Turnagain Pass Avalanche Forecast

Our main avalanche concern today is one that will not go away quickly.  Surface hoar that formed a week ago has been preserved and is sitting below 1-3’ slabs.  Typically surface hoar gets knocked over and blown around before a slab builds on top of it.  That is not the case with our current snowpack.  The snowfall that began on December 13th came in with very little wind and allowed this layer to be buried intact.  We have been investigating this layer over the last several days and we have found it in all pits above 2,700’.

The tricky part with this set up now is that it is gradually becoming more difficult to trigger an avalanche.  We know this based on our test results in snow pits.  Unfortunately, it will be possible to test this layer by traveling in steeper terrain and not get results (NOT RECOMMENDED!)  Exceptions to this were found on Sunburst and in the Summit Lake region, where skiers remotely triggered an avalanche from 50’ away.  In areas such as this where the snowpack is thinner, it will be easier to initiate an avalanche today.

The nature of buried surface hoar is such that it persists as a weak layer in the snowpack for many days, sometimes weeks after it becomes buried.  Because of this we will be tip toeing around the mountains for the foreseeable future.

In order to stay out of trouble it is best to avoid steep terrain.  Terrain on all aspects over 35 degrees should be treated as suspect.  Avalanches, if initiated have the very real potential of propagating across large areas, making escape difficult at best.  There is plenty of evidence to support this and the problem will potentially take a long time to go away.  

Below 2,500’ in elevation the likelihood of triggering a slab avalanche 1-2’ in depth will be less than in the higher elevations.  A crust that has formed in the middle of this newest slab will make it harder to trigger any buried surface hoar that survived the rain and wet snow.  We cannot rule out the potential for triggering slabs in this elevation band and it will be important to keep slope angles low until we see more signs of this layer becoming non-reactive. 

Paying attention to what is above you, including other groups, when in this elevation band (bewteen 1,500-2,500′) will be important as avalanches initiated in the higher elevations could run into the mid elevations today.