Turnagain Pass

No recent avalanches have been reported with the recent storm, but visibility was horrible yesterday.

Yesterday’s storm ended up surprising us with how much snow fell in the Turnagain Pass area, with almost a foot of new snow and 0.8″ of water over the past 24 hours. Unfortunately, the storm left Girdwood pretty dry with only 0.15″ of water. From what we saw in the field yesterday the light and dry new snow was not bonding very well to the old snow surface, which means surface avalanches at the interface with the old snow are likely today. Triggering an avalanche will be most likely be in areas with active or recent wind loading, like along upper elevation ridgelines and cross loaded gullies. Winds have been averaging 20 mph and gusting up to 50 mph at upper elevations which could build wind slabs 1-2′ deep in Turnagain Pass.

With almost a foot of new snow it is also possible to trigger a storm snow avalanche in areas that are sheltered from the wind. Due to the low density of the new snow we didn’t see evidence that the new snow was acting like a slab yesterday afternoon, but an additional 3-5″ of snow fell since we left the field which could be enough to make the new snow more cohesive. In the below treeline elevation band there were some pockets of surface hoar that were buried by this recent storm which could make storm slabs more reactive in these isolated areas. In addition to these surface slab avalanches, dry loose avalanches (sluffs) are very likely on any steep slope and they could entrain a lot of new snow on larger slopes.

To evaluate the potential for surface avalanches it is important to get off the beaten track and use test slopes, hand pits, or other means to check how well the new snow is bonding to the old surface. Any shooting cracks or stiffer feeling new snow on the surface are an indication that the new snow is acting like a slab and the potential to trigger an avalanche is higher. On steeper southern aspects there was an icy surface crust buried by this new snow which could make wind slabs and storm slabs release more easily on this slippery bed surface. In areas with lingering persistent weak layers, like near Johnson Pass and Pete’s, the new snow could reactivate these buried weak layers and extra caution is recommended to evaluate the snowpack conditions before entering avalanche terrain (see additional concern).

Low visibility storm day on Tincan yesterday, with mostly light winds near treeline. Photo 3.15.23

After a long dry spell we are starting to get into a stormy weather pattern and the addition of more weight on the snowpack could start activating older buried weak layers in areas with a thinner snowpack. The areas that have shown signs of harboring buried weak layers in the past few weeks are concentrated along the southern boundary of our forecast zone near Johnson Pass and Pete’s. These area tend to have a thinner snowpack, more similar to Summit Lake, therefore weak layers can persist longer and be easier to trigger with the weight of a skier or rider. We recommend extra caution in these areas, especially once the next round of snowfall and strong winds start on Friday.