I noticed that big jump too...I remember I was awaken by my wife having a coughing fit right around that time. I looked back a few days and I noticed the biggest jumps in pressure were around times I was awaken after a deep sleep, usually about an hour or so before I had to get up.
So before my pressure was 12-16, I've taken it up a notch and set it to 13-17 for now. I'll try that for a week and see how that goes.