[RM]

Avalanche Bulletin - Waterton Lakes National Park

Issued Sat Feb 06, 2016 17:28
Valid Until Tue Feb 09, 2016 17:00
High winds arrived on Friday & Saturday, but brought only a little new snow. Watch for avalanche hazard to increase rapidly with sustained above-freezing temperatures early next week.

        

Danger Ratings: Sunday

alpine treeline below treeline alpine: 3 - Considerable, treeline: 3 - Considerable, below treeline: 1 - Low
alpine: 3 - Considerable
3 - Considerable Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
  • 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.
More...
treeline: 3 - Considerable
3 - Considerable Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
  • 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.
More...
below treeline: 1 - Low
1 - Low Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
  • 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.
More...
Forecast Monday Tuesday
alpine
2 - Moderate 3 - Considerable
treeline 3 - Considerable 4 - High
below treeline 2 - Moderate 3 - Considerable
Confidence: Moderate - Freezing levels are uncertain
High The forecast is based on high-quality information and the nature of the issue makes it possible to render a solid judgement. A 'high confidence' rating does not imply fact or complete certainty however, and such judgements still carry the risk of being wrong.
Moderate The information used to produce the forecast is credibly sourced and plausible, but it is not of adequate quality or sufficiently corroborated to warrant a higher level of confidence.
Low The credibility or plausibility of the information used to produce the forecast is questionable, or the information is too fragmented or poorly corroborated to make solid judgements, or there are significant concerns regarding problems with the sources.

Weather Observations

Past 24 Hr WeatherLittle Prairie 1650m
Maximum (°C)Not Available
Minimum (°C)Not Available
Snowfall (cm)Not Available
Snow Pack (cm)Not Available
Wind speedNot Available
Ridgetop wind directionNot Available
Past 24 Hr WeatherLittle Prairie 1650m
Maximum (°C)Not Available
Minimum (°C)Not Available
Snowfall (cm)Not Available
Snow Pack (cm)Not Available
Wind speedNot Available
Ridgetop wind directionNot Available
Low Moderate Considerable High Extreme
  • 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.
  • 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.
  • 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.
  • 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.
  • Avoid all avalanche terrain.
  • Natural and human-triggered avalanches certain.
  • Large to very large avalanches in many areas.

Problem 1: Wind Slabs

Which Elevation?

Which Elevation? treeline, alpine, below treeline

Which Slopes?

Which Slopes? northwest, north, northeast, east, southeast, south, southwest

Chance of Avalanches?

Chance of Avalanches? possible - likely

Expected Size?

Expected Size? small - large
New snow and extreme Westerly winds have and built Wind Slabs in unusual areas: these may include lower than usual in start zones, and in typically wind-sheltered terrain.

Travel and Terrain Advice

  • Use ridges or ribs to avoid pockets of wind loaded snow.
  • If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Problem 2: Deep Persistent Slabs

Which Elevation?

Which Elevation? treeline, alpine

Which Slopes?

Which Slopes? north, northeast, east, southeast, northwest, west, southwest, south

Chance of Avalanches?

Chance of Avalanches? unlikely - possible

Expected Size?

Expected Size? large - large
Facets sit atop at crust buried around a meter deep. This layer generally requires large triggers, but will increase in sensitivity during periods of warm temperatures. Another persistent weak layer still exists about 50cm deep in isolated areas

Travel and Terrain Advice

  • Use caution on wide-open slopes - these are the most suspect.
  • Carefully evaluate big terrain features by digging and testing on adjacent, safe slopes.

Problem 3: Loose Wet

Which Elevation?

Which Elevation? below treeline, treeline, alpine

Which Slopes?

Which Slopes? west, northeast, east, southeast, south, southwest, northwest, north

Chance of Avalanches?

Chance of Avalanches? possible - likely

Expected Size?

Expected Size? small - large
This problem is expected to develop early next week with warm temperatures. It may exist on all aspects, however solar aspects will be the most suspect.

Travel and Terrain Advice

  • Avoid ice climbs exposed to steep rocky terrain on solar aspects during the middle of the day.
  • Watch for clues, like sluffing off of cliffs, that the snowpack is warming up.

Problem Glossary

Loose Dry:
  • Are usually small, but may gain significant mass on long steep slopes.
  • Are typically limited to steep terrain (40+ degrees).
  • Stabilize soon after a storm, usually within a few days.
Loose dry avalanches are best managed by:
  • Avoiding terrain traps and large steep slopes until the surface has stabilized.
  • On large steep slopes, occasionally move across the fall line to avoid being caught by your own sluffs from above.

