Tuesday, November 27, 2012

"Facetnating" Near-Surface Facets & Surface Hoar

This week I visited Bogus Basin twice, not to ski, but to get familiarized with a site used by BSU GeoPhysics Graduate Students to research snow hydrology. Calm weather, cold nights, and relatively warm days slightly below 0 Deg-C, have created ideal conditions that favor facetting at the snow surface as well as the deposition of surface hoar.  Enjoy the pictures of surface hoar, facetted crystals, near-surface facets that I found at Bogus Basin today.

Surface Hoar 
Surface Hoar
Classic "cupped crystals", and some NSF in the right side.
Classic Near Surface Facet (NSF)
Classic "Cupped" facetted crystals
Add caption
Large Surface Hoar Crystals
Mix of SH & NSF Crystals 

Most Facet-nating Picture of SH crystals!
It is likely that surface hoar deposition and significant near-surface facetting is also occurring at many locations in central Idaho mountains. We should not be surprised if these crystals become  a weak layer, once they get buried by the next precipitation event (Late Wednesday).

The pictures of these crystals were captured with a digital camera in micro mode and a 20x Carson magnifier between the camera lens and a crystal card.

During the next week or so, I will attempt to capture pictures of rounds next to facets. That will allow readers to fine tune their "visual pattern recognition" skills to efficiently identify facets, mix crystals (rounded facets, or facetted rounds), and sintered round crystals.

This winter I became a team member of BSU GeoPhysics team, and I will be pursuing a PhD in Cryosphere Science (frozen water). Yesterday and today, were two great days to prepare the Bogus Basin snow study plots ready for research activities.

Andrew working in the Snow Study Plot at Bogus Basin.
BSU GeoPhysic Team after a productive day.

Monday, November 26, 2012

Copper Mountain November 25th 2012

Sunday turn-out to be a remarkable day to go backcountry skiing at Banner Summit. My original plan was to explore new terrain in the Cape Horn area, up Lola Creek drainage, but the view of Copper South face was as tempting as a perfect coral reef surf break with offshore winds and 6 feet waves, or as tempting as an Argentinean Asada (BBQ) dinner ... well you get the idea.

Thus, we promptly parked at the Bull Trout pull out, exchanged topo maps to the right one - Copper Mountain topo map. We were thrilled to be in the tails of Chris Johnson and his faithful companion, Andrea. No breaking trail for me in the morning!

Bull Trout Pull-Out, Steven getting ready
Bull Trout Point in the background
The coverage above 7500 feet is pretty adequate at all aspects, but some care is required to avoid buried obstacles. At all aspects, the coverage below 7500 feet is about 20-30 cms, and my party as well as other reported contact with stumps and rocks.

Temps close to zero degrees Celsius yesterday afternoon below 7500 feet of elevation greatly helped in settling the recent snow, and this process should continue early this week. The snowpack settlement at lower elevations will provide for an adequate base layer for the next precipitation event forecasted later this week.

Temps at the 8000 feet stayed cool all day - right in the minus 4 degrees Celsius, and a light breeze from the NW. The top 20 cms of new light density snow remained fluffy all day long.

Andrea good looking skiing
Today I snapped only a handful of pictures, I forgot to erase old pics form the camera, and I ran out of memory. But the next video with my ski partner, Steven M., will provide the reader with a good idea about the snow conditions:

The snowpack at 8400 feet in a SW (260 degrees) is summarized next:

Steep gradients at the top 20 cm of the snowpack resulted in facetting of the new snow, and although the snow came dense, the facetting resulted in outstanding good riding conditions. Not surprisingly, the snow was "right-side-up" due to temps cooling as the storm progressed.

Notice the increase in hardness as depth progressed from 20 to 40 cm.  The old snow layer at 40 cm produced moderate scores for trigger and slip (CTMQ2) and no propagation potential. During one of the multiple compression tests, one failure occurred at the 60 cm depth, with a "sudden collapse", but it should be noted that the sliding plane was very poor, thus I regarded the fracture plane quality as a Q3.

This might sound like indoctrination, but it is important for BC skiers to recognize structural weaknesses in the snowpack. I am sorry to bore most readers, but for the benefit of some I will highlight the FOUR lemons that can be identified in the above snowpit profile:
  • L1: Weak Layer (WL) < 1.0 meter in depth
  • L2: WL < 10 cm in thickness 
  • L3: Slab is present above WL
  • L4: WL = Persistent Grain Type (PGT) = Facets
The fifth lemon was not present; grain size difference between WL grains and slab grains larger than 1.0 mm. A threshold of four or more lemons indicates a concerning snowpack structure.

