textproduct: Detroit/Pontiac

KEY MESSAGES

- Dry and cool Wednesday through Friday morning.

- Rain returns by Friday evening and continues into Saturday.

DTW THRESHOLD PROBABILITIES

* Low for thunderstorms 20-23Z this evening.

* High for ceilings at or below 5000 ft tonight.

PREV DISCUSSION

Issued at 232 PM EDT Tue May 19 2026

DISCUSSION...

Pressure fields clearly show the prefrontal trough tracking through western sections of the CWA. This trough will serve as the focus for continued convection. Southwest gradient winds have been gusting 30 to 40 mph this afternoon, indicative of some decent wind fields. With temperatures reaching the mid-80s and dew points in the mid-to- upper 60s, MLCAPEs have reached 1500+ J/kg south of M-59. Per latest SPC mesoscale analysis and DTW ACARS data, the CIN/cap has eroded completely. Thus, further shower and thunderstorm development is expected through the rest of the afternoon. A severe thunderstorm watch is in effect for the eastern two-thirds of the CWA until 7 PM, but there is a good chance it may be canceled earlier.

Localized/scattered damaging wind gusts should be the dominant hazard, given the mainly unidirectional low-level flow and good downdraft capes. However, because of the earlier start to activity and weak convergence along the prefrontal trough, it may be tough to sustain updrafts to support organized severe storms (barring any interactions with outflow boundaries).

The actual cold front still needs to move through during the evening hours, and additional storms will be possible with any leftover instability. However, expect this prefrontal activity to deplete much of the fuel for the main front.

Upper-level confluent flow and sprawling high pressure (1032 MB) will be in place tomorrow through Friday morning over the Great Lakes region, supporting dry and cool weather.

Rain showers will return by Friday evening, however. Longwave troughing over the Rockies will capture and send a subtropical shortwave and moisture-laden warm front into southern Lower Michigan by Friday night. 850 MB dew points are progged to reach into the lower teens (Celsius) on Saturday. EPS probabilities for 24-hour rainfall exceeding half an inch are in the 60-70 percent range for the bulk of southeast Michigan.

MARINE...

Small Craft Advisories remain in place into this evening as southwest winds gust around 25 knots along the land/marine interface. The development of strong to severe thunderstorms is increasingly likely this afternoon into the evening, favored across southern Lake Huron and locations south. A Severe Thunderstorm Watch is now in effect until 7PM EDT. Wind gusts aoa 45 knots will be the primary hazard for severe weather development. Passage of the cold front will end the severe weather threat, veering winds from the southwest to northwest through the evening. High pressure builds behind the front, bringing lighter winds through the midweek period.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422- 441>443.

Lake St Clair...Small Craft Advisory until 10 PM EDT this evening for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT this evening for LEZ444.