Wednesday, December 31, 2008

Winter Corner - December 31st 2008

This the last day of the year, and I was itching to go touring today. More importantly, I was interested in checking the snow coverage, ski conditions, and take a look at the snowpack structure.

The snotel data for Mores Creek summit suggest that the average SWE and precipitation might be reached during the next 24-48 hours as a storm arrives during the night. Although the ski lines above the 7,000 feet are fine, the ski out can made more fun (read less BRUSHY!) if average snow depth is finally reached. Last time, as I was coming out of Freeman, a snow bridge collapsed under me. I do not know what was funnier; the visual of last third of my ski/skins encrusted in ice and snow or my "cat like" skin-up from the creek banks! More snow will make the snow bridges above Mores Creek more reliable.
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I decided to tour Winter Corner since I was limited in time. But I also wanted to get snow pit data from a NNW exposure at 7,000 feet. Below a picture from the top of Winter Corner looking to the north. This ski line drops 1,000 feet, where the top is an open slope and the lower half wide spaced old growth forest.
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The ski conditions were interesting. Skiing in open slopes and meadows was fast (it almost felt slippery) in top of two crusts, where the bottom wind crust was supportable on my Big Atua skis. If you ventured too close to the trees - snow melt from Monday warm temps formed GESTAPO snow, with an amazing level of instructional content! The top melt freeze crust was delicate, and my boards easily broke through. Above this crust there was an ample supply of graupel. The graupel is spread uniformly across the whole hill. I observed the same graupel yesterday (Tuesday) while skiing at the local resort (Bogus Basin). Check the picture of the graupel included below:
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The next picture is an experiment with mix results, where I used my camera in top of my magnifier. Kind of Cool! Notice the size of the graupel. The squares are 1 x 1 mm. We will have to pay attention to this potential weak layer with the new snow arriving tonite.
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The snow pit is chart is included below:
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This snow pit is almost identical to the snow pit data shared in this blog for Freeman peak last December 28th. The new 20 cm of snow was today's trail breaking and riding surface. Both snow pits were to the ground, thus the snow depth went from 1.2 to 1.4 meters.

Two compression tests failed failed today (CTM11-Q2, CTM12-Q2) at the basal facet layer 10 cm above the ground. Extended Column Tests (ECT) for fracture propagation did not failed, most likely due to the weak layer exceeding the 1 meter depth. I did not conducted the Propagation Saw Test (PST) for fracture propagation, but based on the PST performed at Freeman Peak few days ago, I expected same results - a very energetic fracture propagation. Below a picture of the second column about to be tested.
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During the two CT tests the full columns were displaced approximately 3-4 cm. See the picture below for the displaced column. The tests were conducted on a 28 degrees slope. It is possible that a similar test on a steeper slope would have fully displaced the column, deserving a Q1 rating. However I rated the energy (quality of shear) as Q2.
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Another compression test was conducted but with a column isolated only to a meter in depth. The result was CTH24-Q3 on a storm interface at 90 cm formed during the December 26th storm.

The pause in storms have allowed the snowpack to adjust to the sudden snow loading and warm temperatures have allowed for the the sintering of the snowpack. It is reasonable to expect that it will be more difficult to trigger the weak facet layer buried at 1.3 meters considering its depth, and the bridging effect of the denser snow above. Not many places in Mores Creek are steep enough and at the same time lack the ground cover to be able to trigger deep slab avalanches, but be very picky. I suggest a HIGH dosis of prudence and caution as it is NOW easier travel farther. I expect some of the mini-cirques at the 8,000 feet elevation to be spooky - to say the least.

I will be looking forward to see many of you next year.

Happy NEW year! And may the new year bring many face shots days, and many years of good health to all of you.

