It's because Bernake announced that some day in the near future, like a year from now, if employment improves, if the US economy doesn't falter, etc., QE X (4? 5?) will be phased out. Because of this statement, and only because of this statement, the US dollar surged.
Sorry, it was a false alarm. Canadian $ will probably go back to par with the US after a few weeks, or maybe a few months, if all is quiet.