I'm planning to travel to Whistler by bus for a skiing trip. Is there a place close to the skiing gondolas where I can leave my bag for a few hours?
There are lockers in the Ski rental facility:
There are day lockers next to the ski rental facility downstairs at the blackcomb lodge. In spring 2016 the cost is $C 10 small and $C 12 large. There are no overnight lockers. If you rent from whistler blackcomb you can store your skis (and poles) with them overnight but have to take your boots with you.
I've messaged the Whistler Tourism Center and they've replied the following:
If you need to store suitcases the UPS store will have luggage storage for $10 a bag. If you are trying to store a small backpack there are lockers in the Carlton Lodge.
The small locker is sized approximately 30cm by 10cm. The large one is approximately 40cm by 20cm. Not big enough to put in a suitcase, but big enough for a backpack or a pair of skiing shoes. The large one costs $12/day and the small one is $10/day.