Saturday, April 12, 2008

Pilot Peak - April 11 - Soft Pow Skiing

After the great conditions at Pilot yesterday April 10th, it did not feel right not going again to Mores Creek Summit.

It was bluebird day, tranquil weather with some light winds. It was cool through the morning (-1 deg C), reaching +5 deg C by noon, and +8 degrees C ( 46 deg-F) by mid-afternoon.

During trail braking there was a mix of cool dry snow with wet snow - I broke trail from Mores Creek Summit to the "Knob" at Pilot's and for the first time I was taller than my friend Mike L. I forgot to dry my skins the night before, therefore the snow was sticking badly to my skins. Sometimes I was 6-8 inches up - I am not joking! The day was saved THANKS to my chap stick! I used the whole thing on the skins to be able to skin-up the rest of the day.

Considering the instability observed the day before at Pilot, we carefully selected a representative pit location below the NE summit of the Knob. This is an area that get frequent visits and it is not easy to select a location that has not been affected/compacted by skiers/riders.

Compression tests at 7400 feet, NE-45 degrees aspect, 32 degrees steep gave the following results:

  • CTEQ3 -20 cm - WL = facets on top of thin melt freeze crust - same results for two CT tests.
  • CTHQ3-50 cm (SAME as prior day at Pilot - NE 7400 feet) - WL = rounded facets on top of a decomposing crust.

  • ECTPNP - same failures as previous CT tests - failure at 20 cm but no fracture propagation.
Keep in mind that fracture propagation tests are relatively new, and their effectiveness in shallow surface instabilities (20 cm) might be questionable. However, other observations during trail breaking did not provided evidence of fracture surface instability nor fracture propagation propensity.

In summary, in simplistic terms we had two green flags and two red flags;
  1. Little available energy for fracture initiation.

  2. Little propensity for fracture propagation
  3. The slab strength was low (CTE). Even when the layer of concern was shallow (20cm), the variability in density due to sun baking was creating areas of more cohesive snow (slab).

  4. The structure was poor, with 4 lemons; Weak Layer (WL) buried in the top meter, WL = Persistent grain type - facets, change in hardness of more than one step, and a WL thickness of less than 10 cm.

With the above information, it made sense to stay away from steep slopes, considering the the snowpack was getting stressed by the thermal heat input. We skied the Knob mostly northerly aspects. The steepness for that area tops at 32-34 degrees, and it was not wind loaded by the Thursday snow transport event, thus we felt comfortable skiing them.

Below a picture and video clip of Mike L. skiing the goods.

As you might notice from the pic and video, the skiing at N and NE aspect was winter like. We avoided the East aspects expecting some unsupportive crusts. We skied out via a southeasterly ridge with a supportable crust covered by 10 cm of creamy snow. The heat of the day produced enough free water in top of the snow to create areas of "sticky skiing" below the 6500 feet level, but it was still very skiable.

It is very likely that the temperatures of this weekend will produce a very supportive crust on east aspect slopes once we get a solid overnight freeze. And in a matter of days we should be able to ski corn at most of Mores Creek East and South aspects. But it is unlikely, that the weekend heat could nudge the NW, N, and NE slopes into a spring snowpack. What we can expect is that the instability observed Thursday should be history by now!

Thursday, April 10, 2008


For 16 backcountry ski seasons I had a PERFECT score, until today. And it had to be the day I was skiing alone! Today I triggered a slide on a steep slope, and went for a ride, but I was able to ski out of it before getting strained through some trees. I was glad that "training kicked in".

Below a topo map for the runs I skied today at Pilot Peak:

Lines in blue are the uptracks, and in red the skied runs. The skier triggered avy (SS-AS-D1.5-R2-N, 30 cm) occurred at one of the 3 runs clustered together, the leftmost one - which is one of the steepest lines (40 + Degrees) in that area. I am glad that I chose NOT to ski the avalanche path below the cornices, and to the left of where the Avy ran. The line below the cornices was getting loaded due to today's strong winds.
The skiing was FANTASTIC - lots of powder can be found at NW, N, and NE aspects, particularly at the 7000 feet level. The East aspects were a little tricky with pockets of breakable crust. South-East and South aspects were skiing wonderful with 5-10 cm of cream on a very carvable and supportive crust layer. And it is still pretty much winter at Mores Creek Summit, with no signs yet of spring.

The following picture shows the area I skied the 3 runs. The picture was snapped after the first run.

