Understanding an avalanche

Our newsroom has been consumed just keeping up with fresh information about the flooding and storm impacts.  No time this week for a deeper look at anything.  But, this would have been a good topic:  Mark Moore of the Northwest Avalanche Center grabbed my attention during a news conference about the weather on New Year’s Eve.

He declared that the avalanche danger had become  “extreme.”  He explained, with a series of slides, how it’s not just having a large snowfall that makes for an avalanche.  It’s the type of snow and the temperatures during each successive snow-storm that make for a big hazard.  We saw this come true on the mountain passes last week, and especially this week.

This landslide/avalanche near Snoqualmie Pass took out not only all the layers of snow, but several  inches deep of soil as well — and a ski lift.  (I haven’t done any deeper research on this, but I’m pretty sure it has the same fundamental cause as the all-snow avalanches.)

Avalanche and landslide at Hyak (Snoqualmie Summit East)

Avalanche and landslide at Hyak (Snoqualmie Summit East) (WSDOT)

Check out the full gallery of photos posted by WSDOT.

And for a nice info-graphic explaining the underlying science, plus a profile of the scientists, see Tom Paulson’s story in the P-I (published just before the Hyak slide came rumbling down).