textproduct: Detroit/Pontiac

KEY MESSAGES

- Rain shower chances return Wednesday morning to early afternoon.

- Much colder air arrives by late week and holds through the weekend resulting in frost/freezing potential.

DTW THRESHOLD PROBABILITIES

* Low for ceiling 5000 feet or less late tonight. Moderate in the morning. High Wednesday afternoon and evening.

PREV DISCUSSION

Issued at 247 PM EDT Tue Apr 28 2026

DISCUSSION...

Localized mid-upper level positively tilted trough axis currently lifting in Quebec has allowed for a temporary bout of 1000-500mb geopotential height rises over Southeast Michigan this afternoon. Plan view perspective of saturation on isentropic surfaces supports steeper isentropic downglide and greater absolute dry air advection occuring after 18z. With the drier air and mature boundary layer late expectations are for a temporary clearing trend this evening. Temperatures should quickly fall into the upper 40s to lower 50s by the late evening.

Combination of approaching composite trough axis with emerging left exit region dynamics off of southern stream jet streak will provide synoptic scale support for Ohio River Valley low pressure system late tonight and Wednesday. While a signal exists in the moisture progs for saturation and baroclinic leafing within the 850-500mb layer extending up into Southeast Michigan, no significant frontogenesis is progged locally across Southeast Michigan. As a result, this is expected to be a low QPF event with perhaps a tenth or two possible south of Detroit. No big changes are anticipated to the gridded forecast which has PoPs at 40--60% chance mainly between 08-18z.

A large upper level closed low pressure system and troughing is forecasted to take residence and persist over areas from Lake Superior northward to Quebec and James Bay from Thursday through at least the end of the period Monday. The coldest stretch is anticipated Friday and Saturday with 850mb temperatures of -6 to - 7C. Frost and Freeze headlines will at least need to be considered Wednesday through Saturday nights with lows expected to be in the upper 20s to lower 30s. Persistent troughing will bring steep midlevel lapse rates and a good pattern for afternoon precipitation chances. Most days will see a chance of rain, however, Thursday afternoon could see a few wet snowflakes across the Thumb region as the absolute vorticity maximum and cold air aloft emerges out on Lake Huron.

MARINE...

Exiting surface low pressure continues across James Bay into northern Quebec tonight, causing the pressure gradient to steadily relax. This eventually leads to weaker winds, veering anticyclonically toward the north. Remaining Small Craft Advisory should expire on-schedule as winds/waves respond to decreasing flow into the evening hours. A more diffuse surface pressure field emerges on Wednesday as the central Great Lakes becomes positioned between several weak surface high pressure centers to the west. Mid- level troughing likely persists overhead on Wednesday with a weak surface reflection lifting through the Ohio Valley. This lends potential for periods of light showers, but a lack of instability precludes any thunderstorm concerns. Water-level winds generally hold northwesterly through the rest of the workweek with additional chances for weakly forced light precipitation. High pressure then attempts to build in from central Canada/CONUS over the weekend. Low predictability exists in the large-scale pattern evolution as eastern Canada low pressure retrogrades toward the Great Lakes. No additional marine headlines are expected through Saturday given latest wind/wave trends.

DTX WATCHES/WARNINGS/ADVISORIES

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