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Avalanche Forecast

Archived

Mar 27th, 2022–Mar 28th, 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, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Columbia.

High overnight freezing levels and rain are expected to make the snowpack weak at lower elevations, with new wind slabs potentially forming up high.

Look for low angle, higher elevation objectives without overhead cornices. Plan your access and egress route carefully.

Confidence

Moderate - Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

SUNDAY NIGHT: Cloudy with light flurries. Alpine temperature around 0 C. Ridge winds 15-35km/h southwest. Freezing level 1900m.

MONDAY: Mainly cloudy with flurries, 5 cm of accumulation above the rain-snow line. Alpine temperature around 0 C. Ridge winds 15-30 km/h southwest. Freezing level 2200 m.

TUESDAY: Mainly sunny. Alpine high of 3 C. Ridge winds 15-30 km/h northwest. Freezing level rising to 2000 m.

WEDNESDAY: Mainly cloudy with rain/snow, 5-10 cm of accumulation above the rain/snow line. Alpine temperatures around -3 C. Ridge winds 15-40 km/h southwest. Freezing level rising to 1800 m.

Avalanche Summary

Several small (size 1-1.5) skier-triggered wind slabs occurred on Friday and Saturday. Several small (size 1) wet loose avalanches were observed on Saturday as a result of warm temperatures and solar radiation.

The last persistent slab avalanches observed in the region were during the warm-up on March 23rd and 24th. Several large (size 2-3) persistent slab avalanches occurred. These slabs were 70 to 150 cm deep and occurred on all aspects from 2100-2300 m.

Snowpack Summary

5 to 15 cm of recent snow and southwest winds may have formed small wind slabs in lee terrain features in the high alpine. A refrozen crust can be found below the new snow on all aspects to at least 2300m. This crust is expected to break down throughout the day with rain and warm temperatures. Below the crust, the top 10-30 cm of the snowpack is moist. At low elevations, the snowpack may become wet and isothermal.

A weak layer may be found around 50 to 100 cm deep. The layer consists of surface hoar crystals in treeline terrain on northerly aspects or weak faceted grains above a hard melt-freeze crust on sun-exposed slopes (i.e., east, south, west). It has been reactive between 1800 and 2300 m but given the recent rain, it is most likely to be triggered between 2000 and 2300 m. It should still be treated as suspect if you find it in your riding area.

The remainder of the snowpack is 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.
  • A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
  • If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
  • Carefully evaluate steep lines for wind slabs.
  • Extra caution is needed around cornices under the current conditions.

Problems

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.

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.

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.