Avalanche Forecast

Issued: Apr 25th, 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.

snow safety, Parks Canada

Little Yoho.

Avalanche control will take place on Mts Hector, Bosworth, and Stephen. Overnight recoveries are not expected to be sufficient in many or most locations. Avoid early moist snow, isothermal pockets, sunny locations, and overhead hazard.

Summary

Weather Forecast

Thursday and Friday look to be warm with ~ 3500m freezing levels, light winds and weak overnight freezes.

Snowpack Summary

Isolated wind slabs are present in the alpine. 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 near valley bottom.

Avalanche Summary

Ongoing wet snow avalanches are occurring in the afternoons. These vary by aspect and elevation but can get larger as they slop into low elevation isothermal pockets.

Confidence

Problems

Loose Wet

Loose wet avalanches are expected to be common over the next couple of days until overnight freezes return. Be aware of sun, early soft snow, and the slopes above you. Even small wet avalanches hurt.

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

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.

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.

Likelihood

Possible

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 in a few places in the last couple days.

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

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

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Apr 26th, 2018 4:00PM