textproduct: Detroit/Pontiac

KEY MESSAGES

- Showers are likely with a chance of thunderstorms tonight and Wednesday.

- Dry weather with near-normal, pleasant temperatures returns for Thursday and Friday.

DISCUSSION

An upper level ridge axis (~591 DAM at 500 MB) slides east through the central Great Lakes this evening. Height falls tonight/tomorrow as a shortwave trough tracking through Montana this afternoon moves through Lake Superior. A moisture axis (PW values around 2 inches) over the Midwest to fold over/northeast into southern Lower Michigan Wednesday morning, with a cold front slowly tracking through southeast Michigan during the day. Showers are likely, but clouds and earlier timing likely limit instability, supporting only a chance of thunderstorms. The far southeast section of the CWA (ADG- DTW-PHN) stands the best chance of building up enough instability to draw some concern for strong thunderstorms, as wind fields are elevated (40 knots 850 MB). As such, gradient winds during the day will increase ahead of the cold front, and local probabilistic guidance suggesting wind gusts 25-30 mph. Machine learning also indicating a 2-5% percent chance of damaging winds over southern Monroe county, in line with the SPC Day 2 outlook. Any marginally severe chance will be dependent on later timing of activity.

Just a modest cooldown is expected for Thursday as 850 MB temps dip back toward 10 C underneath drying northwest winds. Fast pseudo- zonal flow over northern CONUS with an upper level ridge arriving Friday should maintain dry weather into Saturday morning before a low chance of showers arrives for the second half of the weekend. The amplitude of the trough swinging through varies amongst the medium range models. None-the-less, euro ensembles support just a modest cool down for Sunday, with temperatures remaining slightly above normal.

MARINE

South turning southwesterly winds strengthen tonight into Wednesday as seasonably strong low pressure system tracks across southern Canada into Hudson Bay. While a gust or two two could reach entry- level gales over central Lake Huron, winds are expected to peak around 30kts. Small Craft Advisories are in effect for the Saginaw Bay/tip of the Thumb through Wednesday evening as a result. Return of a humid airmass back to the region will support shower and thunderstorm chances for much of the day Wednesday before the attendant cold front crosses late evening. Moderate northwesterly flow follows for Thursday however only a glancing shot of cold advection and a rapidly diminishing gradient has high pressure builds caps winds aob 30kts.

PREV DISCUSSION

Issued at 146 PM EDT Tue Sep 8 2026

AVIATION...

VFR conditions will prevail this afternoon and early evening with ridging and strong anticyclonic flow trajectories in place. A +120kt Pacific upper level jet streak will push into the Great Lakes region later today ramping up thetae and moisture advection across Southeast Michigan. Deepest moisture with upright frontal structure will push into the area from north to south. Decided to go with TEMPO group between 8-12z at KMBS and KFNT. An axis of showers with some potential for isolated thunderstorms is then expected to work through all the terminals between 12-17z Wednesday. Mixed southwest winds of 10 to 20 knots is expected Wednesday.

D21/DTW Convection...Thunderstorms are not forecast this evening. Low potential for thunderstorm activity 14-17z Wednesday.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling 5000 ft or less through this evening.

* Low for thunderstorms on Wednesday.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory from 10 AM to 10 PM EDT Wednesday for LHZ421- 422-441.

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