[MCR] Persistent Weak Layers 2007-2008

With assistance from the CAC forecasting team, I have prepared an article on this year's persistent weak layers that exist in many areas of the western Canadian mountains. The paper can be found here:  http://www.avalancheinfo.net/Media/Persistent%20Weak%20Layers%20and%20the%20Winter%20of%202007-08.pdf

Persistent weak layers that create a deep slab instability are a complex issue that is difficult to describe and discuss in the limited space of an avalanche bulletin. I hope this article will serve as a valuable reference for anyone planning activities in BC or Alberta this winter.

Karl Klassen
Mountain Guide
1735 Westerburg Road
Revelstoke,  BC
Canada
V0E 2S1
250-837-3733
kklassen@rctvonline.net

[MCR] Purcell Mountains, Powder Creek Jan 20-27

Spent the last seven days, Jan 20 – 27, ski touring at Powder Creek Lodge in the Purcell range near Kaslo BC.

 

The first six days of the tour were clear cold and calm, overnight low temps  –20 degrees, daily highs –8. Previous NE winds had created widespread, variably distributed surface slab development in open areas from below treeline to the alpine. We had best luck with ski quality on north and west slopes treeline and below. The alpine zone was super variable ski quality.

 

Snowpack and Avalanches:  The cold temps made for good facetted powder where not wind affected.

The windslabs, which ranged from soft (4F) to hard (P),  5 – 30cm thick, settled and bonded well as the week progressed, giving a couple very small results with ski cutting. No significant cracking, propogating, or whumphing. The early December crust is buried down 130cm at 1900m, hard to no results in snowpack tests. The crust does not exist above this elevation in the Powder creek tenure, though the interface from this date is discernible as a layer of rounding facets. One natural sz 2.5 avalanche occurred mid week on this layer, over a metre deep and 200m wide, on a steep sunny SW facing bowl at 2100m. On Jan 25 there was a sz 2 natural 50cm crown, out of a steep chute, also on a solar aspect at 2100m.

  With this snowpack and stable weather we were able to gain confidence throughout the week, attaining some great alpine ski touring objectives with a thought to minimizing our exposure to over head cornice hazard, solar slopes in the PM, and really rowdy unsupported terrain.

 

The thing now is that last night we received 20cm of low density snow, and more snow is forecast. This sits on a surface hoar layer that formed this week, all aspects and elevations, average size 5mm. The SH sits on a suncrust on steep south slopes.

 This newly buried layer is sure to be a concern when the fresh snow on top settles out and densifies, or the wind creates slab conditions.

 This synopsis will apply to the greater Kootenay Boundary region as the weather patterns have been similar over the area.

 

 Joel McBurney, SG

 Nelson BC

 

 

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[MCR] (no subject)

Selkirk Mountains - Rogers Pass - Mt. Sir Donald basin - Jan.25-08

 

Skied 3 days in the Pass this week today being the latest.

 

Biggest observation is the variability in the current snow surface – I was finding variable wind slabs in the alpine or 20 cm. of loose surface snow (faceted) depending on exposure to wind, some places were totally sheltered and provided great skiing – today there were sun crusts on steeper south through southwest aspects but not on the lower inclined slopes.

 

Then there is the surface hoar – inevitable after so many clear nights – observed 5-10mm. crystals in the valley bottom diminishing to 3-5mm. or less once you reached treeline – on the steep southerly aspects the surface hoar is sitting on the crust – not a great combination once loaded with new snow.

 

As well there was a delicate layer forming on the surface, comprised of large new snowflakes (stellars) that were falling out of the broken skies.

 

Also of note is the number of skiers in the Pass – so lots of lines have been skied over the last week. By the way you could see that surface hoar had grown in some of the old tracks.

 

No recent Avalanche activity everything we saw looked to be several days old.

 

The snow in the forecast will for sure be falling on a poor interface so I know I will be tip toeing around for a while if we receive any significant amount of snow.

 

Safe Travels

 

Scott Davis

Best Ever Adventures

E-mail: sdavis@alpineadventure.com

Check out the website: www.alpineadventure.com

(250)837-9630

Box 2795 Revelstoke, B.C.

V0E 2S0

 

[MCR] Pilsner avalanche

Hello

 

Driving by Field today and noticed a recent slab that avalanched on the approach to Pilsner Pillar.  It was a size 1.5 and would have been nasty as it went down through the trees.  I couldn't see any tracks from climbers (possibly animal triggered??) and it was on a bit of a steeper roll (left side, halfway between the top of the trees and the base of the route).  It looked like the crown was quite deep (60-90cms) and it slid sometime in the last 48 hours.  The slopes above the route looked quite loaded.

 

Take care out there..

 

Mike Stuart
ACMG Alpine Guide

[MCR] Urs Hole Avalanche

Noticed a fresh avalanche today out of the start zone above Urs Hole on
Cascade. It was a Class 2.5 slab that looks like it ran over the climb. It
was a clear sunny day with cool valley bottom temperatures, but the
temperatures at higher elevations were much warmer. Likely the trigger was
due to solar warming. Something to think about right now when choosing
routes with sunny start zones above them.

Brian Webster
UIAGM Mountain Guide

_______________________________________________
These observations and opinions are those of the person who submitted them. The ACMG and its members take no responsibility for errors, omissions, or lapses in continuity. Conditions differ greatly over time and space due to the variable nature of mountain weather and terrain. Application of this information provides no guarantee of increased safety. Do not use the Mountain Conditions Report as the sole factor in planning trips or making decisions in the field.
Please check out http://acmg.ca/mcr for more information.

[MCR] Coast Range - Cereise Ck.

Up at Cereise Ck yesterday.

 

Brrrrr

 

Cold temps hovering around -15C.

Strong outflow winds from the E and NE most of the day producing windslabs in alpine and open treeline features. Due to strength of winds, windslabs forming lower in the slope that you would expect.

I would suggest being very cautious for the next few days until these windslabs settle out.

 

The top 20-30 cm were becoming more facetted with these cool air temps. Whenever this clear spell ends, and the next snowfall comes, I expect this layer will be cause for concern.

Suncrust and windcrust managing to limit good skiing options, but we found excellent mid-boot-high pow in shallow trough features just above T/L and boot-top in tree glades.

Ran into another group that skied a higher gulley feature off Joffre ridge - apparently terrible skiing!

 

Brian Gould
Mountain Guide

[MCR] Pretty Nuts, Jan 20th

Warmer over in the Kicking Horse yesterday. Pretty Nuts in fine shape
although we didn't climb the WI 4 option on the left on pitch 2,
looked like small pillars and sporty. Seems like the place to park is
at the Golden end of the massive concrete retaining wall that starts
100 meters Goldenwards from Pretty Nuts, a small pull out on the
riverside of the highway there. We parked at the chain-up area 300
meters farther away and closer to Golden (just to the east of Lady
Killer) and on the riverside of the highway.

Happy trails

Barry Blanchard
Mountain Guide
Yamnuska Mountain Adventures
_______________________________________________
These observations and opinions are those of the person who submitted them. The ACMG and its members take no responsibility for errors, omissions, or lapses in continuity. Conditions differ greatly over time and space due to the variable nature of mountain weather and terrain. Application of this information provides no guarantee of increased safety. Do not use the Mountain Conditions Report as the sole factor in planning trips or making decisions in the field.
Please check out http://acmg.ca/mcr for more information.