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Avalanche Forecast

Archived

Mar 3rd, 2022–Mar 4th, 2022

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

Regions

Sea To Sky.

The March sun can really pack a punch and destabilize the upper snowpack. Natural and human triggered avalanches remain likely.

Conservative travel habits and patience is key, especially when dealing with a persistent weak layer deeper in the the snowpack.

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack. Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Change is in the air with a strong ridge set up through the weekend. This will bring clear and sunny skies, light northerly wind, and rising freezing levels.

Thursday Night: Some cloud cover with light northwest winds. Freezing levels dropping to 1000 m.

Friday/ Saturday: Mix of sun and cloud. Ridgetop wind light to moderate from the northeast and alpine temperatures near -4. Freezing levels (diurnal) 1000 m overnight and 1500 m during the day.

Sunday: Sunny skies with freezing levels rising to 2000 m during the day. Ridgetop wind moderate from the North and alpine temperatures possibly rising to 0 degrees. 

Avalanche Summary

No new avalanche observations by Thursday afternoon.

On Wednesday, a natural avalanche cycle up to size 3 was reported from the recent storm. A few skier controlled and remotely triggered (from as far away as 40 m) avalanches were also reported. These persistent slabs failed on the mid-February facet/ crust interface buried approximately 50 cm down. They caught people by surprise, but no involvements occurred.  

Snowpack Summary

30-50 cm of wind affected, storm snow sits over a variety of surfaces including sun crusts on solar aspects, a thick rain crust in windswept terrain and facets in shady, sheltered terrain. The recent storm snow has a decent bond in some areas, but a poor bond exists on northerly slopes (NW, N, NE, E) at treeline and in low alpine elevations (1700-2000 m) where the mid-February facet/ crust persistent weak layer has been touchy to skier triggers. Whumphing and remotely triggered avalanches have been failing on 3-5 cm of facets sliding on a hard melt-freeze crust. Some surfaces in windward alpine terrain have been scoured down to this firm crust.

Large and looming cornices have grown during the recent storm. 

A crust/facet/surface hoar interface formed late-January is buried down 40-100 cm. This layer was most reactive between 1700 m and 2000 m. While this layer has been dormant in most of the region lately, large loads such as heavy snowfalls and cornice falls could wake it up and produce very large avalanches.

Terrain and Travel

  • Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet

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.

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.