Avalanche Forecast

Issued: Mar 19th, 2014 9:34AM

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

jlammers, Avalanche Canada

South Rockies.

Watch the temperature and solar warming! Heat and cornices are two great ways to shake-up the snowpack over the next couple of days

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

Wednesday night and Thursday: 10-20cm of snow / Moderate west-northwesterly winds / Freezing level at 1000mFriday: Light snowfall / Light to moderate northwest winds / Freezing level at surfaceSaturday: Mix of sun and cloud / Light northwesterly winds / Freezing level at surface

Avalanche Summary

In recent days avalanche observations have been very limited. I expect more storm/wind slab activity in response to weather forecast for Wednesday evening.

Snowpack Summary

Up to 55cm of recent storm snow has been redistributed by strong winds into deeper deposits in lee terrain. Recent snowpack tests suggest there are still likely weaknesses near the base of the storm snow. The recent accumulations overlie hard rain crusts which exist on all aspects below 2000m and on solar aspects in the alpine. North of Sparwood and in the Crow's Nest Pass area the buried crust seems more specific to previously sun-exposed slopes. Below 1700m rain over the weekend saturated the snowpack, and old surfaces may now exist as a hard refrozen crust where temperatures have dipped below freezing.The deep facet/crust persistent weakness buried at the beginning of February, now down up to 150cm, is still producing sudden results in snowpack tests. I would be very leery of any slopes that have not already avalanched as any activity at this interface would be large and destructive. Likely triggers include a large cornice fall, a large input in a thin snowpack area or solar warming.Cornices have also become large and unstable.

Problems

Cornices

Cornices in the region are now large and fragile. A cornice fall could be destructive by itself, and could also trigger a large avalanche on the slope below.

Give cornices a wide berth when travelling on or below ridges.>Extra caution needed around cornices with current conditions.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 4

Storm Slabs

New snow and wind forecast for Wednesday night will add to an existing storm slab. Watch for triggering in wind exposed terrain.

Choose conservative lines and watch for clues of instability.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Deep Persistent Slabs

In some areas the deeply buried weak layers that formed in early February are still showing reactivity in snowpack tests. Possible triggers at this point include a large cornice fall, a large force in a thin snowpack area or solar warming.

Consider the consequences of the terrain if an avalanche steps down to a persistent weakness.>Caution around convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 20th, 2014 2:00PM