Avalanche Forecast

Issued: May 1st, 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, Wind Slabs and Deep Persistent Slabs.

ian jackson, Parks Canada

Banff Yoho Kootenay.

Get up early and take advantage of the last good freeze for a while. Watch for cornices as they tend to fall off on hot days!

Summary

Weather Forecast

Mixed sun and cloud with some convective flurries are forecast for Tuesday. Freezing levels will be around 2100 m on Tuesday, rising significantly to 3000m by Wednesday as an upper ridge moves into the region from the west. Wednesday overnight there will be no freeze and Thursday looks to be warm and sunny with freezing levels to 3600m.

Snowpack Summary

Variable wind slabs exist on high north aspects. There is moist surface snow and variety of melt freeze crusts in the upper snow pack in all areas 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 but may wake up with solar warming.

Avalanche Summary

Minimal observations today, but suspect some loose wet out of steep solar. Yesterday's wind event triggered numerous loose dry on high north aspects while the warm temperatures triggered loose wet on solar. A few large avalanches failed on the basal layers with either cornice or solar triggers.

Confidence

Problems

Loose Wet

Loose wet avalanches can be expected on solar aspects in the afternoon when the day warms up.

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, South.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Wind Slabs

Recent winds have created soft wind slabs on north aspects in the alpine.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: North, North East.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

The weak basal facets can produce large avalanches with large triggers or heat. Remember that the snowpack is generally strongest in the morning when it is cool.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Valid until: May 2nd, 2017 4:00PM