Turnagain Pass

Triggering a large destructive avalanche 2-4+ feet thick is the concern today. Yesterday there was no natural activity observed but there were two remote triggered avalanches reported. Notably a snowmachiner triggered a slope in Main Bowl that had tracks on it from the day before. Without much sun or a dramatic temperature rise in the forecast today triggering an avalanche maybe more stubborn to trigger but no less dangerous. “Scary Moderate” or “Spicy Moderate” are good ways to describe the conditions today, with the exception of terrain below 1000′ where triggering will be likely due to no freeze for the last 3 days. Keep that in mind in choosing terrain in Placer and Portage. With a deep slab problem it is important to remember no signs of instability may be present before a slope releases, it may be the 1st or the 10th person onto the slope that finds the trigger point and slopes maybe triggered remotely. It is crucial to visualize the consequences if the slope does slide. Are there terrain traps below?  Bigger slope = Bigger avalanche. Thin spots near rocks and along ridgelines are likely areas to find the trigger point. 

Large human triggered avalanches and/or natural avalanches have released daily over the past week from Seward all the way to Girdwood. Some of these avalanches have been remotely triggered while others have released after a skier or snowmachiner were well onto a slope. So far we’ve seen one ‘very large’ natural avalanche, where the crown was a mile-wide, on a NE aspect of Skookum Valley near Placer.  Most of these avalanches have occurred below 3000’, releasing on weak faceted snow on a slick crust, 2-4 feet below the surface. A lot of uncertainty remains in the Alpine where slab depths are much deeper and triggering an avalanche could be more stubborn. Widespread buried surface hoar and facets have been well documented at all elevations. Unfortunately choosing to travel in avalanche terrain with slabs this deep and persistent weak layers is like playing Russian Roulette.  You could get away with it… or have a very bad day…

Main Bowl avalanche yesterday on an East aspect. This was a remote snowmachine trigger from the flatter gentle area below avalanche. No one was caught. Photos: Brian Bird

Snowpit from Tincan yesterday. Check out the slab depth and visualize triggering an avalanche that deep….

 Avalanche activity from the past week

Wet loose avalanches or roller balls today are indicative of solar radiation and/ or daily warming temperatures affecting change on the snowpack. We have been seeing this throughout the week with unusually warm temperatures. It has been above freezing for 72 hours below 1000′. A wet point release could be small to large and has the potential to trigger a much larger, more dangerous slab, particularly on steep southerly aspects. If the sun comes out this afternoon or if rain showers are more intense than forecast, be on the lookout for natural wet loose activity. Pay attention to the surface conditions and sinking in to soft wet snow. 

Cornices have grown significantly since the March 9^th storm, an event that arrived with strong winds and dumped 3-4’ of new snow. Give corniced ridges an extra wide berth and minimize time spent below them. A cornice fall could trigger and propagate an avalanche on a slope below.