Avalanche Forecast

Issued: Mar 29th, 2016 8:30AM

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

rbuhler, Avalanche Canada

Sea To Sky.

Substantial warming and sun on Wednesday afternoon will destabilize the upper snowpack. Extra caution is required around and below cornices, and on steep sun exposed slopes. Check out this new video on warming: https://vimeo.com/160805040

Summary

Confidence

Moderate

Weather Forecast

A ridge of high pressure dominates for the rest of the week. Sunny and dry conditions are expected for Wednesday through Friday. Freezing levels are expected to be above 3000m each afternoon, with cooling overnight. Light outflow winds are expected in the alpine for the forecast period.

Avalanche Summary

On Monday, several size 1 skier triggered avalanches were reported. These were reported as the recent storm snow sliding over a melt-freeze crust. Natural sluffing was reported from solar aspects as well as one size 2 cornice release. On Sunday, a natural size 1 storm slab was reported from a north aspect 40 degree slope at 2000m elevation. Skiers were triggering size 1 soft slabs in wind loaded northeast aspect slopes at 1900-2000m. Explosives triggered storm slabs up to size 2. We have now entered a period with daily melt-freeze conditions and the main concern for Wednesday will be during the heat of the afternoon. Cornices will become weak and could fail naturally.Â Loose wet sluffing is expected from steep sun exposed slopes.

Snowpack Summary

Up to 15cm of new snow accumulated over the weekend in sheltered areas. Over the weekend, southerly winds were loading north aspect leeward slopes. However, outflow winds on Monday are reported to be loading south aspects in the alpine while exposed north aspect slopes are being wind pressed and scoured. Large cornices are lingering and are expected to become very weak this week. Below the surface problems, the mid snowpack is generally well-settled throughout with no notable persistent weaknesses. On Monday, a sun crust is expected to have formed on south aspects. Melt-freeze conditions are expected to be widespread this week with very high freezing levels.

Problems

Cornices

Large cornices are expected to get weak with warming and sun exposure, and natural cornice releases are possible in the afternoon. They can be destructive by themselves, and may also become the trigger for a slab avalanche on the slope below.

Give cornices a wide berth when traveling on or below ridges. >Cornices become weak with daytime heating, so travel early on exposed slopes. >Extra caution needed around cornices with current conditions. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Loose Wet

Loose wet sluffing is expected on sun exposed slopes during the heat of the afternoon. Very high freezing levels may increase the size and run length of natural sluffing.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet. >Start and finish early before the surface crusts melt. >

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Mar 30th, 2016 2:00PM