Some avalanche professionals track the hardness of the sliding plane as a "six" lemon, or snowpack structural weakness. It is worth highlighting that for the weak layer at the 50-60 cm depth, there was not a well defined sliding plane due to facet decomposition of the crust layer at the 60-70 cm depth.

In summary, with the combined results at 40 and 60 cm depths, we assumed moderate likelihoods for avalanche trigger, and slab slip if an avalanche was triggered. Considering the previous moderate likelihoods as well as the structural weaknesses of the snowpack (Four lemons) at the 60 cm depth along with its spatial variability, we only skied slope with angles below 34 degrees.

No other evidence of instability was observed through-out the day; no cracks, local collapse, whumpfing,  nor during testing of steep and small slopes (non-reactive).

Friday, November 23, 2012

Pilot Peak's Snowpack - Start of 2012-2013 Winter

I hope you are getting excited about the start of Idaho's ski season. After yesterday touring and skiing, I am psych-up and eagerly waiting for more snow forecasted for this weekend.

The reader needs to keep in mind that early winter snow conditions are challenging due to the snowpack high spatial variability and notorious advanced facet formation.

Last year I shared thoughts and hints about Trip Planning in the following posting:

MCS Post Dec 5th 20122

Last year posting is a good start, but I am sure you will best appreciate a "show and tell" approach.

So, lets run through some fundamental steps that will prepare us for skiing this weekend.

Weather Forecast for Central Idaho (Copper Mountain - Banner Summit)

The Weather forecast links are included below. The first link offers an interactive map where you can you choose your area of interest. Also include for your convenience, the NOAA links for Mores Creek Summit and Banner Summit.

NOAA - Boise Office

Wx Forecast for MCS

Wx Forecast for Copper Mountain - Banner Summit

First, the abbreviated graphical forecast for Copper Mountain at Banner Summit predicts a 80-90% probability of snow with cold temps. Sounds like POW!
Wx Forecast at noon for friday November 23rd, Copper Mountain, elevation 7500 feet.
Hmm, we need to take a look at a more detail graphical forecast:

Wx Forecast Graphical Output with SI units for Copper Mountain-Banner Summit
The forecast details that the precipitation event starts early Saturday and tapper down a little more than 24 hours latter. The 24 hour total precipitation forecasted at 7500 feet is less than 20 cm of snow. Winds light and out from the SW, however they are close to the 10 mph threshold of Moderate winds, where snow transport becomes concerning. The precipitation temps are mild during during Saturday (-1 to +1 Deg-C), but cool down as the precipitation continues overnight. The winds shift from the NW as the front passes the area by Sunday at 11 AM.

Other valuable information is available at the NOAA Wx site, such as IR maps, Radar of precipitation, and the forecast discussion. You should get familiar with those products as well, but I will not cover them for the sake of keeping this posting brief.

Some of us spend time with models to narrow down what locations will get the most snow.  The next links are my favorites places to go to get fancy:


Mountainweather.com Precipitation Models

But for most the following link is good enough:

NOAA Probabilistic Winter Precipitation Guidance

For this weekend precipitation event, the probability of more than 4 inches of snow is represented by the next contour map:

Central Idaho, and what it looks like Banner Summit, seem to have a 70-80% of getting more than 4 inches in 24 hourd period. In other words, Banner Summit seems to be the region where MOST of the snow is expected to precipitate!

Next we want to KNOW, what the regional forecast centers are predicting for Avalanche Danger.

Payette Avalanche Center

Sawtooth National Avalanche Center

It is somewhat early for the Avalanche Forecast offices to publish the danger rating. Please continue to check the avalanche centers trough-out the weekend! I will comment later in the posting, how you should treat the current conditions.

Based on the weather and avalanche forecast make a plan of where you can SAFELY travel and ski, NOT where you want to go. The best approach is to use Topo Maps to plan your snow travel.

The following link is an excellent site with various versions of topo maps:


This web tool also provides the means to map average "MACRO" slope steepness, where the slope angle can be selected.

Copper Mountain Google Topo map with Slope angles > 32 degrees
Copper Mountain USGS Topo map with Slope angles > 32 degrees
The hillmap application provides topo maps layering, but it laso has a second slope angle tool available, where green corresponds for angles between 20-27, yellow for angles between 28-34°, red for angles between 35-45°, and blue for angles above > 46°

Copper Mountain USGS Topo map
slope overlay, green = 20-27°, yellow = 28-34°, red = 35-45° and blue > 46°
There is another fabulous website with even more elaborate topo maps features such as the superposition of 40 feet contours, slope angle, as well as UTM coordinates.

