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Avalanche Forecast

Archived

Apr 23rd, 2023–Apr 24th, 2023

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

Regions

Glacier.

Sunday's storm will bring snow to higher elevations and rain at and below Treeline.

For the die-hards out there, expect warm, mushy snow down low, while the Alpine should still sport some cold snow up high.

Confidence

Moderate

Avalanche Summary

Expect avalanche activity to increase on Sunday afternoon/evening as lower elevations get saturated by rain and higher elevations receive 10-15cm of snow and moderate winds.

No new avalanches were observed or reported for the last 3 days.

Snowpack Summary

Below treeline, a series of supportive crusts are present, but they break down with daytime warming/rain.

In the upper Treeline and Alpine, N'ly aspects hold dry snow. On solar aspects, a breakable crust overlies a series of buried crusts, which may provide a failure plane for slab avalanches as temps rise.

The Nov 17 basal weakness can still be found in many areas, ~20-40cm above the ground.

Weather Summary

A Spring storm, delayed by a day, hits Rogers Pass Sunday. 10-15cm is expected Sunday through early Monday morning, with mod/strong SW winds and freezing levels spiking around 2000m midday Sunday. Limited to no surface crust recovery expected Sunday night due to rain/cloud cover.

Terrain and Travel Advice

  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
  • Avoid terrain traps such as gullies and cliffs where the consequence of any avalanche could be serious.
  • If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.