February-15
Porter Fork
Elevations, slope angles and aspects
6200-9400'. angles approaching 35°, north and west facing aspects.
Snow conditions
Lower elevations had a rain-rime crust(spongy) extending to almost 7k. It was capped by a skiff of lighter density.
Above that elevation, 2-4" of dense and creamy new snow also capped by light density.
Surface hoar was observed in mid elevation terrain-8000-9400'.Didn't make it higher.
Day time heating quickly warmed exposed aspects. Those will probably have a crust.
Avalanche activity
A return to the scene to view another slide, this time on the shoulder of Gobblers.
The crown was 2-8" deep, deepest on the looker's right flank, next to the treed sub ridge.
An inch or so of new snow + some drifting covered the fracture and path.
The slide was 100'+ wide. According to my altimeter watch(gear head), it ran about 800 vertical feet, barely making the lower gully rollover.
Weather
Partly cloudy with some pesky mid-upper elevation cloud banks moving though in the afternoon. Mild temperatures with light winds.
Snow pit
Had a look at the crown in several locations from flank to flank.
Easy to moderate shears on small grained facets formed on January 6-8th.
Surface hoar was the weak layer in only one spot, looker's left, 2" crown, easy shear, Q1.
Hoar was flattened not upright.
crown profile?
Evaluation
The rare and elusive hoar frost rears it's ugly head, claimed responsible for all slides.
I found it to be spotty on the aspect and avalanche examined.
Instability is probably localized Wind drifting, especially on mid elevation break overs, should be approached with caution.
Instabilities from day time heating, so active with the first warm up, should be more isolated with over night cooling and weather guess of cloudy skies.
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