I'm a bit in the same boat - I'd like a heads-up that something like this or last week's "Crack Me If You Can" is coming up, without drowning in a sea of other NetSec/InfoSec/OpSec/PhysSec chatter. And ideally, more than 24 hours before it starts, so I could arrange my schedule and responsibilities around it better.

Is there something I should be subscribed to that would do this? Everything I've seen so far is a one-off ("subscribe to XYZco hackathons") or swings the other way to kitchen-sink levels of inclusion (DEF CON, Black Hat, etc.).

Sounds like you'd be interested in https://ctftime.org/ if I understand you correctly. Contains list of current and upcoming CTFs going on as well as write-ups for them when finished. Decent site for people trying to expose themselves to as much CTF competition as possible.