorable diurnal timing as well as the lingering drier resident airmass (PW near 0.6"/Td near 50F). This AM activity does augment the column moisture profile as top-down saturation occurs by late morning supporting afternoon convective potential as a peak of ~500J/kg of MLCAPE develops. Greatest chances for convective showers and perhaps a thunderstorm continue to look favored over the Saginaw Valley/Thumb where the faint surface 'warm front' stalls providing a weak convergence axis in addition to closer proximity to the parent PV anomaly.

Another brief period of low amplitude mid-level ridging follows Saturday night into Sunday morning before a Plains shortwave ejects into the Ohio Valley late Sunday. Mid-range model trends have held with a more southerly track in the wave resulting in the attendant warm front holding near or just south of the state line. Given northerly flow over lower MI from northern Ontario high pressure, expect a sharper cutoff to the precip shield than the current broad brushed likely PoPs from the NBM. Areas south of M-59 stand the best chances to see showers Sunday night-Monday morning with heaviest rainfall totals (around 1") confined to near the Ohio border.

Thermal troughing continues to hold over the Great Lakes through midweek maintaining seasonally cool conditions with highs in the lower 70s and lows in the lower 50s. Next chances for showers and thunderstorms come Wednesday with the arrival of a weak upper Midwest shortwave.

MARINE

A ridge of high pressure will build in tonight through tomorrow morning which will diminish wind speeds and gust intensity overnight. A diffuse area of high pressure will then hold over the Great Lakes through the weekend which will support lighter winds. Periodic rain showers will be possible as multiple upper-level disturbances move over the region. A low pressure system will then arrive over the Ohio Valley and southern Great Lakes Sunday night to Monday morning, This will bring the next likely chances for rain and some embedded thunderstorms and some stronger wind gusts, mainly across Lake Erie and Lake St. Clair.

PREV DISCUSSION

Issued at 100 PM EDT Fri Jun 19 2026

AVIATION...

Scattered to broken VFR CU developed on schedule late this morning, with at least scattered clouds persisting through the hanging around for the afternoon. Breezy westerly winds topping out around 25 knots will continue, but then quickly subsiding early this evening and backing to the southwest.

The next low-pressure system tracks into the western Great Lakes tonight. This system produces scattered showers that move into southeast Michigan with pockets of MVFR ceilings toward sunrise Saturday. As the low moves through northern Lower Michigan on Saturday, continued redevelopment of showers expected, but mainly over the Thumb region and northern taf sites. There is also a low chance of an isolated thunderstorm both late tonight and Saturday. D21/DTW Convection... Very low chance of a thundestorm late tonight into Saturday.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5 kft this afternoon, moderate late tonight and Saturday.

DTX WATCHES/WARNINGS/ADVISORIES

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