Wind drifted snow and significant recent snowfall sit atop old, weak snow from our January dry spell. Human triggered avalanches within the wind blown snow are likely today. Any avalanches involving the old snow could be stubborn to trigger, but high consequence. Keep a distance from avalanche terrain on cold slopes at all elevations, even if informal observations tell you otherwise.
Wind slabs have developed over the past several days and new ones are forming again today as winds continue. Some natural activity has been observed, and human triggers are likely today. Wind slab avalanches could “step down” into the old snow that’s causing our Deep Persistent Slab concern, resulting in large avalanches.
Prior to February 10th, we experienced a monthlong dry spell that created a layer of weak, sugary snow and crusts on the surface of cold slopes. Since February 10th, we’ve received several feet of new snow that’s settling into a thick slab of stronger snow above weaker old snow. This is an unfortunate structure that provides little feedback with informal observations, and may not produce an avalanche unless someone triggers the slope in just the right place – or if they trigger a Wind Slab avalanche that “steps down” into deeper weak snow.
With little or no feedback from the mountains, it’s easy to get lulled into complacency regarding this avalanche type. If you’re not seeing avalanches or other signs of instability on this deeply buried weak layer, don’t assume it can't happen.
Windblown snow and recent new snow on top of an old, sugary weak layer is creating complex avalanche conditions that might not provide much feedback until it's too late. Maintain wide margins today and vigilance into the near future – this is an unusual situation for the region that could last a while. A rain event on Tuesday could make things exciting, in a bad way.
