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

For avalanche courses and backcountry guiding in Hakuba please visit www.mountainlife.jp. For 10 seasons this blog has provided valuable info without a single ad nor any payment. Please support us.

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
20170329 Clear Nil ~ 2cm ~ ~ 146cm
20170327 Clear Nil ~ 1cm ~ ~ 150cm
20170326 Clear Nil ~ 0cm ~ ~ 152cm
20170325 Clear Nil ~ 3cm ~ ~ 157cm

Hakuba Backcountry Weekly Snowpack Summary

THIS IS NOT AN AVALANCHE BULLETIN. I WILL BE WRONG SOMETIMES. I WILL NOT KNOW IMPORTANT THINGS. IT IS INCOMPLETE. IT MAY QUICKLY BECOME OUT OF DATE. I AM NOT AN EXPERT AND FEW PEOPLE ARE.

I'll update this rolling summary of the weather and consequently the snowpack every week - I'm too busy and unpaid to do it more often. I'm attempting to divide the summary into elevation bands. This makes it more difficult, but Hakuba has a backcountry elevation range of about 2500m. That is a lot of terrain vertical scale and the snowpack develops very differently in each elevation band as the season un-winds, and winds-up. This is the kind of avalanche info I would want if I were going to another place to backcountry ski in avalanche terrain.

Use at your own risk. If you die, it is your fault, not mine.

Who am I? I'm damian, owner of Hakuba MountainLife, local backcountry guide. Ten years in Hakuba's backcountry. Member of the Association of Canadian Mountain Guides in the backcountry ski guide stream. Professional Member of the Canadian Avalanche Association. Professional Member of the Japan Avalanche Network. Instructor of over 55 Avalanche Canada AST1 and AST2 courses. [This info is provided so that you can verify if you want to trust me or not. The listed organizations do not endorse anything on this blog.]

FINALLY... please remember the "Avalanche Triangle". On the sides of the triangle are three important elements of avalanche risk management: Terrain, Weather, Snowpack. In the center of the triangle is the the fourth element, the Human Factor (briefly, your personality). This weekly summary is about the snowpack. Only one of four elements, and the least important. Master the others.

Hakuba Backcountry Snowpack Summary as at 2017.01.31

It has been too long since my last update to give a detailed daily summary. I hope this will do for the major events:

+ 25th: the end of a cold 5 day period of storm snow accumulation
+ 27th: very windy, followed by low wind light snowfall
+ 30th: low density convective snowfall, followed by rain to 1900m, followed by a rapid load of new snow from a winter Siberian flow

There were a few skier triggered and natural small avalanches later in the period.

If you would like to comment, please do so on the relevant post on the Hakuba MountainLife Facebook page www.facebook.com/mountainlifejp

The Japan Avalanche Network avalanche bulletin for Hakuba is available here. www.nadare.jp. IMPORTANT!! Please understand very clearly that it is fundamentally different to avalanche bulletins in other countries: it is only a statement of expected conditions as at 7am. It is NOT A FORECAST of expected hazard over the day. YOU need to judge whether increasing temperature, rain, heavy snowfall, intense solar radiation or wind will increase the avalanche hazard as the day progresses. This is not ideal, but there are genuine and challenging Japan-specific reasons for this limitation.

Below Treeline (BTL). 400-1900m band

  • Most recent snowfall was 30cm on the 30th
  • The rain on the 30th has left a thick ice crust under the new snow
  • Below the crust is a warm well settled snowpack of little significance to instability
  • Dangerous glide cracks are opening and some may fail as full depth slabs on low elevation sunny slopes

Treeline (TL). 1800-2100m band

  • Most recent snowfall was 50cm on the 30th
  • The rain on the 30th has left a thick ice crust under the new snow up to about 1900m
  • Below that crust is a layer of lower density snow that fell just before the rain on the 29th evening
  • Below that low density snow is a hard wind-buffed bed surface that was created during the intense 27th wind
  • The deeper snowpack is probably not of great relevance. There will be sun crusts on solar aspects, dense old windslab plus settling storm snow from before the 27th wind.

Alpine (ALP). 2100-3000m band

  • Most recent snowfall was around 100cm on the 30th in the mid-alpine elevation band
  • On the surface is some combination of windslab and storm slab.
  • Under that is more old windslab and possibly a layer of lower density snow from the evening of the 29th, though perhaps it would be hard to find.

The next few days

A cold burst of moderate snowfall from a Siberian flow will start night of the late afternoon of the 1st of February and continue to some degree until the morning of the 3rd.

Read the avalanche bulletin (see link and comments further up page). Also listen to Doug at Tsugaike

Look for signs of instability. That buried layer of low density snow beneath the Jan 30th rain crust may produce avalanches and signs of unstable snow for a few days. Or it may not.

With current cold air and the warm crust from the rain event relatively close to the surface, there may be a rapid breakdown of the low density snow under crust. This process is called faceting and it would create a more persistent weak layer associated with the crust. Dig around and look for loose crystals like white sugar around the crust. They are facets. If you get some on your shovel they will be loose and slip and bounce around like sugar would. Compare that to some other snow taken from beneath the surface - it would look and behave differently on your metal shovel blade. If you find facets, you'll know it when you see them. It is great to look for them, but do not decide to ski a riskier slope just because you didn't find them.

Who knows what will happen with the coming additional load of new snow, but if that buried layer of low density snow is unstable, the extra weight may activate it. Or, if the crust starts to facet, then the extra load may produce avalanches on that layer as well. If you see avalanches, shooting cracks or hear whumping, please share that important info. We are all in this together. Remember that the layer of low density snow, the crust and any faceting, will change as you change elevation. Possibly the most troubled elevation band will be around treeline?

I'll be less aggressive with the coming storm than I was with the last one.

Seasonal Comparisons