Toured up into the Raggedtop zone to check on the snowpack structure in this
part of the Girdwood Valley.
Mostly cloudy with light rain below 1,000′ and snow above. Winds light from the
east above treeline. Skies began to clear and precip ended around 1pm. Temps
warm, mid 30’s to around 30F at 2,500′
Signs of instability:
Collapsing – Yes. We had 4-5 collapses radiating ~20-40′ around treeline (2,000-
2,500′). Failing layer suspected to be facets below Dec drizzle crust.
Cracking – minor. A few small fresh wind drifts on steep rollovers cracked 3-6″
deep 10′ wide.
Snow surface conditions:
Below 2,000′ Wet and saturated.
2,000-2,500′ Trace of new snow and sticky old snow from 1/5.
Above 2,500′ An inch of new snow – dry but dense.
The same poor structure that exists at Turnagain also exists in Girdwood Valley.
In general: The bottom of the pack consists of 20-30cms of crust/facet combos.
Above this is a 50-70cm slab (slab is all Dec/Jan snow). The weakest layer is
right below the slab and consists of 1mm facets below the Dec drizzle crust. The
driz’ crust is attached to the slab and degrading.
We dug 2 pits:
Pit 1 (2,500′ NE facing)
ECTP 27 Sudden Collapse (failure 60cm down in facets below Dec crust)
PST 35/100 (end) down 60cm (same weak layer as ECT’s)
Pit 2 (1,700′ NE facing)
ECTP 20 Sudden Collapse (Failure 45cm in same facets below Dec crust)
Pit result bottom line: Hard to trigger the slab but once it fails propagation
propensity is high. Large avalanches are likely/possible if one hits the trigger