CalTopo for Copper Mountain-Banner Summit

Topo maps such as the next image are easily generated and printed with CalTopo:
The topo maps links and functionality listed above will allow indivduals to plan what slopes to avoid during the present conditions, and where to set the up-track and the ski down paths. Please use this web tools, or buy mapping programs for your PC, GPS, and/or powerful phones.
CalTopo  with 40 feet intervals, slope angles, and UTM coordinates: Copper Mountain-Banner Summit

So we are are back to present snowpack conditions at SW Idaho, and the best data I have available for making inferences is from Pilot Peak snowpit last Thanksgiving Day. The "Thanksgiving" snowpit was located to the West of Pilot Peak at an elevation of 7930 feet, in a northerly aspect with a 20 Deg East aspect, and at a slope angle of 20 degrees. The snowpit site was not wind loaded and well protected from the elements (sun effect and/or wind erosion). In fact the site was selected to maximize the chance of checking the stability of the recent snow in top of the October old snow. The October snow consolidated into 10 cm of "knife" hard melt-freeze layer, and no basal facets (depth hoar) were detected between the ground and the melt-freeze layer.

Above the old "knife" melt freeze layer there is a 5 cm thick layer of 2 mm facet grains, overlaid with a  30 cm slab with hardness ranging from "four finger" above to the weak layer to Fist hard at the surface. This weak layer is reactive to Extended Column Tests (ECT) and compression tests (CT), with ECTP7Q1(SC) and CT11Q1(SC) scores. The SC stands for sudden collapse, which is characterized as a Q1 score.

The video with ECT test included in yesterday's posting is posted again to avoid first time readers of this latest post to have to go to a previous posting. Again, notice the sudden collapse of the entire extended column.
Two Compression Test (CT) produced CT11Q1(SC) at the 35 cm weak layer. The next picture shows the 30 x 30 cm column prior to the CT test. Notice how the sides of the compression column are cleared to eliminate interference at the sides of the column. This is an important detail to reliably evaluate slip likelihood (Q1 scores) after the triggering and propagation of a fracture failure.

The PST Results were PST10/100 (SF). Check the slab fracturing prematurely in the video included below. PST results can be unreliable for thin slabs, due to the Slab Fracture phenomena. Performance of PST testing improves for thicker slabs.
The ECT test results at a snowpit location where basal ice layer is thinner and less uniform it does not shows propensity to fracture  propagation. This was anticipated, although it is nice to verify it . The results for this test are scored as ECTN12.
The snowpit profile is summarized next:
A second weak layer was identified 20 cms from the snow surface. It is an extremely thin layer of large and long faceted crystals (maybe a variant of planar surface hoar crystals). This failure was clearly observed when doing the shovel tilt test and it failed with easy scores (5 deg tilt). The slab above this weak layer (SH?) slides off, and can bee seen in the third video included above.

So how do we use all the information gathered in the study snowpit at Pilot Peak?

We discussed in the previous posting the importance of perceiving the environment in order to avoid 76% of human errors. Situational Awareness when traveling in avalanche terrain is facilitated by the use of the stability quadrants. The stability quadrant methodology suggested a high likelihood of triggering and propagating a fracture failure, as well as a likely slab slip in terrain steeper than 35 degrees. The stability quadrant also quantifies the structural weaknesses responsible for slab avalanches, and characterized as a poor and concerning snowpack structure. But perception is not sufficient to further reduce human errors, and an additional 20% of errors can be further reduce by better comprehension or understanding of the environment.

