Decent snow up top yesterday though you wouldn’t have known it in the valley. As forecast we have clear blue skies today, temperatures were measured at -7 on top and -6 at the base but already we’re measuring 0.5 degrees at 800m and -5.5 at Happo-ike so probably around -4 at the top of the lifts. Winds have come up a little with 10m/s from the West.
Tomorrow is looking to be much like today. Yahoo are forecasting warm temperatures with rainfall in the valley Friday and Saturday; here’s hoping its cold enough for snow. By Sunday temps are predicted to drop slightly with snow falling.
SNOW STABILITY INFORMATION AS AT WED 28th:
Moderate snow fall on Saturday left 10 – 20 cm of new storm snow across the Hakuba mountains. The winds were moderate and from the west‚ south west creating lee loading on East aspects and cross loading North slopes. Saturday cleared during the night and radiative cooling over the past 4 nights has sucked a lot of moister from the snow pack creating light low density snow at the surface as well as continuing to grow the newly forming facets around the brittle crust created on North aspects at an elevation of 1600 – 2000 m. South aspects have once again been receiving a lot of daily solar radiation and have produced a melt freeze crust that will warm up in today’s warm solar radiation‚ especially around rocks and trees and on steep slopes and under cornices.
Multiple size 1- 2.5‚ loose avalanches were observed on all solar radiated aspects between 1200 m and 2600 m‚ January 23rd in the Hakuba mountains. These loose slides were releasing in steep‚ convex terrain from rock outcrops‚ trees and under cornices. Two ski triggered loose slides size 1.5 on the North aspect in steep (40 degree)‚ sparsely treed terrain.
Tests on North aspect terrain in the Goryu area‚ January 23rd at 2000 m found easy compression tests with sudden collapse fracture characteristics down 15 cm at the new snow / melt freeze interface that was created by yesterday’s warm mist up to 2000 m. This weak layer also produced a moderate result in an Extended Column Test as well as a Reuch Block Test; RB4. The Grauple layer that has been reactive over the last week is showing greater bonding and consolidation. Tests on his layer were producing Hard results and only producing breaks. One RB6 was produced. The new snow on Saturday did in fact put some greater stresses on the snow pack and an avalanche incident on the north aspect off of Happo One BC was reported on Sunday afternoon.
There was an avalanche involvement and full burial of 1 snowboarder in the Mumeisawa basin off the Happo North side. The slide was apparently self triggered from a step east facing open slope with a few sparse trees at 2050 m. The victim was carried an apparent 600 m or so down the tight valley at the base of the Mumeisawa basin to his burial point at approximately 1750 m.
Thanks to some quick action by close bystanders and members of the injured recreationalist’s party the victim who was fully buried was located and dug out of the debris with in less than 15 minutes. Once the victim was uncovered and treated for shock the very lucky and thankful crew waited for Nagano Mountain Police Rescue to arrive by helicopter. On the Police helicopters swift arrival the victim was hoisted and then flown to hospital by helicopter.
Tests on the snow pack and investigation (at a distance) of the accident site found the following:
Crown fracture; 20 – 60 cm deep (observed from a distance)‚ was a width of 100 m and the terminus of the deposit was 600 m below the start zone.
Tests near the incident on eastern aspect at the same altitude in the Happo Ike area found weakness at the new and past snow interface at around 30 cm below the surface. below that that the snow pack was settling and grains are rounding and increasingly strength. Compression tests found moderate sudden collapses at the 30 cm layer and moderate resistant planer down 50 cm from the snow surface.
1 recent avalanche involvement on Happo One North face on Sunday has signaled a warning to all back country users and indicating that some areas may still be unstable in the lee slopes. Beware of cornices and avoid steep convex terrain below rock outcrops‚ areas of sparse trees and below cornices on lee slopes at all elevations. Caution as temperatures increase through the day. South faces will be receiving strong solar radiation today and may be sliding off areas that did not slide on Friday as there will be a very hard sun crust underlying the new storm snow. Be extremely careful in steep unsupported terrain especially around areas that will warm quickly; rocks‚ trees and steep slopes under cornices.
Avalanche Danger will increase with the addition of any new snow and increased wind as well as intense solar radiation.
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
Warming of surface snow causing instability in surface and near surface layers
Solar radiated cornices becoming weak with direct solar radiation.
Use caution if crossing solar radiated slopes.
Increased caution advised around rocky outcroppings‚ cliffs and well spaced trees in start zones.
Due caution on cross loaded slopes
Surface hoar frost created overnight
Poor bonding at or around buried crust
Facet layer around buried crust
Due caution in steep and convex terrain
Danger level 3 : Considerable
Natural avalanches possible. Human triggered avalanches probable.
Danger level ratings are set for conditions at tree line and may vary from below tree line and High Alpine areas. Use this information as a guideline only.