Turnagain Pass

With a few inches of snow overnight, plus the addition of 4-8” at treeline today, the upper elevation slopes could see a total of a foot of new snow by this afternoon. There are two main things that will keep this new snow from bonding quickly: (1) The storm will be “upside-down” – due to a rise in temperature with snowfall. This creates a situation where more dense snow is deposited over less dense snow forming a slab/weak layer combo. And (2), there are several slopes that received enough wind over the past few days to create a hard wind crust/slab that will act as a bed surface for this upside-down storm to fall on. A few of these hard surfaces had a couple inches of weak snow on top that will also help to keep the new snow from bonding right away.

In addition to the Storm Snow concerns we also have Wind Slab avalanches. East winds have ramped up overnight and should continue to be in the moderate to strong range on the ridgelines. Even if snow totals do not amount to much there is still plenty of snow available for transport to form 1-2’ deep wind slabs. These will likely be soft and easy to trigger.

Watching for all the obvious signs of instability will be key today. These are:
Recent avalanches
Shooting cracks, whoomphing and collapsing in the new snow
Heavy snowfall
Wind loading

Below treeline we will likely see wet snow falling on a crust. Watch for any new snow in these areas to have a hard time sticking to the crust as there will be 2” of weak snow sandwiched in between. This weak snow is the few inches that fell on Wednesday which began to facet with the cold temperatures Thurs/Fri. We may not accumulate enough snow at these elevations for it to become a problem but something keep in mind.

With warmer temperatures, the addition of a foot or so of snow (~1” of water equivalent ) and strong wind there is the possibility of adding enough load on certain slopes to wake up a deep slab here or there. This storm does not look big enough to induce a deep slab avalanche cycle similar to last Sunday/Monday, but we can’t forget the possibility remains that one of these larger slides could occur. The 4-8” of well developed faceted snow near the ground from our early season is still weak enough and present in our start zones to warrant concern.