Avalanche Forecast

Issued: Mar 23rd, 2014 9:09AM

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

South Columbia.

Expect to see sunny breaks over the next couple days. Brief periods of solar radiation could be enough to trigger stubborn persistent slabs or cause cornice failures. Conservative route selection remains crucial at this time.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain on Wednesday

Weather Forecast

A weak ridge of high pressure will be the main feature for Monday. Unsettled conditions are expected for Monday night and Tuesday before the next frontal system arrives Tuesday afternoon or evening. Precipitation is expected for Wednesday and Thursday. Monday: A mix of sun and cloud, freezing level am: surface pm: 1200m, ridgetop wind: light variableMonday Night: Scattered flurries 1-3cmTuesday: Mostly cloudy, freezing level am: 500m pm: 1500-1800m, ridgetop wind: light S-SWTues. Night/Wednesday: Snowfall 15-25cm, freezing level am: 500-1000m pm: 1400m, ridgetop wind: light SW-W

Avalanche Summary

We are still seeing relatively small inputs, like periods of strong winds or brief sunny breaks, trigger 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.On Saturday, we received reports of isolated skier-triggered storm slab avalanches up to size 1.5 in the upper 20cm.Â Early reports from Sunday suggest increased natural and human-triggered avalanche activity up to size 1.5 within the recent storm snow, typically down 20-35cm.

Snowpack Summary

The upper snowpack may have various non-persistent weak layers within the recent storm snow.Â This includes small surface hoar in sheltered areas, thin sun crusts on solar aspects, rain crusts at lower elevations, and/or small facets. These layers are not widespread and are not expected to persist very long but they continue to produce small slab avalanches.Â Weak cornices and stubborn wind slabs may also be a concern in some areas.There are three persistent weak layers that remain a concern.Â The mid-March sun crust/surface hoar layer is down 50-80cm. Recent snowpack tests suggest that the reactivity of this layer is becoming more isolated but many areas still have the potential for human-triggering. The early-March crust/facet/surface hoar layer is down around 80-120cm. Human-triggering has become less likely but the layer still has the potential to produce large avalanches and we continue to see activity stepping down to this layer. The mid-February crust/facet/surface hoar layer is typically down at least 1.5m and direct triggering has become unlikely.Â However, large triggers like cornices or smaller avalanches can still trigger this layer and produce very large avalanches.

Problems

Storm Slabs

Weaknesses exist within or under the recent storm snow and could be triggered by the weight of a rider, especially in steep wind-loaded terrain. Also, expect some loose wet activity on solar aspects when the sun is out.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

The early-March and mid-March weak layers are still reactive to human-triggering and have the potential to produce large avalanches. The early-March layer is particularly tricky and conservative terrain selection remains crucial.

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

2 - 5

Deep Persistent Slabs

The early February weak layer is still active and has produced some stunning avalanches recently. Very large avalanches may result from smaller avalanches stepping down, a cornice fall, or a rider finding the sweet spot.

Be aware of thin areas that may propogate to deeper instabilites.>Be aware of the potential for large, deep avalanches due to the presence of deeply buried weak layers.>Avoid rock outcroppings, large convexities and anywhere the snowpack is thin and/or variable.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Valid until: Mar 24th, 2014 2:00PM