Anyways... pull up a map of Chiwawa river road. Road ends at mine called Trinity. We've had our old rental beast, Magestic back there many times DURING good weather, boondocking right along the river and loved it.
This time of year that route will be closed for snowmobiling well before even the Goose Creek Campground, so do not count on camping there at all (where you may be going to ride the dog sled will be right at the end of the Chiwawa road as far as you can travel without a tracked or pawed vehicle).
You may be able to boondock in the Fish Lake Sno Park or Wenatchee Airport Sno Park (we need to check on that because we're going snowmobiling in that area soon, first time snowmobiling WITH the RV), but you really don't want to sleep at the Fish Lake Sno Park at all (the Wenatchee Airport Sno Park is better for that if legal because it's an actual lot and not just the shoulder of the road). You most certainly WILL need a Sno Park pass (and they do check).
There is a state park near the Wenatchee Airport and a Thousand Trails CG. You can also contact the Lake Wentachee Recreation Club to see if you could stay at their site for cheap.
You must carry chains if you do not have 4WD and snow tires.
Here's what Trinity currently looks like:
http://www.zeitcam.com/webcam/trinity