Complex sentence: Severe weather had already affected northeastern Ontario the evening before with this same cold front; during the late morning of the 7th the front had stalled across the Bruce Peninsula, where newer convection produced a couple of weak tornadoes near the towns of Wiarton and Grand Valley.
Split into simpler sentences: Severe weather had already affected northeastern Ontario the evening before with this same cold front. During the late morning of the 7th the front had stalled across the Bruce Peninsula, where newer convection produced a couple of weak tornadoes near the towns of Wiarton and Grand Valley.