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Avalanche Forecast

Feb 28th, 2019–Mar 1st, 2019
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: South Rockies.

Human triggered avalanches remain possible, especially in wind loaded areas and at lower elevations where buried surface hoar layers exist.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

THURSDAY NIGHT - Cloudy with scattered flurries, 5 cm / southwest winds 10-20 km/h / alpine low temperature near -15FRIDAY - Mainly cloudy with isolated flurries / southeast winds 10-20 km/h / alpine high temperature near -18SATURDAY - Mainly sunny / east winds 10-15 km/h / alpine high temperature near -25SUNDAY - Sunny / northeast winds, 10-20 km/h / alpine high temperature near -17

Avalanche Summary

On Monday, size 1 wind slabs were reactive to human traffic. One size 2.5 natural wind slab avalanche likely occurred overnight Monday.Several size 2 wind slab avalanches were triggered with explosives on Friday after a bout of strong to extreme southwest winds. Slab depths ranged from 20-60 cm.A MIN report from Grizzly Peak in the Elkford area last Thursday describes a persistent slab failing on the mid-January persistent weak layer as a group ascended a steep slope near treeline. See the report here.

Snowpack Summary

Up to 15 cm of new snow and previous variable wind directions will mean that wind slabs can be found on all aspects at upper elevations.  Older wind slabs will be buried under the new snow and may be difficult to detect.A weak layer of facets (sugary snow) and surface hoar (feathery crystals) that was buried in mid January is down approximately 40-80 cm.  This layer is most prominent between 1600 m and 1900 m, but it has been found up to 2200 m in some areas. This weak layer may exist in combination with a crust on south facing slopes.  Recent snowpack tests and avalanche reports suggest that this layer remains reactive to human triggers.The bottom half of the snowpack is composed of weak, sugary facets.

Avalanche Problems

Wind Slabs

Previous variable wind directions have likely formed wind slabs on all aspects.
Use caution in freshly wind-loaded features, especially near ridge crests and in steep terrain.If triggered, wind slabs may step down to deeper layers resulting in large avalanches.Keep an eye out for reverse loading created by variable winds.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2

Persistent Slabs

A weak layer of surface hoar is buried around 40 to 80 cm, and is most prominent between 1600 m and 1900 m.
Use added caution in open terrain features such as cutblocks, gullies and cutbanks.Be aware of the potential for wide propagation.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 2.5