This personal blog contains snow, avalanche and weather data along with weekly commentary that may be useful in planning your Hakuba backcountry outings.

More important than anything else

1. Hakuba Avalanche Bulletin by the Japan Avalanche Network.
2. Understand the Avalanche Danger Scale.
3. Know what the avalanche problem is and how to avoid it.
4. Carry beacon, shovel and probe in the backcountry. Know how to use them.

Other useful info

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Recent weather data recorded at 6am each day for the preceding 24 hours. Altitude 800m.

Date Cloud Cover Precip type and rate Rain Altitude 6am temp Max temp Min temp 24hr New Snow 24hr New Water Equiv 24hr New Density Storm Total Snow Depth Baro Pressure
20180121 Few Nil ~ -5C 5C -6C 0cm ~ ~ 0cm 105cm
20180120 Few Nil ~ -5C 2C -6C 0cm ~ ~ 0cm 108cm
20180119 Overcast S < 1cm/hr ~ -1C 6C -1C 1cm ~ ~ 1cm 111cm
20180118 Overcast Nil 1600 1C 4C 1C 0cm ~ ~ 0cm 115cm

180120 Hakuba Backcountry Snowpack Summary

Recent small-small/medium windslab avalanches that have stabilized. New ones may form with new wind snow transport. That stuff just comes and goes. Snowpack below treeline is reaching below-average depth due to two heavy rain events. Around 800m the snowpack is only 110cm deep! The snowpack above about 1700m is at average or notably above average depth in some areas. There has been decent soft snow fun skiing in the right places since the last rain (evidence https://www.facebook.com/mountainlifejp/videos/1718253661572223/)

There are two rain crust in our snowpack. One was buried on Jan 9th and reaches about 2200m elevation which is about 150-200cm deep, depending on where. The other is still on or very near the surface, from the rain on January 17th and reached about 1900m elevation +/-

The 9th rain crust (and potentially a deeper crust) produced some large avalanches on steep terrain around 2000m when the rain from the 17th stressed the snowpack. I'd say that after that event, we can start to forget the 9th crust from an avalanche stability perspective and focus on the newer surface crust. This crust will be important as it is about to be buried by a large windy cold storm.

This newer crust from the 17th rain extends to about 2000m, where it is thin and friable and breaking down with clear nights. Below 1900m it is mostly a nasty skiing surface breakable crust, and becomes quite thick below 1700m. After a small snowfall 18th evening, and wind redistribution, the crust has remained on or very near the surface on the 18th, 19th, 20th and will remain on or near the surface until the next storm arrives on the 22nd. That's about 5 days, including some moderately cold clear nights. Generally, but not always, rain crusts that remain cold and on the surface for numerous days then get quickly buried are less stable during the rapid storm accumulation than crusts which were formed by rain and then get quickly buried as rain turns to snow within a 6 hour period.

The last crust from the 9th proved not to be much of a problem. False sense of security as a result? Overconfidence? Uncertainty is the name of the game. Being right is not. How big is your cloud of uncertainty, and how bad will it be if you lose the bet? Personally, I'll continue with my rule of "don't trust the crust." I'm a cautious and prudent person who doesn't like thick and hard widespread sliding surfaces (ice) that may have developed a weak layer on top (facets) after 5 days of being exposed to the the surface air. I don't know any magic trick to always be right. I just don't know. So my attention turns to what I do know for reliable unchanging fact: we have large steep low-elevation serious avalanche terrain where the crust is thick and widespread on the surface: Happo, Goryu, Kita Hiyo, Daihoraku etc etc.

SUMMARY OF THIS CRUST SITUATION, according to the simple and elegant 'Avalanche Risk Management Triangle':

SNOWPACK and WEATHER: surface rain crust of significant thickness which will have been exposed to the air for 5 days is going to get rapidly buried by a windy cold storm coming soon. We are uncertain how it will react. But it is not an ideal snowpack recipe for avalanche danger. Don't just focus on the crust instability - also remember Storm Slab and Wind Slab avalanche during the coming storm. They may have nothing to do with the crust at all.

TERRAIN: The crust exists in significant thickness on every aspect below 1900m +/- 100m. This includes notable steep large unsupported and convoluted slopes with terrain traps, which will all receive a lot of storm snow and wind loading.

HUMAN FACTOR: we are powder hungry after a poor few days. We are competing for easy-access snow with all sorts of crowds and groups in town. AND... this is the first snowpack situation like this for the season, in fact it is not very common in any season (crust are common, 5 day delays for burial are not). Watch out for terrain familiarity fooling you into snowpack unfamiliarity.

BACKCOUNTRY AVALANCHE RISK MANAGEMENT CONCLUSION: Combine snowpack, weather, terrain and Human Factors. Then assess and measure your uncertainty versus past experiences and honest personal risk tolerance. Plan backcountry trips thoughtfully in advance with small groups of people you trust and can openly communicate. Pull back where appropriate. There is a lot of terrain that can be skied with improved safety margins if required. None of it is trophy terrain, but the mountains don't owe any of us a trophy.

^ that summary section is what I attempt to teach in AST1, and more so AST2, avalanche courses. It is how I guide professionally. And it is how I ski the backcountry on my own time.

DEEPER PROBLEMS?

I have wondered about a deeper weakness in the higher alpine snow pack over the last month. Thank you to the person who shared some snow pack info last week from higher elevation. It didn't reveal anything deep and weak, but that is only one data point out of a mountain range. Our colder than normal November 2nd half and all December will have produced facets deeper in the snow pack. These will be associated with a high elevation very thick deep crust that formed in early November. And that will all change significantly with elevation between say 2000m and 2800m. That's about all I can speculate. The higher elevation snowpack has been stressed numerous significant times and produced large avalanches earlier in the season as a result. Probably that's all there is to come from any deeper problems? Until spring? I have no idea but it would not get too worried about it. This isn't Colorado.

-damian, MountainLife Backcountry Guiding, www.mountainlifebackcountry.com

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