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Avalanche Forecast

Archived

Mar 23rd, 2022–Mar 24th, 2022

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

Regions

Purcells.

Continually evaluate conditions as you travel through terrain. Avalanche danger is improving, but temperatures remain warm and riders have recently triggered avalanches on a persistent weak layer. 

Confidence

Moderate - We have a good understanding of the snowpack structure and confidence in the weather forecast Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

WEDNESDAY NIGHT: Variable cloud cover across the region. Light rain/snow expected, possible heavier on the western side of the region. Light southwest ridgetop winds trending to strong in the high alpine. Freezing level falling to around 1400 m.

THURSDAY: Mostly Sunny. No new rain/snow expected. Light variable winds, with some periods of strong northwest in the high alpine. Freezing level rising to around 1750 m. 

FRIDAY: Partly cloudy with light rain/snow. Light southwest ridgetop winds, trending to moderate northwest in the high alpine. Freezing level around 750 m overnight, rising to 2000 m through the day.

SATURDAY: Mostly cloudy. Possible light rain/snow. Freezing level around 2200 m. Light southwest ridgetop wind trending to strong in the high alpine. 

Avalanche Summary

On Tuesday and Wednesday, widespread loose wet avalanches were reported due to warm temperatures and/or sunshine (mostly size 1-2, a couple size 2.5 or 3). East of Kaslo, a naturally triggered size 2.5 windslab was reported on a north aspect in the alpine. 

Several natural and one human-triggered wind slab 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 2000 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

  • If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Be alert to conditions that change with elevation.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
  • Avoid steep slopes when air temperatures are warm, it is raining, or solar radiation is strong.

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.

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.

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.