Avalanche Forecast

Issued: Apr 5th, 2018 4:42PM

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

ghelgeson, Avalanche Canada

Cariboos.

We're still managing a midwinter snowpack at and above treeline and the persistent slab problem requires thoughtful terrain selection.

Summary

Confidence

High -

Weather Forecast

The current weather pattern looks more like February than April, but we'll take it! Freezing levels are expected to rise just a bit over the next few days and light daily snowfall should continue through the weekend FRIDAY: Broken cloud cover, freezing level beginning at valley bottom rising to about 800 m, light variable wind, trace of snow possible. SATURDAY: Broken cloud cover, freezing level beginning at valley bottom rising to around 700 m, light variable wind, 1 to 4 cm of snow possible. SUNDAY: Broken cloud cover, freezing level beginning at valley bottom rising to about 1500 m, moderate to strong west wind, 1 to 3 cm of snow possible.

Avalanche Summary

On Wednesday a natural size 3 cornice failure was observed on an unknown aspect, the cornice did not initiate any other avalanche activity. Small loose dry sluffing was also observed on south facing aspects between 1500 and 2100 m suggesting that the cool temperatures are preserving cold snow, even on southerly aspects.Explosives control in the region yielded several persistent slab (size 3) and shallower storm slab (size 1.5) releases on north to northeast aspects in the alpine on Monday. Persistent slabs had 90 cm fracture depths with the shallower storm slabs at 40 cm.

Snowpack Summary

Last week's storms brought 60 to 100 cm of new snow to the region. The snowfall was initially accompanied by strong south winds and then followed by strong north winds, so a mix of old/stubborn and newer, more reactive wind slabs can now be found on a range of aspects at higher elevations. In sheltered areas, this storm snow has been gradually settling into a slab above a persistent weak layer buried in mid-March that consists of crusts at low elevations and on south aspects, and surface hoar on shaded aspects at higher elevations. The structure of storm snow above this layer isn't uniform, however, and recent storm slabs have been observed running on an interface down about 40 cm as well as at the late-March crust. Other persistent weak layers from early January and mid-December are still being reported by local operators, but are generally considered dormant.

Problems

Persistent Slabs

Weak layers of crust and surface hoar from last month are now buried up to 90 cm deep and have shown prolonged reactivity since the last storm. Manage the uncertainty around triggering these layers by sticking to lower angle, supported slopes.

Use caution around sheltered steep or convex slopes where buried surface hoar may be preserved.Choose well supported terrain without convexities.Minimize exposure to steep planar south-facing slopes - especially if they see sunshine.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 3

Wind Slabs

Strong and shifting winds have blown loose snow into wind slabs on a wide range of aspects in wind-affected areas. The most recent strong winds came from the north, so be especially cautious around recently loaded south aspects.

Be especially careful with wind loaded pockets near ridge crests and roll-overs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 6th, 2018 2:00PM