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Archived

Avalanche Forecast

Apr 24th, 2018–Apr 25th, 2018
Alpine
Below Threshold
The avalanche danger rating in the alpine will be below threshold
Treeline
Below Threshold
The avalanche danger rating at treeline will be below threshold
Below Treeline
Below Threshold
The avalanche danger rating below treeline will be below threshold
Alpine
Below Threshold
The avalanche danger rating in the alpine will be below threshold
Treeline
Below Threshold
The avalanche danger rating at treeline will be below threshold
Below Treeline
Below Threshold
The avalanche danger rating below treeline will be below threshold
Alpine
Below Threshold
The avalanche danger rating in the alpine will be below threshold
Treeline
Below Threshold
The avalanche danger rating at treeline will be below threshold
Below Treeline
Below Threshold
The avalanche danger rating below treeline will be below threshold

Regions: Little Yoho.

Warm temperatures are here. Wednesday should be reasonable, but Thursday and Friday look to be very warm. If you are out in the mountains, start and finish your day early.

Weather Forecast

Expect a weak freeze Tuesday night (1500m freezing levels) and a warm day on Wednesday (2500m freezing levels). Thursday and Friday look to be warm with ~ 3700m 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

Avalanche control today produced mixed results with no results in higher elevation wind exposed areas and large isothermal loose wet avalanches in sheltered lower elevation areas. A skier triggered size 2.5 persistent slab avalanche occurred on Mt Fairview late in the day Sunday. We have also seen numerous cornice triggered slabs to size 3.

Confidence

Avalanche Problems

Loose Wet

Loose wet avalanches are starting by mid morning on steep East facing terrain. This pattern will continue for the next while as temperatures increase. Plan your day to be off steep solar aspects early and watch for sun effect on the slopes above you.
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: North, North East, East, South East.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 2

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: 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.
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