Avalanche Forecast

Issued: Mar 29th, 2017 4:39PM

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

swerner, Avalanche Canada

Cariboos.

The sun packs a punch this time of year. If it shines you can expect the recent storm snow to become weak and reactive. Overhead hazards like cornices may fail and trigger large slab avalanches from the slope below.

Summary

Confidence

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

Weather Forecast

A weak upper trough behind the current low will continue to bring unsettled conditions to the Interior. Periods of clear skies and sunshine may happen Thursday afternoon. Thursday: Another 10 cm could arrive by the morning with a trace throughout the day. Cloudy with some sunny skies and alpine temperatures high near 1 degree and freezing levels 1700 m. Ridgetop winds L-NW. Friday: Mostly cloudy with a trace of snow. Ridgetop winds L-SW and freezing levels near 1500 m. Saturday: New snow 5-10 cm. Ridgetop winds M-SW and freezing levels 1600 m.

Avalanche Summary

On Tuesday, no new avalanches were reported. A natural cornice fall up to size 2 was observed on Monday. With continued precipitation, warming 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 recent storm snow has fallen at upper elevations. This now brings 30-70 cm of accumulated snow over the past week 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 lower elevations, there may be multiple crust layers in the upper snowpack which are now generally 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

Wind Slabs

Recent wind from the SW has redistributed the new storm snow in exposed terrain at higher elevations forming reactive wind slabs. Cornices are large and may become weak with daytime warming, sun exposure, or during stormy periods.

Give cornices a wide berth when travelling on or below ridges.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.

Aspects: North, North East, East, South East, South.

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.

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

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.

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

Likely

Expected Size

1 - 2

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