rime/freezing fog part of rotation?

hi there everyone,

I'm reading in more than one spot that the suggested rotation in 4.0 includes rime or freezing fog. Problem is that as far as I can tell, they're both passive/procs.

Am I missing something? Why would it be listed as part of the priority/rotation?

Thanks for your time.
Priority. . as in if it's up, you use it. That's the basic idea of a priority system as opposed to a rotation. It allows for more proactive playing.
Thanks very much for the reply, catharlex.

I know what a priority is. I just don't know why they list it. I can't seem to "cast" rime or freezing fog, as it procs on it's own. Or is the author telling me to cast HB when it procs?

Thanks again.
HB when Rime procs.
Oblit when KM procs, FS if you are going to have some downtime before your next Oblit.

Since our runes can come off CD early and at random its pretty impossible to have a set rotation where before our runes were static and unchanging as long as we followed one rotation. That is where the big difference is now. Or how I understand it anyway.
It means you use Howling Blast to consume the Rime/Freezing Fog proc.