Late Season Information

This is Steve Karkanen from the West Central Montana Avalanche Center with a few late season observations and safety information posted April 12, 2010.

Although we issued our last avalanche advisory on April 2, weather conditions of the past several days more closely resemble conditions we expect in mid-February, not mid-April. We received a report of a skier triggered slab avalanche on the NE-E aspect of St. Joe Peak in the Bitterroot last week (4/4/10). The person reported that it failed on a faceted layer deep within the snowpack.

Today (4/12) we received an excellent report from a group of experienced backcountry snowmobilers who triggered a large slab avalanche in the southern Bitterroot Mountains northeast of Salmon, Idaho. This area is several miles outside our advisory area but the snowpack conditions are very similar to what we have further north. They estimated the crown to be 2000 feet long and it piled over 10 feet of snow into terrain traps at the bottom of the slope. This involved the newest wind loaded snow failing initially then stepping down to the more deeply buried weak layers. Check out the pictures on our photo gallery.

Much of the mountain snowpack in western Montana is at 60% of normal but temperatures are staying cool allowing some great late season skiing and riding for those willing to work a bit harder and maybe ride over a bit more dirt than usual to get to the goods.

Some things to consider when you do get out there. Don’t forget to take all your avalanche safety equipment with you and have your transceiver strapped on and turned on. I know of at least two examples this year of very experienced people either not having their transceiver on them or leaving it at home then being caught in an avalanche. In one case, fortune kept an individual on the snow surface and alive. The other case is much more tragic and we may never know why a transceiver was not strapped on. It would not have made any difference in the outcome here as the person was skiing solo when caught.

Snow conditions in April and early May can be epic in the Northern Rockies. Avalanche conditions can be just as memorable so take the time to check the stability of the slope you want to recreate on. The north or more shaded slopes this year are still holding the nasty buried facets responsible for a fatality and many close calls in our area the past few weeks. That layer is now two and a half months old but given the right conditions, it can fail with big consequences.

The most common avalanche condition will be new snow melting and sliding as the sun hits it or when temperatures rise above freezing. Be very careful around cornices, they grew pretty big during the last storm and will be more sensitive than the cornices that developed earlier this year.

If you get out and find conditions worthy of passing along, please do contact us at [email protected] or call our office number at 406-530-9766 or 406-329-3752.
For more general information about backcountry conditions or questions about access and travel, please contact the local Forest Service Ranger District Office in the area where you plan to recreate.

Have a safe fun summer!