Heavy new snow is loading a complex upper snowpack, increasing the avalanche hazards. Layers that have shown weakness, but failed to propagate, in the past week could be activated by the new load. Winds out of the Southwest are strong enough to transport new snow. Expect wind slabs to form on North and East aspect ridgelines and on the lee side of cross loaded gullies.
New heavy snow is falling on poorly bonded snow that sits on top of the stout Lucky Friday Crust. It’s too early to say for sure exactly how this will set up, but all the ingredients for an avalanche are there: load, weak layer, and bed surface.
Overnight winds from the West that will likely shift to the Northwest today, with gusts into the 30mph range, mean new snow will be transported onto the East and Southeast side of ridges and cross loaded gullies. Throughout the storm winds will move around the compass rose. Be on the lookout for pillows of wind drifted snow and density changes on steep start zones.
Yesterday Kyla and I toured up Tiger Peak from Burke. As we neared the ridge calm and mild weather gave way to strong winds and low visibility. The North aspect was soft and fun, but we did find remnants of buried surface hoar a foot from the surface. It failed with medium force in Column Tests, but did not propagate in our Extended Column Test. The dominant feature of the upper South and East aspects we skied was the stout Lucky Friday Crust blanketed by 4ish inches of soft poorly bonded snow. At lower elevations we dodged exposed hazards while scraping on the hard crust.
The generally stable weather we enjoyed for the past couple weeks has given way to significant weather change today with Pacific moisture entering the region, followed by an Arctic cold front that should hit us by Saturday. Last night 5-8 inches of heavy snow fell on top of a somewhat complex upper snowpack consisting of crusts and poorly bonded layers that have shown a propensity to fail, but not propagate. It’s hard to predict exactly how the upper snowpack will react to the new load, but anytime we get this much precipitation avalanche danger rises. The Lucky Friday Crust remains stout, especially on southern aspects, with poorly bonded snow on top. Throw on 8” of new snow load and we have the ingredients for avalanches: bed surface, weak layer, and load. At least the snow is coming in “right side up”: the density and characteristics of the snow will change from warm wet snow produced early in the storm to cold light snow as the temperature drops tonight.
Until the weather settles its important to proceed with caution. As snow accumulates throughout the day avalanche danger will go up. Dial back your terrain choices until the snowpack settles and we get a feel for the new dynamics at play.
If you do get out to play, please let us know what you find by submitting an observation. Thanks.
