textproduct: Detroit/Pontiac

KEY MESSAGES

- Showers with some possible embedded thunderstorms this evening. Severe weather is not anticipated.

- Above normal temperatures through the middle of the week.

- Additional chances for showers and thunderstorms Friday.

DISCUSSION

Isolated to scattered showers have developed along an elevated cold front/upper wave with narrow forcing between 750-650mb. The rain showers, which now extend through the Tri-Cities and Thumb, will progress through SE MI this evening. Overall convective buoyancy is weak with only a couple hundred J/kg MUCAPE to work with within a weakly capped environment. Surface dew point depressions around 25 degrees under a mini- inverted v sounding brings low-end potential for isolated wind gusts to 40 mph with any convective development. Some small hail will also be possible noting 1-6km bulk shear values around 25-30 knots. Thunderstorm development will be most favorable south of M59 where the modest cape gradient resides.

Shower chances end late tonight as the line exits south of the state with diffuse high pressure filing in overnight. This will support clear skies through the morning hours along with light winds. Accounting for the expansion of light shower development this evening, some patchy fog or a haze will be possible closer to daybreak given the clearing trends, but overall, model trends for decreasing visibilities remain very low at this time. Influence of the diffuse high pressure system with daytime mixing will promote clear skies through tomorrow afternoon allowing temperatures to peak aoa 70 degrees. The exception will be under the lake influence across portions of the Tri-Cities and Thumb, where northerly flow caps temperature highs in the 50s to 60s.

Expansion of a closed low system across the west coast inland and phasing with a mid-level wave across the western Canadian provinces will reinforce a strong longwave ridge across the Midwest and Great Lakes. 850MB temperatures around 12C set up across the Great Lakes Thursday and Friday as the ridge axis approaches and moves across the state. This will support above normal temperatures with daytime highs in or nearing the 70s for Thurs-Fri, with cooler temperatures within the lake shadow. There will be a low-end chance for a pop-up shower Thursday with the passing of a weak shortwave and increasingly likely chances for showers and storms Friday into Saturday once the trailing trough and cold front approaches the Great Lakes.

MARINE

A weak disturbance passes over the region this afternoon and evening, with scattered showers and thunderstorms tracking near southern Lake Huron, Lake St. Clair and western Lake Erie. A weaker pressure gradient offers lighter wind than experienced this morning, but localized higher gusts will be possible in any storms. A weak cold front clears the area tonight with light north to northwest wind following. Light wind carries through Wednesday into early Thursday as high pressure settles in. The next low begins to take shape over the northern Plains on Wednesday, eventually sending a warm front into the Great Lakes late Thursday into Friday. This brings moderate southeast flow and the next chance for showers and storms.

PREV DISCUSSION

Issued at 1248 PM EDT Tue Apr 21 2026

AVIATION...

An elongated, narrow corridor of showers now evident lifting across lake Michigan and southeast Wisconsin on pace to move across southeast Michigan this evening. While some embedded thunderstorms currently exist within this line, instability remains more meager locally so confidence in tsra occurrence will remain low. Brief increase in intensity may lead to some intervals of MVFR. Otherwise, prevailing VFR conditions will exist within a modestly gusty southwest wind. Forecast will maintain a window for lower stratus to emerge within the immediate post-frontal environment early tonight. Plausible the low level environment remains too dry to support a greater coverage. Any stratus development effectively clears as drying northwest flow develops through the early morning hours. Enough near surface moisture may remain to support some shallow fog formation.

For DTW/D21 Convection...there is a low chance of thunderstorms this evening between 23z and 03z as a cold front settles south across the airspace. If thunderstorms do develop, they are not expected to be severe.

DTW THRESHOLD PROBABILITIES...

* Medium for ceilings at or below 5000 feet this this evening between 23z and 07z.

* Low for thunderstorms between 23z and 03z.

DTX WATCHES/WARNINGS/ADVISORIES

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