Avalanche Forecast

Issued: Mar 18th, 2016 3:00PM

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

mike.koppang, Alberta Parks

Kananaskis.

Warm temps and strong solar radiation input are likely to trigger a round of natural avalanche activity this weekend. Use caution and be thinking about the sun and potential for full depth large avalanches.

Summary

Confidence

High - Due to the quality of field observations

Weather Forecast

The weather this weekend is looking to be clear with relatively light winds and warm temps. Freezing levels are expected to climb up to around 2000-2200m on Saturday and higher on Sunday so this will be the first big pulse of spring heat into the snowpack. This heat will likely wake up the basal instabilities in a few places and trigger some larger avalanches so use caution.

Avalanche Summary

There was a recent sz 3 off of Mt Nestor on Friday that was on a NE aspect around 2900m likely triggerred by a cornice collapse. There were also a few more sz 2 avalanches on solar aspects around 2400m that appeared to be failing on one of the recent march crusts. In addition to this, there was also numerous loose dry avalanches up to sz 1 on all aspects.

Snowpack Summary

Very little wind affect is being noticed throughout the forecast region. Windslabs are isolated in both treeline and alpine areas confined to ridgelines, gullied features and crossloaded slopes. The snowpack differs depending upon which aspect you are on. On solar aspects, there are a series of crusts in the top 100cm of the snowpack that are producing moderate sheers. On more polar aspects, the snowpack is more settled with only the basal weaknesses such as facets and depth hoar being the main concern. Forecasters were noticing whumpfing from thin shallow snowpack areas while travelling into alpine terrain today. Be especially cautious around these thinner snowpack areas as these are likely trigger points for a skier. Cornices are still very large at this time and we have seen numerous collapses over the past few days causing large destructive avalanches. Solar radiation that is likely to occur over the weekend is only going to decrease the stability making these problems more prominent. Use caution and be thinking about the sun and full depth, full path avalanches.

Problems

Persistent Slabs

Persistent slabs up to 50cm thick are present in lee and cross-loaded features in alpine areas and in very specific locations at treeline. Solar aspects where these slabs are overlying a crust will be a concern with solar radiation.

Choose well supported terrain without convexities.>Caution in lee and cross-loaded terrain near ridge crests.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 5

Deep Persistent Slabs

Heat from over the next few days may awaken some of the deeper layers. Stability will be quick to deteriorate on solar especially in thin rocky areas.

Be aware of the potential for large, deep avalanches.>Avoid convexities or areas with a thin or variable snowpack.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

3 - 6

Cornices

As temperatures warm up, cornices collapses will become more likely. Recent cornice collapses have been shown to trigger full depth large avalanches so give these features a wide berth.

Stay well back from cornices.>Pay attention to overhead hazards like cornices.>Cornices become weak with daytime heating. >

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

Elevations: Alpine.

Likelihood

Likely - Very Likely

Expected Size

3 - 6

Valid until: Mar 19th, 2016 2:00PM