Avalanche Forecast

Issued: Mar 30th, 2017 4:23PM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs, Persistent Slabs and Loose Wet.

swerner, Avalanche Canada

North Columbia.

Warming and solar induced avalanches are likely. Smaller wind slabs, storm slabs or cornice fall could "step down" and release persistent weak layers resulting in large avalanches.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain on Friday

Weather Forecast

Drier, sunny conditions expected on Friday and then back to unsettled weather for the weekend.Friday: A mix of sun and cloud. Alpine temperatures near -2 and freezing levels 1500 m. Ridgetop winds light from the South.Saturday: Snow amounts 5-20 cm. Alpine temperatures near -4 and freezing levels 1500 m. Ridgetop winds moderate -strong from the West.Sunday: Mix of sun and cloud. Alpine temperatures near -5 and freezing levels 1100 m. Ridgetop winds light with strong gusts from the West.

Avalanche Summary

On Wednesday, numerous storm slabs up to size 2.5 were observed. Several size 1 storm and wind slabs were also reactive to rider triggering. On Friday, natural activity will remain likely with the strong input of solar radiation, warming and continued wind. Fragile cornices are also suspect, they are large enough and act as heavy triggers for deeper slab avalanches to release on the slopes below. If you're traveling below treeline where the avalanche hazard is lower than it is in the alpine you should remain diligent with your terrain use, mitigate overhead hazards by avoiding or lingering in run-out zones where large avalanches could come down from above. Check out the recent Forecaster Blogs for more details.

Snowpack Summary

30-50 cm of recent storm snow has accumulated at upper elevations. The new snow is dry up high and moist from 1800 m and below. This now brings 80-120 cm of accumulated snow which overlies a rain crust below 2000 m or a sun crust on solar aspects at higher elevations. New wind slabs are developing on leeward slopes and behind terrain features and large, fragile cornices exist along ridgelines. At higher elevations, the February weak layers are down 150-190 cm and woke up during last week's storm with many avalanches stepping down to them. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches and cornice falls have also stepped down to these layers last week resulting in some very large full depth avalanches. These layers remain a concern during this stormy period ending with warmer temperatures and sunshine. The snowpack does not adjust well to change, and these deeper weak layers should remain on your radar through the forecast period.

Problems

Storm Slabs

New storm snow and wind have formed reactive storm slabs. Cornices are large and fragile. They may fail with daytime warming, sun exposure, or during stormy periods

The new snow will require several days to settle and stabilize.Minimize exposure to overhead hazards and sun exposed slopes when the solar radiation is strong.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 3

Persistent Slabs

A cornice fall or smaller slab avalanches could trigger deep, destructive avalanches on buried weak layers. There is a low likelihood of triggering but a high consequence if triggered. These avalanches would likely run full path.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.If triggered, slab avalanches or cornices may step down to deeper layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Loose Wet

Warmer temperatures and rain will deteriorate the lower elevation snowpack, initiating loose wet avalanches that may slide easily on a buried crust. If the sun shines this problem could extend high into the alpine on solar aspects.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Be alert to conditions that change with elevation.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 2

Valid until: Mar 31st, 2017 2:00PM