Comprehension of the environment based in the snowpit at Pilot Peak on Thanksgiving Day is summarized next:
  1. Spatial variability (thickness and presence) of the basal ice layer at Norterly aspects adds significant uncertainty to the snowpack stability at the 35 cm facet weak layer. This will be exacerbated at elevations at 8000 feet or more. Similar poor stability and poor snowpack structure conditions should be assumed across SW Idaho.
  2. Temperature gradients above 1 deg per 10 cm, will continue to affect the snowpack on its entirety reversing the sintering of the slab layers form by this week NEW snow.
  3. The melt freeze layer at the 5 cm layer will decompose due to faceting metamorphism driven by the much steeper gradients at the surface of the snow.
  4. We should expect the formation of depth hoar at all elevations and aspects above 7500 feet covered by this week snow.
  5. The top 5 cm of near surface facets (NSF) will become a weak faceted layer once they get covered by new snow during Saturday's storm.
  6. East, South, and West aspects below 7500 elevation have very limited snow coverage, making snow riding dangerous due to buried obstacles.
  7. The facets (possibly a thin layer of surface hoar - SH) buried 20 cm deep might become active after the next snow loading event, possibly this Saturday.
  8. The loading of the snowpack during the next loading event (Saturday storm) will result in some localized whumpfing, as evidenced by the "sudden collapses" observed in the stability testing this past Thanksgiving Day.
  9. After the snow forecasted for Saturday settles, probably by early next week, test results for trigger likelihood will become moderate. The thicker slab will make trigger likelihood less likely, but the consequences will be much higher due a thicker slab, maybe 50 cm, and the barely covered buried ground cover such as rocks, stumps, fallen logs, among other terrain features.

2013 Thanksgiving Skiing!

Pilot Peak - West Glades

Pretty cool picture ... this was yesterday, mid-morning of 2013 on Thanksgiving Day. Ten centimeters of recrystallized snow in top of a dense and supportive layer that made skiing very pleasurable.

The NRCS Snotel telemetry at Trinity Mountain appeared encouraging with close to half meter of snow, and although the Mores Creek Summit Snotel looked discouraging, I felt confident the skiing at MCS will be fun above 7000 feet at protected northerly aspects. In addition the significant drop in temperature after November 21st held the promise of facetting the surface of the snow to create good riding conditions.

Snow Depth = Blue Line
Top Red Line = Temps
The link included below will get you to a map of Idaho with SNOTEL sites. Move the cursor over the sites and the name of the location is interactively shown. The most popular locations used by backcountry riders are: Mores Creek Summit, Trinity Mountain, Banner Summit, Big Creek Summit, Bogus Basin, Brundage Reservoir, Vienna mine, and Galena two sites.

The situation looked grim at the Mores Creek Summit Pass (6100 feet), where the dirt road to Pilot Peak starts. But as elevation was gained, particularly above 7400 feet, it started to look wintery.

I21 and Pilot Peak Road
Pilot Peak road at 7000 feet
Pilot Peak at 7500 feet
Pilot Peak Summit from the West
Skiing was fun, and the ski touring was superb on a strikingly calm and cool day. The Central Idaho Mountains views from Pilot Peak Summit and West Glades were magnificent. It could have been perfect if two fools in a vehicle would have not attempted to go up Pilot Peak road and torn-up the snow where otherwise could have been great skiing back to the 6800 feet level, before having to get off the skis, and hike down to Idaho 21.

This is a good time to highlight WHY backcountry recreationists will benefit from checking the snowpack. Below a picture of the current snowpack at Pilot Peak west glades.

Snowpit at 7930 feet, North 20 degree aspect, West of Pilot Peak.
On its most basic expression, we go through the effort of excavating a snowpit to identify a slab or layer of denser and cohesive snow in top of a weak layer characterized by cohesionless snow. Most skier triggered avalanches are slab avalanches. The next image summarizes the statistics in the US for skier triggered avalanches (HS-hard slabs, SS-soft slabs, WS-wet slabs, WL-Wet loose, DL-dry loose).

There are many different approaches and philosophies about how to best make an stability assessment. One of the techniques is based in the Stability Quadrants to reduce the most significant data from our complex environment. The stability quadrant is based on the events leading to a slab avalanche;
  1. Triggering of a fracture failure
  2. Self-propagation of the fracture
  3. And if the terrain is sufficiently steep and has a low coefficient of friction it will result in the downhill slide of the slab
The stability quadrant provides a structured methodology to assess each of the elements of the slab avalanche: trigger likelihood, propagation likelihood, and slip likelihood. The next slide illustrates how the avalanche triangle (Snowpack, Terrain, Weather) are assessed through the Stability Quadrant lenses and applied to the terrain.

Data reduction is critically important because it is intrinsically linked to the perception of elements in the environment. Most human errors are caused by inadequate or poor perception of the environment. The stability quadrant methodology compels the user to adequately perceive its environment - The Snowpack, The Terrain, and The Weather!

Casual observation of Pilot's Peak snowpack at 7930 feet in a North aspect revealed a slab structure, where the top 30 cm of cohesive snow is undermined by a 5cm layer of cohesionless snow sitting in top of a 10 cm layer of hard ice. Not Good!

Slab that starts as very soft (Fist hard) and gradually become consolidated (4-Finger hard)
Very loose snow in the glove, sugar like, below a slab of cohesive snow.
So what do we do next? Well ... the FUN is about to start!

