Archived

Avalanche Forecast

Dec 19th, 2014–Dec 20th, 2014

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

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

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Northwest Inland.

Avalanche danger is increasing as the storm slab continues to develop.

Confidence

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

Weather Forecast

Very strong Southerly winds moving in from the coast. 3-5 cm by Saturday morning, 5-8 during the day on Saturday. Winds becoming moderate Southwest by Sunday morning with another 5-8 cm and then a few more cms during the day. Monday cooling and drying out with strong Westerly winds.

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 developing above a mix of crusts, settled storm snow, and surface hoar. Loose dry snow may slide easily off of the old surface crust.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Deep Persistent Slabs

The new storm load may overload the deeply buried weak layer combination of crust, facets, and surface hoar.

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

Aspects: All aspects.

Elevations: Alpine.

Likelihood: Unlikely - Possible

Expected Size: 2 - 4