Avalanche Forecast

Archived

Feb 20th, 2015–Feb 21st, 2015

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

South Rockies.

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Confidence

Good - The weather pattern is stable

Weather Forecast

A cold front slowly moving in from the northeast will being continued light perception through Saturday with higher accumulations (up to 10cm of snow) expected on the eastern slope. Sunny and dry conditions are expected for Sunday and Monday. Winds will be predominately light from the northeast to northwest through the period. A slight cooling trend is expected with the passage of the front and freezing levels will hover around valley bottom over the weekend before climbing back up to 2000m on Monday.

Avalanche Summary

No new avalanches have been reported recently

Snowpack Summary

A thick, solid crust can be found at the surface on all but highest alpine slopes. It sounds like the best riding is in the North of the region where the curst does not extend as high and a thin dusting covers old wind pressed snow in alpine. The recent winds have been light to moderate from the southwest and I suspect that you can find isolated thin windslabs in lee features. Below 2100 to 2400m the crust is effectively capping the snowpack and protecting a couple of buried persistent week layers. The mid-January surface hoar is around 60 to 80cm down. The mid-December crust is becoming harder to find but where it does exist (mainly at treeline elevations) it is over a meter down. At upper elevations where these layers are note protected by the crust it could still be possible to trigger an avalanche form a thin or rocky spot.

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.