Avalanche Forecast

Issued: Mar 27th, 2012 10:26AM

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

Avalanche Canada ghelgeson, Avalanche Canada

Summary

Confidence

Fair - Intensity of incoming weather is uncertain on Thursday

Weather Forecast

The Gulf of Alaska drives a relatively moist weather pattern for the second half of the week. The region should pick up around 5 cm Tuesday evening along with moderate southerly winds. Wednesday: Another 5 cm of snow are expected. Freezing level is relatively well behaved staying around 1500 m. Winds out of the SW, light at treeline, moderate in the alpine. Thursday: 5 - 15 cm expected above 1000m. Winds SW, mod at treeline, strong at ridge top. Friday: Snowfall starting late in the day, 10 - 15 cm expected by Saturday morning.

Avalanche Summary

Numerous point releases out of steep solar aspects where observed. No large avalanche activity reported from the region.

Snowpack Summary

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 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
A modest amount of new snow along with moderate SW winds will form fresh wind slabs immediately lee of terrain features like ridge crests and ribs. Slope cuts are an appropriate tool for this hazard for those well versed in the technique.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Cornices

An icon showing Cornices
Cooler temps, cloud cover & limited solar input combine for a lower likelihood of cornice failure, but it is still possible. Consider giving cornices a large berth when traveling on ridge lines where falling through a cornice could be disastrous.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
There haven't been any reports of large deep avalanches for a few days now, but, I'd suggest keeping it in mind as you travel. Human triggering is most likely where the snowpack goes from thick to thin, especially near rock outcroppings.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

5 - 8

Valid until: Mar 28th, 2012 9:00AM