Avalanche Bulletin
更新日時: 2025/02/07 05:30
Hakuba
Alpine Fair
Treeline Fair
Below Treeline Good
信頼度：○ good □ Fair △ Low
Travel and Terrain Advice
Very dangerous avalanche conditions. Careful route setting and conservative decision making are needed on this day. Even if the snowfall temporarily abates during the day, the avalanche danger level will remain the same, and significant snowfall is forecast. Even if you are below treeline, avoid steep slopes with convex or unsupported features. Weakly bonding snow has been identified. Please carefully select a safe point off avalanche terrain where you can rest and wait for your fellow skiers to ski. For inexperienced groups, we recommend skiing in powder snow within the ski resort. When doing so, please be sure to observe the ski area.
Avalanche Problem
ウインドスラブ Wind slab
There is a very strong wind blowing on the main ridge. That wind travels over and around the terrain and down to the lower elevations, forming wind slabs in various places.
ストームスラブ Storm slab
In a large area below treeline (east - south - west), a persistent weak layer is causing avalanches with slab thicknesses of 50-80 cm with human stimulation. This weak layer is becoming deeply buried, and as a result, its triggering sensitivity is reduced. However, if an avalanche is triggered, its size can be large. Avoid very steep slopes that are infrequently used by humans, or terrain that is convex or unsupported.
概要
Avalanche
Several storm slab avalanches of size 1-1.5 were reported yesterday (6th) below treeline. Directions are broadly east to west. They all occurred at the boundary of the Melt-Freeze crust (buried on February 3). Elevation is unknown due to stormy weather.
Snowpack
Below treeline, there is a thin Melt-Freeze crust formed by high temperatures and weak rainfall on February 3, and bonding remains poor. The weak layer is faceted snow. The snow continues to fall, increasing the density and thickness (load) of the slab on top of the crust. Therefore, although the triggering sensitivity is reduced, the scale of the avalanche can be large. Due to continued stormy weather, information at higher elevations is limited.
Weather
The JMA is forecasting southerly winds, cloudy, with occasional snow, and a daytime high of 1 °C (418 m elevation) for northern Nagano Prefecture. At 703 m elevation (Hakuba), the temperature is -6.3 °C (as of 5:00 a.m.). There has been some snowfall in the past 12 hours, but no increase in snow depth. The Nagano District Meteorological Observatory forecast 50 cm of snowfall for northern Nagano Prefecture at 4:24 a.m. on February 7 in the 24-hour period ending at 6:00 a.m. on February 8. At the main ridge line (elevation 2,400 m), temperatures are -18°C, with northerly winds averaging 17-19 m/s and with maximum wind speeds of 25 m/s or higher.