Loose Wet:
  • Are more powerful than loose dry avalanches due to their higher density.
  • Are often limited to sunny slope aspects.
  • Are commonly confined to the warmest part of the day.
Loose wet avalanches are best managed by:
  • Avoiding start zones and avalanche paths when the snow becomes moist from daytime heating, from rain, or does not freeze overnight.

Wind Slabs:
  • Vary in size from small to medium.
  • Occur on steeper lee and cross-loaded portions of slopes (typically 35+ degrees).
  • Are often limited to specific terrain features such as lee ridge-tops.
  • Can often be recognized by the appearance of the snow surface, changes in surface snow hardness, hollow, drum-like sounds and/or shooting cracks.
  • Winds that vary in strength and direction can produce complex and unexpected wind slab patterns.
  • Stabilize fairly soon, usually in a few days to a week.
Wind slabs are best managed by:
  • Recognizing and avoiding areas where wind slabs have formed, until they have stabilized.

Storm Slabs:
  • Vary in size from small to very large.
  • May be soft slabs, fooling people into underestimating slab potential.
  • Tend to occur on moderately steep slopes (35+ degrees).
  • May occur in all terrain, but are larger and more frequent in the alpine.
  • Stabilize soon after a storm, usually within a few days.
Storm slabs are best managed by:
  • Conservative terrain choices during and after storms until the storm snow has stabilized.

Wet Slabs:
  • Involve wet layers in the snowpack, typically including deeper layers.
  • Tend to be large.
  • Occur when water forms or penetrates below the surface of the snowpack.
Wet slabs are best managed by: 
  • Avoiding start zones and avalanche paths when the snow becomes wet from daytime heating, rain, or lack of an overnight freeze.

Persistent Slabs:
  • Slide on buried persistent weak layers, which often form during clear periods and may involve deeper layers from multiple storms.
  • Vary in size from medium to very large and may cross terrain barriers to involve multiple slide paths.
  • May occur on very gentle terrain, even slopes of 20 degrees or less.
  • May be localized to specific elevations, aspects, or regions.
  • There are often no visible signs of persistent slab instability.
  • Lack of avalanche activity and lack of danger signs are NOTreliable indicators of stability.
  • Compression tests and Rutschblock tests may locate persistent weak layers.
  • Stabilize slowly, tending to persist for several weeks or longer.
  • Often have dormant periods, becoming active again when the weather changes.
  • Are prone to lingering pockets of instability that persist long after most areas have stabilized.
  • Tend to release above the trigger, making it difficult to escape.
  • Are often triggered remotely from a long distance away.
Persistent slabs are best managed by:
  • Very conservative terrain choices.
  • Allow extra time for persistent slabs to stabilize and use a very cautious approach to new terrain. Be especially cautious after storms or during warming periods.

Deep Persistent Slabs:
  • Slide on deeply buried persistent weak layers, which often form during clear periods or rain-on-snow events early in the season.
  • Involve thick, hard slabs, sometimes the entire snowpack.
  • Tend to be very large, commonly cross terrain barriers to involve multiple slide paths.
  • Tend to occur on larger slopes of moderate steepness, typically 30-40 degrees.
  • May be localized to specific elevations, aspects, or regions.
  • There are often no visible signs of persistent deep slab instability.
  • Lack of avalanche activity and lack of danger signs are NOT reliable indicators of stability.
  • Stabilize slowly if at all, persisting for months and often the entire season.
  • Dormant persistent deep slab instabilities often become active again when the weather changes, especially after storms or with warm spring weather.
  • Tend to release above the trigger, making it difficult to escape.
  • Are often triggered remotely from a long distance away.

Deep persistent slabs are best managed by:

  • Very conservative terrain choices and a very cautious approach to new terrain.
  • Be especially cautious after storms or during warming periods.

Cornices:
  • May trigger large slab avalanches on relatively stable slopes below.
  • Are often associated with recent wind loading and/or temperature changes.
  • Can be triggered from ridges, sometimes breaking surprisingly far back onto ridge tops.

Cornices are best managed by:

  • Approaching corniced ridges cautiously.
  • Avoid travelling on or near overhanging cornices and limit time spent exposed to slopes below cornices, especially soon after wind events and during periods of warming temperatures.

