28 Feb 2012

Slide yesterday near Russet lake.                                                                                                       Lee Harrison Photo

Hi Wayne, we were skiing today on lower Russett Ridge, north facing slope @ approx 5800ft, just getting into treeline and popped a soft slab with 40cm crown, 30 m wide and ran 150 -200metres, the depth of the debris at the runout was close to 2m, there is a slight convexity at the crown and the slope was well loaded.  Thanks for your blog.

At 2280 meters the temperature was - 15.5  at 06:00 hrs. The winds were 25-35 KPH from the SSE. At 1550 meters the temperature was - 10.5, 81 % relative humidity and the barometer is on a downward trend. No new snow overnight. In the valley it is - 9. Will start snowing today, we could see as much as 20 cm by tomorrow morning. 

Word on the street is  that there is some buried surface hoar towards the Hurley area, Duffy is still producing size 1 slides on preserved stellars, and the Whistler area is similar. 

For the latest Avalanche Advisory click here: Avalanche Advisory

It was a very busy Saturday past, with many stories of avalanche activity. Through the grapevine there was an involvement on the Duffy where a skier fractured their leg after hitting a tree and getting partially buried. Would like to find out more about this involvement?? Two snowshoers were involved in a size .5 slide on Decker Saturday and heli evacuated on Sunday.  Two skiers were involved in a size 2 avalanche behind Flute on Saturday,  in some very steep terrain. One individual suffered a knee injury and was air lifted out of the gully on Sunday. Check out the image below.

Thanks to Braden Douglas for the google image of where the slide was. Hard to see but the individual ended up just above where the marked area becomes thin. The fracture line is at the top with their tracks approaching the crown line. 

For an East Coast avalanche check this out: Tuckermans Ravine

Below is some information on Avalanche Dynamics:

When an avalanche occurs, as the snow slides down the slope any slab present begins to fragment into increasingly smaller tumbling fragments. If the fragments become small enough the avalanche takes on the characteristics of a fluid. When sufficiently fine particles are present they can become airborne and, given a sufficient quantity of airborne snow, this portion of the avalanche can become separated from the bulk of the avalanche and travel a greater distance as a powder snow avalanche. Scientific studies using radar, following the 1999 Galtür avalanche disaster, confirmed suspicions that a saltation layer forms between the surface and the airborne components of an avalanche, which can also separate from the bulk of the avalanche.

Driving a (non-airborne) avalanche is the component of the avalanche's weight parallel to the slope; as the avalanche progresses any unstable snow in its path will tend to become incorporated, so increasing the overall weight. This force will increase as the steepness of the slope increases, and diminish as the slope flattens. Resisting this are a number of components that are thought to interact with each other: the friction between the avalanche and the surface beneath; friction between the air and snow within the fluid; fluid-dynamic drag at the leading edge of the avalanche; shear resistance between the avalanche and the air through which it is passing, and shear resistance between the fragments within the avalanche itself. An avalanche will continue to accelerate until the resistance exceeds the forward force.