Complex sentence: On Monday, March 24, as the first low-pressure system from the storm weakened and moved northeast from the Great Lakes into eastern Canada and New England, it stalled over the Ohio River basin and triggered more rain and thunderstorms.
Split into simpler sentences: On Monday, March 24, the first low-pressure system from the storm weakened and moved northeast from the Great Lakes into eastern Canada and New England. The system stalled over the Ohio River basin and triggered more rain and thunderstorms.