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Avalanche Forecast

Archived

Apr 21st, 2013–Apr 22nd, 2013

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

Regions

Purcells.

The Public Avalanche Forecasts come to an end on Monday. Starting Tuesday you can find spring messaging under the "Forecast Details" tab below.See you next Season!

Confidence

Fair - Due to limited field observations

Weather Forecast

An upper ridge stalls off the coast bringing sunny skies and dry cool conditions through Tuesday. By mid-week freezing levels will rise to 2000 m.Monday: Mostly sunny skies. Ridgetop winds will blow light from the NW and freezing levels will rise to 1800 m. Tuesday: Broken cloud cover and a chance of flurries. Ridgetop winds moderate from the NW and freezing levels 1800 m. Wednesday: The stationary ridge of high pressure continues bringing sunny skies and freezing levels up to 2000 m. Ridgetop winds will blow light from the SW.

Avalanche Summary

No new avalanche activity has been reported.On Friday, numerous size 1.5-2 wind slab avalanches were skier triggered. All of which were from 35-40 degree slopes on NE aspects above 2100 m. All of these avalanches failed within the recent storm snow interface approximately 30 cm down, and on the early April interface around 80 cm down. One of these was remotely triggered from 15 m away, size 2.

Snowpack Summary

Up to 20 cm of new snow overlies a variety of old snow surfaces. These consist of melt-freeze crusts, buried surface hoar and surface facets. Touchy wind slabs exist on lee slopes and behind terrain features. Cornices on ridgelines or huge, and will likely become weak with daytime warming. They pose a threat to slopes below. Surface snow will likely become wet and deteriorate on solar aspects.Deeper in the snowpack a weak interface buried in early April is down about 60-120 cm and consists of a crust and surface hoar. Earlier this week, very large avalanches were reactive on this interface in neighboring regions. The bond may be getting stronger, but I would still use caution and be suspicious of large, steep upper elevation 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.

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.