Turnagain Pass Avalanche Forecast

Cold weather and light winds have helped Sunday’s new snow stay mostly loose and unconsolidated while it slowly settles and adjusts. If you are just tuning in now, the ‘sleeper storm’ over the weekend dropped highly varying amounts of snow to the area; quick recap: Placer Valley 2-3+’, Turnagain Pass 10-14″, Girdwood Valley 7-10″ and Summit Lake 4-6″. The new snow fell on a weak old surface consisting of near surface facets and surface hoar. This is keeping it from bonding quickly, but the good news is, the slab (new snow) is so weak and loose in places only sluffing is occurring (no slab). Determining whether the new snow will act as a slab is the current question and will determine what type of avalanche could be triggered. Furthermore, the deeper the new snow the larger the avalanche will be if a slab is triggered – such as in the Placer Valley.

Questions to ask:  What is the character of the new snow? Is it loose and unconsolidated or is it becoming ‘slabby’ with daytime warming on Southerly facing slopes? A slope around noon could be stable only to heat up at 3pm and become unstable, taking out your prior tracks. Was it affected by the winds during the storm and stiffer, aka a wind slab? Any slope where the new snow is acting like a slab will be suspect for triggering an avalanche. How well the slab is bonding with the old surface should be suspect as well – expect poor bonding until proven otherwise. 

As for avalanche activity yesterday, there were a handful of snowmachine and skier triggered slides. We had a report of several soft slabs releasing near the toe to of the Skookum glacier in the Placer Valley. In the heart of Turnagain Pass on Cornbiscuit ridge, a skier triggered a shallow soft slab on a Southerly facing slope that was warming during the day. There were also a few small pockets skier triggered on Magnum.

Photo: Snowmachine triggered soft slab avalanche in small terrain around 18″ thick. It was taken near the toe of the Skookum glacier. Photo: Rusty Allen

Photo: Shallow 12″ soft slab triggered by a skier on a South facing slope during the heat of the day. Photo: Adam Baxter

Photo: The annotation says it all. Winds during the storm have likely created a stiffer ‘wind’ slab resting on weak faceted snow on this higher elevation slope. Photo: Peter Wadsworth

Watch your sluffs. The new snow sat under cold skies last night and this will only encourage it to become looser today – meaning sluffs could be larger and run further than expected. However, southerly aspects may sport a thin sun crust, if this is the case, sluffs will be limited. 

Photo: Skier triggered long running sluff on the North side of Cornbiscuit. Photo: Peter Wadsworth

As always, give cornices a wide berth and minimize exposure under them. 

GLIDE AVALANCHES?  Limit time under glide cracks. There is one still opening on Seattle Ridge, left of the up-track, and some in the Skookum Valley along with others scattered about.