Chago

Friday, December 26, 2008

Freeman Peak 12.26.2008

This is the first blog post after Christmas Day. And what a Christmas present we received - lots of NEW snow. Today skiing was nice, but the snow was slightly creamier than last Monday. This is the result of NE winds densifying the snow and new snow in the 10%+ moisture content. During my ski out I found the best and softer snow under the protection of old growth forest trees.
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Some of you are aware, the Avalanche conditions in the Sun Valley area are rated HIGH. My last three visits to the West Central Idaho backcountry show a different picture.The lower elevation of the West Central Mountains compared to the Sun Valley area terrain (Galena Summit, Boulders, Smokey, and Sawtooth Mountains) limited the snow cover early in the season. And at elevations above 7,00o the weak layer is mostly interlocked with the ground cover.
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Today as I skinned up to Freeman via the East ridge, below 7000 feet , it was impossible not to notice the many local collapses and cracks. Below a picture of one of the many cracks from Today.
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Above 7000 feet I did not observed any more local collapses and crack propagation. It is likely that the reason behind the collapse below 7000 feet is the more than 2 feet of snow in top of brush and ground cover. Snow is just sitting in the "air" until collapsed by trail braking.
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Below a picture of today's snowpit at 7200 feet. The pit aspect was NNE, and it was located on Freeman main East ridge, well below the ridge to avoid wind loading effects. The pit location was selected away from trees. Notice that the pit location was not steep, only 25 degrees.
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I was expecting a more complex snowpit. That was not case as you can see in the "Full study" snowpit data included below.
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I would like to remind the reader that the above pictures and chart are magnified by "clicking" on them!
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The compression tests were fair (CT scores of 20 and 22). "Sudden Collapse" failures occurred at the facet layer above an ice crust with shear quality of Q2. This weak layer is buried below 100 cm. The facet layer was relatively thick, about 10 cm. I was surprised that unlike other winter packs, there was no defined "cup" shaped depth hoar. Furthermore, the 2 mm facets on this layer right above the ground is part of a 7 cm thick decomposing ice layer.
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The temperature gradients (showed in the pit chart above) are not sufficient to enhance the formation of depth hoar, or promote the growth of the existing facets.
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Two fracture propagation test were conducted; Extended Compression and Propagation Saw Tests. The ECT was negative - no fracture propagation was observed. The PST failed after undercutting a length of 20 cm the weak layer (below 100 cm). The PST fracture propagation was energetic and the full 1 meter column was displaced by 5 cm after the collapse. It is likely that the "false positive" of the ECT was caused by small brush at the base of the column. In addition ECT cannot effectively transmit stresses below the 1 meter.
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Finally a review of the snowpack structure suggest the following structural weaknesses:
  • Weak layer is a "Persistent Grain Type".
  • Difference of hardness greater than one step from layer above.
  • Difference of hardness greater than one step from layer below.
  • Difference in grain size greater than 1 mm.
  • Weak layer thickness less than 10 cm.
  • Weak layer buried below 1 meter.

It should be noted that the last three structural weaknesses are right on the "borderline". Considering that the PST column displaced downhill on failure, I am not willing to ignore the 10 cm weak layer thickness criteria. And that the standard two CT tests collapsed, again I am not ready to discount the 1 meter depth criteria.

Based on the above the above tests and pit evaluation, the stability quadrants can be summarized:

Mores Creek area has abundant ground cover to lock the snowpack in place for instabilities near the ground, which is the case at this time. There are some areas where that is not true, thus caution should be exercised on steep slopes in the 7500-8000 feet elevation range. During the summer I have observed such areas. Maybe next summer I should catalog those areas for future reference.
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As noted earlier, above 7000 feet in elevation I did not observe any signs of instability. But the 6000-6500 feet elevation at NE exposures, some fractures can be found. The layer released was a soft slab between 20-30 cm, very likely a storm interface. This layer was identified in the snow pit, but during stability tests it was unremarkable.
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The next picture from Freeman Peak ridge (6300 feet) shows another soft slab release (1/3 from the top).

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One last comment; I continue to be concern about how many continue to use the bottom of the creeks to skin-up to Freeman and Pilot Peaks during periods of potential instability. During my 14 years of touring this area, I have seen avalanches release and come down into the creeks from the south aspects above the creeks. And these creek bottoms are DEADLY terrain traps!

Avalanches capable of burying people seem to be rare at Mores Creek Summit area, but they happen! Keep in mind that these south aspects have thinner snowpack, sparser ground cover, experience radiation recrystallization (near surface faceting) as well as Melt-freeze top layers are formed. All of this factors make the south aspects risky during periods of significant snowfall.

Below a topographic map of Pilot Peak , Freeman Peak, and Winter Corner areas. The red lines denote safe ridge access I use during instability and/or periods of snowfall. The ski runs in yellow are steep enough to slide during periods of instability. Keep in mind that these are NOT the only areas of avalanche danger!

