Tenki and Yuki Diary 8 Feb 08

Know the weather = know the snow pack = know the stability.

Steep Deep Japan Hakuba  weather data for the 24 hours to 7am for 860m asl Max temp 4C, min temp -7C and  -2C at 7am. 1cm of new snow during the night and still falling at around 1cm per hour.  Barometer remains steady.

Field observations: MY JAN data for the day can be found here, I encourage everyone to use this valuable and progressive resource provided by the Japan Avalanche Network. Yesterday we travelled in the backcountry to 2000m asl. I recorded -10C around midday and the winds were above 30kph (a local resort shut their top lifts at that speed).  Gusts on higher ridges were strong from SW-W-NW and snow transport became intense as the day progressed.  Snow fell at 1-2cm per hour all day.  By the end of the day wind blown snow had accumulated in windlips and on lee slopes by as much as 50cm in the deeper areas.  30cm was typical.  We found an unstable snowpack on NE aspects, in places stability was very poor and considering the terrain character, our only choice was to retrace our steps and return along the safe route that we had travelled during the day.  

In the Goryu area (about 3km along the ridge near Tengu Yama) I found a surprisingly thick layer of facets below the now decaying and unstable 080112 rain crust, which is about 90cm deep in that area.  Above the rain crust is a mix of bonded slab and soft slab sliding on a sun/warm weather crust from 080206, with other weak interfaces in the mix as well.

It is worth noting that the stability seems to have an average rating of poor, with one day improving to fair and the next day - or nearby in a nearby location - it deteriorates to very poor.  Its hard to find good stability and I recommend that you approach the Hakuba snowpack right now with the assumption that poor stability is the norm.

Please also refer to the Hakuba backcountry travel advisory from the guides at Evergreen Outdoors.