Without much of a change in weather for the daylight hours today, our avalanche issues remain the same as they have been all week, listed below. However, things may take a turn tonight… it’s looking more and more like somewhat of a northwest wind event is developing. Starting around sunset the northwest ridgetop winds are forecast to increase and peak in the 30-35mph range with stronger gusts by early tomorrow morning. If these winds show up early and start moving the plethora of loose surface snow around, be on the lookout for quickly developing new wind slabs.
Back to today. Although a few clouds are streaming in, only light westerly winds are on tap and travel into the Alpine could be easy again. If you are headed out and haven’t been following the forecast the past few days, here are your avalanche issues:
Persistent Slabs: Buried under the last snowfall (from 1/28-1/29) is a layer of surface hoar and near surface facets. The snow on top is variable in depth, only a few inches toward Summit Lake and up to 2′ where winds have loaded it on the north end of Turnagain Pass and Placer Valley for example. Any slope, or portion of a slope, that harbors stiffer wind blown snow over this weak layer is suspect for triggering a slab avalanche. With a couple inches of fresh snow on Tuesday, visual clues may be difficult for sussing out wind loaded zones. Feeling for whumpfing and looking for cracking in the snow around you will be key. Quick hand pits are also a great way to take a look at the top 1-2′ feet and see if you can shear off a block easily. The good news is, slabs are becoming harder to find as top of the snowpack is faceting and becoming looser each day with the cold weather, essentially eroding the slab.
Loose snow avalanches (sluffs): Continue to watch your sluff. These have been high volume and fast running on steep and sustained slopes. There is a lot of very loose and non-cohesive snow out there that is keeping these on our radar. These can cause a lot of grief if they carry us into terrain traps like cliffs, trees, or rocks.
Cornices: Large cornices are peeling away from ridgelines and cracks are opening. Be sure to give cornices plenty of space along the ridge and minimize the amount of time you spend below them.
The thin white line… Clearly seen is the the weak layer of buried surface hoar (16″ down in this pit). There is more air than snow in this layer, which is why it shows up so white when backlit and why it fails and collapses easily at times. The notations in the photo can be boiled down to: this layer is still reactive and can produce an avalanche if there is a slab on top, though becoming stubborn to do so. 2.4.21.
Summit Peak in the Summit Lake area, SE face. Shallow wind slab triggered by what appears to be a sluff from above. We are still determining if this was a natural avalanche that occurred yesterday. No people were in the area that we know of. 2.4.21. Alex McLain.
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