The snowpit data is summarized next:

Early in the day, I skied two moderate lines (less than 34 degrees steep, and uniform without convexities). Before the third run, I spent time on a Snowpit Plus to gather stability data. The snowpack where the SnowPit + and tests were conducted provided data for a Strong snowpack (CTH), little fracture initiation energy available (Q2&Q3), no fracture propagation capability, and moderate structural lemons (Weak Layer metamorphosis was observed - advance rounding of facets - suggesting sintering of the weak layers).

Based on the snowpit data, I proceeded to a much steeper ski line. After ski cutting a couple of significant wind-loaded pillows at the top of the ski line without any reactivity, I dropped in.

While skiing down something caught my attention (not sure - but I think it was the rumbling noise behind me). I looked over my shoulder, and I saw a wall of snow about half a meter high coming to me at a very high rate of speed. As I started to ski to the right in order to move out of the avy's way, the avy NOW all around me started to accelerate me and get my legs from below me. My first thought was "Puneta (cursing in Spanish) - I am by myself" - and instantaneously collected myself to concentrate on the task at hand. FIRST keep the skis below the body at ALL COST and turn to the side of the slide - while at the same time I VERY VERY VERY forcefully pushed the poles into the bed surface to arrest my speed, and allow the turbulent wave and leading edge of the avy to pass me. After the turbulent wave passed - I regained good control of the skis - and skied away from the avy through less turbulent snow flow.

The next two pictures show the slide about halfway up of its track, looking uphill. On the second picture I used the camera zoom.

My concern about this avy was the speed and the strainer trees through which this avy ran. The avy ran not more than 300 feet and the debris field was not very deep, perhaps 30-50 cm. The next two pictures show the debris between the trees.

The MISTAKE I made was to forget last Sunday (April 7th) observations, which I will include again for reference:
Interestingly enough, these areas were always in protected aspects, suggesting a recent surface hoar event. Q2 scores and other observations suggest that the snowpack is gaining strength, not surprising considering the warm temperatures. It is likely that similar stability assessment could apply to Mores Creek Summit and other Central Idaho Mountains since surface hoar or near surface faceting tends to affect a large region.

With the above snowpack assessment, it is important that we do NOT let the guard down. Avys are still possible in steep terrain. Such terrain is very limited in the Bogus Basin sidecountry. But it can be found in some areas of More Creek Summit along with unforgiving terrain traps.

After the slide I climbed back up again - and found facets above a crust below 30 cm of snow. That layer was not present at the snowpit location. Also, I underestimated the effect of today's wind at the ridge top - where the snow became brittle and slabby and able to initiate and propagate fractures.

For the small size of this slide I was surprised how much punch it carried! I had never ridden a slide- until now - but had seen many. It will be prudent to stay vigilant during the next few days, since the forecasted warmer temperatures can further raise the avy risk temporarily (next 48 hours).

And remember - There is no better piece of data for INSTABILITY than an actual AVALANCHE!

Monday, April 7, 2008

Bogus Basin Sidecountry & Early April Snowpack Conditions

Winter is NOT giving up! This was ANOTHER weekend of powder skiing !

A review of Mores Creek "snow water equivalent" (SWE) chart shows that we continue on track for average snow year. The offset between precipitation and SWE lines are due due to the October "rain" (no snow) precipitation.

The SWE chart is valuable in tracking the point at which we hit the maximum snow depth for the season. After the maximum is reached, and SWE start to decrease, then the snowpack enters a transition from winter to isothermal. A transitional snowpack deserves attention to avoid wet slabs and other type of wet snow slides.
The biggest concern early on the transitional phase are wet slabs, since they are unpredictable, can be large, and are as destructive as mid-winter dry-slabs. As the snowpack starts warm-up and generate free water, wet slab avalanches instability results due to the interaction of a weak layer and free water. Wet slab avalanches are more likely when 'persistent weak layers' (PWL) are present in the snowpack.
Keep in mind that this year the Central Idaho snowpack region developed several PWL that could be re-activated. such as the SCARY Thanksgiving rain crust involved in many of this year avy incidents! Also there is evidence of other PWL formed during the March high pressure. And as you will see later on this blog there is new potentially problematic layer at ~30 cm,. Please be prudent and EXTRA watchful, since this PWL can easily become active during the warming of the snowpack in the upcoming days.
Now - lets get back to touring and riding ...
I spent Sunday - April 6th visiting Bogus Basin sidecountry. There were two areas I wanted to visit before the season is over; Bob's Knob and The North Fork of the Clear Creek. Last year meager amounts of snow did not allow to ski this areas in optimum conditions.

