Turnagain Pass

After several days of snowy weather, low visibility and a natural avalanche cycle, mostly clear skies are expected today. This will make travel above treeline inviting. If you are headed out in the backcountry please understand there are dragons lurking in the snowpack. Two dragons to be exact: 1) a layer of buried surface hoar sits 1-2′ below the surface and is showing signs of being reactive, 2) weak snow near the ground exists at elevations above 3,000′. These issues are also being seen in the Summit Lake region.

The New Year’s storm that began Dec 31st and ended yesterday, Jan 3rd, added 1-2′ of snow in most areas, possibly more at the higher elevations. This snow fell on a layer of surface hoar and near surface facets, creating a persistent slab problem. Rain fell up to 2,300′ at one point during the storm, which has formed crusts in the top foot of the snow at elevations below 2,000′. Above ~2,000′ where moist to dry snow exists without crusts are where triggering an avalanche is most likely. Things to keep in mind:

1-  Human triggered avalanches 1-2′ thick are most likely above 2,000′
2-  Remote triggering from the top, side or bottom of a slope is also likely
3-  Avalanche size is expected to be large enough to bury and kill a person 
4-  The larger the slope the larger the avalanche

Performing quick pits to assess the bonding of the New Year’s snow to the weak snow below is a great idea, but not something to completely hang your hat on. The buried surface hoar may have been blown down in your pit, yet remains lurking on the slope you plan to ride. Today and tomorrow are days to be extra cautious as there are too many signs pointing to an unstable snowpack. Along with the buried surface hoar problem, wind slabs and cornice falls are possible along ridgelines. One of these avalanches can trigger a larger avalanche below. 

Check out these videos. The first is the general snowpack set-up, the second is a close up/snow motion video of the collapse and propagation of the buried surface hoar found yesterday on Sunburst: 

Runnels from the rain exists around 1,600′. At these lower elevations the wet snow is freezing into a crust and triggering an avalanche is unlikely.

In the Alpine, above 3,000’, weak sugary snow (basal facets) sits near the ground. The storms over the past few days have added additional load to slopes that already have a hard slab 3-5+ feet thick. At these elevations, human triggered, large and dangerous deep slab avalanches ARE still possible. This is a high consequence avalanche problem that is impossible to outsmart and can take a long time to heal. Keep this in mind as improving visibility in the next few days may allow for travel to the Alpine. It is really important to remember that triggering an avalanche in the upper layers of the snowpack may then initiate a deep slab avalanche. Cautious route-finding is essential. This includes thinking about the remote trigger potential from below.