For snowpit and stability tests you need the following gear:

Probe with meter marking, metal shovel with extendable handle, snow saw, and pole able to connect to saw.
Avalanche professionals, snow scientists, and snow geeks (like me!) strongly recommend the Extended Column Test, most commonly known as ECT. This stability test allows to assess the trigger, propagation, and slip likelihood. Included below, a short video of an ECT conducted at Pilot during Thanksgiving Day. Pay attention to the propagation and sudden collapse (SC-Q1) of the whole column during the wrist taps (Easy Trigger),

Using the snow stability framework and the ECT we have learnt the following about the snowpack at Pilot Peak's northerly aspect with an elevation of 7930 at a non-wind loaded site with 20 degrees of steepness:
  • The trigger likelihood of triggering a SLAB avalanche is HIGH.
  • The propagation likelihood of the slab across the slope is HIGH.
  • The slip likelihood is considered HIGH when either the block experiences a "sudden collapse (or SC)" or easily slides out during the test. This type of slip mode is denominated Q1. The ECT of this video experiences a SC, thus the slip likelihood is HIGH.
For more details about ECT, please check the next link for a most awesome and fantastic video. The video demonstrates how to build an ECT isolated column of 30 by 90 cm, and how to perform the test. Please stick to it, at the five minute mark you will be able to clearly see the propagation failure.

At the center (or heart) of the stability quadrant the SLAB structural weaknesses are responsible for its triggering, propagation, and slip potentials. The snowpack structural weaknesses are thoroughly evaluated depending on your level of training and experience. For the Snowgeek I include below the anti-crack fracture equation with the various elements responsible for structures that drive fracture initiation and self-propagating fractures in the snow.

Ian McCammon developed a methodology of evaluating structural weaknesses known as snowpack "lemons". This methodology allows to determine if there is a CONCERNING snowpack with a POOR structure if the addition of lemons totals 4 or more.  This methodology is quick and fits pretty well for most recreationists needs. Below a link with technical paper.

After the stability test (ECT) is completed, the offending or concerning weak layer is identified. Using the "Lemons" identified by Ian McCamon, we can proceed to evaluate structural weaknesses of the snowpack at Pilot's Peak West Glades:
  1. The Weak Layer is in the top meter - YES, the weak layer was buried at 30-35 cm
  2. The Weak Layer is less than 10 cm thick - YES, the Weak Layer was 5 cm thick.
  3. The Weak Layer hardness difference with the Slab is one step or more - YES, a slab is present.
  4. The Weak Layes consist of persistent grain types (PGT) - YES, there are loose and sugarly FACET crystals.
  5. The Weak Layer and slab grain size differs by more than 1 mm - YES the facets are 2 mm, way bigger than the less than 0,5 mm round grains of the slab.
There are a total of 5 Lemons identified, more than 4 lemons, indicating the the snowpack structure is POOR and very concerning.

To summarize:
A quick snowpit reveals the presence of a slab.
An ECT is used to identify Trigger, Propagation, and Slip likelihoods. 
The ECT identifies the most concerning weak layer. 
The "tester" proceeds to characterize weak layer structure; 
  1. depth of weak layer.
  2. thickness of weak layer.
  3. presence of slab above weak layer.
  4. presence of persistent grains (facets, near surface facets, surface hoar, depth hoar, faceted rounds) in the weak layer.
  5. and compare grain sizes of weak layer to slab grains. 
With practice this process can be completed in no more than 20 minutes.
After playing in the snowpit, it was time to go skiing. Later in the day I ran into an acquaintance, Ken, after I skied a nice slope with moderate angles (mid twenties), since I did not think it was a good idea to ski slopes with angles above 30 degrees, particularly when I was solo touring.

A very good looking slope!
I do like this turns, they are Ken's
Ken, removing skins.
The snow coverage above 7500 feet was not bad at all!  Open glades were looking quite tempting. Don't you agree?

After several laps at Pilot Peak West Glades, it was time to ski out. At the 6800 feet we got off the skis, and hiked down the road.

Ken with skis on his backpack
Transition from skis to booting.
Chago messing around!
Tonight I will make another posting at MCS Blog for those interested in additional snowpack observations, spatial variability, as well as other other stability test results observed at Pilot Peak during Thanksgiving Day. I did not wanted to go to BIG in the first posting of snow conditions for the 2013-2014 Season.

I hope you enjoyed your Thanksgiving Day! Cheers!