Today's skiing was invigorating; creamy snow on east aspects, and surprisingly nice powder at North aspects above 6000 feet. At or below 6000 feet elevations a carvable and supportable base was evident at all aspects. There was a thin crust at E aspects under the new 8 cm of new snow, but I rarely felt it. Ski penetration of 30 cm on the new 8 cm snow and the old low density + 20 cm snow was an effective cushion, that kept edges away from the nasty crusts buried deeper in the pack. The bad news is that the temps were warm, 0 degrees C in the morning to a moderately balmy 6 degrees C in the afternoon. I will be surprised if a new crust did not develop on the new snow. The trick for this week is to head to higher elevations - hint - Banner Summit / Copper Mountain Area!

Last Wednesday two friends skied at Freeman, and one of them (Mark) shared with me that there was a funky slab developing at North and NE exposures. Mark emphasized that it was not the typical snow temperature densification, but that something did not feel right! Such observation also motivated me to get to the backcountry and take a look careful at the snowpack.

The snowpit was located at Bob's knob East Bowl; NE aspect, 35 degrees, 6500 feet elevation. Below the pit profile and data:

The layer of concern is 30 cm deep. The strength for the 30 cm slab was moderate (several CT and ECT produced scores of 12). The shear quality was Q2 with "sudden collapses" but not planar failures, suggesting moderate fracture initiation energy. But it FAILED fracture propagation tests such as the NEW Canadian Extended Saw Test and the Extended Column Compression test.
The Extended Column test (ECT) test was repeated several times due to the fact that the "Extended Column Saw" test was VERY energetic in propagation the fracture and collapsing the one meter long column! A total of three standard ECT tests were performed, but only one failed.
The failures occurred above a thin crust, where a thin layer of facets averaging 2 mm in size were present. There were some 3 mm facets crystals too.
In summary, we have a snowpack with moderate strength, moderate fracture initiation energy, available energy for fracture propagation, and poor structure (weak layer in the top meter, weak layer thinner than 10 com, weak layer consists of persistent grain type - facets, difference of more than 1 mm in grain size, and hardness difference of more than 1 step on the layers of concern). I use a methodology that incorporates snowpack strength, fracture initiation, fracture propagation and snowpack structure as independent risk factors in order to minimize "FALSE STABLES".
After completing the snowpit, while breaking trail on a protected North aspect lightly timber and shady spot, a localized whumf was experienced. Furthermore, while trail-breaking some localized steep rolls exhibited slab instability. Interestingly enough, these areas were always in protected aspects, suggesting a recent surface hoar event. Q2 scores and other observations suggest that the snowpack is gaining strength, not surprising considering the warm temperatures. It is likely that similar stability assessment could apply to Mores Creek Summit and other Central Idaho Mountains since surface hoar or near surface faceting tends to affect a large region.

With the above snowpack assessment, it is important that we do NOT let the guard down. Avys are still possible in steep terrain. Such terrain is very limited in the Bogus Basin Sidecountry. But it can be found in some areas of More Creek Summit along with unforgiving terrain traps.
Before moving on - take a look at the Snow Pit recorded temperatures - SO FAR ... there are no indications that the snowpack above 6000 feet at NW, N, and NE aspects is becoming isothermal. We will have to wait a little bit longer for consolidated and corn skiing on those aspects.
Below a short video clip of Bob's Knob.

The following topo map shows the location of Bob's knob. The green line shows the access most people use to get to Bob's knob. The Blue line is the access used by few others. As usual the red line is where I skied.

The next picture shows the run (tree run in the near horizon) to the right in red in the above topo map. The next picture was taken halfway down from the run in the left in the topo map.

But the BEST skiing today was found at the headwaters of the North Fork of the Clear Creek, to the south-east of Deer point. The snow on this basin is very protected from the winds, particularly the W and NW winds. A topo map for this area in included below.

The purple lines show were some group did some damage (probably Saturday), as you can see in the next picture:

Below a picture of my last run of the day, which is the rightmost red line in the topo map:

My hope is that by sharing on this blog other places besides the well known Mores Mountain, Pilot Peak, and Freeman Peak areas will encourage the backcounrty users to explore least known areas of Bogus sidecountry and Mores Creek Summit.