textproduct: Detroit/Pontiac

KEY MESSAGES

- Dry conditions with near normal temperatures are expected through Saturday.

- Heat and humidity build back into the region Sunday-Monday with highs around 90 degrees and heat indices in the low to mid 90s.

- Isolated strong to severe thunderstorms are possible Sunday, with a more organized strong to severe weather threat looking to arrive Monday.

DISCUSSION

Another pleasant day today as surface high pressure remains centered over the central Great Lakes with most areas seeing highs around 80. Skies clear again overnight with the loss of diurnal cu allowing lows again to fall towards the mid-upper 50s. Surface ridge axis shifts over southern Ontario Saturday setting up light southwesterly low level return flow pushing temps back around late July averages in the mid 80s. This shift also marks the expansion of broad central CONUS mid-level ridging into the far western Great Lakes setting the stage for a more active close of the weekend locally as a series of ridge riding shortwaves drop into the region.

First of these waves sweeps across lower MI Saturday evening with no fanfare given the resident dry airmass. Its passage however does begin to fold in a piece of the richer theta-e airmass over the upper Midwest with gradual advection top-down in the column over the course of Saturday night. Lower level moisture looks to become established by early Sunday morning, coinciding with the arrival of the second wave, supporting scattered shower chances, particularly over the Saginaw Valley who reside under the left exit region of the upper Midwestern jet streak. A few embedded thunderstorms not out of the question as several J/kg of elevated instability accompany this moisture advection. This activity wanes by midday Sunday as the wave reaches Lake Erie/northern OH leading more importantly to a window for afternoon destabilization ahead of the next wave reaching the area in the evening. While SE MI is only under the edge of SPC's Day 3 marginal currently, this shortwave shouldn't be discounted with current mid-range model solutions all advertising an arrival in the ~21-00Z timeframe (NAM is a touch later towards 03Z). Favorable timing within the diurnal window would support MLCAPE values between 1000-1300 J/kg with bulk shear around 35-40kts. The main potential limiting factor, seen best in the 12Z RRFS, is a more robust morning convective scenario resulting in stronger trailing subsidence/capping that any evening convection would need to overcome first.

Some lingering showers/storms are possible to start Monday morning though the main convective chances come late Monday as the next wave reaches the western Great Lakes. Timing window is more muddled as model solutions range from late Monday afternoon (Canadian/NAM) to Monday night (GFS/ECMWF). That said, this system brings the strongest kinematics of any in the wave train as a mid-level trough digs into the upper Great Lakes. As such, even in the overnight arrival scenarios, organized severe convection would be in play (all of SE MI is under a SPC Day 4 15% risk outlook).

MARINE

High pressure remains centered over the central Great Lakes this evening maintaining light southerly winds outside of some shoreline effects towards Thunder Bay. Influence of said high wanes over the course of Saturday as a series of systems are set to drop out of the upper Midwest into the Great Lakes. First chances for a few thunderstorms arrive late Saturday night-Sunday morning though greater potential for scattered storms, including a strong to severe storm, is expected Sunday night.

The next notable storm system arrives on Monday, as low pressure tracks across the northern Great Lakes. Strong thunderstorms are possible as the cold front works through the central Great Lakes during the evening hours. Northerly winds behind this system late Monday night into Tuesday have the potential to reach 25 knots over southern Lake Huron.

PREV DISCUSSION

Issued at 145 PM EDT Fri Jul 24 2026

AVIATION...

Low impact weather prevails today as high pressure remains well established across the airspace. The center of the surface high is currently parked over Southeast Michigan, but drifting eastward, which has kept winds rather light and variable. Flow should trend more south-southwesterly with time today. Diurnal cumulus has blossomed with SCT-BKN coverage above 5 kft AGL. The loss of daytime heating this evening will cause low clouds to quickly dissipate by nightfall. Some high cirrus debris may stream through aloft tonight, while winds trend toward calm. VFR cumulus clouds return between 15Z and 16Z Saturday with winds becoming more uniform and southwesterly as the high breakdowns over northern Ohio.

D21/DTW Convection...No thunderstorms forecast.

DTW THRESHOLD PROBABILITIES...

* None.

DTX WATCHES/WARNINGS/ADVISORIES

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