textproduct: Detroit/Pontiac

KEY MESSAGES

- Mild and breezy today.

- A chance of thunderstorms this evening into tonight. Some storms may be strong or severe south of the I-69 corridor.

- Much cooler temperatures return Tuesday and last through the end of the week.

DTW THRESHOLD PROBABILITIES

* Medium for thunderstorms this evening and early tonight.

* Low for ceiling at or below 5000 feet today, then medium this evening and early tonight with convection.

PREV DISCUSSION

Issued at 300 AM EDT Mon May 4 2026

DISCUSSION...

Subtle mid level height rises and warming in the 900 to 700mb layer today will result in a formidable mid level cap by afternoon. There will be a good deal of sunshine through much of the day given the subsidence and dry air. Deep layer mixing up to 7k feet with 850mb temps forecast to rise to +10 to +11C this afternoon will support high temps in the mid 70s across much of the forecast area today. While not as windy as yesterday, model soundings still indicate a solid core of southwest winds of 25 to 30 knots in the mixed layer, which will support peak gusts in the 30-35 MPH range.

The gradual northward advection of a little higher boundary layer moisture (characterized by sfc dewpoints in the 50s) from the Ohio Valley into the southern portions of the forecast area late this afternoon and evening is shown by the 00Z model suite. This will support modest instability with 0-1km ML CAPE forecast to reach 1k J/kg per latest HRRR. SREF Surface based CAPE actually ranges from 1500 to 2000 J/kg in the far south. Forecast strengthening of the low to mid level SW wind fields across the nrn Ohio Vally this evening may support enough forced ascent across the srn portions of the area this evening to initiate convection. 0-6km bulk shear values during the evening are forecast to be a modest 20 to 30 knots. Model soundings do however indicate ample mid level dry air, suggestive of the potential for localized damaging winds and large hail. The HRRR and 3km NAM do indicate a localized axis of increased 0-3km helicity along the lead edge of the northward advancing boundary layer moisture axis during the evening, which may be supportive of a few supercells.

A surface cold front will be driven into Se Mi overnight courtesy of long wave trough amplification/mid level height falls across the Upper Midwest and northern Great Lakes. An influx of deep layer moisture will advect into Se Mi along and ahead of this front, with the surface based instability forecast to transition to elevated instability. This will support high chances for showers and thunderstorms. There is some variation among the hi res suite as to the available elevated instability, ranging from very little up to 1500 J/kg, with HREF around 500 J/kg. Given increasing deep layer shear profiles, lingering strong to possibly severe storms into the overnight are at least possible predicated on enough available instability.

The surface cold front is forecast to slowly move east of the forecast area on Tuesday. Favorable upper jet dynamics and potential short wave impulses lifting northeastward along the mid level baroclinic zone is forecast to increase frontogenesis along the elevated portions of the frontal zone Tuesday, possibly into Tuesday night. Recent 00Z model runs have trended a little more southeastward with the axis of forcing over southeast Michigan, in line with recent trends in the ensemble members. This will place the better chances for rain generally southeast of a Bad Axe to Owosso line, with the chances for heavy rain (over and inch) now more probable just east of the forecast area. Shallow post frontal cold air will lead to notably cooler temperatures on Tuesday. The long wave trough is forecast to hold across the upper Midwest and Great Lakes region through the end of the week, leading to seasonally cool temperatures with daytime highs in the 50s and nighttime lows in the 30s and 40s.

MARINE...

A brief lull in the slightly more elevated wind speeds will be likely through the late morning to early afternoon hours, outside of the Saginaw Bay where the southwest fetch remains favorable for localized higher winds. Some gust potential around 20 knots also remains possible across Lake Erie and Saginaw Bay given the brief reduction in stability through the morning hours. This lull in breezy conditions will be supported by increasing stability through the day as much warmer air surges over the Great Lakes. Isolated to scattered showers and embedded thunderstorms will be possible within the warm sector later this afternoon and evening, most favorable across Lake Erie and Lake St. Clair. Any stronger storm development will be capable of producing gusts aoa 34 knots. A broken line of showers will be possible with the cold front, with wind direction veering northwest in the wake of the front. Small Craft Advisories remain in effect through the Saginaw Bay as wave heights build towards the 4 ft mark, with the stronger wind potential favored for this evening through early tomorrow morning.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422.

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