Avalanche Forecast

Issued: Dec 8th, 2014 8:24AM

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.

rbuhler, Avalanche Canada

Cariboos.

The storm is expected to bring strong winds and rapidly rising freezing levels. Expect avalanche danger to increase as the storm develops. If you see more than 25cm of new snow tomorrow, expect your local avalanche danger to be HIGH.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The storm system is expected to bring around 15mm of precipitation to the south of the Cariboos region on Tuesday and 5-10mm to the north of the region. Winds are expected to be strong from the SW and freezing levels will climb as high as 2000m by Tuesday afternoon. On Wednesday and Thursday, freezing levels should remain around 2000m and winds will remain moderate or strong in the alpine. There is currently some uncertainty regarding precipitation amounts for Wednesday and Thursday with models currently showing another 10-30mm.

Avalanche Summary

The storm snow is reactive to ski cutting and is producing isolated avalanches up to size 1. I expect wind loaded areas in the alpine to be the main concern at the moment but this will become more widespread as the storm progresses.

Snowpack Summary

Around 15-30cm of new snow sits on a weak layer of surface hoar. Reports from the region suggest that anywhere from 50-150 cm of settling snow overlies one or more weak layers which formed during November. Snowpack tests suggest that these weak layers are getting harder to trigger but still have the potential to produce large avalanches if triggered. Recent wind has created wind slabs in lee features in exposed alpine terrain.

Problems

Storm Slabs

We are at the early stages of a storm slab problem. Wind loaded features are the main concern at the moment. As we add warming and new precipitation to the equation, this problem is expected to become more widespread.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Minimize overhead exposure; avalanches triggered by windloading may reach run out zones.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

Likelihood of triggering a deep weak layer is expected to increase with new storm loading and warming. Any slopes that did not avalanche during the last storm cycle should still be considered potentially hazardous.

Avoid common trigger zones including thin snowpack areas, near rocky outcrops, and steep alpine slopes.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Dec 9th, 2014 2:00PM