Wow, you've been there that long and haven't been to Squaw??? That place is the crown jewel of Tahoe area riding without a doubt. Squaw is one of the sickest mountains out there. Only Jackson Hole or Whistler compare. It's that incredible. It also gets tracked fast.
For pow, I would say hit Alpine or Kirkwood depending on where you are staying. Saying you are going to Heavenly, Alpine, and Squaw is kind of funny. It's a loooong drive from Heavenly to Squaw or Alpine and vice a versa. If you are South Shore, hit Heavenly (not recommended), Kirkwood (highly recommended), or Sierra. If you are on the North Shore, Alpine and Squaw are awesome. Homewood is a fun little mom 'n pop operation. Sugar Bowl comes highly recommended too.
As far as powder goes, you'll probably need some snow. The lower altitude there makes for warmer temps that make a freeze thaw cycle happen. So unlike Colorado where it stays cold, stuff firms up. It also makes for a much more stable snowpack without a doubt. Look for North facing stuff hidden in the trees for powder. That will be your best chance at finding some.