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Enjoy the rest of the Holidays!

Monday, December 22, 2008

Pilot Peak - The Glades - 12.22.2008

Skiing at Mores Creek Mountain was fun today; cool weather, fantastic snow and great friends!
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As expected and typical of unconsolidated snow, trail breaking required considerable work. Depending on elevation between 40-50 cm of new snow was sitting on top of a poorly bonded and facetty snow, that kept collapsing under the skis.
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Below 6600 feet the snowpack showed lots of cracking and collapsing. But at higher elevations the snow was surprisingly non-cohesive, even when the water content was in the ~ 8%. The snow was not sufficiently "Champagne" light to guarantee face shots on every turn, but on the steeper runs, if you allowed the skis to run you could get "near" face shots!
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During our drive, as we approach Mores Creek Summit, several south facing road cuts showed signs of instability with recent fracture crowns from the the storm snow. However, no natural releases were observed anywhere in the Pilot Peak South, East, and North exposures at all elevations we skied. As noted earlier cracking and localized whumpfing was experienced elevations below 6600 feet, but no fracturing or local collapses were observed between 6600 and 7400 feet of elevation.
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Stability assessment on the slopes we skied is summarized in the chart included below.
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This is also a good opportunity to encourage the use of Rose diagrams. Included below today's observations captured in a Rose Diagram.
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On this link you can get a pdf version of the Rose diagram for your personal use:
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The conventions used to record snow observations can be found at American Avalanche Association website:
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The snowpack across Idaho mountains have a very WEAK structure. Today we did not find evidence of instability on the slopes we skied, but we were conservative. We did not skied anything steeper than 32 degrees, and for the most part we skied two north-east facing glades with sparse trees.
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As the snowpack continues to be loaded the triggering likelihood in the Idaho West-Central mountains area will augment, as well as the shear energy, in particular for steeper slopes. Furthermore, time will allow for the formation of cohesive slabs due to sintering metamorphosis. Please do not let your guard down!
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Feliz Navidad!

Sunday, December 14, 2008

2008-2009 Backcountry Ski Season

Today was my first ski day of this season. A late start considering that last year I was already skiing late in October.

Fritz, my son, and I toured Big Creek Summit today Sunday.



We found almost a meter of snow at the 7400 NNE aspect. The top 400 feet of skiing consisted of epic face shots. But below the 7000 feet the low density snow did not have a base. We managed to avoid serious damage to the boards, but it was definitely sketchy with the many rocks, deadwood, and stumps barely covered by the recent snow.

The snow pit for Big Creek is included below. Click on the image for a better view of the pit profile.



Stability tests (ECT and CT) and snow pit analysis suggested stable conditions. The weak layer below 60 cm deserves to be monitor. This facet weak layer might become reactive as the snowpack continues to be loaded and the top 60 cm gain strength thus becoming cohesive.

The snotel for Big Creek (6589 feet) reported a snow depth of 21.9 inches. That was consistent with our observations at the same elevation.

Mores Creek summit snotel reported today a snowdepth as high as 37 inches, considerably higher than the low 20 inches reported for Big Creek and Banner summits. Did anybody skied Mores Creek or Banner summit areas this Sunday? Can we get a ski and snow conditions report for Pilot/Freeman Peak or Copper mountain?

Wednesday December 17th I will conducting an Avalanche Awareness Session at the Fish and Game (Walnut Street). The event starts at 7:00 PM. The avalanche awareness topics to be covered are summarized in the following document Avi Awareness v2.pdf and it can be found in th efollowing link

http://santiago.livedrive.com/files

During the season I will continue posting useful documents.

