Avalanche Forecast

Archived

Feb 8th, 2019–Feb 9th, 2019

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural and human triggered avalanches likely.

Alpine

Below Threshold.

Treeline

Below Threshold.

Below Treeline

Below Threshold.

Regions

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Very dangerous avalanche conditions will develop Friday night and Saturday. New snow and wind will stress weaker, older snow, setting the stage for large and deadly avalanches. Stay off of steep slopes and don't linger near or under any slope steeper than 30 degrees. You could trigger avalanches from far away or from the bottom of overhead slopes.

Discussion

Snow and Avalanche Discussion

We expect that a weak snowpack in the eastern portion of the East Slopes Central forecast zone will be pushed to the breaking point for large natural and human triggered avalanches by new snow and wind over the weekend. Since a similar shallow and weak snowpack likely exists in portions of the East Slopes South zone, we are expecting very dangerous avalanche conditions to develop Friday night and Saturday here as well.

Forecast Schedule and No Rating

At this time, we do not have enough specific snowpack information to issue an avalanche hazard rating for the East Slopes South zone. However, even when No Rating is applied, applicable avalanche conditions and backcountry travel advice will be provided throughout the season. When weather systems produce very dangerous avalanche conditions in adjacent zones, NWAC will issue an avalanche warning for this zone as well.

Snowpack Discussion

Regional Synopsis coming soon.

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.