Start Date: 12.21.17 Name: Savage, Hatch Operation: SAC
 Drainage/Route:  Copper Mt Observed Terrain:  7000-9000: most aspects Zone/Region:  Banner Summit
 HN24: ? HST: 20cm Sky: CLR Precip: Temps: -10F to 10F
 Ridgeline Wind: Light from the N
 Blowing Snow: Prev Snow Available for Transport: Small amounts
 Comments: Wind obviously blew from W/SW for awhile during the storm and then switched to the N/NW.
 No. Location Date Size Type Trigger Aspect Elevation Comments
 6 Williams Peak Within past week 1.5 SS N S 9800-10200 appeared to be D1.5-2 slides viewed from HWY with binocs
 2 Merrit Peak Within past week 2 U U NE 10000 Both slides estimated 2-3' crowns, not very wide, released in cirques under cliffs a ways below ridgeline. Appeared to be triggered by sluffs/cornice/smaller slabs coming through the cliffs above.
 15 Sawtooths Within past week 1 L N alpine Observed several small sluffs throughout the range from Cabin Ck area to Goat Ck drainage.
 Comments: No activity at all observed near Copper Mountain/Bull Trout Lakes area.
 HS: 90-115cm around 8000-8700': 30-50cm on southerly below 7500'  
 Upper Pack: 15-25cm PP (storm snow) sitting above near surface FC on shadys and a sun crust + facets on solars and margins 
 Middle Pack: FC above knife hard Thanksgiving crust 
 Lower Pack: mostly ice forms from Thanksgiving weekend rain event and subsequent freeze 
Avalanche Characteristics
Character/Avalanche Problem:
Wind Slab


Likelihood of Triggering

Spatial Distribution:
  Primary Concern Comments: We jumped on some isolated drifts at middle elevations and got 1 to crack with a lot of effort. We avoided wind loaded slopes at upper elevation (near the top on the shady side of the peak).
 Comments: Obvious wind loading from the W/SW winds early in the storm, but it may have unloaded/scoured those same slopes when the wind switched to the N/NW and created wind effect on W/SW aspects later in the storm. Lots of stiff wind features above 8700' on the NE side that I would not have gone near. On non-wind loaded slopes, there isn't quite enough load to be a problem from what I saw (see test scores below).
 Stability Test Results: 8500' SW: ECTN on density change in new snow about 10cm down
8450' NW: ECTN x 2 on near surface FC 20cm from top - this interface would not propagate (even with additional loading steps) but it would come out "whole" if you pulled on it from behind after performing the ECT test (see photo)
 Marked with checkmark if observed:
 Cracking (isolated) Depth: 20-50cm Length: 1m
 Snow Stability Rating for your observed area: Good Confidence: HIGH Trend:
 Comments (aspects and elevations of instability, etc): Good stability in non-wind loaded terrain. I would not assign a stability rating to wind-loaded slopes as we avoided all consequential wind-loaded terrain.
 Comments: Wind-loading: the change in wind direction was obvious, probably prevented more widespread loading and activity on N-E lee slopes. Some very stiff wind features mixed in with the softer slabs.
Non-wind loaded: not quite enough load/slab to have an honest persistent slab or storm slab problem (avalanches failing on the near surface FC below the storm snow) from what I saw. Cold temps were slowing the settling/consolidation in the new snow, so changes in slab characteristics in the upper part of the snowpack will be subtle and could creep up on us with continued small storms.

Williams crowns.jpg
Crowns from natural slides during storm on Williams Peak.

ECTN NW8400.jpg
ECTN but getting closer to being a problem in sheltered terrain.

Copper wind loading.jpg
Wind loading on NE aspect near top of Copper.