Avalanche Bulletin
更新日時: 2025/02/04 07:00
Niseko Yotei Yoichi Shiribeshi
Alpine Fair Changes in wind direction through the day will require ongoing assessment of new wind loading
Treeline Good Changes in wind direction through the day will require ongoing assessment of new wind loading
Below Treeline Good Strong winds will affect the snow at lower elevations today.
信頼度：○ good □ Fair △ Low
Travel and Terrain Advice
Watch for new wind loading as the wind increases and changes direction from SE to SW today. Dig down to check the reactivity of the Persistent Slab layer, especially in the Northern part of the region (Kiroro, Kokusai).
Avalanche Problem
ウインドスラブ Wind slab
There is a lot of soft snow that is available for wind transport. Expect new Windslabs to form throughout the day, and watch for reverse loading on different slopes as the wind changes direction to SW this afternoon.
点発生乾雪雪崩 Dry Loose snow
Use caution around steep slopes with terrain traps: creeks, gullies, etc. This is more of a problem in the East part of the region (Shiribetsu area)
持続型スラブ Persistent slab
A layer of Surface Hoar, Facets and a Crust that was buried on January 28th is still reactive in the Northern part of the region (Kiroro, Kokusai). This layer is buried by 40-100cm of snow and has been triggered recently by skiers in areas where the buried Surface Hoar layer is well preserved.
概要
Avalanche
In the Niseko range a size 1 Windslab was triggered by a skier on a North asp in the Alpine yesterday afternoon. The slab was 10cm deep and 8m wide, and failed on a freshly buried Surface Hoar layer. Shooting cracks were observed, propogating up to 20m in the same area. On Mt Shiribetsu a Loose Dry avalanche was triggered on a NE asp that ran for 400m. In the Kokusai backcountry multiple size 1 slab avalanches were triggered that failed on the Jan 28th SH / crust PWL. These avalanches were on slopes which were in the sun, causing the slab to become more cohesive and reactive.
Snowpack
In the Niseko region 40-50cm of storm snow overlies the Jan 28th PWL. This PWL consists of the following snow grain types: Surface Hoar, Facets, a crust on solar asp, and a crust on polar asp below 400m. In the Northern part of the region up to 100cm of storm snow overlies the Jan 28th PWL. A buried graupel layer can be found down ~20cm within the storm snow. A new crust exists on the surface below ~1000m on solar aspects and new Surface Hoar growth was observed in sheltered areas yesterday.
Weather
A low pressure system over Hokkaido will bring us strong SE winds this morning, switching to strong SW winds this afternoon. Light snow fall is forecasted with 5cm expected by the end of the day. Skies will be overcast and temperatures are forecast to be warm, with a high of 3C in the valley bottom today.
