Flight Aware is a good site for tracking the timeliness of flights. Looking at the recent LAX-AMS flights, they tend to come in +/- 15 minutes of the scheduled arrival. If early, you'll be good, if late, making the 50 min. connection could be very tight.
As it'll be the end of November weather could impact your travel. AMS is normally pretty good in handling winter weather, but anything can happen.