Baker BC - very reactive surface layer observation

Figured there would be some interest in a super reactive surface layer observed yesterday (1/22 at 11 am) in the Baker backcountry.  General description is 12"+ of very low density snow over high density snow - speculation can be concluded from telemetry below.

The blue square on the topo shows exact location (below Slate Mountain) of the photo.  Sluffs would run on steep slopes near the 4400' contour in the topo, but on lower angle slopes many compression fractures would instantly appear without sluffing as shown in the photo.  Very cool when safely managed, but pretty scary in most terrain.

Telemetry, photo, and location hopefully allow for much entertainment.

Northwest Weather and Avalanche Center
Mt Baker Ski Area, Washington

MM/DD  Hour  Temp  Temp    RH    RH  Wind  Wind  Wind  Wind  Hour Total 24 Hr Total
         PST     F     F     %     %   Min   Avg   Max   Dir Prec. Prec.  Snow  Snow
             5020' 4210' 5020' 4210' 5020' 5020' 5020' 5020' 4210' 4210' 4210' 4210'

---

1 22  1200    23    26   100    96     2     6    17   159  0.01  0.07     2   124
  1 22  1100    23    26   100    94     2     7    16   157  0.01  0.06     2   127
  1 22  1000    23    25   100    96     2     8    16   169  0.01  0.05     2   127
  1 22   900    22    25   100    97     0     7    18   158  0.03  0.04     2   236
  1 22   800    21    24   100    97     0     3    11   143  0.00  0.01     0   125
  1 22   700    21    24   100    96     2     6    11   163  0.01  0.01    10   125
  1 22   600    20    23   100    96     3    10    20   168  0.00  0.00    10   125
  1 22   500    20    24   100    97     9    15    22   176  0.00  0.00    10   125

---

  1 22   400    20    23   100    97     6    12    18   181  0.00  0.71    10   125
  1 22   300    20    23   100    95     8    16    24   173  0.00  0.71    10   125
  1 22   200    20    23   100    97    10    15    23   179  0.00  0.71    10   125
  1 22   100    19    23   100    95     7    15    26   175  0.00  0.71    10   126
  1 22     0    20    23   100    95     1     9    16   182  0.02  0.71     9     5
  1 21  2300    20    23   100    95     2     8    16   195  0.02  0.69    10   126
  1 21  2200    21    23   100    95     5    11    19   195  0.01  0.67    10   126
  1 21  2100    20    23   100    96     3     8    20   204  0.05  0.66     9   126
  1 21  2000    20    24   100    93     4     7    17   199  0.01  0.61     9   125
  1 21  1900    21    24   100    97     1     7    13   184  0.01  0.60     9   328
  1 21  1800    22    25   100    98     2     9    18   189  0.01  0.59     8   125
  1 21  1700    22    25   100    95     3     8    14   192  0.02  0.58     8   125
  1 21  1600    23    26   100    97     3     9    14   199  0.02  0.56     8   125
  1 21  1500    25    27   100    97     3     8    15   204  0.04  0.54     7   324
  1 21  1400    25    27   100    97     3     8    16   209  0.00  0.50     7   124
  1 21  1300    25    28   100    96     1     5     8   247  0.00  0.50     7   124
  1 21  1200    25    28   100    95     1     5     8   247  0.03  0.50     6   125
  1 21  1100    25    28   100    98     4     6     8   193  0.02  0.47     4   124
  1 21  1000    25    28   100    98     1     5     8   130  0.05  0.45     4   349
  1 21   900    25    28   100    99     2     6    10   146  0.05  0.40     5   123
  1 21   800    25    27   100    99     3     6    11   170  0.07  0.35     4   122
  1 21   700    26    28   100   100     5    11    20   141  0.08  0.28     2   122
  1 21   600    28    31   100   100     7    15    26   190  0.13  0.20    14   121
  1 21   500    30    33   100   100     7    10    17   217  0.07  0.07    13   117

