Avalanche Forecast

Issued: Jan 7th, 2015 8:53AM

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

rbuhler, Avalanche Canada

Sea To Sky.

Avalanche conditions are improving quickly but problems still exist. Use extra caution on steep south facing slopes when the sun is out.

Summary

Confidence

Fair

Weather Forecast

A strong warm ridge of high pressure is the dominate feature for Thursday. Mostly sunny conditions are expected with alpine winds remaining light. Freezing levels may reach as high as 3500m with the warmest layer of air sitting around 2000m (+5 deg C or warmer). Conditions are expected to change on Friday. The warm air will break down and freezing levels should fall to around 1000m by the end of the day. Alpine winds are expected to be moderate from the SW and it will be mainly cloudy. Between Friday afternoon and Saturday morning, 3-6mm of precipitation is expected. Saturday is forecast to be cloudy and mostly dry. Freezing levels should remain around 1000m and alpine winds should be light.

Avalanche Summary

No new slab avalanches were observed on Wednesday but a couple size 1 loose wet sluffs were ski cut.Â Reports from Tuesday of natural and explosive triggered slab avalanches up to size 2.5 on leeward slopes. Loose activity was also reported on steep solar aspects. Natural avalanches are not expected on Thursday expect possibly loose wet sluffing from steep terrain features.Â Ski triggering is unlikely in areas that are capped with a supportive surface crust.

Snowpack Summary

Rain and warm air melted the snow surface at most elevations and cooling Tuesday overnight refroze the surface creating a supportive crust. Reports are suggesting the upper 30-40cm of the recent storm snow is/was moist or wet. Below this is dry storm snow that is less dense creating upside-down conditions but this is expected to settle out quickly with continued warm temperatures. The total storm slab is around 50-70cm thick and sits on a previously variable snow surface that included wind affected surfaces, a freezing rain crust or sun crust, and/or surface hoar or sugary facets in sheltered terrain. The bond between the storm slab and the layer below is reported to be gaining strength but may still be touchy in isolated areas. In the middle and lower snowpack we might find the mid-December surface hoar or crust/facet weak layers. These are now typically buried 1m or more. The old surface hoar layer may be found in sheltered shady areas at and below treeline, while the crust/facet layer is expected to be more widespread but also more variable.

Problems

Storm Slabs

Triggering storm slabs in not likely in areas that are capped with a surface crust. Caution is still required in drier areas or where the crust is breakable.

Minimize exposure to sun exposed slopes when the solar radiation is strong.>Avoid steep, open slopes with convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Loose Wet

If the snow surface is moist or wet, sluffing is expected from steep terrain features. Use extra caution on or below sunny slopes. A wet sluff has the potential to trigger a larger slab avalanche.

Be cautious of sluffing in steep terrain.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

Persistent weak layers down over 1m remain a concern. A smaller avalanche may step down to one of these layers or a heavy trigger like a cornice fall may be able to trigger one of these layers.

Avoid steep slopes below cornices.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely

Expected Size

3 - 6

Valid until: Jan 8th, 2015 2:00PM