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Archived

Avalanche Forecast

Mar 28th, 2017–Mar 29th, 2017
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: Northwest Inland.

Wind slabs have been building at higher elevations: Carefully assess conditions as you travel and be alert to changes in the snowpack.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

We'll have lingering flurries in the wake of the snow from Monday-Tuesday. The next significant weather arrives Friday. WEDNESDAY: Cloudy, sunny breaks and lingering flurries (5cm possible) light southerly wind, freezing levels 1200m, alpine temperature around -4 C.THURSDAY: A short-lived clearing during the day. Light-moderate south wind, freezing level around 1100 m with alpine temperature around -3 C.FRIDAY: Snow throughout the day (5-10cm), moderate southwest wind, freezing levels 1300m.

Avalanche Summary

On Monday, skiers were able to trigger a Size 1 wind slab on a north aspect at 1600m in the north of the region. On Sunday, a Size 2 natural wind slab (average depth 40cm) was reported on a northeast aspect near 1800m in the south of the region.On Saturday, several wind slabs to Size 1.5 were reported on (east) northeast aspects in the north of the region.The incoming weather will continue to add load to the persistent slab, and human triggering remains possible in steep or unsupported terrain.

Snowpack Summary

Variable and unsettled weather has given 5-20cm of new snow in the past few days. Winds have been moderate to STRONG south though westerly, and many exposed surfaces are either heavily scoured or wind-pressed firm. That said, there have been some reports of wind slabs forming on northeast aspects in the south of the region. Recent warming and sun have likely left a crust on solar aspects and below 1300 m (reportedly breakable crust below 1000m). Snow from the past week or so has settled into a 20-60 cm thick slab above an older crust interface. Reports suggest the bond to the crust is poor and has resulted in a reactive slab, in addition to weaknesses down 30-35cm within the storm snow itself (giving sudden planar results in snowpack tests).Weak sugary snow near the ground has been a dormant instability, but it may still be possible to trigger in steep rocky terrain.

Avalanche Problems

Wind Slabs

Moderate to strong southerly winds and some incoming snow will create more wind slabs on north through east aspects at upper elevations.
Be aware of thin areas that may propogate to deeper instabilites.Be careful with wind loaded pockets. Be aware of wide variation in snowpack depthUse caution in lee areas. Recent wind loading have created wind slabs.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Persistent Slabs

A 20-60 cm thick slab above a rain crust has been reactive to human triggers. Most activity has been in wind-affected terrain. Persistent slabs also have the potential to step down to deep basal weaknesses near the ground.
Choose well supported terrain without convexities.Avoid steep convexities or areas with a thin or variable snowpack.If triggered the persistent slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1 - 3

Loose Wet

Watch out for wet snow at lower elevations or on sunny slopes if the sun comes out during the day.
Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2