"45-55F weather."

Dressing for 45-55F weather is pretty easy. Dressing for 10,000-13,000ft climbs will be more difficult.

What the temp is at the bottom from the top of the climb varies, and your body temp between the beginning, middle and end of the ride varies. Also as the other posters mentioned, there will be a comfort difference between climbing and descending.

Your layering has to take all of this into account.