Home > Trip Reports > Jan 12: Kendall Knobb - Chewy like taffy.

Jan 12: Kendall Knobb - Chewy like taffy.

1/15/08
WA Snoqualmie Pass
3947
7
Posted by savegondor on 1/12/08 12:41pm
Snowpit video: http://www.youtube.com/watch?v=lw6T_zDbrRA


Again, I skied the Kendall Ridge from exit 53 I-90.  We started in heavy snow which below 3800' changed to mixed precip later in the day.  Dug a pit on an Eastern lee slightly wind-loaded exposure at 4900':  Shovel compression test let loose the top 8-10 inches in unconsolidated sluff.  Shovel test with a fair amount of force produced a fracture and column slide at 20-24 inches.  So top 8 inches was new and fluffy, the next 10-15 were well consolidated on top of an unknown weak layer (possible surface now depth hoar) followed by 2-3 feet of very consolidated 1 finger snow which also slid after 8-10 very hard jumps on the Rutschblock test.  Rutschblock also replicated the 22 inch slab fracture on first light hop.  Conclusion:  Top 22 inches of recent storm snow not bonded very well yet to snow below it.  Stayed on 15-20 degree slopes.  On this aspect all snow below top 4 feet to the ground (last 4-6 feet) was well bonded and consolidated with the big rain crust at about 2-3 feet off the ground.

Ski analysis:  The skiing sucked.  Heavy snow became snot.  You know it's bad when you put a wad of snow in your mouth and it's chewy like taffy and behaves a bit like gum for the first 20 seconds. 

BTW: There was a snowshoer enjoying our skin track.  Bad Karma.  There were also a few "green circle" skiers on AT gear.  I guess everyone is starting to get out there whether they are ready for it or not.  There were also a couple sledders who had snowshoed and were sledding 35-45 degree slopes below some cliff bands.  My guess is they were still huffing it in the dark (if they aren't buried) at 8pm.  They were way up near the outlet of the lowest Kendall Lake. 
Might want to look up "depth hoar". It is not buried surface hoar.

author=loom link=topic=8787.msg35271#msg35271 date=1200266249]
Might want to look up "depth hoar". It is not buried surface hoar.


Well, I wasn't sure which it was...  I'd have to know a bit more about the crystal structure and go back and look at the telemetry for the time period in question.   

Depth hoar forms later right?  Like a layer of frost, only at a certain depth?  I'm geeky enough to want to know the difference, and whether the two may co-exist.  Could surface hoar become depth hoar? 

I wouldn't worry too much about it, as long people understand what you're telling them.  I thought you were pretty clear.  I have no problem calling surface hoar depth hoar once it's buried.  That way you don't have to say "surface hoar that got buried".
sorry if I'm getting remedial, but my laypersons understanding is that: Hoar frost can form anywhere in the snowpack where there is a high temperature gradient, and where there is space for formation.  Typical example is between the ground and snow in a shallow snowpack, where cold air and warm earth (relative to the air) create a temperature gradient, but can also form between layers or adjacent to crust within the pack.  Surface hoar forms the same way, the temperature gradient existing between the <relatively> warm snow and <relatively> cold air, that's why it forms when it's clear out.
I think the other poster is saying that their definition is that facets must develop within the snow pack in order to be called "depth hoar".
Cheers guys

Depth Hoar has radically different structure and mechanical failure modes from Surface Hoar. Check it out! (in fact, check out the whole page if you've never seen it, it contains large chunks, but not all of, Bruce Tremper's informative avalanche text.

Edit: In fact, if you find the page informative, go grab his book! I've found it well worth the many times I've re-read it.

Thanks for the links TS.  I'm now going to call it surface hoar buried in the snowpack.  Very interesting how they definitively say surface hoar is the culprit in avalanche accidents in maritime climates.

Nice report.

I'm glad we don't typically have to worry too much about depth hoar in WA. During my one trip to CO in the winter  in '93 (when I incidentally took a level 1 avy class with a few well known experts including Tremper teaching - good stuff!!), they had something like 3+ feet of depth hoar with just a little over a foot of newer snow on top. It was a very weird snowpack - lots of whoompfing VERY tricky to ski especially with the much-skinner telemark skis of the time. We of course stuck to very mellow slopes given the conditions. If you hit your turns at all hard, POP down into the depth hoar and time to pull out the shovel to dig out your skis, which had sunk deep into the sugary hoar. I realized when moving to WA that our snowpack issues were so different that was well worth re-taking level 1 with Gary Brill - much different emphasis.

author=Jim Oker link=topic=8787.msg35430#msg35430 date=1200435807]
Nice report.

I'm glad we don't typically have to worry too much about depth hoar in WA. During my one trip to CO in the winter  in '93 (when I incidentally took a level 1 avy class with a few well known experts including Tremper teaching - good stuff!!), they had something like 3+ feet of depth hoar with just a little over a foot of newer snow on top. It was a very weird snowpack - lots of whoompfing VERY tricky to ski especially with the much-skinner telemark skis of the time. We of course stuck to very mellow slopes given the conditions. If you hit your turns at all hard, POP down into the depth hoar and time to pull out the shovel to dig out your skis, which had sunk deep into the sugary hoar. I realized when moving to WA that our snowpack issues were so different that was well worth re-taking level 1 with Gary Brill - much different emphasis.


Ok, yeah, thanks for the input. 

I have skied those exact conditions in Montana.  Month old snow exposed to 0-10 degree nights.  Three, four feet of the stuff, had no substance, skis punched right to the ground.

So now I have a new question.  Would you consider the whole of that snowpack 'depth hoar'?  On the one hand I hear of depth hoar forming as a layer in the snowpack, and on the other I have experienced the snowpack itself changing in characteristics.  For example, the 'sugar snow' that formed from a lot of sublimation and gradients - cold nights and relatively warm days.  So the fresh question:  when a snow crystal changes can that sometimes turn into what we are calling depth hoar?  Or upon closer examination of the snow would we find depth hoar forming among the rotten snowpack?  or both?

Seems to my mind that depth hoar would refer only to a specific kind of new crystal forming within the snowpack and not the rotten nature of our i.e. Rocky Mountain sugar snow. 

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savegondor
2008-01-12 20:41:07