Avalanche Forecast

Issued: Mar 25th, 2019 4:03PM

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

jsmith, Avalanche Canada

Lizard-Flathead.

Small loose wet avalanches may gather mass, become much larger, and run farther into low angle terrain than expected.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

MONDAY NIGHT: Increasing clouds / Moderate to strong, southwesterly winds / Alpine low 1 C / Freezing level 2000 m.TUESDAY: Cloudy with flurries/ rain in the valleys; 3-10 mm. / Moderate to strong, southwesterly winds / Alpine high -2 C / Freezing level 1700 m.WEDNESDAY: Mostly cloudy / Light, northeasterly winds / Alpine high 0 C / Freezing level 1700 m.THURSDAY: Mix of sun and cloud / Light, southeasterly winds / Alpine high 2 C / Freezing level 2000 m.

Avalanche Summary

On Sunday, there was a report near Fernie of a skier triggered, size 2.5 wet slab avalanche that began as a loose wet avalanche and then gathered mass which ran much further than expected through low angle terrain. The below link shows a smaller example of this sort of avalanche.Last Thursday reports show continued skier triggered loose wet avalanches reaching size 1.5 on sun-exposed aspects. Check out this video of our South Rockies Field Team HERE.Last Wednesday, several avalanches that began as loose wet point releases, then triggered small slabs which entrained or gouged out additional mass, significantly increasing the size and destructive potential of the avalanche.

Snowpack Summary

The prolonged warm spell has transitioned sun exposed slopes in the alpine and all aspects at treeline and below towards becoming isothermal (0 C throughout the snowpack). In these areas that have entered spring conditions, the avalanche hazard will fluctuate greatly depending on the strength of the overnight freeze and how quickly the snowpack is warmed up each day. Check out this guide to managing avalanche hazard during spring conditions HERE.In areas that remained more sheltered from the heat, like northerly aspects in the alpine, there may still be a dry snowpack with a well settled slab sitting on weak facets (sugary snow). Human triggering of persistent slabs on this layer may still be possible; especially in rocky alpine terrain with a shallow or highly variable depth snowpack.

Problems

Loose Wet

This problem is more likely at lower elevations where there was a weak or no overnight re-freeze. Sunshine and air temperatures above 0 C can rapidly increase the likelihood of triggering loose wet avalanches.

Cornices become weak with daytime heating, travel early on exposed slopes.Avoid sun exposed slopes when the solar radiation is strong, especially if the snow is moist or wet.Avoid terrain traps such as cliffs and gullies that increase the consequence of small avalanches.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

Human triggering of large persistent slab avalanches are most likely on north facing slopes in rocky, alpine terrain with a shallow or highly variable snowpack depth.

Pay attention to changing condition with elevation and/or aspect.Avoid steep, rocky terrain in the alpine where there is a shallow or highly variable snowpack depth

Aspects: North, North East, North West.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 2.5

Valid until: Mar 26th, 2019 2:00PM