Avalanche Bulletin
更新日時: 2025/02/03 07:00
Niseko Yotei Yoichi Shiribeshi
Alpine Fair Hazard will increase to Considerable in the afternoon when the wind increases
Treeline Good Hazard will increase to Considerable in the afternoon when the wind increases
Below Treeline Fair Hazard rating BTL is Considerable in the Northern part of the region (Kokusai, Kiroro) where the Jan 28th SH PWL is well preserved and still reactive to skier triggering.
信頼度：○ good □ Fair △ Low
Travel and Terrain Advice
Assess for Storm slab reactivity within the new storm snow, and the bond of the storm snow to the Jan 28th PWL. Watch for new Windslab formation this afternoon when the winds increase to moderate from the SE. Rising temperatures through the day will increase reactivity of the avalanche problems.
Avalanche Problem
ストームスラブ Storm slab
40cm -100cm of storm snow overlies the Jan 28th PWL. This new snow is starting to bond to the PWL but was still reactive yesterday in sheltered areas where it overlies Surface Hoar. Avalanches were also triggered yesterday that failed within the storm snow. Assess for any density changes within the storm snow, where stiffer snow overlies softer snow, as this can indicate conditions for a Storm slab avalanche.
ウインドスラブ Wind slab
New Windslab is expected to develop this afternoon lee to SE winds.
点発生乾雪雪崩 Dry Loose snow
Use caution around steep slopes with terrain traps: creeks, gullies, etc.
概要
Avalanche
In the Niseko range a size 1 Stormslab was triggered on a South asp at TL yesterday. The avalanche was 10cm deep, failing on a layer within the storm snow, likely due to the sun making the surface snow turn into a slab and become more reactive. In the Northern part of the region several Stormslabs were triggered BTL yesterday that failed on the Jan 28th PWL. These avalanches were 30cm deep, likely failing on buried Surface Hoar. A size 1 Windslab was also triggered at TL on a NE asp in this area.
Snowpack
In the Niseko region 40-60cm 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 below 1200m, and a crust polar asp below 400m. In the Northern part of the region up to 110cm of storm snow overlies the Jan 28th PWL. A graupel layer within the storm snow has been reactive to skier traffic. Solar input caused the surface snow to slab up and become more reactive in areas that saw some sunshine yesterday.
Weather
A low pressure system moving up from the South will bring us moderate SE winds this afternoon, increasing to strong winds overnight. Cloud cover will increase through the day with snow fall forecast to start in the late afternoon. The freezing level is forecast to reach 100m today.
