Avalanche Forecast

Issued: Apr 1st, 2015 9:44AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Cornices.

ghelgeson, Avalanche Canada

South Rockies.

Warmth remains the primary driver of avalanche hazard as we shift into a more spring like pattern. Minimize your exposure to large slopes if the snowpack is becoming moist or wet.

Summary

Confidence

Fair

Weather Forecast

Thursday: Freezing starting near 1000m, rising to about 1600m in the afternoon. Partly cloudy skies. Light variable winds at all elevations. No significant precipitation expected.Friday: Freezing level starting at valley bottom, rising to about 1700m throughout the day. Mostly clear skies. Moderate SW winds all elevations. No significant precipitation expected.Saturday: Freezing level hovering around 1500m. Moderate SW winds at treeline, strong SW winds at ridgetop. Scattered cloud. No significant precipitation.

Avalanche Summary

No new activity to report from Tuesday. On Monday a few large avalanches were reported: Our field team was in the Crown Mountain area where they noticed a large slab avalanche on an extreme E/NE face that was likely triggered by cornice fall. In the neighboring Waterton region cornice failure resulted in two large avalanches that stepped down to the mid-February interface on NE facing features at 2400m. On Saturday in the neighboring Lizard Range cornice fall produced a size 2.5 avalanche.

Snowpack Summary

Both Monday and Tuesday brought good overnight temperature recovery to the region with temps getting down to +0.8c at 960m. These colder temps are forming a surface crust that should become supportive if it isn't already. On Wednesday ridge-top transport of snow was observed which is likely resulting in wind slab formation in the alpine. The snowpack is reportedly isothermal as high as 2000m at this point and even the highest elevations are probably not far off. The mid-March rain crust is down 35 to 70cm and has shown a good bond with snow above. Old persistent weak layers are still intact in the mid and lower snowpack and there may be potential for these layers to wake up with a big cornice fall, sustained warming and/or a significant rain event.

Problems

Wind Slabs

Upper elevation winds have been generally out of the west at slab-forming speeds for the past 72 hours. Stay on guard for fresh and potentially touchy wind slabs, especially if your travel plans include terrain immediately lee of ridge-crest.

Travel on ridgetops to avoid wind slabs on slopes below, but be careful with cornices!>Be careful with wind loaded pockets, especially near ridge crests and roll-overs.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Cornices

Large, vulnerable and dangerously heavy chunks of snow hang precariously over many ridge-lines. While cornice failure is problematic enough on its own, don't discount the ability for falling chunks of cornice to release bigger slab avalanches.

Give cornices a wide berth when traveling on or below ridges. Remember that cornices become weak with daytime heating.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Apr 2nd, 2015 2:00PM