Avalanche Forecast

South Rockies

Date issued

Mar 24, 2018 - 4:19 PM

Valid until

Mar 25, 2018 - 2:00 PM

Prepared by

swerner

New snow and strong westerly winds are building thicker and reactive wind slabs on leeward aspects. If the sun pokes out it may initiate a natural avalanche cycle win the recent storm snow.

Regular season
Sunday - March 25, 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 - March 26, 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

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.

Below Treeline

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.

Tuesday - March 27, 2018
Alpine

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.

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.

Below Treeline

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.

Avalanche Problem 1: Wind Slabs

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

Changing winds from East to West continue to be strong, redistributing the new storm snow onto most aspects. Wind slabs will likely be reactive to skier/rider triggers. Loose dry avalanches may occur from steeper terrain features.

Travel and Terrain Advice
  • Watch for signs of instability such as whumpfing, or cracking.
  • Use caution in lee areas in the alpine and tree line.
  • Avoid large slopes with thin-thick snow coverage and convex features.

Avalanche Summary

With 20 cm of new snow overnight and a bunch of wind I suspect there may have been a widespread natural storm, wind slab and loose dry avalanche cycle on Saturday.
Periods of sunshine forecast for Sunday could trigger a round of natural slab avalanches and loose dry/wet avalanches.

Snowpack Summary

Up to 35 cm of new snow, accompanied by strong easterly winds in the beginning of the storm and now switching to the southwest are forming wind slabs on a variety of aspects. Forecast snow for Saturday will add to these totals and may initially have a poor bond to the underlying old snow surfaces which consist of crusts up to 2100 m and dry snow or surface hoar on north aspects above 2100 m. Snowpack testing on the March 15th surface hoar interface (down 20-40 cm on sheltered North aspects) has shown no significant results in the Barnes area. The mid-pack is is well consolidated.

Deeper in the snowpack (50-80 cm down) a surface hoar buried mid-February may exist. This interface is dormant.

Digging towards the bottom of the snowpack you'll find a combination of crusts and facets that are reportedly widespread.

Weather Forecast

Sunday: Mix of sun and cloud with snow amounts 2-5 cm. Ridgetop wind strong from the West. Alpine temperatures near -7 and freezing levels 900 m.

Monday: Mostly cloudy and snow 2-5 cm. Ridgetop winds strong from the southwest. Alpine temperatures near -2 and freezing levels 1200 m.

Tuesday: A mix of sun and cloud Ridgetop winds strong-extreme from the West. Freezing levels 1000 m.

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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