Archived

Avalanche Forecast

Apr 16th, 2015–Apr 17th, 2015

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

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

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Northwest Inland.

Tricky winter conditions exist at higher elevations. Localized solar radiation, snow and winds will destabilize the snowpack. Use a conservative approach to terrain and watch for signs of instabilities.

Confidence

Poor - Due to the number of field observations

Weather Forecast

The next pacific front hits the North and Central coast Thursday evening bringing anywhere from 2-10 mm. Lingering cloud, periods of sunshine and convective snowfall may occur on Friday. Ridgetop winds will be moderate from the West and freezing levels near 1000 m. Saturday and Sunday will be mostly cloudy with light precipitation. Ridgetop winds will be strong from West and freezing levels rising to 1100 m Saturday. Warm moist air will reach the North on Sunday and freezing levels will rise to 2300 m.

Avalanche Summary

No new avalanche observations have been reported. On Friday, touchy wind slabs and storm slabs are likely, especially in areas that receive higher snowfall amounts. If the sun pokes out, solar radiation will be strong and deteriorate the upper snowpack. Watch overhead hazards like cornices, solar triggered slab and loose wet avalanches.

Snowpack Summary

Recent storm snow has likely formed touchy storm slabs. Strong westerly winds have redistributed this new snow and has formed wind slabs on leeward slopes and behind terrain features. The lack of bond between the new wind slabs and storm slabs over the older snow surfaces buried on April 9 th (surface hoar, crusts and facets) are the primary concern. The March 25th surface hoar / crust layer is reportedly unreactive, however; with the new load of wind and snow this should remain on your radar as it may re-awaken. Large ripe cornices are also of concern and will be a problem with additional loading, especially when the sun and warm temperatures come back.

Avalanche Problems

Wind Slabs

Strong winds have redistributed recent storm snow into wind slabs on leeward slopes. They are especially touchy where they sit on buried facets, surface hoar and/ or crusts. Cornices are large and may weaken with solar radiation.

Avoid freshly wind loaded features.>Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.>Pay attention to overhead hazards like cornices, especially if the sun is shining.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 3

Persistent Slabs

Additional snow loading on the mid- March persistent weak layer could bring it back to life. Smaller slab avalanches may step down to this layer, initiating large and destructive avalanches.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar, facets and/ or a crust.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 5