Avalanche Forecast

Issued: Apr 3rd, 2018 4:51PM

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.

cgarritty, Avalanche Canada

Cariboos.

Lingering problems are maintaining heightened avalanche conditions. Persistent slabs still need to be managed with conservative terrain selection.

Summary

Confidence

High -

Weather Forecast

Tuesday night: Flurries bringing a trace to 5 cm of new snow. Moderate to strong southwest winds.Wednesday: Mainly cloudy with isolated flurries and a trace of new snow. Light to moderate southwest winds. Freezing level to 900 metres with alpine high temperatures around - 11.Thursday: A mix of sun and cloud. Light northeast winds. Freezing level at valley bottom with alpine high temperatures around -12.Friday: Mainly cloudy with isolated flurries and a trace of new snow. Light southeast winds. Freezing level to around 1300 metres with alpine high temperatures of - 4.

Avalanche Summary

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.Reports from Sunday included several large (size 2) recent natural persistent slab releases. These were noted on south aspects from 2000 to 2300 metres, with failure planes at the late-march layer mentioned in our snowpack discussion.Reports from last week showed evidence of a natural avalanche cycle during and following the storm, with storm slabs in the size 2-3 range reported on all aspects between 1700 and 2500 m. South aspects were the most reactive with numerous large and very large (size 2.5-3.5) avalanches running on the buried sun crust.

Snowpack Summary

Last week's storms brought totals of 60-100 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 and stubborn and newer, more reactive wind slabs can now likely 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 4th, 2018 2:00PM