AIARE 1 Avy Course

CB Avalanche Center 2016-17 Observations

Location: Crested Butte Area
Date of Observation: 01/21/2017
Name: Tim Brown and Chris Pruden
Subject: AIARE 1 Avy Course
Aspect: North, South, West
Elevation: 8,900’ to 9,500′

Weather: Overcast skies with a short period of high thin clouds and strong solar radiation, Light winds from SW, no Blowing Snow, Air Temp ~ 20*F, short period of S2 with 5cm total accumulation of rimed new snow.
Snowpack: Observed no new avalanches, cracking or collapsing. The 20cm of storm snow since Thursday was F hard and its bond to the old snow surface varied with aspect: poorly bonded to 5mm SH above a 2cm thick 1F hard crust on S aspects, well-bonded to the crust on W aspects (found no SH here), and semi-well-bonded to 3mm SH on a N aspect ~9500′.

A profile on a S aspect at 9,200′ with HS 150cm and PF 20cm revealed a 20cm thick, poorly-bonded soft slab of F hard storm snow over 5mm SH overlying a 2cm thick, 1F hard layer at the old snow interface (CTE SC, ECTP5). Compression tests showed Moderate SC results on 2 more interfaces, one just below the crust on a layer of 1mm FC and another down 34cm from surface. Neither of these interfaces showed a propensity for propagation in ECTs (both ECTN 15 and ECTN 17). We found 3 more buried crusts, but snowpack tests produced no alarming results on these or the 4F hard, 2mm moist basal facets.

Compression tests on the W and N aspects produced no sudden results.

The snow surface quickly warmed and formed a soft (4F hard), 2cm thick crust on S aspects that was quickly covered by an additional 5cm of new snow by 2pm.