Avalanche Forecast

Issued: Mar 29th, 2017 4:52PM

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.

swerner, Avalanche Canada

North Columbia.

Forecast precipitation, wind and warming is expected to keep the avalanche danger elevated. If the sun pokes out expect the new storm snow to become reactive and watch overhead hazards like cornices.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

A weak upper trough behind the current low will continue to bring unsettled conditions to the Interior. A short lived ridge may show sunny skies on Friday.Thursday: Another 10 cm could arrive by the morning with a trace throughout the day. Mostly cloudy with alpine temperatures near -7 degree and freezing levels 1500 m. Ridgetop winds L-NW. Friday: Cloudy with possible sunny breaks. Ridgetop winds L-SW and freezing levels near 1500 m. Saturday: New snow 5-10 cm. Ridgetop winds M-SW and freezing levels 1700 m.

Avalanche Summary

On Tuesday, several storm slabs up to size 2 with one size 3 were observed. With continued precipitation and wind, natural avalanche activity will likely continue. 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

Up to 30 cm of new storm snow has fallen at upper elevations. This now brings 30-70 cm of accumulated snow over the past week which overlies the mid-March 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 lower elevations, there may be multiple crust layers in the upper snowpack which are now generally well bonded. At higher elevations, the February weak layers are down 120-150 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.

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.

Use ridges or ribs to avoid pockets of wind loaded snow.Minimize exposure to overhead hazards and sun exposed slopes when the solar radiation is strong.The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - 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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 30th, 2017 2:00PM