Hey BirdCamFan,
Unlikely to have been a juvenile peregrine, they tend to avoid trees, risk of injury kind of high the way they fly and hunt - that's not to say they don't, just rarely. And at this point, it looks like all our peregrines have vamoosed, the young ones going before the adults. So even more unlikely it was a peregrine. (Sorry
)
There are two species it could have been ...
First is a merlin, smaller than a peregrine but their plumage is almost the same as a juvenile peregrine. And they are woodland specialists so you you see them in/out/around/through trees all the time. Particularly in urban areas like Winnipeg where they are regular nesters at this point and there are more than a few pairs in the area you described.
Second is a Cooper's Hawk - size of a peregrine but the juvenile plumage isn't so similar to a juvenile peregrine. This year I have had more calls about Coopers than I have ever had before, they are everywhere this year. And they are more falcon looking in their head/beak shape than any of the other "hawks".
Regardless of what you saw, it was a good catch considering you were driving AND where you were driving! Congrats!
TPC