Observation Date
2/8/2014
Observer Name
Andy Rich
Region
Salt Lake » Big Cottonwood Canyon » Days Fork
Location Name or Route
Alta to Spruces
Weather
Sky
Obscured
Precipitation
Heavy Snowfall
Wind Direction
Southwest
Weather Comments
Periods of heavy snowfall with strong sw ridgetop winds. Poor visibility and flat light further complicated already difficult routefinding conditions. Couldn't really get any pictures with the wind/snow/light...
Snow Characteristics
Snow Characteristics Comments

Several density inversions and weak layers in the new snow- some probably from temperature but the wind deposited areas were definitely the most sensitive. Sheltered areas had ~30 cm of creamy medium density new snow that skied really well if you could find areas that were safe enough to ski steep enough- which were few and far between- otherwise it was really pretty slow.

Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Wind Loading
Cracking
Collapsing
Red Flags Comments
Stacking the red flags high- obvious signs of instability were abundant.
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Increasing Danger
Problem #1 Comments

No doubt the most sensitive areas we saw were the recently wind (cross-) loaded slopes heading north from Alta. Considering the amount of cracking and collapsing we got on the skin track up (mostly s and e aspects), I'm pretty amazed that we didn't trigger slides on slopes around us. We did have to reverse our routefinding a couple times and choose areas that we don't normally travel to stay on scoured slopes. Cracking up to 50 cm deep and 20 meters long- although again hard to really tell with the poor vis. We traveled along the LCC/BCC ridgeline for a while and skied into Silver and then Days. Again I was surprised at the lack of activity in response to cornice drops (active cornice growth hanging over N aspects), ski cuts and skiing of the more northerly facing slopes considering the incredibly prolific cracking and collapsing on the southerly aspects. I did trigger a number of small (15 cm x 10 m crown at the largest), wind slabs on north slopes, but in terrain where I would have expected something more substantial. The wind loaded areas that were not at the tipping point today didn't seem far from it- tonight and tomorrow afternoon should be a different story.

Forecaster Comments: Noted that Andy and party here didn't use/follow the standard uptracks with his head down; instead to be extremely deliberate about terrain choices to move through terrain in a High danger situation.

Avalanche Problem #2
Problem
New Snow
Trend
Increasing Danger
Problem #2 Comments

I did some digging around on N and W aspect sheltered slopes (~9800') that weren't wind loaded to see how all the weight was affecting the bonding with the facets that were buried at the end of Jan. I was seeing Q2/RP shears ~60 cm down with moderate strength but I wasn't able to get slides to fracture at this interface despite my efforts. (I did get 1 slope to fracture- crown, flanks and all but didn't move- that I suspect may have been at this interface, but couldn't get in the starting zone to be sure- looked like it was barely supported by the stauchwall.) But with that planar shear and some more stress being added, the pump is primed. (Side note, yesterday- Friday- we got substantial cracking and an ECTP 15 Q1 at this same interface on a N aspect slope at ~7500' in BCC so if there's any loading at low elevations I would expect persistent instability on shaded aspects and valley bottoms there as well.)

Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
High
Coordinates