In case you aren't getting enough Google Now inside the normal interface, it looks like the Google app is bumping out into some users' notification trays with new, richer, higher priority notifications.
While it's hard to say when the rollout began, some users on version 220.127.116.11 of the Google app (myself included) have begun noticing new notification settings in the Google app, toggling notifications for "substantial changes in weather condition," sports, places, and "stories and videos." Other users' settings lists still stop at "priority notifications."
So far we've only seen weather notifications - which offer temperature changes or other condition changes expected for the next day - and sports notifications in person. While I've seen a few weather notifications on my own device, reader Matthew O'Sullivan shared the shot below, showing both a weather and sports notification.
We can't be sure when these notifications will roll out to everyone, but they do seem at least a little more useful than the lower priority notifications the Google app used to serve up, and they're super easy to turn off if they get annoying.