Like a long lost friend from far away, winter weather has finally returned to the east side. And everything seems rosy until you realize that your buddy comes bearing some baggage that you’d forgotten she had. And now you have to deal with it too.
All the welcome new snow coming into our region is sitting on top of a weak, complex snowpack that we are usually unaccustomed to here in the Sierra. The Ridiculously Resilient Ridge that had parked itself over California until recently had kept things dry and the snow cover thin, with few exceptions. So as new precipitation rolls in we will likely see the usual avalanche problems of wind and storm slabs, but weak layers persist underneath and could fail under the new load creating avalanches that are quite large and difficult to predict.
The storm on Saturday left 11” of new snow around Mammoth, and between 3 and 5” elsewhere. This snow was light and dry from June Mountain north, but dense and heavy further south. As the snowfall tapered off mid day, Southwest winds increased and sensitive wind slabs developed on northerly slopes. Snow levels were relatively high between 8,100’ and 8,500’ with rain below. This added little in the way of new snow to the already meager snow depth at that elevation. The new snow sits atop a variety of surfaces, from rain crust, to near surface facets, to melt-freeze. This means that bonding between old and new snow will be variable as well.
Significant new snowfall and stronger southerly winds are expected beginning Monday morning. And though it will be a welcome change to the high and dry, it will likely add to an already complicated avalanche danger. Pay close attention to changing conditions and make conservative terrain choices.
Early season obstacles are not yet completely buried. Be wary of rocks and trees just under the surface.