Heavy snowfall on Sunday night and during Monday will lead to Wind Slab avalanches on North and East slopes at and above treeline. As we approach a foot of new snow we will also begin to see avalanches below treeline. These will likely be Dry Loose avalanches, but Storm Slabs are also possible. Avoid steep, unsupported terrain.
Wind Slab avalanches are likely as overnight snowfall will be accompanied by a Moderate Southwest Wind. Wind Slabs avalanches have the potential to be large. As the wind shifts more westerly and strengthens during Monday expect variable loading patterns, and the possibility that some wind blown snow could be settling into glades and bowls further downslope.
With heavy rates of snowfall, and well over a foot of new snow in the forecast, Storm Slab avalanches could become a problem as the storm progresses. We often look to a foot of new snow as a general threshold for when we start worrying about Storm Slab avalanches. Even with less snow, you may see cracking on test slopes, or evidence of more consolidated (slabby!) snow in your skin track and in hand shears. This is a good indication to avoid consequential terrain.
Temperatures will generally be dropping during this period of heavy snowfall, and that often points us toward a "right-side-up" snowpack with weak unconsolidated surface snow and the resulting Dry Loose avalanches. With Dry loose avalanches it is important to avoid terrain that could increase the consequences of an otherwise "small" avalanche; avoid terrain traps and gully features that might funnel the sluff.
Remember that Dry Loose and Storm Slab avalanches are not always mutually exclusive. Slight variations in elevation, aspect, or even the configuration of a slope may create slabbier snow. Rely on your skin track observations like test slopes, and hand shears to evaluate which avalanche character is present.
Sunday was marked by a return to wintry weather, with the highest snowfall totals near the Cascade Crest. It was cold and snowy throughout the day. Field observations show today's snow bonding well to older snow layers (at least initially). My primary avalanche concerns will exist in the storm snow.
