Avalanche Forecast

Issued: Apr 26th, 2018 4:00PM

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, Persistent Slabs and Cornices.

stephen holeczi, Parks Canada

Little Yoho.

Really warm days ahead. The typical spring statement is still the best; start and end early!

Summary

Weather Forecast

Continued warm temperatures with freezing levels up to 3500m for both Friday and Saturday. Temperatures have been slightly inverted with better freezes at valley bottom as long as skies are clear overnight, but temperatures will stay above freezing in the alpine. Mainly light winds through the next 2 days with potential for precipitation on Sunday.

Snowpack Summary

Crust or moist snow on all solar aspects depending on temperatures. Buried temperature crusts to 2000m on all aspects and to ridge top on solar slopes, including the Mar 15 crust down 40-70 cm in the alpine. Moist snow at lower elevations, with the entire snowpack becoming moist below treeline in the afternoons.

Avalanche Summary

Ongoing wet snow avalanches typical for this time of year are occurring as the day warms up. These vary by aspect and elevation but can travel far as they entrain isothermal snow.

Confidence

Problems

Loose Wet

Loose wet avalanches are expected to be common over the next couple of days as it warms up. Starting and ending very early are the best defense. Even small wet slides are very powerful and destructive.

Use extra caution on slopes if the snow is moist or wet.Watch for clues, like sluffing off of cliffs, that the snowpack is warming up.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2.5

Persistent Slabs

A few deeper avalanches have occurred in the last few days. Some stepped down to the March 15 crust. On shaded aspects these were likely sliding on facets formed at the same interface. This will wake up again with intense heating or large triggers.

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

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 2.5

Cornices

Cornice failures are occurring on a regular basis now with warm temperatures and intense solar inputs. These large triggers have caused failures on the persistent weak layers deeper in the snow pack over the last couple days.

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

Likely

Expected Size

1 - 3

Valid until: Apr 27th, 2018 4:00PM