Avalanche Forecast

Issued: Jan 17th, 2015 7:53AM

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

jlammers, Avalanche Canada

Cariboos.

A storm on Sunday will increase the Avalanche Danger. Conservative terrain selection will become increasingly important.

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain on Sunday

Weather Forecast

A moist pacific frontal system will cross the region on Sunday bringing moderate to locally heavy amounts of snow. Weather models are in high disagreement with forecast snowfall amounts ranging from 15cm to 30cm falling between Sunday morning and Sunday night. Unsettled conditions with light flurries are expected on Monday before a dry ridge of high pressure builds on Tuesday. Winds are expected to be strong from the southwest on Sunday, dropping to light and westerly on Monday and Tuesday. Freezing levels will peak at about 1100m on Sunday and Monday, and then drop to surface on Tuesday.

Avalanche Summary

Natural and human-triggered wind slab activity to size 1.5 was observed in response to new snow and wind on Friday night. With more snow and wind forecast for Sunday, I would expect the developing storm slab to increase in size and reactivity. An avalanche in motion may also "step down" to a deeper, more destructive weak layer which was buried in mid-December.

Snowpack Summary

Up to 25cm of new snow fell on Friday night. The new snow, which has been distributed into deeper deposits in higher wind-exposed terrain, overlies widespread 5-15mm surface hoar, a sun crust on steep sun exposed slopes, and/or wind affected surfaces in the alpine. More snow and wind forecast for Sunday will add to the size and reactivity of this developing storm slab. The problematic mid-December surface hoar/crust layer is typically down 50-80cm below the surface and remains sensitive to human triggering is some areas. The reactivity of this persistent weak layer appears to be quite variable but still has the potential for large, destructive avalanches in some areas. The layer appears to be the most reactive at and below treeline.

Problems

Storm Slabs

New snow and wind on Sunday will add size and reactivity to a developing storm slab. The new snow is expected to be especially reactive due to underlying weak crystals.

Be cautious as you transition into wind affected terrain.>The new snow will require several days to settle and stabilize.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

New snow and wind may spark renewed activity on weak crystals buried in mid-December. Although less likely, avalanches at this interface would likely be destructive in nature.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Use conservative route selection, stick to moderate angled terrain with low consequence.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Jan 18th, 2015 2:00PM