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Avalanche Forecast

Archived

Jan 13th, 2019–Jan 14th, 2019

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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The Bottom Line: The avalanche danger will rise as the day warms up. Get off of steep, sunny slopes if you see rollerballs or find wet snow on the surface. Loose wet avalanche debris is heavy, and can pack a punch. Don't these slides ruin your day. There still remains an isolated chance of triggering a deeper slab on older weak layers.

Snow and Avalanche Discussion

Folks should realize that there is a fair amount of uncertainty with our snowpack and how the warming will influence it, particularly above 6,000ft. There is also a lot of variability within the zone. The current snow surface is a mixed bag. On sunny aspects, it is likely crusted over early in the morning, and becoming wet and heavy by mid day. The snow has been remaining cold and dry above 5,000ft on shaded aspects, and small surface hoar growth has been observed. The storm snow from January 8th and 9th sits over a crust from January 3rd. A thin layer of weaker snow has been found just above this crust, and is worth checking out how these are bonding. A round of control at Mission Ridge on the 10th pulled out a number of large wind slabs. One of these on a Northwest aspect at 6300ft broke through the crust and ran on weaker snow near the ground, exposing rocks. On steep southerly aspects, a number of loose wet avalanches have been observed.

Problems

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.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of 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.