It may partially reverse a bit near the mouth for short periods (and thats more of a milling about) but just think about it for a bit - If the river currents reversed, the bay would be flowing into the Saginaw and then into the Tib and Shiawassee, causing massive flooding, breaking dams, overflowing banks, etc. A partial and temporary reverse of the river where it spills into the bay is one thing, a reverse of the whole system (which it would have to be if you claim the river was flowing the other way in Saginaw) is unlikely, if not impossible. Gravity overpowers wind.