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Avalanche Forecast

Archived

Dec 18th, 2013–Dec 19th, 2013

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

Regions

South Rockies.

This forecast is based on limited data. If you are out in the mountains, we would like to hear from you at [email protected]

Confidence

Poor - Due to the number of field observations

Weather Forecast

An arctic ridge builds on Thursday bringing dry conditions. The next Pacific low pressure system hits the North Coast on Thursday and will reach the southern interior on Friday bringing light precipitation for Friday and Saturday.Thursday: A mix of sun and cloud, treeline temperatures around -15C, light NE winds switching to W as the front approachesFriday: Increasing cloud cover, light snowfall beginning in the afternoon, treeline temperatures around -10C, light westerly windsSaturday: Light snowfall, treeline temperatures around -10C, light SW winds

Avalanche Summary

No new avalanches reported.

Snowpack Summary

There appears to be a lot of snowpack variability across the region.  Snowpack depths at treeline seem to vary from 50 - 110 cm with high variability in wind-exposed areas. There are several persistent weak layers which are still being discussed in the region.  There is a lot of uncertainty as to the reactivity of these layers and it may vary across the region.  We highly recommend digging and investigating these layers in your local area before exposing yourself to avalanche terrain.  Nearest to the surface is the mid-December (~Dec 10) facet/surface hoar/crust interface which does not seem to have enough snow on it yet to create a widespread problem.  Next is the late-November/early-December interface which is made up of surface hoar, a crust, and/or facets.  This layer is typically down 30-70cm and is most likely to pose the biggest problem for the region at the moment.  The mid-November crust is likely in the middle of the snowpack and may be faceting. Near the base of the snowpack is the early-Oct crust/facets and potentially depth hoar which may still have the potential to create avalanche problems, especially in thin snowpack areas. 

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.

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.