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Avalanche Forecast

Feb 5th, 2015–Feb 6th, 2015
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
4: High
The avalanche danger rating in the alpine will be high
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.

Avalanche danger is high due to loading from new snow or rain, and wind.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

The second pulse of warm and mild weather associated with the low pressure system off the coast is expected to spread moderate to heavy precipitation over the region tonight (10-15 mm) and through Friday (10-15 mm).  Freezing levels could reach up to 2000m during the night and lower back down to 1800m tomorrow. A third wave of moisture with similar characteristics as the one before will be drifting inland on Friday night bringing another 15 mm of precipitation during the night and through Saturday. Freezing levels are expected to be around 2000m. Sunday is still looking warm but somewhat dryer. Winds are forecast to be moderate to strong from the southwest for the whole period.

Avalanche Summary

Several skier and explosive triggered avalanches up to size 2 out of treeline and alpine start zones were reported. Sluffing and shooting cracks were also observed as a slab was developing in the afternoon.

Snowpack Summary

Around 10 mm of heavy snow, or rain below 1500m, has accumulated over 5 cm which is sitting on a variety of surfaces; on a surface hoar and crust combo (referred to as the “late January surface hoar/crust” further down) in more sheltered areas, on a thin breakable crust in more wind affected areas or over windslabs on northeast aspects in the alpine. Significantly more load  is expected to add on to the snowpack through the night and tomorrow (total 20-30 mm as rain up to around 2000m) driving the avalanche danger to rise and making travelling conditions very dangerous in the backcountry. The rain is expected to weaken the late January crust/surface hoar layer, therefore increasing the likelihood of avalanches stepping down to deeper weak layers. The mid-December crust/facet/surface hoar combo found down 50-95 cm and could come out of its dormant stage making for some very large avalanche potential .

Avalanche Problems

Storm Slabs

Snow or rain continues to accumulate making natural avalanches more likely to slide. Windslabs developing on northeast aspects at higher elevation and wet slabs/loose avalanches problems at all elevations are incorporated into this problem.
Avoid avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Avoid regrouping in runout zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 4

Deep Persistent Slabs

The load from the new snow and rain soaking the surface snow could lead to avalanches stepping down to the deeper weak layers.
Be aware of the potential for very large, deep avalanches due to the presence of buried surface hoar and crust/facet layer.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 5