Date issued

Apr 20, 2018 - 4:00 PM

Valid until

Apr 21, 2018 - 4:00 PM

Prepared by

stephen holeczi

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.

Regular season
Saturday - April 21, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Below Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Sunday - April 22, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Below Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Monday - April 23, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Below Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Avalanche Problem 1: Wind Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

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.

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

Avalanche Problem 2: Loose Wet

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

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.

Travel and Terrain Advice
  • Use extra caution on slopes if the snow is moist or wet.

Avalanche Problem 3: Persistent Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

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

Travel and Terrain Advice
  • Avoid shallow snowpack areas where triggering is more likely.

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.

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.

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.

Danger Ratings Explained

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Natural avalanches possible; human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

4 - High

Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Natural avalanches likely; human-triggered avalanches very likely.

Large avalanches in many areas; or very large avalanches in specific areas.

5 - Extreme

Avoid all avalanche terrain.

Natural and human-triggered avalanches certain.

Large to very large avalanches in many areas.

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