Winds are increasing today, moving cold snow along the surface and creating unstable slabs along downwind slopes with little to no tree cover. On cold slopes with all types of tree cover, recent snow is settling into a thick slab of stronger snow above weak, old snow from our dry January. Avalanches that fail within this old snow could be difficult 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 increase. Some natural activity may even become possible later in the day once enough new windblown snow accumulates. With multiple layers of windblown snow, wind slab avalanches could “step down” into deeper layers and even into the old snow that’s causing our Deep Persistent Slab concern.
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. Beginning on February 10th, we’ve received several feet of new snow that’s settling into a thick slab of slightly stronger snow above slightly 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 isn’t a possibility.
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.
