Avalanche Forecast

Issued: Apr 28th, 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.

conrad janzen, Parks Canada

Banff Yoho Kootenay.

Saturday could be a great day for spring skiing! Cool temperatures are forecast which should provide good travel on crusts, with 20-30cm of soft snow on N aspects in the alpine. Start early enough to be back down by noon when things start heating up!

Summary

Weather Forecast

A weak ridge is moving in Friday night with forecasts for a good overnight freeze. Saturday should see drier and sunnier conditions with clouds and flurries beginning in the afternoon and 5-10cm of snow overnight into Sunday.

Snowpack Summary

Another 5-10 cm of new snow Thursday night with light winds. 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

Minor sluffing out of steep cliffs and some pin wheeling on steep solar slopes on Friday.

Confidence

Problems

Loose Wet

Clearing skies and sunshine on Saturday morning will rapidly moisten the new snow on solar aspects increasing the likelihood of loose wet avalanches. Start early and be off steep solar aspects by mid-day as the temperature increases.

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

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.

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.

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 29th, 2017 4:00PM