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Weather Summary

Cumulus humilis and lenticular cloud pods covering about 15-20% of the sky for the majority of the day, high, thin stratus covering 80-90%. Allowed for plenty of direct solar radiation from morning through mid afternoon. Upper stratus deck becoming thicker in the mid afternoon. Temps very mild. Winds calm at lower, light at middle, low end of moderate with occasional strong gusts at upper, blowing out of the W.

Avalanche Observations

Map of listed avalanches: Avalanche Observation Comments:

I intentionally triggered about 5 D1-1.5 wet loose slides today. I observed numerous natural wet loose slides (most are likely from Tuesday, maybe a few from Wednesday? impossible to say with certainty). I also found a few persistent slabs that failed during the storm.

Snowpack Observations

Goals were to look for more persistent slab activity and look at wet snow issues. Interesting overlap of wet snow and dry snow problems out there today.

Weak freeze overnight, surface crusts breaking down quickly, snow was wet and cohesionless below these crusts (at lower). Only took about an hour or two of direct sun to break these crusts down at lower and middle elevations. In treed areas, the overlying crust was quite weak (thanks to LW out) and was not ski supportable. In middle and upper elevation terrain I was able to trigger a handful of D1-1.5 wet loose slides on NE-E-SE-facing slopes. The problem was a bit stubborn in areas where the new snow/rain hadn't slid, and was reactive on bed surfaces from recent persistent slabs thanks to the stack of weak facets present there.

I spent some time glassing back into the Lola/Collie area and saw a few small (maybe persistent?) slabs as well as some D1-1.5 wet loose activity from Tuesday's rain-on-snow event. I also found a D2 persistent slab complex (3 separate crowns that likely ran simultaneously). Above this slope there was significant cracking on lower angle slopes. I was able to make it down to this crown and found that it had failed on a subtle MFcr+FCsf combo that was buried by the storm (2/27 interface).

Here's how I'm thinking about the persistent problem in this area: it seems like some slabs broke at the new/old interface (2/27) with clear persistent slab characteristics. Others appear to have broken closer to the base of the Jan/Feb trickling snowfall (lets call it 1/20). There are a variety of layers between 1/20 and 2/27, but these are very difficult to differentiate on shaded slopes. On solars, 2/14 MFcr presents a pretty clear marker and is widespread. Long story short, its fairly complicated from a slope-scale perspective. On a synoptic scale, its easier: a variety of weak layers exist in the upper 20-45cm of the snowpack. Several of these have produced natural avalanches and likely will continue to during periods of loading. The possibility for human-triggered avalanches involving these layers will linger for days after loading events.