---

  1 21   400    30    32   100   100     4     7    12   217  0.11  2.24    12   349
  1 21   300    30    33   100   100     4     8    11   217  0.09  2.13    12   115
  1 21   200    30    32   100   100     4     8    12   155  0.11  2.04    12   116
  1 21   100    31    33   100   100     4     9    13   131  0.18  1.93    11   116
  1 21     0    31    33   100   100     4     9    14   146  0.16  1.75    11   118
  1 20  2300    30    33   100   100     5     8    13   153  0.16  1.59    11   117
  1 20  2200    30    32   100   100     6     8    11   164  0.17  1.43    10   349
  1 20  2100    30    33   100   100     3     6    11   149  0.16  1.26     9   115
  1 20  2000    30    33   100   100     2     5     9   133  0.21  1.10     8   307
  1 20  1900    31    33   100   100     0     3    11   150  0.06  0.89     7   323
  1 20  1800    30    32   100   100     0     3    10   147  0.08  0.83     6   328
  1 20  1700    31    32   100   100     1     5    11   136  0.09  0.75     6   113
  1 20  1600    31    33   100   100     1     4    11   119  0.09  0.66     5   112
  1 20  1500    31    32   100   100     1     4    11   130  0.05  0.57     4   112
  1 20  1400    31    33   100   100     1     6    13   134  0.06  0.52     4   111
  1 20  1300    31    33   100   100     2     7    13   161  0.06  0.46     4   111
  1 20  1200    31    33   100   100     2     7    14   150  0.08  0.40     2   111
  1 20  1100    30    33   100   100     4     8    12   164  0.11  0.32     3   111
  1 20  1000    31    33   100   100     6     9    11   162  0.09  0.21     3   110
  1 20   900    30    33   100   100     6     8    12   155  0.05  0.12     2   110
  1 20   800    29    32   100   100     6     9    13   153  0.03  0.07     2   110
  1 20   700    29    31   100   100     4     8    12   152  0.02  0.04     1   109
  1 20   600    28    31   100   100     4     7     9   156  0.02  0.02     1    84
  1 20   500    28    31   100   100     6     9    13   168  0.00  0.00     1   110

Cool!

That's really wild Dave -- good to see it in low angle stuff, scary elsewhere for sure...

I was riding just outside of the ropes at the ski area on Sunday. I actually set the first track coming back into the ski area from the Elbow and saw lots of loose running sluff that was easy to handle. At the end of the day I was traversing across a roll and noticed shooting cracks so I retreated to lower angle/well tracked terrain. I was up again yesterday and knew that there was heavy wind transport overnight. I had pretty good luck going into Oy Valley and the Elbow again and again found myself on the upper traverse off the top of chair 8 at the end of the day. I ski cut 2 spots and had storm slab that was about 12" deep pop very easily.

Did anybody see the loose wet slide that tore through the bottom of Oy Valley on Saturday afternoon? I checked out the debris on Sunday but could not identify a crown line. I suspect that it came off of the Football Field or the double barrel chutes. It looks like it flowed around the high point and then the two flow paths met in the bottom of the gulley. It's a terrifying amount of snow that looks similar to the slide from late February of last year.

On Sunday 1/22 We experienced similar disconcerting settling and a small slide. We were in the lower pitch (~600vf) of the swift creek trees coming off Kulshan ridge. Coming off the Kulshan ridge was way too scary for us on this day (and anyone else apparently). We took the usual skin track out of swift creek and then made our way south along the bottom of Austin pass about 2-300 yards. Our goal was to stay in low angle, low elevation trees and pick conservative lines. The snow was amazing, such that it was refilling on every lap.

In this vid I was tucked off in a safe spot on a bordering treed slight ridge watching my buddy run thru to the next safe spot. We had identified the convex rollover that moves in earlier laps and made efforts to stay off of it.

In the next run there was a navigation mistake and he ended up in a wind created runnel that we couldn't make out from above, given the tough viz. The snow settled with a turn in and moved about 4 feet before stopping. With a bit of nervous radio communication, we made an escape plan. I found a safe observer spot and he pointed it the hell out of there. At the bottom we regrouped over hot totties and decided to call it a day.

All the snow that moved was soft wind slab about 4-6 inches deep. The bit that moved in the video was filled in by the next lap, ready for the next bold skier. The deposition we skied thru was not hard at all, and if we didn't see it move would have assumed to be big sluff. It likely wouldn't have buried a skier but it certainly could have smashed one into those tress to injury.

With Swift being the go to place in higher danger with high wind, it's good to remember that the skier's right high wall just at the entrance to each of those first three chutes heading south of the main Swift bowl toward Huntoon all are short convex wind-slabbed rollovers, and the gullies will allow the skier-triggered slide snow to concentrate and accelerate in the gut - and if you don't high-side out like he did, you'll get flushed through the little trees in front of you if it runs far enough.

