With a day-off yesterday I was well ready to ride all morning but woke up to the sound of bears on the roof. Not bears exactly but light rain and warm temperatures that had the snow falling off in big noisy heavy clumps. Not what I needed on my day off but the heavy snow should do well for clumping down the bushes and smaller trees that have been burdening the tree runs around. Temperatures dropped later in the day and the precipitation turned back to snow in the valley.
Goryu are reporting 10cms of new snow this morning and the base has noticeably increased over the last week to a depth of 245 cms at the top. Hakuba is covered in high cloud this morning, -6 up top and around -4 in the valley.
SNOW STABILITY INFORMATION AS AT MON JAN 19th:
We had rains at the low level earlier‚ but we have been getting heavy snow at the higher places. Fractuation in temperture causes instability in snow packs. There is possibility to cause natural avalaches due to developing and collapsing cornices caused by strong wind around the ridges. Please be cautious of temperture change and rain in alpine zone.
The sun crust of January 4th is still proving to be a weak layer now under 20 – 90cm of wind affected new snow. Facets were found above and below the crust Sunday in 3 pit locations all dug on solar aspects in the Tsugaike shizen during the Evergreen Outdoor Center Avalanche Safety Training course. Compression tests found easy results in the top wind affected new snow and moderate results just above the crust with the new lighter snow not bonding to what might be buried surface hoar or developing facets. There is still the Dec 23rd rain crust is also still a concern as we receive more snow and today’s strong solar radiation puts extra stress on those lower layers.
Avalanche Observation:
The large size 3 avalanche on the south face of Happo traveled from the crown fracture beside Happo’s Grat Quad lift at 1600 meters right down to the first of the large concreate dams just short of Gentaro dam at 900 meters. The total length of the slide was over 1 kilometer and the deepest area along the Crown was 130cm and only about 20 cms at the flanks or side of the avalanche. Definitely the facets‚ around the rocks as well as the above and below the Jan 4th sun crust‚ are the root of the reason for this large slide. New snow and moderate North westerlies will continue to put increased weight on the dense slab over riding the January 4th sun crust.
Fracture Profile Tests at the site of the slide were finding hard compressions at the crust in an area of deepest crown but had we more time to spend investigating we would have also dug at an area of approximately 20~40 cms and might have observed Easy ~ Moderate compressions as week layers around rocks and at more scoured areas.
Be extremely careful of entering into lee slopes from scoured ridges or convex terrain and around warming rock bands.
Areas of deep snow pack will have greater stability than the thin and areas where overnight radiation of heat has created near surface faceting and faceting crystals around the areas of shallow crust. Big alpine bowls may be slow to stabilize and may propagate very wide due to the very tensile nature the present wind effected alpine snow pack.
Continued caution around cornices should be practiced and these areas avoided all together. CORNICES ARE VERY FRAGILE in today’s solar radiation!
Heavy snowfall
Rapid increase of wieght on snow pack
Increased snowfall adding load to buried week layer
Cornice fall
Rapid air temperature decrease
Cornice fall
Falling tree bombs (Possible triggers and cause of avalanches as well as overhead hazards)
Development of cornices in lee slopes
Lee side loading
Windward scouring of ridges and rock out-crops creating uneven loading of slopes
Due caution on cross loaded slopes
Wide propagation due to wind slab
Stay away from steep and convex terrain
TEMPERATURE IN THE VALLEY: -6
TEMPERATURE AT 1800m: -4
BASE DEPTH (GORYU):
245 cm at 1800m
95 cm at the base