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Avalanche Canada swerner, Avalanche Canada

Sea to Sky Avalanche Forecast

Apr 24th, 2019 4:01PM

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

Wind slabs at higher elevations may be reactive to human triggers especially where a winter-like snowpack still exists.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

THURSDAY: Mainly cloudy with light precipitation. Alpine temperatures near 3 and freezing levels 2100 m. Ridgetop winds moderate from the southwest.

FRIDAY: Mix of sun and cloud with isolated flurries. Alpine temperatures near -3 and freezing levels 1700 m. Ridgetop wind moderate from the West.

SATURDAY: Cloudy with sunny periods. Alpine temperatures near -6 and freezing levels 1700 m. Ridgetop wind moderate to strong from the West.

Avalanche Summary

No recent avalanche observations have been reported. On Monday, reports indicated that isolated pockets of moist snow produced small loose wet avalanches with daytime warming.

Last Saturday, a significant avalanche cycle occurred after the storm around the Whistler Backcountry. A natural wet loose avalanche cycle to size 2 was observed on all aspects from 1900-2200m. Wet slab avalanches to size 3 were observed on loaded northerly features in the alpine. Natural cornices failures to size 2 were also observed and explosives control work triggered cornices size 2-2.5. Further south in the region, cornices failing naturally triggered large (up to size 3) slab avalanches on the slopes below.

Snowpack Summary

In the alpine, up to 10 cm cold wind-affected snow is holding onto northerly aspects. Southerly winds have produced isolated wind slabs around ridges and in the immediate lee of slopes in the alpine. Cornices have been failing recently.

A crust is found on solar alpine slopes and all aspects below. Warm overnight temperatures are preventing strong crust recovery as you lose elevation. Expect thin surface crusts to break down quickly with daytime warming and rain. Below treeline the snowpack is saturated and rapidly melting.

Problems

Wind Slabs

South-southwesterly winds have produced isolated pockets of wind slab around ridges and in the immediate lee of slopes. Cornices may be touchy, give them plenty of space.

  • Be careful with wind-loaded pockets, especially near ridge crests.
  • Cornices may be touchy and could trigger wind slabs on slopes below.

Aspects:

North, North East, East.

Elevations:

Alpine.

Likelihood

Possible

Expected Size

1 - 1.5

Loose Wet

The likelihood of loose wet avalanches will depend on the extent of overnight crust recovery and the pace at which the warms and rains through the day.

  • Avoid terrain traps such as cliffs and gullies that increase the consequence of small avalanches.

Aspects:

East, South East, South, South West, West.

Elevations:

Alpine, Treeline.

Likelihood

Possible - Unlikely

Expected Size

1 - 1.5

Valid until: Apr 25th, 2019 2:00PM