textproduct: Detroit/Pontiac

KEY MESSAGES

- There is a Marginal to Slight Risk for severe weather today. Severe weather will be possible this morning mainly south of M59, with additional chance near the Ohio border this afternoon.

- Heavy rainfall and localized flooding will also be a threat today due to heavy rain the past few days and the potential for training storms in a very moist environment.

- More seasonable temperatures and lower humidity are slated to return this weekend.

DTW THRESHOLD PROBABILITIES

* High for ceiling 5000 ft or less today and tonight.

* High in thunderstorms this morning. Low this afternoon and evening.

PREV DISCUSSION

Issued at 326 AM EDT Fri Sep 4 2026

DISCUSSION...

Active early September weather pattern continues one more day as the northwest flow remains over the region, downstream of the strong Plains ridge which will reamplify today. Currently, the stalled front remains draped across southern MI but has been muddled a bit by the large convective complex that rolled through Thursday afternoon and evening. That complex also pushed the main instability gradient westward. The next mid level wave is already initiating convection over WI which will work through SE MI early Friday morning. This wave will have skinny elevated CAPE and moderate mid level lapse rates but alot of moisture with PWATs still running around 2 inches and surface dewpoints pushing 70 again. Though the developing complex will be outrunning the instability, expectations are for the low level jet to help keep activity going into SE MI this morning. And if the WI convection can generate a decent cold pool to help it along, that would help increase coverage and strength of storms this morning. Combing through all the CAMs, the window for morning convection looks to be around 10-16Z with a large amount of variability. SPC Day 1 outlook just came out with pocket of Slight Risk south of a line from Grand Haven to Lake St Clair, giving credit to the strong cells currently over WI. We really need to see how things line up locally today, how much can the instability gradient push back into SE MI and where does the front come back together. Could very well see the morning convection reinforce the gradient to the west and south, preventing the best CAPE from advecting back in. Regardless...we're looking for a round of convection this morning, possibly lingering toward noon. QPF values range from 0.5 - 1 inch across the area with the highest totals south of I69. After the morning convection, we remain under the active 850-700mb frontal band with weak low level jet still going and all the moisture still so expecting scattered showers to continue through the afternoon. Wind and hail will be possible with the strongest cells, but flooding may become a primary threat as we've now had 2 days of heavy rain and todays showers and storms will again be primed for heavy rain. Any training of storms, especially over those areas previously hit, may result in urban and small stream flooding.

Confidence goes way down for afternoon/evening storm chances. Outflow from earlier convection and surface frontal placement will dictate where the next area of convection can initiate. In addition, there are solutions that advertise the elevated front continues to activate. Lack of stronger mid level forcing should help minimize chances for larger convective complexes and stronger storms from developing. Will have to see how the morning convection plays out first.

With the front sagging back southward, may locations will be cooler today with highs 80 or less. Locations around the Ohio border will be south of the front the longest with less chance of early day convection so temps may again rise into the mid 80s. With the high dewpoints lingering one more day, heat indices may touch 90 briefly this afternoon. High pressure builds south across the region this weekend into next week which will bring cooler temps the rest of the weekend and into next week with highs in the upper 70s.

MARINE...

A stalled frontal boundary draped over Lower Michigan and the eastern Great Lakes drifts southward again today. This leads to periods of additional thunderstorms for portions of the central Great Lakes. Saginaw Bay will be most susceptible to getting clipped by early morning convection, before thunderstorm clusters organize further south along the front. Waterways south of Lake Huron would be the next point of arrival, with ongoing storms possibly passing through mid-morning. Once again, prevailing winds and waves should stay below threshold criteria amidst a weak surface pressure gradient, but the continued humidity favors rapid development of strong to severe storms. Such storms may be capable of gusts in excess of 40 knots and/or hail in excess of 0.75 inches. MWSs and SMWs could be required to address short-term local watercraft concerns. Some hi-Res models indicate a secondary round might develop further south sometime this evening. No long-fused marine headlines are expected through the weekend as the ridge over central CONUS eventually weakens and dislodges eastward. Local gusts should remain just below Small Craft Advisory criteria Saturday, albeit with increasing wave energy given onshore flow orientation. Drier weather is forecast for Saturday and Sunday, possibly through early next week.

HYDROLOGY...

Another thunderstorm complex is coming together over WI late tonight which will track southeastward across the area this morning. A subtropical air mass remains in place today which will allow for torrential rainfall rates of over 1 inch per hour, but relatively brief residence time of these rates has mitigated a more widespread flooding threat thus far. There is the potential for some training of storms which would result in pockets of amounts in excess of 2 inches. This would support a localized flooding threat especially if this occurs over any urban areas or locations that received heavy rain already in the past 24 hours.

DTX WATCHES/WARNINGS/ADVISORIES

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