Observation: Public
Observation Details
Name:
Josh HirshbergObservation Date:
March 8, 2021Submitted:
March 8, 2021Zone or Region:
East NorthActivity:
Skiing/SnowboardingLocation:
WA Pass, Hairpin ValleyTriggered Avalanches
Did you trigger any avalanches?
YesWas it intentional?
YesAvalanche Type:
Soft SlabSize:
Size 1: Relatively harmless to peopleElevation:
7320ftAspect:
EComments:
I intentionally triggered a very small wind slab just below a ridge crest in soft recent snow. 1ft deep x 6ft wide. It ran 10 feet downslope and stopped.Observed Avalanches
Did you observe any avalanches?
YesAvalanche Type:
Dry Loose (Sluff)Size:
Size 1: Relatively harmless to peopleElevation:
Above 5600ftAspect:
Comments:
We observed a number of dry loose avalanches generally size D1. Small, natural avalanches were triggered by sun today on W-N-E aspects near and below treeline. We saw a few that were triggered by skiers up to D1.5 in very steep to extreme terrain (>40deg) on NE, 5,900ft.Also notable, we watched a natural cornice fall from a rock spire on NNW, 7,250ft, around 12:10p. No avalanche resulted. The cornice itself easily could've injured a person.
Signs of Unstable Snow
Observations
Roughly 5cm of snow accumulated overnight with near 20cm since Saturday. Skies were clear until about 11:30 then became broken w high, thin clouds by 14:00. Ridgetop winds were intermittent, gusting to moderate out of the southwest in the AM, and becoming mostly calm in the afternoon. Transported snow followed suit w brief intense bursts of blowing snow in the AM. Air temperatures stayed cold in the shade, staying below freezing at least to 5,000ft maybe lower. Much colder temps at upper elevations.
Fresh wind slabs were shallow and soft in isolated to specific terrain. In places, it was possible to travel on leeward sides of ridges while avoiding small pockets of wind slabs. Cornices are very large and are still looming. We saw multiple slopes with debris from cornices that have fallen since March 1st. Snow surfaces warmed on solar aspects at all elevations. We found sun crusts from the 7th to at least 7,000ft.
Aside from the surface instabilities noted above, the upper snowpack is free of major layers of concern. Near treeline, on NE we found hard, resistant, and planar hand shears ↓35cm where older wind-drifted slabs overlaid 0.5mm decomposed precip particles. At 6,100ft E aspect, the height of snow was 315cm and snowpack tests yielded no results. The only strong-over-weak layering was down 50cm from the surface on 0.5mm decomposed precip particles. This could coincide with observations of small facets at a similar depth found further east.
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