textproduct: Detroit/Pontiac

KEY MESSAGES

- Dry and cool through Friday.

- Rain returns by Friday night and continues into Saturday morning.

- A little milder this weekend, with chances for thunderstorms Saturday and Sunday.

DTW THRESHOLD PROBABILITIES

* Low for ceilings at or below 5000 feet tonight and Thursday.

PREV DISCUSSION

Issued at 259 PM EDT Wed May 20 2026

DISCUSSION...

Application of a mid level short wave across Lake Superior and NW Ontario and persistent mid level confluent flow across the eastern Great Lakes will allow sfc high pressure to expand eastward from Upper Mi/Lake Superior into upstate New York Thursday. The position of this high will lead to persistent east-northeast winds across Se Mi through the end of the week. Ample dry air circulating around the low/mid level anticyclone and broad large scale subsidence will maintain a dry forecast into at least the first half of the day Friday. The loss of diurnal clouds this evening within ongoing low level dry air advection will allow a general clearing trend during the night, increasing radiational cooling potential and warranting lows in the 30s and 40s. The inland push of the marine layer this evening suggests the coolest readings will be across the thumb region, which various ensemble members suggest min temps in the low to mid 30s. The gradient will support light surface winds and some increase in high level moisture is forecast late. This will warrant a mention of just patchy or areas frost in the thumb region. The large scale subsidence will limit overall mixing depths for the next few days. This and the persistent easterly flow off the cool lakes will keep temperatures a little below seasonal norms for late May. High will mainly be the 60s, with cooler readings expected along Lake Huron.

Latest probabilistic guidance is quite high with rain chances late Friday into early Saturday, resulting from a short wave forecast to lift into Lower Mi from the southern Mississippi Valley. Good moisture transport is forecast with this wave. Precipitable water values are forecast to increase to 1.2 to 1.5 inches within a respectable mid level isentropic ascent. With very little instability forecast, this looks to be more of a rain event Friday night. Recent forecast trends toward a more closed low to mid level circulation over Lower Mi on Saturday is suggestive of some diurnal instability warranting a chance for thunderstorms. Much of this will be predicated on the efficiency of low level warm air advection. While variance among model ensembles increase during the weekend, a secondary mid short wave is forecast to move into the region Sunday, with increased chances for higher instability. This will warrant another chance for thunderstorms.

MARINE...

High pressure is sliding east across the northern Great Lakes today and will hold through Thursday. Initially the increased northeasterly gradient from the high running up against the front just south of the region will increase winds just enough to necessitate a small craft advisory for the Lake Huron nearshore waters through this evening til midnight. As the high pressure system moves over the Great Lakes on Thursday, winds will begin to veer to the northeast and will hold northeast-east through Friday. The next low pressure system is then expected to enter the Great Lakes from the south late Friday into Saturday which will bring the next potential for showers and thunderstorms. The easterly winds will increase late Friday through Saturday with gusts possibly exceeding 25 knots through that period.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until midnight EDT tonight for LHZ421-441.

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