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Avalanche Forecast

Archived

Mar 1st, 2022–Mar 2nd, 2022

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

Regions

Lizard-Flathead.

Though natural avalanche activity will taper off, conservative decision making is essential to let the snowpack adjust to the recent 90+ mm of load that the Lizard Range has received. 

Seek out low angle, well supported terrain away from overhead hazard.

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

Convective pulses and freezing levels are hard to pin down. There is also a system just south of the border that could clip our region for greater than forecast precipitation amounts over the next couple of days.

Tuesday Night: Precipitation continues with 5-10 mm, moderate southwest wind, uncertainty around overnight recovery, treeline temperatures around zero.

Wednesday: Flurries possible 5-10 cm, light to moderate southwest wind, but freezing could still rise to about 1700 m during the day.

Wednesday Night: Light flurries 0-5 cm, light variable winds, freezing levels should drop back to valley bottom.

Thursday: Overcast with flurries 5-10 cm, light variable wind, freezing levels 1300-1500 m, treeline highs around zero.

Friday: Light flurries ease overnight, some clearing during the day, freezing levels drop substantially, treeline highs of -3.

Avalanche Summary

A widespread storm slab avalanche cycle with size 1-3 avalanches on a variety of aspects and elevations was reported from the Lizard Range on Tuesday. Check out this recent MIN report taken from within the ski area boundary looking out of bounds towards the Mammoth Droppings.

Snowpack Summary

The storm started cool and ended warm. The Lizard Range has received over 90 mm of water from this system which has translated to about 40-50 cm of heavy, upside down type snow. Rain runnels have been reported up to 1700 m. All of this new load sits on a variety of old surfaces like sun crusts on south-facing terrain, freezing rain crusts, old wind-pressed snow or cold, weak snow crystals on shaded aspects. Moderate to strong southwest winds have likely contributed to cornice growth as well.

Storm slabs or loose wet avalanches may step down to old persistent layers such as the surface hoar layer buried at the end of January. The distribution of this layer is spotty in nature but has produced avalanches and snowpack test results in the past week, mostly in the Flathead. While it does not appear to be as widespread or reactive in the Lizard Range, it has been found in some locations. 

The lower snowpack is well consolidated, with a crust/facet layer from early-December found near the bottom of the snowpack. It is currently considered dormant but with big rain on snow events, operators will be on guard. Check out the forecaster blog for more information. 

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Use small low consequence slopes to test the bond of the new snow.
  • Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
  • Storm slabs in motion may step down to deeper layers resulting in large 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.

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.

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.