Monthly Archives: January 2012

Tuesday, January 31, 2012

This advisory expires in 24 hours

AVALANCHE WARNING

BOTTOM LINE:

We expect natural avalanches possible, human triggered probable.

DISCUSSION:

19 inches of snow accumulated overnight bringing the total height if snow at the Independence Mine NWS site to 70 inches. This is significant weather event.

Winds at Hatcher ranged from light to moderate with strong gusts capable of moving snow into new soft slabs. Hard slabs are not expected due to moderate wind speeds, however winds can be extremely variable at Hatcher Pass. Carefull assessment  for new slabs structure and sensitivity as well as carefull route fuinding will be imperative to anyone considering traveling in avalanche terain today.

Note that it is not recommended to travel in or near avalanche terrain unless you are an expert. If you are an expert, you will most likely wait for better visibility and allow the snowpack to adjust to the new changes for at least 24 hours before putting yourself into a potential avalanche predicament.

Problem areas include thinner snowpack micro features that were stripped by the winds earlier this season, such as micro ridge features, exposed roll overs, and broad ridge features that tend to get scoured by the winds, You will find a very weak structure in these areas that will be challenged to support new wind slabs and loads. Other considerations include investigating the bond between the new snow and the old snow interface and upper elevation starting zones near ridgelines that could be freshly slabbed. Expect this new load to challenge the stability of the snowpack on all aspects and elevations. Not only do the thicker areas have a weakness in between the hard slab layering, but the thinner areas are not well supported either. For more information view recent pit profiles.

Remember, that if you just have to get out there and eat up some of this new snow, traveling on 25 degree slope angles out of the runnout of steeper slopes significantly decreases your chances of triggering or being caught in an avalanche. Use an inclinometer and asses your alpha angles.

–Jed Workman