Turnagain Pass

Could all this rain crust be forgot, and never brought to mind?

Could all this rain crust be forgot and buried in no time!

Call me optimistic, but hopefully the 3-6″ snow expected during this New Year’s Eve storm is at least enough to improve riding and skiing conditions. Light snowfall with sustained winds at 10-15 mph began early this morning and is expected to continue until this afternoon before this system passes. This combination of wind and snow will make it possible to trigger an avalanche up to a foot deep on wind loaded slopes in the alpine. Fresh wind slabs are most likely to be found just below ridgelines, on the downhill side of convex rollovers, and in gullies. It is possible that these slabs might be forming on top of a recent round of surface hoar that formed in isolated pockets on top of the recent crusts, which will make them particularly sensitive to human triggers. From what we know so far, this appears to be the exception rather than the rule.

You might be able to recognize a fresh wind slab from a distance as a smooth, rounded pillow of drifted snow. You should also be able to feel the difference in the surface conditions on a freshly wind loaded slope- be on the lookout for a ‘punchy’ feeling, or stiff snow sitting on top of weaker snow. Wind slabs often give warning signs like shooting cracks, collapsing, and other avalanche activity when conditions are unstable. You can seek out more information by testing small terrain features before trying to move into steeper terrain, and step back from the bigger objectives if you notice any warning signs. Even though the potential size of avalanches will be relatively small today, the firm and low-friction bed surfaces will make avalanches fast-moving and make it difficult to get off of a slope if you do trigger something. Today it will be important to pay attention to how the weather is contributing to instability, dialing things back if we end up on the heavier end of the predicted snowfall totals or if you see any of the red flags mentioned previously.

It ain’t much, but it’s something. Let’s keep our fingers crossed that we hit the higher end of these storm totals today! Graphic courtesy of NWS Anchorage.

New snow and winds will be building fresh slabs on top of crusts like these throughout the area. Breakable rain crust on Goat Mtn. yesterday. 12.30.2021

At this point it is unlikely a person will trigger an avalanche on the weak layer of faceted snow buried 2-5′ deep in most parts of the advisory area, and shallower towards the south end of Turnagain Pass, Silvertip Creek, and the Summit Lake area. The light snowfall expected today will not be enough of a load to put any kind of significant stress on this weak layer, and in the aftermath of the melt-freeze cycle from earlier in the week it would be very surprising if we saw any avalanche activity on this layer. That said, the weak snow is still there, and it is a layer that we will continue to track. It is still worth considering this weak layer while making terrain choices, and avoiding consequential terrain that funnels into terrain traps like gullies or ravines, cliffs, or trees.