Who cleared the Redhorn Pass?
 

The Fellowship found their way blocked, not just by snow but also by an avalanche when they tried to use the Redhorn Pass. Yet after the fall of Sauron, Galadriel and people of Lorien used the pass on their way home. Who cleared it in the meantime?

Summer.

Remember, the Fellowship was travelling south during winter. The hobbits are returning home in the late summer / fall. There was a whole summer full of good warm weather in between to get some snow to melt off.

While I'm sure G55 is completely right and it was merely the change of the seasons, I will impishly also suggest that, as Galadriel and Celeborn's party were all Elves, they could have just flit over the snow banks like Legolas. :p