Avalanche Forecast

Issued: Mar 21st, 2014 9:20AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs, Persistent Slabs and Deep Persistent Slabs.

rbuhler, Avalanche Canada

Cariboos.

The snowpack remains complex due to stubborn buried weak layers. Very large, destructive avalanches are still possible. Conservative route selection remains crucial at this time.

Summary

Confidence

Good

Weather Forecast

A weak frontal system should bring light precipitation to the interior midday Saturday but the Cariboos, especially the north, may only see scattered flurries. A ridge of high pressure builds in its wake on Sunday and should persist through Monday. The next system is expected for Tuesday. Saturday: Light precipitation 1-2mm, freezing level am: surface pm: 600m, ridgetop wind light SE-SWSunday: A mix of sun and cloud, dry conditions, freezing level am: surface pm: 900m, ridgetop wind light W-NWMonday: A mix of sun and cloud, dry conditions, freezing level am: surface pm: 1300m, ridgetop wind light S-SW

Avalanche Summary

Reports from Thursday include several natural storm slab avalanches up to size 2 releasing down 30-40cm. Also reported was a natural cornice fall triggering a size 2.5 avalanche which released on the early-February weak layer.Generally, we are still seeing relatively small inputs, like periods of strong winds or brief sunny breaks, trigger deeper persistent slab avalanches. Many of these events have occurred on southerly aspects from slopes in the alpine or at treeline. Extra caution is advised when the sun is out.

Snowpack Summary

Around 30-40cm of recent storm snow fell earlier in the week. There may be a variety of layers within the storm snow including thin sun crusts, graupel balls, and maybe even small surface hoar from brief clearings overnight. Also, expect wind slabs in exposed lee and cross-loaded terrain from recent SW-W winds. This storm slab sits on a layer of surface hoar and/or sun crust. A couple other notable persistent weakness layers remain a concern in the mid-snowpack. The surface hoar/sun crust combo buried in early March is now down around 60-80 cm. The early-February surface hoar/facet/crust combo is down 90-150cm and widespread throughout the region. Smaller avalanches stepping down and cornice falls have the potential to initiate an avalanche on this deeply buried weak layer. The mid and lower snowpack remains weak and facetted in areas with a relatively shallow snowpack.

Problems

Storm Slabs

Weaknesses exist within or under the recent storm snow and could be triggered by the weight of a rider, particularly in steep wind-loaded terrain.

Choose well supported terrain without convexities.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

The early March sun crust/ surface hoar combo should not be underestimated. While there's a lot of uncertainty and complexity surrounding this layer, it's important to note that human triggering is most likely at treeline.

Use conservative route selection, stick to moderate angled terrain with low consequence.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Deep Persistent Slabs

The early February Persistent Weak Layer is still active and has produced some stunning avalanches recently. Very large avalanches may result from a surface avalanche in motion, a cornice fall or a rider finding the sweet spot.

Be aware of the potential for large, deep avalanches due to the presence of deeply buried weak layers.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 22nd, 2014 2:00PM