Tenki and Yuki Diary 3 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 3C, min temp -9.5C.  -3C at 7am. A somewhat unexpected plummet in the barometer to 908mbar and 15cm if extremely light snow arrived during the night.  The new snow is the lightest of the season with a density of 30kg/m³  which equates to an amazingly blower 3.2% water. Wind is calm in the valley, and light in the peaks.

Field observations: Yesterday we travelled in the backcountry to 1550m asl.  The midday the temperature was -4.6, calm wind, no snowfall and thin overcast conditions - brighter in the morning.  my JAN weather and snow stability report can be found here.  I encourage people to use the valuable resource provided by JAN.

On the NE aspect in the Otari area we didn't observe an instability, although there is a significantly less dense layer of preserved dry stellars (8cm thick) buried under 30cm of relatively dense soft snow.  The weak stellar layer is on top of a dense old snow layer.  Continued loading of new and blown snow will test the shear strength of this buried weak layer.  Under the right terrain and weather conditions and given a trigger, this weak layer of stellars could easily produce a dangerous soft slab avalanche.

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