Archived

Avalanche Forecast

Dec 18th, 2014–Dec 19th, 2014

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

1: Low

The avalanche danger rating below treeline will be low

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

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.

Avalanche danger is increasing as the new storm moves in from the Southwest.

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Very light snow overnight combined with moderate to strong Southeast winds and freezing levels at valley bottoms. Very light snow during the day on Friday with light to moderate Southwest winds. Light snow (5-10 cm) by Saturday morning combined with very strong Southerly winds. Snow and strong Southwest wind continuing during the day Saturday with another 5-10 cm expected to accumulate. Unsettled on Sunday with flurries or light snow, moderate Southwest winds and freezing levels at valley bottoms.

Avalanche Summary

There are no new avalanche reports from the region. The forecast new storm is expected to develop a new storm slab that may increase avalanche activity.

Snowpack Summary

The new storm is expected to develop a storm slab above the dusting of new snow which overlies weak surface hoar reported to exist up to at least treeline elevation. Below the new snow you'll likely find wind-scoured surfaces and old wind slabs in exposed terrain, and settled storm snow closer to treeline. Near the base of the snowpack, weaknesses such as the mid-November crust-facet layer are still of concern. I'd use extra caution around steep, unsupported high elevation terrain as avalanches at this interface could propagate over wide distances.

Avalanche Problems

Storm Slabs

A new storm slab is expected to develop over the next few days as forecast snow and wind move into the region from the coast. Recent windslabs may be difficult to locate due to the new snow. Some loose dry snow may slide easily off of the old crust.

Use ridges or ribs to avoid wind loaded and cross loaded slopes.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Deep Persistent Slabs

Persistent weaknesses buried in November remain a concern for professionals in the region. Watch for shallow snowpack trigger points on steep, unsupported slopes.

Avoid convexities or areas with a thin or variable snowpack.>Be aware of thin areas that may propogate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood: Unlikely - Possible

Expected Size: 2 - 4