textproduct: Detroit/Pontiac

KEY MESSAGES

- Showers and thunderstorms this afternoon with low probability for an isolated strong to severe storm.

- Breezy and cooler conditions arrive Sunday with scattered showers through Sunday night.

- Mainly dry weather Monday into Tuesday with a warming trend. The next chance of showers and storms is possible late in the day Wednesday.

DTW THRESHOLD PROBABILITIES

* Low in thunderstorms this evening.

* Moderate in ceilings aob 5000 feet Sunday.

PREV DISCUSSION

Issued at 320 PM EDT Sat Aug 22 2026

DISCUSSION...

A cold front passing across the area remains the focus for numerous showers and thunderstorms this afternoon. This is tied to an amplifying upper trough inducing divergence aloft and deep forcing along the frontal zone. This is enough forced ascent to produce high coverage of convection, but instability remains a limiting factor to the severe threat due to relatively cool surface temperatures and slow diurnal recovery in the wake of morning convection and persistent cloud cover. Radar trends over the past hour suggest the forcing is likely outpacing the recovery of instability, indicating a shrinking window for stronger to severe storms. Bulk wind shear of 30 kt remains the favorable parameter for some organized updrafts, and will continue to monitor storm trends as the front works through over the next couple hours. The main threat in any stronger convection remains wind gusts of 40 to 60 mph. Portions of Shiawassee, Livingston, and Washtenaw Counties received 2 to 3 inches of rain this morning, so these areas may also be susceptible to localized ponding/flooding as the line of showers works through. The surface front clears the area by around 6pm with weak instability lagging behind to keep a spottier coverage of showers and possibly a thunderstorm through this evening before forcing clears out.

The trough driving the cold front will continue to amplify tonight into Sunday with an anomalously deep closed low developing all the way up to 300mb. Forecast ensemble mean 500mb heights sit about 2 standard deviations below climatology for this system, which stalls just northeast of Georgian Bay into early next week. Its downstream placement will direct a steady feed of drier, cool air into the Great Lakes during this period, sending temperatures well below normal. Highs in the 70s and lows in the 50s will be likely Sunday and Monday. Northwest wind will be breezy to around 25 to 30 mph each day.

A strong vort max will dive southward directly across the area Sunday afternoon and evening, inducing higher lapse rates and a diurnal flare-up of shower activity. Soundings show respectable depth to narrow CAPE to allow for a chance of thunderstorms, but severe weather is not expected. Highest coverage of showers is favored target the Thumb where early season lake effect processes begin to come into play. By Monday, precipitation chances drop off and more sun is in store as gradual upper height rises commence. Thicknesses rebound as well, allowing a slight uptick in high temps.

A shortwave ridge passes over the region Tuesday into early Wednesday as the upper low slowly exits east and another shortwave trough works across central Canada. The resultant high pressure brings another dry day with a step up in high temps to around 80 degrees. Flow organizes out of the southwest on Wednesday as the upstream wave works into the western Great Lakes. This advects in higher moisture and a chance of showers and storms late in the day. The associated cold front is slated to track through by Thursday morning but additional showers will be possible through the rest of the day as the trough stalls in the vicinity.

MARINE...

Ongoing passage of a cold front will continue to support a line of showers and thunderstorms that will progress across the Great Lakes for the remainder of the evening hours. Any stronger thunderstorms will be capable of producing localized wind gusts aoa 34 knots. Wind direction will quickly veer from south-southeast to northwest in the wake of the front with cooler air supporting breezy conditions. A prolonged window for these breezy conditions are expected through tomorrow and a greater portion of the day on Monday, with gusts on the order of 20 to 30 knots. A longer fused Small Craft Advisory remains in effect for both wind gust concerns and for building wave heights in and around the Thumb given the sustained northwest flow. Otherwise, there will be a low chance for rain showers across Lake Huron tomorrow afternoon and evening with a very low chance for waterspout development. High pressure then builds in late Monday and settles in on Tuesday, bringing lighter winds to the area.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until 10 AM EDT Monday for LHZ421-441.

Small Craft Advisory until 4 AM EDT Monday for LHZ422.

Small Craft Advisory from midnight tonight to 10 AM EDT Monday for LHZ442-443.

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