Saw the wrinkling of the snow surface last week in the Cariboos (as in your picture), daveb. The set up was as follows: Low density snow with a thin layer of surface hoar deposited on top of it followed by 9" of very low density new snow (5% water content) that fell at a snowfall rate of 1-1/2" per hour. Entire slopes broke up into a wrinkled pattern.

At times energy would propagate out from the skiis (presumably through the surface hoar layer) for about 50-75' from a skier's position. The 9" of new snow would then begin to break up. Slopes over about 40 to 42 degrees would slide as a very soft slab, but those under that angle would merely wrinkle.

Here's what I think was happening: As the not cohesive snow began to fail on top of the surface hoar it would begin to move downslope, but because the underlying snow was so weak the moving snow would begin to move turbulently, and was only able to dive into the underlying low density snow which then stopped the momentum of the failing new snow. So the slope would wrinkle but not slide until a critical slope angle was reached.

This abnormal failure mechanism was certainly interesting to me, thanks for reviving this thread Gary. It appears the Baker snowpack I observed was less complex than the Cariboo snowpack you observed. Baker was low density layer on high density layer with no apparent weak layer separating the two. Cariboo had the surface hoar weak layer between the low & lower density.

Nonetheless, both snowpacks behaved similar. Compression fractures/wrinkles (CFW) on lower angles & 50’-75’ propagation (close to what I observed) of very soft slabs on steeper slopes 40-42 degrees (also close to what I observed).

What I found really interesting about the CFW is the partial failure (as opposed to full failure, ie an avalanche). It was intriguing the snowpack had enough cohesion to store the energy necessary to propagate, but once the energy was released there was no avalanche, just CFW.

Gary, your Cariboo snowpack analysis got me thinking nerdy about the Baker snowpack. At Baker, since there was high density snow below the CFW layer I observed, the only action was in the CFW layer. Seems like when the CFW appear, the layer must consolidate (the snow density increases and void air space decreases). With less void air space, more contact, and therefore more cohesion, must be occurring between snow flakes in the layer. There must have been enough consolidation to increase cohesion and bring the sliding snow to a halt.

Interesting. I think the Cariboo example was easier to understand. What's difficult to understand in your Baker case, daveb, is how the energy was able to propagate for 50-75', which is quite a ways, and infers a weak layer. So maybe, somehow the energy propagated through the very low density new snow. But that is hard to believe because it is difficult to understand how new snow that is not at all cohesive is able to transmit energy?

The guide in the Caiboos said that wrinkled snow occurs there about 3 times a season. I think that it doesn't slide because it has so little cohesiveness. It is easy to understand why it would break up (lack of cohesion) but in your Baker case was the underlying higher density surface still soft and porous or was it firmer as if it had a skin on top of the layer? i.e. Is my diving theory realistic?

The guide also suggested it (FCW as you call it) is something someone ought to study. But as it is the first time I've seen extensive wrinkling, I would think the research scientist might be in for quite a wait for data points.

I worked one winter at Mica Creek, which is due east of Blue River a short distance and that winter I never saw this phenomemna.

I had a small revelation/why didn't I think of that moment. Skinning from the Baker upper parking lot to Bagley Lakes, we observed a very thin frozen water layer on the surface. This layer was not apparent where the CFW (as you probably guessed I just made that up) were observed. The wind was howling, as it commonly does, on the way to Bagley Lakes so it probably kept any snow from accumulating on this layer. In the trees, however, the snow probably accumulated on the layer which then provided the sliding surface for the CFW. That makes the observation much less mysterious.

I had a small revelation/why didn't I think of that moment.  Skinning from the Baker upper parking lot to Bagley Lakes, we observed a very thin frozen water layer on the surface.  This layer was not apparent where the CFW (as you probably guessed I just made that up) were observed.   The wind was howling, as it commonly does, on the way to Bagley Lakes so it probably kept any snow from accumulating on this layer.  In the trees, however, the snow probably accumulated on the layer which then provided the sliding surface for the CFW.  That makes the observation much less mysterious.

In your Baker example, that would mean that the energy propagated through the low density new snow that was cohesionless. That may also have been the case in the Cariboos. Perhaps there is enough structure, as ephemeral as it is, to enable propagation. The surface hoar in the Cariboos was just a small amount, not big crystals or anything.

Today's avalanche at Mount Baker. Titled as "once in 100 years".





Unstable, indeed!

^^Whoah....

