Avalanche Forecast

Issued: Apr 23rd, 2017 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, Cornices and Deep Persistent Slabs.

aaron beardmore, Parks Canada

Banff Yoho Kootenay.

The impact from solar radiation will be significant tomorrow. Start early, and finish early.

Summary

Weather Forecast

Clear skies and the potential for intense solar radiation are forecasted on Monday. By Monday evening expect a small system to move through the forecast region with up to 15mm of precip. Wind will remain light with variable direction for the next 3 days. Freezing levels will rise to almost 2000m in the hottest parts of the day.

Snowpack Summary

The snowpack is totally dependent on aspect and elevation now. At treeline and above, melt freeze crusts exist to ridge top on solar aspects, while on north aspects, dry surface snow still exists above ~2400m. Below treeline the snowpack becomes wet during the day and is becoming isothermal. The weak basal facets remain present in alpine areas.

Avalanche Summary

Forecasters received a report of a party of 2 being involved with a size 2 avalanche that was cornice triggered. Both party members were caught and partially buried. They self rescued with minor injuries. A couloir in the Boom Lake area is the best we have for location, aspect elevation etc.

Confidence

Problems

Loose Wet

A limited overnight freeze on Sunday night will create loose wet problems at lower elevations and on S and W facing terrain at higher elevations. Travel early to manage this problem.

Pay attention to sluffing off cliffs and steep solar terrain, signs of a warming snowpack.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Cornices

Cornices continue to fail. Minimize your time underneath these and remember that a cornice failure could also trigger the deep persistent slab on the basal facets.

Cornices become weak with daytime heating, so travel early on exposed slopes.Give cornices a wide berth when travelling on or below ridges.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

The snowpack is gaining strength, but the weak basal facets continue to produce sudden collapse results and can produce large avalanches with large triggers or heat. Stick to planar, supported slopes with a deeper snowpack when entering steep terrain

Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Apr 24th, 2017 4:00PM