Avalanche Forecast

Issued: Apr 29th, 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.

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

Good ski conditions continue. Watch for the quality of overnight freeze on your tour, and be off sun affected slopes early. Triggering of the deep persistent layer is currently going to be from a heavy load (cornice) or with high solar input. SH

Summary

Weather Forecast

5-10cm overnight along the divide and only a few cm to the East with mainly cloudy skies for the first part of Sunday. A mix of sun and cloud for the afternoon.

Snowpack Summary

30-50cm of settled snow from this past week. There are a variety of melt freeze crusts in the upper snow pack on all aspects and elevations except for due north above 2300 m. A basal weakness remains at the bottom of the snow pack. It is currently only reactive to large triggers like cornices but may wake up with solar warming.

Avalanche Summary

No new avalanches observed Saturday.

Confidence

Problems

Loose Wet

Clearing skies Sunday afternoon will moisten the new snow on solar aspects increasing the likelihood of loose wet avalanches.

If triggered the loose wet sluffs may step down to deeper layers resulting in large avalanches.Pay attention to sluffing off cliffs and steep solar terrain, signs of a warming snowpack.

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

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Cornices

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

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

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Deep Persistent Slabs

The weak basal facets can produce large avalanches with large triggers or heat. Remember that the snowpack is generally strongest when it is cool and 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: North, North East, East, South East.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Apr 30th, 2017 4:00PM