Avalanche Forecast

Issued: Mar 27th, 2013 10:38AM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Persistent Slabs, Cornices and Loose Wet.

swerner, Avalanche Canada

Northwest Inland.

Be aware of changing conditions with daytime warming and sunny skies. Watch solar slopes and overhead hazards.

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

Continued sunny skies and spring-like conditions will persist through to Friday. The next low pressure system is expected to arrive later Sunday night. Thursday: Sunny skies. Alpine temperatures -1.0 and freezing levels 1500 m. Ridgetop winds blowing light from the West. Friday/Saturday: Sunny skies, partial cloud later on Saturday. Alpine temperatures -1.0/ -4.0 and freezing levels 1300 m. Ridgetop winds blowing light from the West.

Avalanche Summary

Numerous loose wet avalanches from steeper solar aspects up to size 2.0.

Snowpack Summary

Cornices have become well-developed and could easily become unstable during periods of warm weather or direct solar radiation. Most snow surfaces exist on solar aspects up to 2300 m, forming a melt-freeze crust overnight.Northern areas of the region have experienced strong winds that have redistributed storm snow on lee aspects creating stiff wind slabs. 35 - 65 cm of recent snow sits on a variety of old snow surfaces, including crusts, previous wind slabs and a buried surface hoar layer (March 9th). Last week, the March 9th surface hoar layer has been touchy in many areas and many large avalanches have released on it. Currently, this layer seems to be less reactive, but is still a concern (low probability-high consequence) . Recent snowpack tests are showing hard, resistent shears. This layer may be healing in some places, but I would remain conservative and continue to dig and test before diving into my line. The distribution of the surface hoar is variable and it may not exist, or be reactive, in every drainage. Where it does exist, it appears to be present at all elevations.

Problems

Persistent Slabs

A 30 - 60cm slab sits on the March 09 surface hoar/crust combo. The distribution of this layer seems to be variable. However if triggered, a large destructive avalanche may occur with consequences. Remote triggering from afar is possible

Be aware of thin areas that may propagate to deeper instabilites.>Dig down to find and test weak layers before committing to a line.>Plan escape routes and identify safe zones before committing to your line.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 7

Cornices

Large developed cornices loom over slopes. Failure may initiate large avalanches failing on the March 09 persistent weak layer. Cornices will likely become weak if the sun is shining. Wind slabs may be found on lee slopes and behind terrain features.

Extra caution needed around cornices with current conditions.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 6

Loose Wet

Clear sunny skies and warmer afternoon temperatures may promote deterioration within the upper snowpack. If surface snow becomes moist or wet, loose wet avalanches are likely. Watch solar aspects.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Valid until: Mar 28th, 2013 2:00PM