Avalanche Forecast

Issued: Mar 28th, 2012 4:00PM

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

Avalanche Canada ghelgeson, Avalanche Canada

Summary

Confidence

Fair - Due to variable weather conditions

Weather Forecast

6 - 12 cm are expected Wednesday evening before a fast moving convective storm impacts the region Thursday bringing 10 -25 cm, with the western portions of the region set to receive the greater snowfall. Winds Thursday will be out of the W starting the day near 30 km/h, increasing to 40 gusting 70 in the afternoon. Freezing level stays around 1300m. Friday: The system exits to the east Friday while winds remain strong. Sunny periods are expected in the afternoon. The freezing level will be on the rise, topping out near 2000m. Saturday: The ridge intensifies resulting in high intensity solar input for the region. The freezing level starts the day around 1500m, climbing to 2000m in the afternoon.

Avalanche Summary

A few size 1 human triggered wind slab avalanches were reported Wednesday. There were also a few small cornice failures which resulted in relatively small size one avalanches.

Snowpack Summary

10 cm fell Tuesday evening accompanied by moderate winds. In wind exposed locations this new snow has been formed into wind slabs 15 - 30 cm in depth. Below this lies a well settled snowpack.Spring the season has arrived, and it's not just calendar spring either, it's really felt different in the mountains the past week. The snowpack is far from isothermic, but the mercury has climbed above 0 as high as 2500m over the last 7 days. These warm temps have really helped to settle out the upper snowpack. Professionals throughout the region are reporting a very well settled & firm upper snowpack with minimum concerns in the upper 150cm.The exception are slopes below 1000 meters, which did not refreeze Tuesday evening. These slopes are likely rain soaked at this point too, making for a sloppy wet snowpack at lower elevations.The spring sun is increasing in strength as each day grows by a few minutes. It takes very little time for S, SE & SW aspects to feel the heat of the sun now. W & E facing slopes are just starting to be affected by the sun as we head into the tail end of March.The effect of the sun becomes very important at this time of the year. We're expecting 5 - 10 cm of snow above 1500 m the next few days. As soon as the sun comes out, watch for roller-balling & pin-wheeling to start surprisingly quickly. Wet point release avalanches won't be far behind on slopes receiving direct sun.There's a lot of strong snow between recreationists and the February surface hoar layers and it's been a few days since there was a large deep avalanche in the region. That being said, it could still be triggered. I'm thinking of three different scenarios at the moment:1. The most likely scenario is a large cornice or icefall failure impacting the slope below and producing a very large avalanche. Managing this piece of the hazard puzzle is done by monitoring what's happening above you. Cornices or slopes receiving direct sun are suspect. If you feel like there's a question as to whether or not a piece of cornice is warming to its breaking point, then, there's no question, it's time to get off that slope.2. Just last weekend an experienced party remote triggered a very large avalanche in Glacier Park near Mt. Tupper. This makes me think that it may still be possible for skiers or sledders to trigger very large avalanches failing 1.5 - 2m in depth. The most likely location for this type of failure is where the snowpack goes from thick to thin. This is most likely near ridge crests, the edges of slopes and especially around rock outcroppings.3. While I don't foresee it occurring in the next few days, a slope that does not experience an overnight refreeze is suspect for producing large avalanches. This is something to think about as we flip our calendars to the April page.

Problems

Wind Slabs

An icon showing Wind Slabs
New snow will combine with gusty W winds Thursday resulting in widespread cornice growth & wind slabs capable of producing avalanches to size 2.5. Increased caution is appropriate with large cornices looming overhead.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Storm Slabs

An icon showing Storm Slabs
The region is expecting 6 - 12 cm Wed. afternoon and an additional 10 - 25 Thurs, with the greater accumulations in the west. The storm snow may be touchy as it interacts with old melt freeze crusts and previous thin windslabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
There hasn't been any activity on this layer since the weekend, but a large trigger like cornice fall or a wind slab avalanche may trigger a deep slab. Human triggering is unlikely, but possible in thin snowpack locations & near rock outrcroppings.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

5 - 8

Valid until: Mar 29th, 2012 9:00AM