Tenki and Yuki Diary 13 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 0C, min temp -10C and  -10C at 7am. 26cm of new snow in the last 24 hours, quite heavy 83kg/m3, equivalent to 9.1% water.   Barometer steady at 905mbar. Wind is moderate from the west and snow continues to fall about 1cm per hour.

Field observations:  Yesterday we found low altitude moist heavy snow as the storm started warm and will become colder with deeper snowfall.  This is the better way for snow to fall, unlike cold snow followed by warm.  This storm is a great example of the classic winter weather pattern in the Japanese Alps and Hakuba.  It is called 'Fuyugata' and comprises a low pressure system in the Pacific to the NE of Japan, combined with high pressure over China.  The result is very cold air drawn southwards out of Siberia, over the relatively warm Sea of Japan where heavy storm clouds form.  When those cold clouds hit the Japanese Alps we get a lot of cold snow.

This new snow has arrived with winds over 30kph in the peaks, which is high enough to produce moderate 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.

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