Avalanche Forecast

Issued: Mar 10th, 2019 3:22PM

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

shorton, Avalanche Canada

South Coast.

Avalanche danger will increase as a storm arrives Monday and continues into Tuesday.

Summary

Confidence

Moderate - Timing of incoming weather systems is uncertain

Weather Forecast

SUNDAY NIGHT: Increasing cloud overnight, 15-30 km/h west wind, alpine temperatures drop to -2 C.MONDAY: Snow starting midday and rapidly accumulating in the afternoon, with 15-20 cm by the evening, 30-50 km/h southwest wind, treeline temperatures near -1 C, freezing level 700 m.TUESDAY: Snow continues in the morning and eases off in the afternoon, total accumulation of 30-45 cm over the course of the storm, 20-30 km/h northwest wind, treeline temperatures near 0 C, freezing level 900 m.WEDNESDAY: Mix of sun and cloud, light northwest wind, treeline temperatures near 0 C, freezing level 900 m.

Avalanche Summary

Recent avalanche activity has been limited to small slab and loose avalanches in the top 20 cm of snow (size 1). Check recent MIN reports for some examples here and here. Looking ahead, the most likely problem will be storm slabs that form with the incoming storm, however the lingering persistent weak layer in the North Shore Mountains still poses a low likelihood - high consequence problem.

Snowpack Summary

Fresh snow will start to accumulate on Monday. Strong southwest wind will likely form drifts and slabs in exposed terrain. The new snow is falling on a sun crust on steep southerly slopes, and possibly on weak surface hoar crystals on sheltered and shaded slopes.A layer of weak and sugary faceted grains sits on a melt-freeze crust about 50 to 120 cm deep. The layer is likely most prominent in the North Shore Mountains and on north aspects. This layer continues to be reactive in snowpack tests. The problem is not typical for the region and we expect this persistent weak layer to continue to linger.The lower snowpack is generally strong.

Problems

Storm Slabs

Reactive slabs could form as early as Monday evening as a strong windy storm is poised to hit the South Coast region.

Minimize exposure during periods of heavy loading from new snow and wind.Use caution on open slopes and convex rolls Use caution above cliffs and terrain traps where small avalanches may have severe consequences.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 1.5

Persistent Slabs

A weak layer is buried 50 to 120 cm deep in the North Shore Mountains. The layer consists of weak faceted grains above a crust. This layer could become more reactive with the additional load of the new snow.

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

Aspects: All aspects.

Elevations: Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Mar 11th, 2019 2:00PM