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Niseko Avy Bulletin

Niseko, Hokkaido, Japan Avalanche Bulletin.

Niseko Avalanche Bulletin for Monday, December 24th

Eddie Schoen

Note: this bulletin is published in the pm and effective for the following day. Be alert to differences in the forecast and actual snowfall amounts and weather activity overnight.

Backcountry Avalanche Danger Rating

  • Upper (>1000m): MODERATE

  • Mid (800-1000m): MODERATE

  • Lower (<800m): LOW

Current Avalanche Problems

  • Storm Slab | Likelihood: Possible | Size: small - medium

  • Persistent Slab | Likelihood: Unlikely | Size: small-medium

Comments

Today was hopefully our last day of settled weather for the foreseeable future. Forecast models are calling for up to 12cm of fresh snow to fall overnight and throughout the day tomorrow. I wouldn’t be surprised if we see upwards of 20cm. There are a few problems to be alert to over the next few days as we enter this storm cycle. First, surface instabilities up high. Wind affected slopes recently developed firm surface conditions, so with forecasted winds we could 20-50cm of fresh storm slab on potentially slippery bed surfaces. Look out for this below corniced ridgelines, and especially on E -> SE aspects. Various surface crusts have been observed at lower elevations, especially on solar aspects. These surface crusts are quite brittle based on our observations, so little problem in and of themselves. Cold temps mean that this storm snow should come in light and fluffy, so watch for sluffs on steeper features.

The more complex problem that is popping up on my radar is a persistent slab. I hesitate to even put this one in the public forecast, but I’d rather mention it and be wrong than chance someone getting caught by surprise on this. Several observers have noted reactivity in mid-pack layers (buried 40-80cm below the surface). Personally I have seen a few weird results in column tests on these layers, which seem to vary in character and spatial distribution, but have been noted on various aspects below 1000m. This problem is unlikely, and my confidence level on it is poor, but I think it’s worth mentioning. Not sure if Persistent Slab avalanches are even in the vocabulary out here, but being from Colorado, they are a problem I am quite attuned to. They are unpredictable, hard to trigger, and often seem dormant until they go big. If you are skiing steep and unsupported terrain in the backcountry, it’s worth a few extra minutes to dig around and see what kind of layers are lurking under the surface. Make good decisions out there, and ski some epic Christmas pow.

As a local guide and avalanche professional, I have chosen to share this hazard assessment in the interest of encouraging better information sharing within the local community. This avalanche bulletin is to be used at your own risk and is based on very limited data gathered by myself and other guides working for Japan Powder Connection. Please use this information in addition to other resources and take responsibility for your own actions in the backcountry. Also, please respect and abide by all Niseko Area Rules. This information applies only to backcountry areas accessed externally from area resorts. This information is published the evening before and in effect for the following day.

As always, remember that making good decisions in the backcountry takes years of practice and experience. Having the gear is a small part of the equation. Take an avalanche safety course and hire a properly trained guide so you don’t learn the hard way!

Resources:

Japan Powder Connection - Professional Backcountry Guides and Instructors

Niseko Avalanche Information - Niseko’s avalanche information page. Not a ‘bulletin’ by Western standards, but Shinyasan has been doing this for 20+ years and knows these mountains far better than myself.

Snow-Forecast - Niseko Area Weather Forecast

Niseko Now - Local Weather and Conditions Summary