Jasper is a great town in the Rockies, one night each way from Vancouver. But the Canadian only runs twice a week each way, so the timing is tricky.
If you left Vancouver on a Monday afternoon, you could arrive in Jasper about noontime on Tuesday, then return leaving Jasper either Wednesday morning or Saturday morning. If you left Vancouver on the Friday afternoon departure, you'd arrive in Jasper about noontime on Saturday, but you'd already have missed the Saturday westbound, so you'd have to stay until Wednesday.
In terms of weather-related delays at that season, the westbound is far more likely than the eastbound to be seriously late. On our last westbound trip, in February 2019, the train arrived in Vancouver 23 hours late, and it had been as much as 30 hours late around Edmonton. However, VIA has added a lot of padding to the schedule since then, and they seem to be having fewer cases of extreme tardiness.