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Avalanche Forecast

Archived

Feb 12th, 2021–Feb 13th, 2021

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

Regions

North Rockies.

Human triggered avalanches remain possible, but time and cold temperatures have reduced their sensitivity to triggering. Watch for wind slabs in funny places in the alpine as east/southeast winds continue to blow. Read about managing these conditions in this forecaster blog.

Confidence

Moderate - Uncertainty is due to extremely variable snowpack conditions reported through the region.

Weather Forecast

Brrrr! Cold temperatures look to be with us through the weekend. The weather models are hinting at more seasonal temperatures beginning Tuesday.

FRIDAY NIGHT: Overnight low temperature around -30 C, moderate southeast wind, no snow expected.

SATURDAY: A few clouds, daytime high temperature around -15 C, strong southeast wind, no snow expected.

SUNDAY: Broken cloud cover, daytime high temperature around -10 C, moderate to strong west/southwest wind, no snow expected, potential for a few cm of snow Sunday night.

MONDAY: Broken cloud cover, daytime high temperature around -5 C, moderate to strong west wind, trace of snow possible.

Avalanche Summary

This avalanche was spotted around Tete Juane, sounds like an older avalanche, likely ran before the cold snap. Other than that there have been no recent avalanche observations.

There were a few small human triggered avalanches reported around treeline near Pine Pass last weekend. These failed on the recently buried surface hoar layer. 

There were some other observations from throughout the region over the weekend that would suggest ongoing instability associated with that weak surface hoar layer. Reports ranged from whumpfs and shooting cracks, to visual observations of large surface hoar crystals

On February 3rd there were reports of numerous natural avalanches 20 to 40 cm in depth running at and above treeline. A southwest slope produced a size 3 natural avalanche. These avalanches presumably ran on surface hoar which was producing very touchy conditions. There are some great visuals of this activity in this MIN.

Snowpack Summary

There is about 25-50 cm of snow resting on buried surface hoar which is most prevalent above 1600 m. It likely reaches into the alpine too, we're just not sure how high it extends. It may be present down in the trees in some places too. This surface hoar seems to be deepest, and most sensitive to triggering around the McBride area.

Below 1600 m this snow sits on a crust. 

There are presently no deeper concerns in the snowpack.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
  • Carefully evaluate big/extreme terrain features before committing to them, it's not full "go" time yet.

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.

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.