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Avalanche Forecast

Archived

Apr 15th, 2023–Apr 16th, 2023

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

Regions

Purcells, Dogtooth, East Purcell.

Remain cognizant that a weak, unpredictable layer continues to lurk near the bottom of the snowpack, avoid thin, rocky start zones and shallow areas with variable snowpack depths.

Check for signs of windslab avalanche danger like shooting cracks, especially near ridgetops and in cross loaded gullies.

Confidence

Moderate

Avalanche Summary

On Friday, near Golden, a small (size 1) naturally trigger wet slab avalanche was observed on a south aspect and failed to ground on smooth shale slopes. Numerous other small (size 1) loose wet avalanches were observed on steep south aspect terrain. Additionally a few storm slab avalanches were trigger on south aspect terrain during a period of warmings and clearing.

We suspect that the weight of a human could still trigger windslab avalanches below ridgetops and in cross-loaded gully features. Also, warm temperatures and intense spring sun can quickly make loose wet avalanches likely.

On Wednesday, west of Golden, a few small, touchy windslab avalanches were reported. They were triggered remotely from 20 meters away, by skiers skinning along a ridge.

If you are getting out in the backcountry, consider making a post on the MIN (Mountain Information Network). You can share riding conditions, avalanche or snowpack observations, or even just a photo or two. Heck, tell us what you had for lunch if that was the most eventful part of your day.

Snowpack Summary

At treeline and above, 15-30 cm of recent snow fell with moderate to strong southwest wind, forming windslabs in leeward terrain. A variety of crust, surface hoar and/or facet layers that were buried in mid March through early April may exist in the upper snowpack. None of them seem to be a current avalanche problem. Most professional operations in the forecast area are tracking their own local layer of concern to see if they become active with increasing temperatures, or more load from new rain or snow.

Below treeline, expect to find moist or refrozen surfaces, and shrinking snowpack depths.

The mid snowpack is generally settled and strong, although west of Invermere, some professional operations are still monitoring a layer of weak, feathery surface hoar crystals that was buried in mid January.

The lower snowpack includes a widespread layer of large, weak facets and/or depth hoar crystals. This weak layer has been responsible for several very large and destructive avalanches throughout the season, including one last Thursday.

Weather Summary

Saturday Night

A mix of clouds with periods of clearing. No new precipitation is forecast. Freezing level 2200 m descending to 1200 m. Moderate to strong southwest ridgetop wind. Treeline low around -2 °C

Sunday

Mostly cloudy. 1-5 cm of snow expected in the alpine. Freezing level at 1800 m, rising to 2200 m. Moderate to Strong southwest ridgetop wind. Treeline high around 2 °C

Monday

Mostly cloudy. Possible trace of snow expected. Freezing level at 1300 m overnight rising to 1600 m. Moderate south west ridgetop wind. Treeline high around 0 °C

Tuesday

Mostly sunny. 1-5 cm of snow expected. Freezing level around 1000 m overnight, rising to 1500 m. Light southwest ridgetop wind. Treeline high around 0 °C

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Use caution above cliffs and terrain traps where even small avalanches may have severe consequences.
  • Be especially cautious as you transition into wind affected terrain.
  • Be alert to conditions that change with aspect and elevation.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

Problems

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

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.