Are trace amounts of carbon dioxide really causing a "persistent and dramatic decline in the snowpack of the mountains of the West"?

From a typical poorly-researched alarmist article in the Washington Post:

The persistent and dramatic decline in the snowpack of the mountains of the West is caused primarily by human-induced global warming and not the result of natural variability of weather patterns in the region, researchers reported today.

I submitted this comment:

If the decline of the snowpack is so "persistent", how do you explain the massive accumulations of snow this year in many western states? Aspen broke an all-time record for December snowfall; Steamboat has received 24.5 feet of snow so far this season; stories of avalanches and collapsed buildings are all over the net.

Some supporting links are here, here, and here.
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Note that in this related article, the researchers claim to have a model that magically "suggests" that "about 60%" of river flow changes are due to alleged man-made warming.

I wonder how many slight model tweaks would result in a number less than 50%.

Update: According to this post, the snowpack in the Sierras is 115 percent to 123 percent of normal for this time of year.