Where exactly are those pics taken? For a non Baker regular, im trying to get an image of where you are say in relation to the base of Chair 8

Maybe a few more minor details....? Like where, when, natural or triggered (by whom?), etc. etc. etc. Not to mention, "titled" by whom?

Thanks.

mark

Maybe a few more minor details....?  Like where, when, natural or triggered (by whom?), etc. etc. etc.  Not to mention, "titled" by whom? 

I was wondering about this too. A little detective work quickly revealed the answers: right-clicking on the photos to "Open Image in New Window" showed the URLs which were from the Mt Baker Ski Area website. Visiting the snow report page (be sure to scroll down) found those two photos, along with a third photo and this text:

"Photos of the slide path of the March 15th morning avalanche from the Shuksan Arm wilderness area down into Rumble Gully. This slide is estimated to be a 100 year event. There were no property damage or injuries, but note the destruction of trees."



Some other interesting info on the snow report page:

"SPECIAL NOTICE: due to the warming temperatures and consequent significantly unstable snow conditions, MT. BAKER WILL BE CLOSED TODAY..

Once freezing levels have cooled back down to around 1,000 as forecasted and conditions have stabilized, we will re- open. Temperatures are expected to drop tonight, with yet another foot or more of snow possible for tomorrow.

With this continuous parade of storms, we have received an amazing 110 INCHES OF SNOWFALL in the JUST THE PAST 6 DAYS. March snowfall this month has already surpassed the amount of snowfall we received in the entire MONTH of March back in our World Record year of 98-99 so this has been quite a month so far!"

Well, actually, that last sentence is NOT TRUE: the ski area has received 159" so far in March 2012 (through this morning March 15) according to their website, but it got 194" during March 1999 (following 303" in February 1999). So this March is likely to surpass that one, but has not yet done so.

Thanks Amar.  I came back to post the origin of those photos and the opinion expressed about a hundred year event, but you beat me to it. 

Those don't look like 100 year old trees to me, but knowing the location I can understand why Duncan might want to present it that way.  Regardless, it must've been impressive.

Mark

Of course, the big daddy of all NW avalanches has to be the Grouse Creek slide of February 1990. The trimline was as much as 400 vft above the gully bottom. God knows how many acres were deforested in that one....

I would guess the bridge has been taken out again in this recent snow and storm cycle.

Yesterday's NWAC avalanche forecast (www.nwac.us/archive/sabsea_2012-03-15-1051.html) had this to say:

"A very large slide on Shuksan Arm just east of the Mt Baker Ski Area ran into Rumble Gulley mid-morning and overran the tree line buffer protecting the base of the Shuksan Arm Chair...depositing debris into the lower part of the run. This slide is reported as the largest ever witnessed in the area by the General Manager...who has been there for over 40 years and who is closing the area to prevent any accidents involving "sidecountry" exposure to the developing extreme danger. Due to very poor visibility, no estimates of the fracture depth are yet available."

That is a photo by Grant Gunderson!

Be safe people

Here's a photo that a friend of my shared (I'm not sure who took this) but I think this tells another part of the story.    Edit:  The photo was taken by Grant Gunderson.   

Actually, that photo tells NONE of this story -- it's a cool photo, but it's from LAST YEAR. Here is the source: www.prints.grantgunderson.com/content/201103173803_Edit.html

Very clearly says 2011 03 17 right in the URL.

Please stop spreading the same misinformation that someone erroneously posted on Facebook ( link to FB post , read the comments).

Actually, that photo tells NONE of this story -- it's a cool photo, but it's from LAST YEAR. Here is the source: www.prints.grantgunderson.com/content/201103173803_Edit.html

Very clearly says 2011 03 17 right in the URL.

Please stop spreading the same misinformation that someone erroneously posted on Facebook ( link to FB post , read the comments).

Let this be a lesson in hearsay. I'll decline from sharing a photo unless I was there and have the full context. Apologies and Thanks for the correction Amar.

- Aaron

The skies cleared Saturday to allow a brief view of the March 15, 2012 avalanche:
There is clearly tons of hang fire still up there. No one was heading out but I could see a few tracks in lower safety line.

We took a lap thru the lower trees into rumble gully check and were amazed at the results. It smelled like a lumber yard. The return route is all different. The gully is now overfull with tons of snow/ice flow with horizontal and broken trees poking out. We made the best of the destruction and 50-50'd some of the trees while following the return.