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Avalanche Forecast

Archived

Jan 8th, 2016–Jan 9th, 2016

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

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Watch for shallow wet snow on steep sun exposed terrain and be mindful of cornices as these are likely to weaken during the warmest part of the day.  Older wind slabs may still be lurking in isolated higher elevation areas.

Detailed Forecast

Mild daytime temperatures and sunshine Saturday should give way to increased clouds late in the day and a chance of a few showers late. This should allow for shallow surface snow melt, breaking down existing surface crusts through the day where they existed. Cooler settled and mostly stable powder is likely on steeper shaded slopes. 

Small loose wet avalanches should be possible on direct, steep, solar aspects. 

Also, watch for any older cornices as the sun and warming may weaken these, especially near midday.

We have lowered the likelihood of triggering an avalanche on an older wind slab, however, it would still be wise to watch for these conditions on specific terrain features. Most likely suspects are steep slopes below ridges or cross loaded ribs, mainly near or above treeline and avoid slopes where being caught in a small slide could have larger consequences, such as slopes above trees, cliffs or where the terrain would funnel snow into a trap, like a creek bed or natural depression.

Snowpack Discussion

 

The deep storm snow from late December is now well settled and appears rather homogeneous in the numerous recent snowpits dug throughout the region. Fair weather following Christmas allowed surface hoar and near surface faceted snow to form extensively.  Snowfall buried this layer January 3rd and 6-12 inches accumulated by early this week along with some wind loading and wind redistributed wind slabs noted. Several avalanches occurred on this layer early in the week.

Mild weather, sunshine and light winds over the past several days with above freezing temperatures in many areas have allowed for this layer to bond and strengthen, making avalanches unlikely. Extensive testing Friday, January 8th by Ian Nicholson on Chair Peak in the Alpental Valley, found this layer to be gaining significant strength from earlier in the week and no failures were noted on the buried layer, now difficult to distinguish about 6 inches below the surface on a NE slope near 5500 ft.  

High pressure returned Thursday and Friday, providing plenty of sunshine and mild temperatures, well above freezing in many areas. This weather has allowed for the recent 6-10 inches of storm snow to further consolidate while sunshine and warming has caused shallow wet snow conditions during the warmest part of the day, followed by surface crusts overnight and mornings. Surface crusts were found on most aspects Friday, causing challenging travel conditions. Thin melt-freeze crusts were even found on steep north slopes. 

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.