Some go0d snow was out there to be found by those willing to look. The snow overnight on Saturday wasn’t a lot but it was enough to leave some powder behind. I was up on Iwatake Sunday and winds were raging everywhere but where we were it seemed…not a soul on the upper half/two-thirds of Happo until afternoon might have meant some unhappy travellers. Yesterday there were still some remains to be had but the winds really hammered the BC (see snow stability information below).
-3 in top of Goryu this morning…yesterday seemed cold but no real frosting overnight on the cars. Overcast with a white sky but rays of sunshine peeking through every now and again. Temps are warm enough now for what snow is left on the roofs to be sliding. Yahoo is calling for some precipitation this afternoon but nothing at this moment in time. Tomorrow looks set to be bluebird with some light snow possibly tomorrow night.
SNOW STABILITY INFORMATION AS AT MONDAY 9th:
Extreme North West winds on Sunday have transported much of the 15-30 cm of new snow that fell across the Hakuba mountains far down the lee ward slopes. The clouds of blowing snow looked like storm clouds coming over the mountains or intense amounts of smoke from forest fires. These intense winds have no doubt scoured wind ward slopes near ridge top and ridge top areas depositing the blown snow a long way down the South and East facing aspects. This new wind deposited snow is over riding the February 7th sun crust and may not yet be bonding well to that sun crust. Lower elevations that were not hit as hard by the winds have 15- 30 cm of new snow resting on past wind effected layers or feb 7th buried sun crust. Solar aspects at lower elevation received intense radiation on Sunday and will no doubt have a melt freeze crust on the surface today.
Compression tests on Happo One at 2200 metres found Moderate to Hard results on 30 degree plus South and East aspects down 30-40 cm at the interface between the February 1st sun crust or wind deposited storm snow and the February 5th storm snow. 2 Reuch Block test also found results on this same layer on a RB5. Both Reuch block tests resulted in quick moving slab fractures. A slightly strong temperature gradient was also observed at around the 30 cm – 40 cm layers and faceting crystals were also found at this week interface.
Compression tests in the Hakuba Norikura area at 1500 m North East found moderate / progressive compressions or breaks down 15-20 cm fracture. Ascending in the same area on South East aspect saw shooting cracks from skis and snowshoes.
Cornices were newly developed and breaking easily during slope testing.
The snow pack in general is very variable in snow depth due to recent strong – extreme winds and intense solar radiation.
2 accidental rider triggered slab avalanches were observed on East aspect steep leeward terrain on Saturday up Happo One.
Be extremely cautious of solar radiated wind deposited lee slopes in steep and convex terrain around rocks and trees. Take due care on windward scoured slopes as it is easy to slip and slide a long way on the exposed ice. Be cautious of semi buried past avalanche debris that is rock hard and may be difficult to navigate.
Avalanche Hazard Rating:
Below Tree Line: Moderate trending to Considerable with intense solar radiation on all solar aspects.
Tree Line: Considerable
Alpine: Considerable trending to poor with intense solar radiation or continued wind loading.
Increased snowfall adding load to buried week layer
Steadily increasing air temperature
Radiative cooling of snow surface causing low density snow and frost at surface
rapid settlement of surface snow causing load on buried weak layers
Extreme radiation and warming of southern exposures
Solar radiated cornices becoming weak with direct solar radiation.
Increased instability of solar aspect start zones especially under cornices and very steep slopes.
Increased caution advised around rocky outcroppings‚ cliffs and well spaced trees in start zones.
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
Surface hoar frost created overnight
Facet layer around buried crust
Wide propagation due to wind slab
Due caution in steep and convex terrain