Saturday, May 17, 2008

Peak 8477 - Banner Summit - May 17th

When I woke-up this morning the I saw that the overnight temps at Banner Summit did not drop below the freezing level, but encouraged by the reported 27 deg-F on the Stanley Web cam [http://www.sawtoothcamera.com/] , I got ready and drove to Banner Summit. The drive was wonderful - there were many large herds of deer and elk along the road heading up to higher elevations as the season transitions to summer. I even managed to see an eagle, marmots, and a rare black weasel.
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In the next chart notice the temps for the last few days (click on image for larger version); the low temps have remained above the freezing level now for a few days for the first time in the season. And as the average temperature rises rapidly the snow depth has taken a PLUNGE! The Snow Depth at Banner Summit - 7000 feet - is below the 30 inch level. Considering the cooler weather forecast by the middle of the week and the current rate of melting, it is reasonable to assume at that snow cover access to Copper and surrounding peaks will probably last two more weeks.
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Folks, the last few days' temperatures are making an impact in the snow country. This morning as I drove to Banner summit, I noticed that the Mores Creek Summit area at the 6000 feet elevation is almost depleted of snow, with Winter Corner the only exception.
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However, the situation is better at the Banner Summit area, where there is still snow at 6000 feet before the second avalanche gate. The window to access Bear Claw Cirque on snow for a second time this season is CLOSING, because the snow is melting FAST at the starting point! I give it not more than one week.
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The situation at 7000 feet is more encouraging. Check the next picture of the ID-21 road with Copper Mountain NW aspect in the background. You might recall that Bob R. and I skied the Summit and NW chutes last weekend - check last week posting for beta, pics, and videos.
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Today I visited peak 8477 across the road from Copper Mountain. For the climb I followed the red route. I got lucky and found snow bridges over the two creek crossings. But I suspect they will not last more than a few days. The green and purple routes indicates the ski down.
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The upper (green) and lower (purple) sections are quite different and discontinuous runs. That is the reason for the different coloring. This year I did not ski Cape Horn mountain, but for your reference I included the up track in yellow. The blue tracks show nice ski runs. The ski run on the SW face of Cape Horn is quite sweet, and in stable conditions it provides one of the most continuous and unbroken lines in the Banner summit area.
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As I climbed up a mostly NE ridge without the assistance of ski crampons - there was no need since the snow did not freeze overnight - I knew the chances of corn were slim, but I kept my hope that the direct north exposure and elevation would do the trick. By 11:oo AM I was at the top of Peak 8477, and as expected there was no corn, but 20 cm of soft slushy snow. Oh, well!, at least I got a nice tour and skied while people in Boise roasted in 90 deg-F weather.
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The next picture shows the view from Peak 8477 looking into the north and down to Cape Horn creek. This slope is shown in the topo map as a green track.
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The next two photos look up into Peak 8477 at the bottom of the top run (green track).
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Below a view of the top of the run in purple. I have not skied this area in the winter, but these lower runs look fun. Good selections when stability or weather keep you at lower elevations.
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The day could not be over without some excitement, provided by walking on ski boot on this log across the Cape Horn creek.
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Next a view of Copper Mountain from the snowmobile trail as I ski down to the parking lot.
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The last photo is a view of the Sawtooths from Grandjean on my drive back to Boise on ID-21.
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Sunday, May 11, 2008

Copper Mountain Chutes - May 10th

Spring skiing Saturday May 10th at Banner Summit was delightful! And again, the weather was perfect - clear skies with light cool winds - and a fantastic ski partner to share memorable turns.

It is worthwhile to mention that if you do not want to boot-up or get into scary situations during skinning-up, I strongly recommend that you get ski-crampons. Saturday touring conditions required the use of ski crampons ALL day due to the firm conditions resulting from a solid overnight freeze. And even later on the day, the corn sat in top of a very hard layer of melt freeze snow.

This spring I have been carefully monitoring the weather and temperatures to be able to ski the days with the BEST overnight freeze. That allows for longer spring skiing days, provides better skiing conditions (no slush!), and minimizes snow instability (wet slides). Notice the temperatures for May 8th and May 1oth. The touring and skiing were superb due to the GOOD freeze on the nights preceding those two days. As usual - on this blog you may "click" the images (pics and charts) to get the full file along with details, and higher magnification.



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This Saturday, we accessed Copper from the North-west. This is not a popular approach, but it is a nice change of pace, and on stable conditions (such as spring) it provides access to elegant steep lines, such as the North chutes about 150 feet below Copper's summit to the NNW. This picture is a small sample of these outstanding lines.
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For your reference I include on this post a topo map of Copper Mountain area. This topo map version is different from last week's blog posting. This map version shows more terrain to the north. The red lines indicate the climbing route we used Saturday. In blue is the standard and most popular climbing route used to access Copper Mountain. The green lines corresponds to the slopes we skied this Saturday.

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The day was surprisingly cool for mid-May, and the snow started to corn-up late - well pass 1 PM on east aspects.

