I ride my fatty a lot. The following is a list of ride areas and resources for you to use in planning your next ride. I will try and update major changes in conditions, but we do live in North Idaho after all and things can change fast...and well, if I just sat at my computer all day making changes I wouldn't be out riding.
Finger waving: When riding on snowmobile trails, please keep an ear out for sleds and yield. I also recommend running lights. Also, as you may know, many xc/skate skiers are not so keen on sharing the nordic trails with fat bikes, if you are sinking in the snow and leaving a rut of more than 1" then pack it up and go back on a better day. If you encounter a skier, yield to them and give a little "howdy do," it goes a long ways in easing tensions. Lastly, bear in mind that many of these rides are in remote areas and that weather and conditions can change very quickly, be prepared and plan accordingly.