[TH]

Avalanche Bulletin - Waterton Lakes National Park

Issued Sun Apr 20, 2014 17:11
Valid Until Wed Apr 23, 2014 17:00
Watch for warm temperatures and potentially some heavy precip this week. Remember, even small amounts of solar heating or rain can weaken snow quickly to cause an increase in the avalanche hazard beyond the posted danger ratings.

        

Danger Ratings: Monday

alpine treeline below treeline alpine: 2 - Moderate, treeline: 2 - Moderate, below treeline: 2 - Moderate
alpine: 2 - Moderate
2 - Moderate Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
  • 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.
More...
treeline: 2 - Moderate
2 - Moderate Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
  • 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.
More...
below treeline: 2 - Moderate
2 - Moderate Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
  • 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.
More...
Forecast Tuesday Wednesday
alpine
3 - Considerable 2 - Moderate
treeline 3 - Considerable 2 - Moderate
below treeline 3 - Considerable 2 - Moderate
Confidence: Poor - Timing, track, or intensity of incoming weather system is uncertain on Wednesday

Weather Observations

Past 24 Hr WeatherLittle Prairie 1650m
Maximum (°C)7
Minimum (°C)-2
Snowfall (cm)3
Snow Pack (cm)164
Wind speedStrong (41-60 km/h)
Ridgetop wind directionSW
Past 24 Hr WeatherLittle Prairie 1650m
Maximum (°C)7
Minimum (°C)-2
Snowfall (cm)3
Snow Pack (cm)164
Wind speedStrong (41-60 km/h)
Ridgetop wind directionSW
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: Loose Wet

Which Elevation?

Which Elevation? below treeline, treeline, alpine

Which Slopes?

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

Chance of Avalanches?

Chance of Avalanches? likely

Expected Size?

Expected Size? small - large
Even short bursts of solar heating can rapidly affect the snow this time of the year. With mild temperatures in the forecast, watch for rain to affect the snow at lower elevations.

Travel and Terrain Advice

  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.
  • Travel early on frozen crusts before the heat of the day.

Problem 2: Wind Slabs

Which Elevation?

Which Elevation? alpine, treeline

Which Slopes?

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

Chance of Avalanches?

Chance of Avalanches? possible

Expected Size?

Expected Size? small - large

Isolated windslabs have developed in open features. These are becoming old however significant transport is still occurring. These may grow or become hidden with incoming snow or weakened with incoming rain.

Travel and Terrain Advice

  • Be cautious as you transition into wind affected terrain.
  • The recent snow may now be hiding windslabs that were easily visible before the snow fell.

Problem 3: Deep Persistent Slabs

Which Elevation?

Which Elevation? alpine, treeline, below treeline

Which Slopes?

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

Chance of Avalanches?

Chance of Avalanches? unlikely - possible

Expected Size?

Expected Size? large - very large
Solar heating and rain has weakened the upper snowpack BTL. With continued warming, a skier traveling through a thin spot or a large load hitting a slope such as a cornice fall or smaller avalanche could potentially trigger these serious slabs.

Travel and Terrain Advice

  • Be aware of the potential for full depth avalanches due to deeply buried weak layers.
  • Pay attention to overhead hazards like cornices.