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Archived

Avalanche Forecast

Mar 15th, 2014–Mar 16th, 2014
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
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
3: Considerable
The avalanche danger rating below treeline will be considerable
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: Northwest Inland.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Snowfall is expected to continue on Sunday before ending Sunday evening. A break between storms is expected for most of Monday before the next system arrives Monday night. Light snowfall is expected for Tuesday. The north of the region can expect less snowfall amounts than the south for the forecast period.Sat. Night/Sunday: Snowfall 5-15cm, freezing level am: 1200m pm: 1000m, ridgetop winds 30-50 km/h S-SW.Monday: A mix of sun and cloud, mostly dry during the day, freezing level am: 300m pm: 600-1000m, ridgetop winds 20-40 km/h W-NWMon. Night/Tuesday: Snow 5-15cm, freezing level am: 500m pm: 1200m, ridgetop winds 30-50 km/h SW

Avalanche Summary

We haven't received any reports from Saturday at the time of publishing but avalanche activity is expected to be occurring in the region.  On Friday, a natural size 2 slab avalanche released on the early-March weak layer down 30-40cm on surprisingly low angle terrain (25-30 degrees).

Snowpack Summary

Conditions are reported to be highly variable. Roughly 30-60 cm of snow now sits on the early-March weak layer consisting of surface hoar and/or a thick layer of faceted snow on shady slopes at all elevations, a sun crust on steep solar aspects, and various wind affected surfaces in exposed terrain. Strong southwest winds have created dense wind slabs on exposed lee slopes and in cross-loaded features. In wind exposed areas, the snow surface is reported to be wind scoured or a very supportive wind-pressed slab. Moist/wet snow or melt-freeze crusts in the upper snowpack are likely at lower elevations, below roughly 1200m. The early February weak layer of facets, crusts, and/or surface hoar is buried down about 60-100 cm. Test results and isolated avalanche activity suggest this layer is still reactive to human-triggering. Basal facets and depth hoar remain a concern in areas with thin or variable snow cover.

Avalanche Problems

Persistent Slabs

The early-March weak layer is still quite reactive to new snow loads and human-triggers.  The slab is now typically 30-70cm thick and continues to produce large avalanches.
Be aware of the potential for large, deep avalanches due to the presence of buried weak layers>Be aware of thin areas that may propogate to deeper instabilites.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 3 - 6

Storm Slabs

New snow is sitting on a crust at lower elevations and wind-affected surfaces in the alpine.  Strong SW winds have been redistributing the new snow into wind slabs on leeward slopes.
Avoid freshly wind loaded features.>Use conservative route selection, stick to moderate angled terrain with low consequence.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 4

Deep Persistent Slabs

The Feb. weak layer is typically down over 1m but continues to produce large, isolated avalanches.  Smaller avalanches are stepping down to this layer and remote-triggering of the layer from thin spots is possible.
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Unlikely - Possible

Expected Size: 4 - 7