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Avalanche Forecast

Archived

Mar 14th, 2021–Mar 15th, 2021

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.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Purcells.

As we move into a nice diurnal temperature swing with good overnight refreeze the likelihood of triggering persistent slabs will decrease. Remain vigilant for lingering wind slabs in more extreme terrain features around ridge crest.  

Confidence

Moderate - Uncertainty is due to rapidly fluctuating freezing levels.

Weather Forecast

Now that the big warm up has passed we’re moving into a nice diurnal temperature regime with good overnight refreeze.

SUNDAY NIGHT: Freezing level lowering to near valley bottom, light to moderate southwest wind, no snow expected.

MONDAY: Scattered cloud cover, freezing level rising to about 2200 m, light variable wind, no snow expected during the day, potential for a few cm of snow Monday night.

TUESDAY: Scattered cloud cover, freezing level rising to about 2000 m, light variable wind, no snow expected.

WEDNESDAY: Broken cloud cover, freezing level rising to about 2000 m, light southwest wind, no snow expected.

Avalanche Summary

On Friday and Saturday avalanche activity was limited to loose wet avalanches to size 1.5 on solar aspects.

Snowpack Summary

Dry snow can be found on shaded aspects at upper elevations. On solar aspects and at lower elevations expect crusty snow in the morning and soft, moist snow in the afternoon. Lingering wind slabs and large cornices still pose a hazard close to alpine ridgelines.

A persistent weak layer of facets 40-60 cm deep that was buried in mid-February was reactive in the north of the region earlier this month but no avalanches have been reported on this layer since Mar. 3rd. There are several other weak layers deeper in the snowpack composed of old surface hoar, facets and/or crusts, all of which have been recently unreactive.

Sunshine and warm temperatures often cause large cornice failures which are hazardous on their own and can also trigger large avalanches on deeper weak layers that the weight of a single rider would not trigger.

Terrain and Travel

  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
  • Carefully evaluate big/extreme terrain features before committing to them, it may not be 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.