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Archived

Avalanche Forecast

Feb 28th, 2017–Mar 1st, 2017
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: South Rockies.

Updated at 9 am. Another 20 cm of storm snow overnight! Reactive storm slabs and loose dry avalanches are likely.

Confidence

High -

Weather Forecast

Wednesday: Snow accumulations 5-10 cm with strong SW winds. Alpine temperatures high of -11.Thursday: Mostly cloudy with some flurries accompanied by strong SW winds. Alpine high of -8 and freezing levels 1300 m. Friday: Snow amounts 5-10 cm with moderate-strong ridgetop winds from the SW. Freezing levels rising to 1400 m.

Avalanche Summary

On Monday, numerous skier controlled wind slabs were reported up to size 1.5 at treeline and alpine elevations. The deep persistent slab problem is a low probability/high consequence scenario that warrants extra caution around large open slopes, especially in shallow snowpack areas. There was a report last Tuesday of a size 3.5 avalanche at Mt Hosmer in the Lizard/Flathead region that released on or stepped down to the deep weak layer near the ground. On Wednesday we had a report from the Lizard range of another size 3.0 deep persistent avalanche on a northeast aspect in the alpine.

Snowpack Summary

Another 20 cm overnight bringing the recent storm snow totals up to 50 cm since Saturday. The new storm snow will likely be redistributed to leeward slopes, building fresh wind slabs. The mid-pack in this region is well settled, but the bottom third of the snowpack is composed of weak facets (sugary crystals). Recent snow profile tests have produced moderate failures that released suddenly down 75 cm on the facetted crystals. In the Crowsnest North up to 45 cm of recent storm snow lies above various old surfaces. Near Elkford up to 30 cm of old storm snow sits above a melt/freeze crust. Approximately 100-120 cm of settled snow sits above the weak layer of sugary facets that developed during the cold spell in December. Snow profile tests indicate hard shears in this location where the facets are sitting on a hard wind crust.

Avalanche Problems

Storm Slabs

New storm slabs will likely be reactive, especially to rider triggering. Thicker slabs will exist on leeward slopes due to wind transported snow.
Use extra caution based on your knowledge and training or avoid avalanche terrain during periods of heavy loading from new snow, wind.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2

Deep Persistent Slabs

A weak layer near the base of the snowpack has the potential for large avalanches, especially in areas with minimal rider compaction or thin variable snow cover.
Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 4