Hatcher Pass

The last avalanche may have occurred on 12/8. This avalanche date and cause has not been verified. It is strikingly similar to an avalanche that occurred previously this season, however, this is newer. It may have occurred naturally due to wind loading. The left side of the photo clearly shows wind scouring which matched the predominant wind direction. Or, this may have occurred by human trigger, unreported, and the tracks were covered by the most recent new snow and wind transported snow.

Hatch Common, NE, 4200′

The last human triggered avalanche was observed on 12/5. This avalanche occurred on a wind scoured aspect where the snowpack is generally thinner. The shallow gully features were cross-loaded, increasing the depth of the snowpack at the site of the avalanche.  Notice there is a lot of rock showing on the untrack and very little snowpack. Thinner, wind scoured snowpacks are often capable of forming weak faceted, sugar snow. This alone is generally not hazardous. However, add wind loaded snow on top, and you now have the recipe for an avalanche.

The red x is the approximated point where the rider triggered the avalanche.  This was a close call. The crown was approximately 2 feet deep, failed near the ground and was D2 in size, large enough to bury, injure or kill a person. This avalanche is now obscured by new snow.

Persistent slabs will continue to be the primary avalanche concern today, on all aspects, at the mid to upper elevations, on slopes 30° and steeper, where it will be possible to human trigger large avalanches. This avalanche problem may allow you to get out onto a slope before you trigger it, making escape difficult to impossible. Natural avalanches will be unlikely. At low elevation persistent slabs are unlikely to human trigger and natural avalanches are also unlikely.

There are two persistent weak layers within the snowpack (pit link here). The first one consists of old, near surface facets buried in the mid pack, 12-18″ below the surface. The second persistent weak layer of basal facets is buried 1-3 feet deep, at, and near the ground, surrounding an old crust. Both of these avalanches will vary from soft slab to hard slab depending on location.

The deeper layer near the ground is the culprit in most of the human triggered avalanches over the last two weeks. This deeply buried layer will continue to be difficult to predict. Remotely triggering this layer will remain possible. A pattern of human triggered persistent slabs on SE to S to SW aspects at upper elevations has been observed over the last two weeks. These aspects contain a thinner, weaker snowpack, where any wind loaded features will be easier to trigger, the classic recipe for an avalanche. Be conservative and use extra caution in these locations.

Note that any one stability test does not provide conclusive information for this avalanche type. We will be playing it smart by employing safe travel protocol, avoiding slopes with terrain traps, and testing the snow in many locations to increase our safety margins. Shooting cracks and whumphing are red flags for this avalanche problem.

There are numerous locations out there where the snowpack is right side up, lacks a slab component, and is fairly shallow, less than two feet deep. These areas tend to be located in the low to mid elevations, in wind protected areas, and on lower angle slopes. In these locations the snowpack is made up of almost entirely weak faceted snow, which is also fun to ride. The biggest hazard here is shallowly buried hazards such as rocks.

Loose dry avalanches will be possible on all aspects, at all elevations, on slopes 40° and steeper but more prevalent on slopes above 45°. These will be small in size.

Some areas, especially at the upper elevations, will have a stiff layer of snow buried in the snowpack with about 4″ of low density snow on top, “dust on crust”. This low density snow will slide easily on the firmer, buried layer. In other areas, where the snowpack is generally more faceted and less firm, it may be possible for dry lose avalanches to dredge and entrain older snow, deeper in the snowpack, which will increase the volume of the avalanche and likely expose rocks at the ground surface.

Any dry loose avalanche risk is compounded in areas with terrain traps and shallowly buried hazards.