textproduct: Detroit/Pontiac

KEY MESSAGES

- Low probability for severe weather today with conditional thunderstorm chances across the area.

- Mainly dry conditions develop Thursday through most of Saturday.

- Renewed chances for showers and thunderstorms late Saturday into Sunday.

DTW THRESHOLD PROBABILITIES

* High for ceiling 5000 feet or less this afternoon.

* Low for thunderstorms this afternoon.

PREV DISCUSSION

Issued at 942 AM EDT Wed Aug 12 2026

UPDATE...

Quick update this morning to add near 100% PoPs across the Thumb as a cluster of thunderstorms moves across the area. Based on upstream MRMS QPE, rainfall amounts of 0.25" to 0.50" will be plausible by late morning. Progressive nature to the cluster (storm motion of 40-45 mph) will push activity into Ontario in the next 2-3 hours. Clearing noted behind the line paired with mixing of fog/low stratus due to diurnal heating lends to decreasing cloud cover through the afternoon.

Several of the 09z-12z hi-res cycles hint at another possible window of thunderstorm activity this afternoon-evening. Forcing is tied to a weak low level wave forecast to track across Lower Michigan and effectively clear out the persistent convergence axis overhead. There will also be a low chance for development on the northern edge of the MCS currently over northern Illinois in similar fashion to yesterday. That said, the MCS position is already south of yesterday's system in an otherwise similar thermodynamic environment favoring the scenarios which keep it south of the state line altogether. Limiting factor again today is subsidence in the 850-600mb layer which has largely prevented convective initiation in this pattern so far.

PREV DISCUSSION... Issued at 359 AM EDT Wed Aug 12 2026

DISCUSSION...

Southeast Michigan remains positioned along the active periphery of a broad ridge currently centered over the southern Plains. Modest northwest flow aloft lingers as several shortwave perturbations work through the mean flow later today. The resident airmass remains moist and conditionally unstable, characterized by surface dewpoints in the upper 60s while a stalled frontal boundary lingers over Lower Michigan. With dewpoint depressions near zero and little to know gradient flow, areas of locally dense fog should continue for several more hours early this morning. Opted for a last minute Dense Fog Advisory along/south of I-69.

Forecast confidence remains low regarding convective evolution over the next 12 hours, in line with the last few days. Latest CAM solutions imply preference toward a persistence forecast approach, focusing on areas south of I-94 as a High Plains MCS should survive into the Ohio Valley. This runs contrary to SPC's Marginal Risk highlighting locations north of I-94. However, scattered activity cannot be ruled out for the northern portion of the CWA once the aforementioned front drifts southward as a weak cold front. The forcing along the frontal slope could trigger some attendant pop-up showers/thunderstorms within an area of stronger shear, steeper mid- level lapse rates, and higher instability. A water-loaded core or overachieving updraft may suffice for a borderline severe wind gust or hailstone. AI/ML models differ significantly, emphasizing the uncertainty between both areas of focus. Coverage should wane late this evening or early tonight.

The existing synoptic ridge axis begins to roll eastward Thursday, but will be reinforced by amplification over western CONUS. Mainly dry conditions are forecast for Thursday with high pressure building in, albeit the Ohio border area could still be susceptible to glancing convection from the perpetual MCS train tracks rolling through Indiana and Ohio. Low predictability exists to close out the week and over much of the weekend as flow weakens aloft and the longwave ridge gets flattened by a Canadian wave. The best chance for another moisture/warm advection surge arrives late Saturday into early Sunday as the Canadian trough tracks into Ontario with a cold front extending into the Great Lakes. Potential exists for organized convection with the frontal passage. A wind shift from south to northwest and a drop in temperatures and dewpoints to follow by early next week.

MARINE...

Weak wind fields will remain in place through Thursday as a frontal boundary hangs around the Great Lakes region before dropping south Thursday night. Periodic chances of showers and thunderstorms will persist through that timeframe. Any strong thunderstorms will have the potential to produce hail and winds in excess of 35 knots. With the lighter winds, there are some weak signals for patchy dense fog over Lake Huron at times, through confidence remains low.

A large area of high pressure builds into northern Ontario Thursday night, allowing north-northeast winds to increase on Friday. Winds are expected to reach at least 20 knots over southern Lake Huron, which may allow waves to approach 4 feet over the southern basin. The ridge extending from the high slides through Friday evening, supporting lighter winds into Saturday morning. Southerly winds will then peak out around 20 knots ahead of a cold front Saturday night, with winds shifting to west on Sunday behind the front.

DTX WATCHES/WARNINGS/ADVISORIES

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