So far the winter storm affecting our region has come through with up to 20” of new snow in the mountains near Bishop and up to 2’ or more around Mammoth since yesterday morning. Up to another 24” is forecast for today and tonight. The mountains are starting to gain some coverage down to ~8000’. All that is good news for our seasonal snowpack, but the rapid loading is bad news for the risk of avalanches in the short term. There has been enough new loading of strong over weak snow in the past 48hrs that avalanches can be expected in many areas and they could be very large and destructive.
And it’s not just new snowfall that has raised the danger level. Strong and variable winds have been building slabs at all elevations. In some cases, new storm and wind slabs are sitting on top of deeply buried, but very weak layers of sugary faceted snow. If these layers fail, from the weight of new snow or from a smaller avalanche suddenly over-running them, the resulting slide could be very large.
In many cases, lower elevation slopes are seeing snow coverage for the fist time in a while. In places where there was snow down lower, like around Mammoth and north to Virginia Lakes, these lower elevations may have enough new snow for avalanches to run to the bottom of the slope. In any case, obstacles that were previously obvious may now be hidden under just enough new snow that you won’t see them coming. In fact, the strong winds may make it hard to see at all. Playing on or near steeper or challenging terrain in the mountains is not recommended today. Even if the weather eases to slightly lighter winds and showery snowfall, avalanche hazards that increased overnight will take time to stabilize.