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Archived

Avalanche Forecast

Feb 6th, 2015–Feb 7th, 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
4: High
The avalanche danger rating below treeline will be high
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
3: Considerable
The avalanche danger rating below treeline will be considerable
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
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Glacier.

We are in the midst of a natural avalanche cycle with copious amounts of rain below 2000m with more on the way. Avoid backcountry travel in avalanche terrain until the temperatures cool and precipitation stops.

Weather Forecast

The year of the pineapple express continues to deliver mild temperatures and heavy precipitation in the form of rain to 2000m with associated strong to extreme southwest winds at 3000m. This storm will persist into tomorrow afternoon before another wave hits. Freezing levels will drop by tomorrow with freezing levels to be around 1500m.

Snowpack Summary

The Jan 30 surface hoar/crust layer, which exists up to 2200m, is down 30-70cm, depth will depend on elevation The upper snowpack will be moist or wet to above 2000m. Jan 15 surface hoar layer is down 70-110cm and tests indicate it is still reactive in some areas.

Avalanche Summary

Natural avalanche cycle and avalanche control in progress along the highway corridor producing avalanches to size 3.5. Avalanches begin dry and end as moist onto their fans. On Tuesday skiers accidentally triggered a size 2.5 avalanche from a SE aspect at 2120m. The avalanche propagated ~200m wide and ran ~600m.

Confidence

Due to the number of field observations on Friday

Avalanche Problems

Storm Slabs

25-30cm of heavy snow over lighter snow will make conditions dangerous until the rain and snow stop and temperatures cool down.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 2 - 3

Persistent Slabs

Rapid loading and warm temperatures are the types of conditions that can re-awaken buried weak layers. Storm slab avalanches may step down to these  layer as well.
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 3 - 4