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Avalanche Forecast

Jan 20th, 2013–Jan 21st, 2013
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
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: South Columbia.

Extent of solar radiation and warming influence is uncertain. Use extra caution as the day progresses especially on South facing slopes.

Confidence

Fair

Weather Forecast

Sunday night and Monday: The ridge of high pressure continues to bring dry conditions, well above normal temperatures.  Inversion with temperatures reaching + 1 C in the alpine, few clouds cover with valley clouds and light NW winds. Freezing level rising during the day to 1200 m.Tuesday: The ridge is moving slowly Eastward bringing more mild temperatures, few clouds and valley clouds and lighter winds from the NW. Slightly cooler temperatures, with freezing level lowering around 800 m. Wednesday: A weak system should reach the region later during the day bringing light precipitation (16 mm), cooler temperatures (-7 C) and moderate Southerly winds. 

Avalanche Summary

A slab avalanche size 2 and numerous loose avalanches would have been triggered yesterday on steep sun exposed slopes.

Snowpack Summary

The warm temperatures and solar radiation forecasted for tomorrow could weaken the windslabs and persistant slabs, especially those found on steep South facing slopes. If surface snow becomes moist, loose wet avalanches could also take place, and even though small in size, they could become a problem if thrown off your feet in a terrain trap.  As a general picture, around 40-60 cm settled storm snow sits above surface hoar, a sun crust (on steep S to SW -facing slopes) and facets. Results on the surface hoar layer vary from sudden planar to resistant planar in the moderate to hard range. It appears to be more reactive in the Northern part of the region, especially in the 1900 to 1500 m. range. The distribution of these weaknesses is patchy, but where they exist, they may be triggered by the warming trend or under with the weight of a person or snowmobile. A strong mid-pack overlies a weak facet/crust layer near the base of the snowpack, which is generally considered inactive.

Avalanche Problems

Wind Slabs

Solar radiation and warm temperatures could weaken some steep wind loaded slopes. Triggering a windslab could potentially step down to a deeper instability.
Cornices become weak with daytime heating, so travel early on exposed slopes.>Be aware of the potential for wide propagations due to the presence of hard windslabs.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 4

Persistent Slabs

A very cautious approach is recommended on steep south-facing slopes and sheltered terrain below treeline with daytime warming and solar radiation possibly weakening the snowpack.
Watch for glide cracks and give them a wide berth>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 5