Avalanche Forecast

Issued: Apr 11th, 2012 10:41AM

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

swerner, Avalanche Canada

South Rockies.

Confidence is poor due to disagreeing weather models, track and timing of the low moving into Southern Alberta. The region may receive heavier amounts of precipitation than forecast. If this occurs, expect the danger ratings to be elevated.

Summary

Confidence

Poor - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

A low pressure center sitting SW of Montana will continue to move SE, this should be arriving in Southern Alberta by Thursday afternoon. Depending on timing and track, this low may spread moderate amounts of precipitation to the BC interior Wednesday night into Thursday. Ridgetop winds will start light-moderate from the South, switching moderate SW through Thursday. Freezing levels will fall to 1800 m. Some lingering flurries may exist into Friday with freezing levels near 1500 m. The weekend will see a fairly inactive ridge of high pressure dominating the interior, bringing sunny skies and freezing levels up to2500 m. Confidence is poor for Thursday/Friday due to the uncertainty of the lows location in Alberta. This could potentially bring more than anticipated (moderate) precipitation amounts to the regions.

Avalanche Summary

Loose snow activity on a SE facing slopes have occurred. Most of this consists of pinwheeling, and point release avalanches involving the surface snow, no slabs.

Snowpack Summary

Spring like warm weather has promoted settlement and bonding within the snowpack. Melt-freeze conditions are existing with moist snow below 1700 m on all aspects, and to ridgetop on solar aspects. Below the surface, down 60-120 cm sits on the March 27th interface. Our field team was out in the region last Saturday; they were able to find the March 27th interface down around 90cm but test profiles did not produce any results on this layer. They were also out on Tuesday, found the layer again which seems to be more prominent on southerly aspects where the crust is thicker. The upper snowpack seems to be bonding to this interface and may soon become dormant. Glide cracks are a concern with the forecast rain below 1500 m. Be sure to give them a wide berth as they are very sensitive and could fail at any moment.

Problems

Loose Wet

Moderate-possibly heavy amounts of precipitation up to 1700 m is expected for Thursday. Watch for loose wet avalanches @ TL and BTL. They may entrain more mass and run farther than expected.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Wind Slabs

Forecast new snow above 1700 m, and moderate Southerly winds may create the perfect a recipe for building wind slabs on lee slopes, and behind terrain features at upper elevations.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

The odd deep slab could still be out there, I'm still suspect of steeper unsupported slopes and places where the snowpack goes from thick to thin, especially near ridge crest and around rock outcroppings.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 6

Valid until: Apr 12th, 2012 9:00AM