That's the key...clusters. The mean is meaningless, it doesn't mean shit...bad puns but you get the point. If you don't believe me, Google the Golden Mean Fallacy.
For God's sake, the mean incorporates a member 25 miles south of Newfoundland!
The feature over northern Cal right now seems to be the turd in the punchbowl. This strengthens and drops southward, creating the vacuum which sucks in our main slug of southern energy.
I mentioned this yesterday, but I can think of quite a few wind driven blizzards with excellent snow growth. Remember March 1993? I was in the Cleveland Super Bomb...nickel sized flakes with 70+ gusts. I think temperature profiles are much more important than wind...and this is not a super-cold profile.