Loose Dry:
  • Are usually small, but may gain significant mass on long steep slopes.
  • Are typically limited to steep terrain (40+ degrees).
  • Stabilize soon after a storm, usually within a few days.
Loose dry avalanches are best managed by:
  • Avoiding terrain traps and large steep slopes until the surface has stabilized.
  • On large steep slopes, occasionally move across the fall line to avoid being caught by your own sluffs from above.

Loose Wet:
  • Are more powerful than loose dry avalanches due to their higher density.
  • Are often limited to sunny slope aspects.
  • Are commonly confined to the warmest part of the day.
Loose wet avalanches are best managed by:
  • Avoiding start zones and avalanche paths when the snow becomes moist from daytime heating, from rain, or does not freeze overnight.

Wind Slabs:
  • Vary in size from small to medium.
  • Occur on steeper lee and cross-loaded portions of slopes (typically 35+ degrees).
  • Are often limited to specific terrain features such as lee ridge-tops.
  • Can often be recognized by the appearance of the snow surface, changes in surface snow hardness, hollow, drum-like sounds and/or shooting cracks.
  • Winds that vary in strength and direction can produce complex and unexpected wind slab patterns.
  • Stabilize fairly soon, usually in a few days to a week.
Wind slabs are best managed by:
  • Recognizing and avoiding areas where wind slabs have formed, until they have stabilized.

Storm Slabs:
  • Vary in size from small to very large.
  • May be soft slabs, fooling people into underestimating slab potential.
  • Tend to occur on moderately steep slopes (35+ degrees).
  • May occur in all terrain, but are larger and more frequent in the alpine.
  • Stabilize soon after a storm, usually within a few days.
Storm slabs are best managed by:
  • Conservative terrain choices during and after storms until the storm snow has stabilized.

Wet Slabs:
  • Involve wet layers in the snowpack, typically including deeper layers.
  • Tend to be large.
  • Occur when water forms or penetrates below the surface of the snowpack.
Wet slabs are best managed by: 
  • Avoiding start zones and avalanche paths when the snow becomes wet from daytime heating, rain, or lack of an overnight freeze.

Persistent Slabs:
  • Slide on buried persistent weak layers, which often form during clear periods and may involve deeper layers from multiple storms.
  • Vary in size from medium to very large and may cross terrain barriers to involve multiple slide paths.
  • May occur on very gentle terrain, even slopes of 20 degrees or less.
  • May be localized to specific elevations, aspects, or regions.
  • There are often no visible signs of persistent slab instability.
  • Lack of avalanche activity and lack of danger signs are NOTreliable indicators of stability.
  • Compression tests and Rutschblock tests may locate persistent weak layers.
  • Stabilize slowly, tending to persist for several weeks or longer.
  • Often have dormant periods, becoming active again when the weather changes.
  • Are prone to lingering pockets of instability that persist long after most areas have stabilized.
  • Tend to release above the trigger, making it difficult to escape.
  • Are often triggered remotely from a long distance away.
Persistent slabs are best managed by:
  • Very conservative terrain choices.
  • Allow extra time for persistent slabs to stabilize and use a very cautious approach to new terrain. Be especially cautious after storms or during warming periods.

Deep Persistent Slabs:
  • Slide on deeply buried persistent weak layers, which often form during clear periods or rain-on-snow events early in the season.
  • Involve thick, hard slabs, sometimes the entire snowpack.
  • Tend to be very large, commonly cross terrain barriers to involve multiple slide paths.
  • Tend to occur on larger slopes of moderate steepness, typically 30-40 degrees.
  • May be localized to specific elevations, aspects, or regions.
  • There are often no visible signs of persistent deep slab instability.
  • Lack of avalanche activity and lack of danger signs are NOT reliable indicators of stability.
  • Stabilize slowly if at all, persisting for months and often the entire season.
  • Dormant persistent deep slab instabilities often become active again when the weather changes, especially after storms or with warm spring weather.
  • Tend to release above the trigger, making it difficult to escape.
  • Are often triggered remotely from a long distance away.

Deep persistent slabs are best managed by:

  • Very conservative terrain choices and a very cautious approach to new terrain.
  • Be especially cautious after storms or during warming periods.

Cornices:
  • May trigger large slab avalanches on relatively stable slopes below.
  • Are often associated with recent wind loading and/or temperature changes.
  • Can be triggered from ridges, sometimes breaking surprisingly far back onto ridge tops.

Cornices are best managed by:

  • Approaching corniced ridges cautiously.
  • Avoid travelling on or near overhanging cornices and limit time spent exposed to slopes below cornices, especially soon after wind events and during periods of warming temperatures.