Page Life Expectancy sudden drop
PLE is a bit of a flaky metric. Sure, it's better when it's high and steady, but if you have more data than RAM, that ain't always gonna happen.

Things that can make PLE drop:


Queries that get large memory grants 
Queries that displace large amounts of pages in memory with new
ones  
Queries that modify many pages and force them to get flushed to
disk
DBCC CHECKDB
Index Rebuilds


PLE is more of a concern if it's constantly low. As with most things, you need to look at your overall wait stats to see if it's an issue.

Since you're looking at My Favorite Monitoring Tool© -- what is it telling you about overall wait stats? If you don't know where to find those, contact support.

The RAM-ifications (wait for it) are that you'll likely need to read those pages back into RAM (there it is) at some point.

Hope this helps!