Quick report
- Red Flags
- Recent Avalanches, Heavy Snowfall, Wind Loading, Cracking, Collapsing
- Red Flags Comment
- <p>Stacking the red flags high- obvious signs of instability were abundant.</p>
Snowpack
- Instability Comment
- <p>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. <strong>We did have to reverse our routefinding a couple times and choose areas that we don't normally travel to stay on scoured slopes.</strong> 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.</p> <p><strong>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. </strong></p> <p>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.)</p>
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.