Considering the steep lines we intended to ski, during the morning climb we checked the snowpack above the 8000-feet level at the head of the chutes There was a 30 cm melt-freeze layer solidly bridging the north aspects. Below this layer the snowpack above 8000 feet at N, NE, and NW aspects continues to have a winter structure, and it is not experiencing any significant melting. Therefore, above 8000 feet we still have a SNOW wonderland!

Be mindful of conditions that could weaken the thick melt-freeze bridging layer. If this bridging layer is weakened due to rain, or a combination of a warm day and a night without a freeze - it is possible to have snow instabilities on steep north (N, NE, NW) terrain above 8000 feet. Do not overlook that the snowpack below 30 cm continues to have a winter-like structure (NOT isothermal).

The first run of the day was to the north of Copper summit. The chutes had a thin layer of windblown snow on top of a firm base that allowed good skiing. Check the video of my friend skiing below one of Copper's Summit cornices.
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The lower 300 feet of the chutes until the run-out hat a very thin layer of corn that made us greedy for more corn.
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Below a picture of the full track of the chute.
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Next we skinned up and yo-yo'd another short (600-feet) slope to the east of Copper summit. This east-facing slope was a moderately steep fun line where we found plenty of hedonistic corn. I include a picture since this east-facing ski run is not intuitive and it is easily missed.
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The next video is a small sample of the corn harvest - this was the third run of the day. It is the same slope shown in the above picture.


In my May 8th blog posting it I shared beta about 'Bear Paw Cirque' - the next picture snapped from Copper's Summit shows the cirque to the right in the background. Peak 9220 can be seen prominently on the left. Before the spring season is over (and weather permitting) I will be visiting Bear Paw Cirque - there are some cool lines that need further exploration!



We concluded the day with a BANG! Late in the day the Copper North Chute developed perfect corn conditions, and we skied a deliciously sweet 1200-feet line. The center chute in the picture below shows the last run skied Saturday before skiing back to the road.


The next video clip shows the skiing at the bottom of the North Chute.


This spring has been so much fun ... the weather and conditions have been favorable for continued skiing, and if it continues it will be a LONG spring season. Soon the Idaho high elevation couloir season will start ... needless to say - it will be epic - so much skiing so little time.

Chago

Sunday, May 4, 2008

Copper Mountain - Banner Summit - May 3rd

The snowcountry continues to have fantastic conditions. Yesterday I visited Copper Mountain in the Banner Summit area.

For those not familiar with the area I included below a map of the Banner summit area. Banner summit is reached by driving from Lowman to Stanley. This area has MANY other peaks with great skiing besides the popular Copper mountain, such as Bull trout point and Cape Horn mountain among others sub-peaks. The map shows the most popular climbing route to Copper Mountain, and another favorite of mine "Peak 92".


There is enough snow at Copper to sustain skiing the South and West faces for another 2-3 weeks. There were some thin spots near the top of Copper south face due to wind scouring, but there is full snow coverage all the way down to the road via the Newman Creek (South). The north and east faces at the 8-9,000 feet still have a winter snowpack. In fact, they were covered by a 6-8 cm layer of creamy soft snow from last weeks storm front. Below the view of Copper ridge to the NE. Peak 92 is the 4th sub-summit. To the center in the background the Sawtooths are visible.



Be prudent with Copper summit cornices. Yesterday the cornices were softening up considerably and did not inspire confidence. And after watching a small overhang cornice break-up on the eastermost chute I got the message. Too Bad!, the north chute shots were very tempting, and the pair of tracks left on the middle chute by a party of two 1-2 days ago did not help. I will have to wait a little longer.

The next video was filmed on the Copper's south 32 degrees south face. As you will see, the corn was very NICE!



At the end of the day, as we were skiing out, we found a digital Pentax camera. the camera has pictures of Copper for a party of four. And the pictures appear to be taken several weeks ago when there was still snow on the trees. There was also a picture of two dogs in a living room. Below the LAST picture snapped by the camera from the summit of Copper with three skiers.



Please contact me if you are the are or know the owner of the lost camera.

Chago

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

SKIER TRIGGERED AVY at Pilot Peak!

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.
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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:
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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.

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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.

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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.
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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.
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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.
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Now - lets get back to touring and riding ...
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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.
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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.
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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.
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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".
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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.
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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.
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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:


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