Turnagain Pass

There were no known avalanches yesterday. The last known avalanche was a skier triggered slab that was reported near the Seattle Creek Headwall on Monday. This slab was around a foot deep and 100′ wide on an easterly aspect around 3,400′ in elevation. The slab failed on weak snow over a thin crust under the storm snow from April Fools’ Day. The skier was able to ski off the moving slab.

Another brief shot of moisture is over the region this morning. However, only a trace to a couple inches of snow is expected before skies are forecast to start breaking up midday. Apart from a little new snow, it will be the southeast ridgetop winds that are more exciting. These winds picked up into the 10-20mph range with gusts near 40mph overnight and should continue through most of the day. How much snow the winds are able to transport is the big question. There was roughly 2-4″ of new snow fell yesterday along with another inch or two today that is available along with any pre-existing snow that is soft enough to move. Sun crusts on southerly aspects may limit some wind transport but from what Andrew and Graham saw yesterday in the Placer Valley, there was ample soft snow.

For anyone getting out today, keeping an eye out for active wind loading, watching for smooth rounded pillows of freshly deposited snow, hollow feeling snow, and cracking in the snow around you will be key. Wind slabs should be easy to suss out and in the foot deep realm. Areas in the higher elevations could sport some slabs up to 2′ deep where winds are strongest along ridgelines. This wind direction is a bit more southerly than we normally see, so really looking for new slabs in places you might not expect will be important, including over rollovers in the mid elevations and cross-loaded gullies.

Sunshine:  If the sun comes out, we can expect to see some rollerballs and wet sluffs on southern aspects as the surface melts. This is similar to what we have been seeing in the afternoons over the past few days.

Cornices:  As always, keep giving cornices an extra wide berth. Not only are the winds adding to them today, but any sun that shines this time of year can really add to destabilizing them further.

Ridgetop southeasterly winds transporting snow above the northwest face of Comet Pk in the Placer Valley yesterday evening. Also seen is an older avalanche that was likely a natural from the April Fools’ storm last Friday. 4.5.22.

Underneath the easy-to-see surface instabilities are a few lurking layers we have to keep in mind. The most concerning layer is the one closest to the surface. It’s the April Fools’ interface that sits in the top 1-2 feet in the snowpack. This layer is composed of small buried surface hoar and near surface facets that sit on a thin crust. It has been hard to get the layer to react in many pits, but it does react at times. It was also the layer responsible for many avalanches last weekend, with the last known avalanche occurring on Monday; noted above on the Seattle Headwall. It isn’t out of the question for someone to trigger another avalanche on this layer and even a wind slab avalanche could step down to it. With sun crusts on southerly slopes, the northerly aspects are most suspect until the sun melts off those sun crusts making south slopes a concern as well.

Deep Persistent Slabs:  The other buried layers are much further down, 3-6′ deep in the snowpack, and are from March. They are also composed of a thin layer of small buried surface hoar and small facets. These layers also show they can fail in just the right place every once in a while. An avalanche releasing on one of them would be very large, but at the same time they are very unlikely to trigger due to the depth and that the weak layer is healing in many places. We will continue to watch them as a big load of snow and/or rapid warming could reactivate them.