The center columns are great for a traditional yurt or if you are making your own. In those cases, many small (2x2) roof poles are used. Center columns help distribute the load and take a bit of weight off the lattice.
With the yurts from places like Pacific, Rainier, or
(probably some others too), the design and materials is different. Engineering has been done! They use at least 2x4 machine-rated rafters and a lot fewer than a traditional yurt (like 20-30 vs 70-90). And they took out the center columns because they didn't need them. Instead you get their Snow & Wind kits, which build up the wall and roof rafters a bit more (I think).
As Jafo said, his yurt is in a pretty snowy area and handles it pretty well. I know North Idaho can get some good snows too. Have you looked at the snow loads in your area?