Avalanche Forecast

Issued: Mar 16th, 2019 4:21PM

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

jsmith, Avalanche Canada

North Columbia.

Warming temperatures have settled the recent storm snow into a cohesive slab sitting on weak facets (sugary snow) that is ripe for human triggers; intense solar radiation will increase the likelihood of natural and human triggered avalanches.

Summary

Confidence

Moderate -

Weather Forecast

SATURDAY NIGHT: Mostly clear / Light, northwesterly winds / Alpine low -5 / Freezing level valley bottom.NOTE: Saturday night is the last night of the forecast period that freezing levels are expected to drop at night. This will significantly increase the impact of day time warming on the snowpack.SUNDAY: Sunny / Light, northwesterly winds / Alpine high 1 / Freezing level rising to 2100 m.MONDAY: Sunny / Light, northerly winds / Alpine high 5 / Freezing level rapidly rising to 2800 m.TUESDAY: Sunny / Light, southeasterly winds / Alpine high 7 / Freezing level rising to 3000 m.

Avalanche Summary

On Friday, several persistent slab avalanches up to size 2.5 were reported on a variety of aspects at treeline and above. The avalanches were failing on facets below the recent storm snow. Human triggered persistent slab avalanche activity is expected to increase with the forecast sunshine and rising freezing levels.On Thursday, a rider triggered size 2.5 persistent slab avalanche was reported on a west aspect at 2000 m. Another size 2, persistent slab avalanche on a southwest aspect at 2300 m. was triggered by a skier from 50 m. away from the slope that avalanched. This suggests that recent storm snow is still very sensitive to human triggers in specific locations. On Wednesday, numerous natural storm slab avalanches up to size 3 and rider triggered up to size 2 were reported on all aspects at treeline and above. Some of the avalanches were triggered remotely from lower angle terrain by skiers 30 m. away from the slope that avalanched.

Snowpack Summary

There is 40-60 cm. of recent storm snow is sitting on a pile of facets (sugary snow), as well as a crust on sun exposed slopes. The recent storm snow has settled into a cohesive slab and is ripe for human triggering. This persistent slab is currently our primary concern.At lower elevations below treeline, a weak layer buried in mid-January can be found approximately 70-120 cm. deep. This layer consists of surface hoar and facets, and may be combined with a crust on south facing slopes. This layer has recently been unreactive, however, the forecast warming event may awaken this layer, resulting in large, destructive avalanches. Steep cutblocks and large open glades at lower elevations are the most likely places to trigger this layer.The lower snowpack is generally considered to be strong, except for shallow, rocky areas in the alpine.

Problems

Persistent Slabs

Warming temperatures have settled the recent storm snow into a cohesive slab sitting on weak facets (sugary snow) that is ripe for human triggers; especially at treeline and above.

Use extra caution on solar aspects where the new snow is sitting on a crust.Avoid steep terrain where the snow feels moist or slabby.Avoid convex slopes on rocky terrain with a variable snow depth.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1.5 - 2.5

Cornices

Sunshine and rising freezing levels will elevate the potential for cornice failures resulting in large avalanches.

Avoid exposure to cornices and sun exposed slopes when the solar radiation is strong.Cornice failures have the potential to trigger large avalanches on deeply buried weak layers.Cornices often break further back than expected; give them a wide berth when traveling on ridgetops.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 3

Loose Wet

Pin-wheeling snow below cliffs is a common sign that loose wet avalanches are becoming more likely.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Avoid steep, sun exposed slopes when the solar radiation is strong.Reduce exposure to over-head hazards such a large cornices during periods of strong solar radiation.

Aspects: East, South East, South, South West, West.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 1.5

Valid until: Mar 17th, 2019 2:00PM