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Avalanche Forecast

Archived

Mar 22nd, 2022–Mar 23rd, 2022

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Purcells.

Avalanche danger will increase during periods of strong solar radiation or rain at lower elevations. 

Head out with a conservative mindset and dial back your terrain choices until the weather cools.

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack. Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

TUESDAY NIGHT: Mainly cloudy. Light to moderate southwesterly winds. Freezing level around 2000 m.

WEDNESDAY: Cloudy with light precipitation. Moderate to strong southwesterly winds. Freezing level around 2000 m.

THURSDAY: Partially cloudy. Light variable winds. Freezing level around 1500 m.

FRIDAY: Partially cloudy with light precipitation. Light southwest winds. Freezing level around 1600 m.

Avalanche Summary

Several natural and one human-triggered wind slabs occurred on Sunday and Monday in the alpine and treeline (size 1-2).

Several notable human-triggered slab avalanches occurred last week, suggesting that the recent snow is bonding poorly to the underlying layers. These occurred on a range of aspects above 2000 m, with the most notable reactivity observed on south-facing aspects. Most slabs were small in the top 20 to 30 cm of snow (size 1), but one larger 70 cm thick slab was remotely triggered from below by a group of skiers (size 2). This avalanche occurred on a south aspect at 2250 m. (read more in this blog).

Snowpack Summary

30-70 cm of settling storm snow exists at higher elevations. Snow depths taper significantly with elevation, with moist and crusty surfaces below 1800 m and on south aspects into the alpine.

In some areas, last week's snow is well bonded to old crust layers, while in other areas the snow has settled into a reactive slab above weak layers around the crusts. At this point, it appears persistent slab problems may exist in the deeper snowpack areas along the western side of the range. The lower snowpack is generally well bonded.

Terrain and Travel

  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
  • Use ridges or ribs to avoid areas of wind loaded snow.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Cornice failure may trigger large avalanches.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.