Avalanche Forecast

Issued: Apr 20th, 2018 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Wind Slabs, Loose Wet and Persistent Slabs.

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

Expect a poor freeze below 2300m Saturday and increased PM danger if the sun pops out. We will be switching to "spring conditions" over the next couple of days. The coming week looks to be a warm one.

Summary

Weather Forecast

10cm along the divide and only a few cm (maybe some light rain) along the eastern slopes expected Saturday. A poor lower elevation freeze can be expected, temps will start to cool as a cold front moves through mid day. Upper elevation SW winds will increase through the day. Next week looks like a dramatic warming trend.

Snowpack Summary

Up to 50 cm of storm snow near the divide affected by strong SW winds Tuesday evening. Several buried temperature crusts exist to 2000m on all aspects and to ridge tops on solar slopes, including the Mar 15 sun crust down 35-50 cm in the alpine. Moist snow at lower elevations, with the entire snowpack becoming moist near valley bottom.

Avalanche Summary

Avalanche control yesterday produced mainly windlslabs in the sz 2 range 20-50cm deep with decent propagations up to 50m wide. Several of these events entrained more mass as they moist snow at lower elevations. During flights, evidence of a natural cycle to sz 3 could be seen in the Banff region mainly Ne facing windslabs from the last 48 hours.

Confidence

Freezing levels are uncertain on Saturday

Problems

Wind Slabs

20-50 cm of storm snow has fallen over the past few days which had intense wind loading earlier in the week. These previous wind slabs are losing sensitivity, but some new snow and strong winds on Saturday will add to this problem in the short term.

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

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Loose Wet

Sun wont be a major issue for most of the day Saturday, but watch for some clearing skies later in the afternoon, especially in the front ranges. With a poor freeze lower elevations could also be a concern if we receive some rain.

Use extra caution on slopes if the snow is moist or wet.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

A few avalanches in the last two days were much deeper than the majority. Some of these clearly stepped down to the March 15 crust and on shaded aspects were likely sliding on facets associated with the same burial date

Avoid shallow snowpack areas where triggering is more likely.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 3

Valid until: Apr 21st, 2018 4:00PM