With a widespread facet layer in place as our primary concern we have widespread weakness that is near natural failure in many places.

This weakness is simply looking for a trigger...

In windloaded areas are that much closer to a state of failure. We have seen wind start natural avalanches in many areas over the last few days during periods of new snow fall. With continued wind transport natural avalanches remain possible.

Human triggered avalanches are also VERY possible in these areas as you have a dual threat with both a faceted weak layer and a windslab riding over the top.

Due to increased loading these slides could also be quite large. Use increased caution in windloaded areas.

With a widespread facet layer in place as our primary concern we have widespread weakness that is near natural failure in many places.

This weakness is simply looking for a trigger...

In windloaded areas are that much closer to a state of failure. We have seen wind start natural avalanches in many areas over the last few days during periods of new snow fall. With continued wind transport natural avalanches remain possible.

Human triggered avalanches are also VERY possible in these areas as you have a dual threat with both a faceted weak layer and a windslab riding over the top.

Due to increased loading these slides could also be quite large. Use increased caution in windloaded areas.

The National Weather Service Forecasts-

Today- Becoming mostly cloudy by afternoon. Temperatures remaining around 30 to 35. Northwest wind 10 to 20 mph diminishing in the morning.

Tonight- Mostly clear. Colder. Lows 19 to 26. North wind 10 mph in the evening becoming light and variable.

New Years Day- Partly cloudy. Highs around 30. Light winds.

Temperatures are quite cold this morning around the region with Mt Roberts having dropped 4c in the last 24 hours to be -4.5c currently. Eaglecrest is a bit cooler at -8C (17f). Temps will continue to cool over the next 24 hours as well.

In the last 24 hours we have seen fair snow and precipitation volumes depending on elevations. Eaglecrest is reporting 23cm(9\") of snow with 35mm of precip for relatively high snow densities overall. Mt Roberts is showing lower snow volumes with 17cm of snow at high snow densities. These are moderate to considerable snow loading rates adding increased stress to the weak layers already in place.

Winds are relatively calm now but were quite high during the snowfall yesterday and into last night. This windloading added increased stress to the snowpack in windloaded areas and actually triggered some natural avalanches last night. This windloading gives us considerable loading danger as well.

With considerable windloading, and considerable snowfall coming to rest on a snowpack with a persistent weak layer of facets from last weekends clear weather the avalanche danger remains CONSIDERABLE today.

Natural avalanches are possible and human triggered avalanches are likely.

As the winds slow today loading rates will diminish and danger of natural avalanches should decrease slightly... but over the last few days we have seen quite a few natural avalanches showing us a weakness exists in the pack. This is a great indicator that human triggered slides are even more likely as the snowpack is simply looking for the slightest trigger be it wind, snow, or a rider...

Be aware out there and choose your terrain wisely.

Today is a great day to limit time spent in avalanche zones. Don't walk your pets above the gates in the Berhands neighborhoods. Also be aware of danger on the Flume and Perseverance Trails.

The idea behind the new forecast model is to give you further information and further considerations as to how to manage the hazard. For every problem there is a link. Simply click on the avalanche problem of the day to learn more.. for example. Here is todays link.

Persistent Slab

Release of a cohesive layer of soft to hard snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

The best ways to manage the risk from Persistent Slabs is to make conservative terrain choices. They can be triggered by light loads and weeks after the last storm. The slabs often propagate in surprising and unpredictable ways. This makes this problem difficult to predict and manage and requires a wide safety buffer to handle the uncertainty.

How they form

Persistent Slabs form when a persistent weak layer is buried by additional layers of snow. The problem persists after storm and wind slab instabilities have stabilized. The persistent weak layer can cycle through periods of sensitivity from reactive to nonreactive due to changes in weather conditions such as new precipitation, wind loading, strong solar radiation, and/or rapid changes in air temperature.

Where they form

The spatial distribution of Persistent Slabs is dictated by the distribution of the culprit weak layer. The weak layer distribution is dictated by the weather patterns responsible for its creation. Thus, Persistent Slab distribution can range from widespread across terrain to very specific terrain features. They can occur at all elevations and on all aspects. Persistent Slabs can be triggered remotely, and on low-angle to steep slopes. Consult the backcountry avalanche forecast to determine where in the terrain this problem exists.

Timing and Triggering

Persistent Slabs can be a problem during any time of the snowy season. Anytime you have a slab resting over a reactive persistent weak layer, you have a Persistent Slab problem. This problem can develop during the fall and last well into the spring.

Recognition

Persistent Slabs can be distinguished from Storm and Wind Slabs by how the fracture lines fail in the terrain. Unlike storm instabilities, Persistent Slabs are commonly triggered remotely, from flat areas, and failures can propagate across terrain features like ridges, ribs, and gullies. It is possible to have a Persistent Slab problem that is susceptible to human triggering but not produce many spontaneous avalanches. The lack of avalanche activity does not always indicate the absence of a Persistent Slab problem. You can look for persistent weak layers in snow profiles, and perform snowpack tests to gauge sensitivity and distribution of a Persistent Slab problem. Consult the backcountry avalanche forecast to determine where in the terrain this problem exists.

Treatment and Avoidance

Persistent Slabs can be triggered by light loads and weeks after the last storm. They are commonly trigged remotely and they often propagate across and beyond terrain features that would otherwise confine wind and storm slabs. Failures often propagate in surprising and unpredictable ways. This makes this problem difficult to predict and manage and requires a wide safety buffer to handle the uncertainty. Intimate slope-scale knowledge and tracking of culprit persistent weak layers and avalanche activity over space and time will aid in assessing the severity and extent of this problem. The best ways to manage the risk from Persistent Slabs is to make conservative terrain choices.