Got an email from the operators of my airport yesterday, advising of some scheduled GPS interference testing coming up soon.
Here's a link to the NOTAM:

https://www.faasafety.gov/files/notices/2017/Apr/FFC_17-01_GPS_Flight_Advisory.pdf

Essentially, expect GPS disruptions in an area centered on Bangor Submarine Base near Bremerton WA.
Multiple dates starting April 6 and on through May 6.
Dates & time subject to change, NOTAM(s) will be updated / issued as required.