Avalanche Bulletin - Glacier National Park - Sat Nov 09, 2019

Issued: Fri Nov 08, 2019 14:12
Valid Until: further notice

In response to COVID-19 and the temporary suspension of many of Parks Canada’s visitor services, public avalanche bulletins will no longer be issued for the remainder of the 2020 spring season. This is a time to avoid the backcountry. Please stay home to help limit the spread of COVID-19, and to minimize demands placed on emergency response teams and the health care system.

Expect rugged and hazardous conditions below treeline if you plan on trying to access elevations where there is enough snow to ski/ride. For those that are determined, be cautious in glaciated terrain where crevasses will be thinly bridged. [DM]

Public Avalanche Forecast
Early Season Conditions:  Friday
Early Season Conditions

Insufficient observations exist to reliably rate the avalanche danger. Expect shallow snow cover with thinly buried rocks and trees just beneath the surface. Avalanche danger often concentrates in gullies and other deposition areas, where windslabs may bond poorly to a weak underlying base. Deeper snow usually exists at higher elevations.

Past 24 hour weather
Station Maximum (°C) Minimum (°C) Snowfall (cm) Snow Pack (cm) Wind speed Ridgetop wind direction
Fidelity 1905m 0 -8 2 74 Light (1-25 km/h) S
Rogers Pass 1315m -1 -3 3 13 Moderate (26-40 km/h) S
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.
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.
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.
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.
Extreme
  • 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? alpine, treeline
Which Slopes?
Which Slopes? north, northeast, east, northwest, west, southwest, south, southeast
Chance of Avalanches?
Chance of Avalanches? possible
Expected Size?
Expected Size? small - large

Naturally triggered avalanches up to size two have been observed from alpine start zones over the past week.

Problem Glossary
Dry Loose
  • 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.
Dry Loose 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.
Wet Loose
  • Are more powerful than dry loose avalanches due to their higher density.
  • Are often limited to sunny slope aspects.
  • Are commonly confined to the warmest part of the day.
Wet Loose 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.
Forecast Details

Weather Forecast

Sadly there isn't any significant snow in the forecast. Flurries will bring ~5cm Friday night, and another 5cm on Saturday before cold arctic air moves in with clearing on Sunday. With only 25cm forecast over the next week, expect rugged conditions to continue for a while yet. Check the Mountain Weather Forecast for updates.

Snowpack Discussion

The snowpack is slowly building at treeline and above, but diminishes rapidly as you lose elevation, with only 13cm at Rogers Pass (the highest point you can start your tour). 80-110cm of snow can be found at treeline but expect more in alpine lees. Inconsistent but moderate sudden planar test results observed on a crust sitting 30cm above ground.

Avalanche Activity Discussion

Several loose and thin slab avalanches up to size 2 were observed from solar aspects on Wednesday. Over a week ago, loose snow avalanches from Macdonald's N face ran more than 100m over bare ground, demonstrating that the valley bottoms are susceptible to overhead hazard even if they are not snowbound.

For More Details

Emergency: 1 (877) 852-3100
Forecasters: (250) 837-7500

Archives

Facebook @ParksMountainSafety