Avalanche Forecast

Issued: Jan 6th, 2018 6:16PM

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

Avalanche Canada mgrist, Avalanche Canada

Expect persistent slab avalanche activity to continue as snow consolidates and loading increases. Adopt a conservative approach in the coming days.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Occasional flurries with minor accumulations through the forecast period.SUNDAY: Cloudy with flurries (5 - 10 cm snow possible) / Light to moderate west wind / Alpine temperature -3 MONDAY: Cloudy with snow overnight, accumulation 3-10cm possible / Light southwest wind / Alpine temperature -3 TUESDAY: Flurries (2-5cm during the day) / Light to moderate southwest wind / Alpine temperature -4

Avalanche Summary

On Saturday, natural and explosives-triggered avalanches to Size 2.5 were reported near Fernie, primarily on north & northeast aspects between 1800m and 2100m elevation. On Thursday there was a report of a skier triggered Size 2 avalanche in Orca bowl involving a group of 11 with 4 people caught and partially buried. See here for details on the MIN. This avalanche occurred on a northeast aspect at 1975m and reportedly running as a windslab sitting on a crust. Additionally, there have been several natural avalanches between 1600m and 1800m on steep or open glades on all aspects. This is where the mid-December layer has been most active.

Snowpack Summary

10cm of new snow by Saturday morning (18mm water equivalent) and warming temperatures has added significant load to the snowpack and increased slab properties above weak layers (see below). A persistent weak layer buried mid-December is 40-70 cm below the surface. This layer can be found in a variety of locations, but most commonly between 1600m and 1800m and consists of crusts on south and west facing slopes and feathery surface hoar in sheltered areas at and below tree line. It has been producing sudden results in recent snowpack tests.At higher elevations, wind has modified the snow pack creating a stiffer snow on top of softer snow condition. The lower snowpack is generally well settled with a thick prominent crust that was buried near the end of November. This crust has generally been reported to be unreactive, however it is possible that it may have been the bed surface for a skier triggered avalanche that happened on Thursday (See Avalanche Activity section above for details).See here for a recent forecaster blog for a summary of the tricky conditions in the snowpack and strategies on how to work around a persistent slab problem.

Problems

Persistent Slabs

An icon showing Persistent Slabs
A weak layer composed of surface hoar and/or crusts is buried 40-70 cm below the surface. This layer continues to be reactive to human traffic. To make matters worse, this layer is seeing more load and warming temperatures.
Watch for whumpfing, hollow sounds, and shooting cracks.Choose supported slopes without convexities at treeline where buried surface hoar may be preservedAvoid exposure to terrain traps where the consequences of a small avalanche could be serious.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Wind Slabs

An icon showing Wind Slabs
Moderate winds have created fresh wind slabs in the alpine.
Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 7th, 2018 2:00PM