Tenki and Yuki Diary 15 Feb 08

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

Yesterday  we discussed  briefly the cumulative snowfall to date vs.  the average season snowfall.   Most are confident that the remaining 400cm of snow will fall before the season is out and the average will be met.   This chart shows  the daily snowfall every 24 hours at 7am along with the  actual snow depth.  Notice the big Christmas storm.  Also notice that we have not had very many big storms since then, yet every other day the snowfall cumulates with little amounts.  It all adds up.  Its also worth noting that the worst avalanche cycle so far this season happened  during late January when no significant storms were rolling through.  30-50cm of new snow with wind on a weak layer,  such a low density cold snow flakes buried below heavier density  accumulations... its enough to kill.  One thing I have leant from this is that the relatively massive Hakuba style storms should not desensitise us during times when they are absent, such as the last month.

Note: this chart is from my own weather study plot at 860m asl in Hakuba. The usual weather report continues below.

Steep Deep Japan Hakuba  weather data for the 24 hours to 7am for 860m asl Max temp -1C, min temp -6C and  -3C at 7am. 5cm of new snow in the last 24 hours, quite heavy 76kg/m³, equivalent to 8.3% water.  The new snowfall continues to be influenced by gusty strong winds and is of variable thickness depending on wind exposure.   The barometer is steady at 909mbar.  Wind is moderate from the west with strong gusts and snow continues to fall about 1cm per hour.

Field observations:  Yesterday I travelled in the back country to only 1000m asl on a northerly aspect (it was an easy piece of terrain that runs directly into my backyard!)  The new storm snow at that altitude has settled quickly and bonded well with lower layers.  Of note was the extensive faceting deeper than 80cm.  The snowpack at that depth was in places loose and running facets with a lot of compacted facets which broke down into loose grains with added force.  In short, it is crumbling and rotten.  A member of the Japan Avalanche Network (JAN) travelled filed the following data for Hakuba backcountry yesterday.  It correlates with the fair stability that I encountered at a similar altitude.  As always, I encourage people to use the valuable resource provided by JAN.

A repeat from yesterday: This new snow has arrived with winds well over 30kph in the peaks, which is high enough to produce moderate to intense snow transport and the creation of windslab much thicker than the depth of new snowfall.  Conditions are primed for avalanches today, particularly above tree line and into the Alpine.  The last time we had a similar weather combination, this avalanche happened (its worth checking that photo combo)

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