Avalanche Forecast

Issued: Feb 15th, 2019 4:48PM

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

Avalanche Canada shorton, Avalanche Canada

Human-triggered avalanches are likely this weekend as the new snow continues to be very reactive. Stick to simple well-supported terrain.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

A low pressure system will linger over the southeast corner of the province until Sunday morning, which will bring steady low density snowfall to the region. Exact amounts are uncertain.FRIDAY NIGHT: Light flurries with 5-10 cm of low density snow, moderate west wind, alpine temperatures drop to -10 C.SATURDAY: Light flurries continue with another 5-10 cm of low density snow, moderate west wind, alpine high temperatures around -8 C.SUNDAY: Scattered flurries in the morning then clearing in the afternoon, light wind, alpine high temperatures around -12 C.MONDAY: Mix of sun and cloud, light north wind, alpine high temperatures around -14 C.

Avalanche Summary

Slab avalanche activity has been reported daily since Tuesday's storm, and is expected to continue into the weekend with the ongoing snowfall.Preliminary reports from Friday, include numerous large (size 2-2.5) explosive triggered storm slabs on south aspects.On Thursday, strong wind formed fresh wind slabs that produced several size 1-2 natural avalanches. The wind slabs were very reactive to human triggering on all aspects. Two large (size 2) skier-triggered slab avalanches were reported at treeline elevations with crowns up to 80 cm thick. Numerous smaller (size 1) skier-triggered wind slabs were also reported, including some triggered from a distance (remotely).

Snowpack Summary

A total of 30 to 50 cm of fresh snow has fallen over the past few days and has been very reactive to human triggering. A strong wind event on Thursday formed fresh wind slabs in exposed terrain (see this MIN report), while low density snow may still be found in sheltered areas. The new sits on a variety of old surfaces that include a sun crust on southerly aspects, variable wind-affected snow, and weak feathery surface hoar crystals at and below treeline. The snowpack hosts two buried surface hoar layers. The February 1st surface hoar is down 40 to 60 cm and has been recently reactive to human triggers. The mid-January surface hoar is 60 to 100 cm below the surface. This deeper layer of surface hoar is most prevalent below treeline on shady aspects, but it does not seem to be a widespread problem in the region. Below that, the snowpack is well settled.

Problems

Wind Slabs

An icon showing Wind Slabs
Strong wind has blown recent snow into touchy slabs on all elevations and aspects. The problem is further complicated by buried surface hoar in the trees.
Keep your guard up, wind slabs have been recently reactive at ALL elevations.Back off if you encounter whumpfing, hollow sounds, shooting cracks or recent avalanches.Choose simple, low-angle, well-supported terrain without convexities.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
Two buried surface hoar layers are in the upper meter of the snowpack; one is down 40 to 60 cm and has been recently active, the other is down 60 to 80 cm. These layers are at a time of enhanced sensitivity as they adjust to the new load.
If triggered, storm slabs in-motion may step down to deeper layers resulting in large avalanches.Caution around sheltered open areas at treeline and below including cutblocks, gulleys, and glades.Surface hoar distribution is highly variable. Avoid generalizing your observations.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Feb 16th, 2019 2:00PM