Avalanche Forecast

Issued: Apr 29th, 2018 4:27PM

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

conrad janzen, Parks Canada

Little Yoho.

This is our last regularly scheduled avalanche bulletin. We will update this as needed during the next few weeks. Refer to our weather stations for current temperatures and precipitation amounts to help plan your trips. Enjoy the spring skiing!

Summary

Weather Forecast

The forecast for April 30th and into the first few days of May is for cloudy days with snow flurries at higher elevations and rain showers at lower elevations. Temperatures will be cooler during the day but over night freezes may be fairly minimal due to the cloud cover, except at high elevations. Freezing levels between 2000-2400 m are expected.

Snowpack Summary

5-10cm of new snow in the alpine on April 29th. Crust or moist snow on all solar aspects depending on temperatures. Buried temperature crusts to 2600m on all aspects and to ridge top on solar slopes. Moist snow at lower elevations, with the entire snowpack becoming isothermal near valley bottom.

Avalanche Summary

We have seen regular loose wet and wet slab avalanches up to size 3 running on all aspects in the afternoon and early evening during the warmest times of the day. Cornice failures have also been fairly regular, occasionally triggering slabs on the slopes below.

Confidence

Problems

Loose Wet

Warm temperatures or rain will rapidly increase the likelihood of loose wet avalanches at all elevations. Pay close attention to the integrity of surface crusts and avoid traveling in avalanche terrain once the crusts have broken down.

Travel early before the heat of the day, and avoid big slopes in the afternoon.Use extra caution on slopes if the snow is moist or wet.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Wet Slabs

New snow, intense heating or large triggers could cause wet slabs in steep terrain, possibly stepping down to deeper weak layers in the snow pack. Avoid exposure to steep slopes if the snow is becoming moist or wet.

Avoid shallow snowpack areas where triggering is more likely.Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Cornices

Cornice failures are occurring on a regular basis with warm temperatures, new loading or intense solar inputs. In some places these large triggers have also caused failures on the deeper weak layers in the snow pack pulling out larger slabs.

Cornices become weak with daytime heating, so travel early on exposed slopes.Minimize exposure to overhead hazard from cornices.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Apr 30th, 2018 4:27PM