Avalanche Forecast

Issued: Mar 20th, 2015 9:25AM

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

Cariboos.

Snow, rain and strong winds combined with buried weak layers make the perfect recipe for avalanches. Check out the new Forecasters Blog @ avalanche.ca.

Summary

Confidence

Good

Weather Forecast

Is spring the new winter? Waves of precipitation will continue overnight Friday and into Saturday. Amounts 10-15 mm on Saturday are expected, ridgetop winds moderate from the SW and freezing levels 1900 m. A dry day with a mix of sun and cloud is forecast on Sunday. Monday will see somewhat cooler temperatures with freezing levels near 1500 m and light precipitation 3-7 mm. The pattern looks to continue as a series of fronts and ridges move across the province throughout next week.

Avalanche Summary

Thursday was a fairly stormy day and observations are minimal but I suspect natural avalanche activity occurred. On Wednesday, natural and skier triggered slab avalanches were reported up to size 2. Both avalanches were reportedly over steeper convex terrain features on northerly aspects above 2100 m. Widespread natural avalanche activity is expected through the weekend with new snow, rain and strong SW winds.

Snowpack Summary

At higher elevations, new storm snow 20-30 cm sits over a plethora of surfaces including moist snow, crusts, wind affected surfaces, and/or old wind slabs. This gives us anywhere from 40-80 cm over the mid-February persistent weak interface. This interface has recently been very reactive and I don't suspect that to change during this stormy period. Strong winds have redistributed new snow into wind slabs on leeward terrain features. Lower elevations up to treeline are sporting spring-like, melt-freeze conditions. The late-January crust/surface hoar layer (over 1m deep) and the mid-January surface hoar (around 1.5m deep) have been dormant for several weeks.

Problems

Storm Slabs

Touchy storm slabs continue to build and sit over a weakness from mid-February.

Avoid freshly wind loaded features.>Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Persistent Slabs

A persistent weak interface buried mid- February 30-60 cm below the surface is responsible for numerous large slab avalanches.

Remote triggering is a concern, watch out for adjacent slopes.>Be aware of the potential for wide propagations resulting in large avalanches.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Loose Wet

Steady rain and warming at lower elevations will saturate and weaken the upper snowpack.

Avoid exposure to terrain traps where the consequences of a small, wet avalanche could be serious.>Watch for clues of instability, like natural avalanche activity, sluffing off of cliffs, and snowballing. >

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Valid until: Mar 21st, 2015 2:00PM