May, 12, 2014, Cascades, Consolidation

As it's that time of year, I'd like to see how different people feel about and define late spring/summer consolidation. Over the years I've spent lots of time skiing sunny,warm snow at this time of the year. I've also seen some of the worst slides of my life in May/June. About 5 years ago I saw a picture of the WHOLE Northside of the Flute/lesser Flute area down to the ground. One long fracture line about 500 feet above tree line, encompassing terrain that I had been skiing since November. The same thing happened that year in Jersey Cream Bowl shortly after the lifts had closed on a hot, spring day. How do you best guard against this? (I'll try to find the pictures)

Flute late spring avalanche (after lifts had closed at Whistler but while Blackcomb was still open.) 2008

www.whistlersnowreport.com/wp-content/ga...y/2008-may/Flute.jpg

Then there's the Grouse Creek wipeout here on Baker a few years ago.
People far more knowledgeable than I have commented here on depth of overnight freezing. There seems to be, to be close to truly free from the risk of the not-super-likely and not-very-predictable catastrophic spring slide, a need to have overnight freezes of adequate depth at some point during the spring period of liquid water percolation down into the pack. I find it very difficult to know what is enough to go anywhere we want afterward. The periods of high probability of upper layer failure are easy (like recently). The security of safety from deep failure to me is not.

To me it seems to come down to how well the snowpack is draining. If water melting at the surface is able to run to the ground, then it's relatively straightforward to grasp the risk of climax slides and where they're likely to occur (typically on smooth, sloped rock such as the entirety of the terrain out the lower gate at Alpental). If that water isn't percolating fully through the snowpack, it may be lubricating a buried weak layer which dramatically increases the risk of wet slab avalanches. Those are the kind that terrify me - loose wet slides are predictable and while not entirely avoidable, usually manageable with ski cutting and smart terrain selection. Wet slabs can release above you and bring an incredibly massive amount of snow down in a much quicker fashion than a wet loose slide.

That said, a wet loose slide can entrain a large amount of snow and run for a very long distance. You need to be aware of those below you as well as attentive to any terrain traps when the risk of wet loose avalanches is present.

How can you determine how well the snowpack is draining? That I don't have a great answer for as digging a snowpit to the ground is exhausting and time-consuming at this point in the year.

Flute late spring avalanche (after lifts had closed at Whistler but while Blackcomb was still open.) 2008

www.whistlersnowreport.com/wp-content/ga...y/2008-may/Flute.jpg

Better link w/ more photos: www.whistlersnowreport.com/photo-gallery/2008-2/may

The heavenly basin shots show how skier compaction doesn't help when things go to the ground. I've talked to Blackcomb Patrol about their spring time decision making and a lot has to do with overnight crust recovery. If there is no crust formed they are more apt to close the alpine early.  I guess timing is critically important

This is the Avalanche report for the area around Whistler. For May 14-16 the level is Considerable and High in the alpine.



Danger Scale
Travel
The avalanche hazard will increase significantly today with solar effect and rising temperatures. The freezing level in the Alpine was above zero last night giving no real crust recovery. Be very cautious of solar aspects and avoid travelling in steep thin rocky areas. Cornices are very touchy and should be given a wide berth.
Activity
Yesterday just outside the ski area, a cornice failure was reported to have caused a size 2 avalanche stepping down into the deeper layers.
Snowpack
Isothermal conditions are now beginning to penetrate deeper into the snow pack.
Weather
The ridge of high pressure is expected to strengthen today giving us warm Alpine temperatures and sunny skies through until Thursday.

Fwiw.

About a week ago In the central cascades, monte cristo area, it was prime for sliding big.

On the flat columbia glacier. Supportable crust(until it warmed),on 2 feet of isothermic mush, on top of a 2 inch deterorating crust, on 2 feet more of mush. Didnt investigate any further. I could definatly see it stepping down. Most of the moderate terrain showed no signs of sliding recently. Most steeper terrain getting sun was sliding non stop, here and there.

Didnt get on anything remotely steep. Figure 11'd on the splitboard back to the lake.

A rather timely discussion for sure ...

Here's an excerpt from the NWAC Special Advisory that was posted Tuesday afternoon just before the prior post in this thread:

"Wet snow deeper than a few inches, pinwheels and small natural wet loose avalanches usually precede larger wet loose snow avalanches. Wet loose avalanches should mainly stay within the most recent snowfall but we can't rule out large or very large avalanches entraining wet snow below. Avoid steeper slopes during peak heating, give cornices a wide berth and be wary of terrain traps where even a small but powerful wet loose avalanche can become deep very quickly."

Another Special Advisory was issued Wednesday evening after the tragic incident, even though the Tuesday Advisory stated the next one wouldn't be issued until Thursday afternoon, but based upon a quick read I didn't notice any significant changes.

I just checked the Avalanche Advisory for Whistler area again today - and it was Low everywhere because of a hard crust. Too bad the cold air didn't travel farther south. Apart from Whistler, their Advisories are also shut down for the year, but they provided this springtime information which I thought very good. A read of this information over the last few days would certainly have discouraged most from big objectives during this hot spell.

blogs.avalanche.ca/spring-conditions-scenario-series/

How do you best guard against this?

When dealing with warming-related hazard, I like to travel on days with lower freezing levels than the highest freezing level since any substantial precipitation, preferably by 2k+. Bonus points for a period of lower freezing levels between then and now. It's not a sure-fire method, but it can help.

June 14/15, 2008 shaped my approach to springtime hazard; a lot of people, myself included, nearly got caught-out by partial exceptions to this rule (big dump, big warmup, little-to-no cooling). A friend's advice to "ski it early" on Wy'east Face on the morning of June 14 may have saved solo-me from getting caught in a substantial slide.

Lowell has a lot of useful things to say about 'Mush Season'

www.alpenglow.org/skiing/high-route-tips/part3-mush.html

Great link Charlie.

Where can one find data on past freezing level? And for forecasts, is there anything other than the "Freezing Level AGL" of the UW models?

When dealing with warming-related hazard, I like to travel on days with lower freezing levels than the highest freezing level since any substantial precipitation, preferably by 2k+. Bonus points for a period of lower freezing levels between then and now.  It's not a sure-fire method, but it can help.

Clear nights for at least a few nights before a tour is another thing I'd prefer to see...

Quite a bit of illuminating information about the snow-pack deep down when you think about it: Chinook pass reports from Stimbuck--I think I get it--read it maybe it will click...

2 days ago, same location, very little change in conditions, other then it took another 500' to get to snow level..

Silver had good snow on the steep west facing pitch from 5400' to the lake. No slushy junk. Maybe other west facing slopes are similar?

Where can one find data on past freezing level? And for forecasts, is there anything other than the "Freezing Level AGL" of the UW models?

mountain-forecast.com is seems pretty accurate.