Avalanche Forecast

Issued: Mar 30th, 2015 9:12AM

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 Loose Wet.

rbuhler, Avalanche Canada

South Columbia.

Winter is returning to the alpine and with it comes new storm instabilities. Storm slabs may be touchy, especially in wind loaded areas. Buried persistent weak layers remain reactive and still have the potential to produce very large avalanches.

Summary

Confidence

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

Weather Forecast

A cold front crosses the interior on Tuesday bringing light precipitation with cooler temperatures. Models are currently showing 5-10mm of precipitation. Freezing levels are expected to stay high Monday overnight and progressively fall to around 1500m by Tuesday afternoon. Alpine winds are forecast to be moderate-strong from the SW switching to the NW. On Wednesday, mainly dry and cloudy conditions are expected with light flurries and possible sunny breaks. Freezing levels are expected to drop below 1000m Tuesday overnight and reach around 1500m on Wednesday afternoon. Alpine winds are forecast to be moderate from the NW. Similar conditions are expected for Thursday with a mix of sun and cloud, light scattered flurries, and freezing levels around 1500m.

Avalanche Summary

On Saturday and Sunday, isolated natural size 2-3 persistent slabs were reported. These occurred on a variety of aspects and mainly above 2000m. At lower elevations, lots of loose wet avalanches were reported. On Thursday and Friday, a widespread avalanche cycle occurred in response to wet and windy conditions. These were a mix of storm slab, loose wet avalanches and persistent slabs up to size 3. Natural avalanches are possible on Tuesday as new snow falls at higher elevations and rain falls down low. Human-triggered storm slabs and persistent slabs are a major concern, especially on steep, unsupported slopes. At lower elevations, be cautious of sluffing from steep slopes when it is raining.

Snowpack Summary

5-15cm of recent snow overlies a wet layer or a crust that formed on Friday when it rained into the alpine. This new snow is moist to around 2100m. In the alpine, strong winds have redistributed the new snow and wind slabs can be expected in leeward terrain features. Several persistent weak layers exist in the upper 1m of the snowpack and remain a serious concern. The mid-March crust/facet layer is down around 60cm and remains reactive to light triggers. Down around 80cm is the mid-February crust/facet/surface hoar layer which has also been reactive to heavy loads like avalanches in motion stepping down, cornice failures, or explosives. Both layers have the potential for wide propagations and very large avalanches are possible.

Problems

Storm Slabs

New snow and winds may form touchy storm slabs at higher elevations, especially in wind loaded areas.

Avoid freshly wind loaded features.>The new snow will require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

Buried persistent weak layers remain reactive to human-triggering and very large avalanches are possible. Smaller avalanches in motion or a cornice failure could easily trigger one of these deeper layers. These slabs may be wet at lower elevations.

Avoid convexities or areas with a thin or variable snowpack.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Loose Wet

Rain at lower elevations will destabilize the upper snowpack and it may be possible to trigger wet sluffing in steep terrain, especially where wet snow overlies a crust.

Be cautious of sluffing in steep terrain during periods of rain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Mar 31st, 2015 2:00PM