Observation: White Pine

Observation Date
12/4/2018
Observer Name
Mark Staples and A. McClean
Region
Salt Lake
Location Name or Route
White Pine drainage
Weather
Weather Comments
Clear, cold and calm.
Snow Characteristics
Snow Characteristics Comments
Beautiful powder and hero skiing. Trail breaking about boot top deep.
Red Flags
Red Flags
Collapsing
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Same
Problem #1 Comments
Nothing new here. ANY slope that had snow before thanksgiving has a persistent layer of weak facets at the ground. This layer is thick and obvious on NW, N, and NE facing slopes. It definitely exist on other aspects but it is less thick and sometimes spotty in distribution.
The MAIN POINT is that its about where snow lingered before T-giving. Some slopes that face other directions but do not receive direct sun due to shading from trees or other terrain features have this old snow. Aspect can help us determine where old snow existed, but you have to be a DETECTIVE and think about where that old snow lingered before Thanksgiving.
Any slope that faces NW, N, & NE has this layer. E facing slopes can have it. Upper elevation (above 9500 feet) slopes facing W and SE can have it. The surest way to know before committing to a slope is by digging and looking for this layer at the ground. This is what we did today. If that layer exists, don't ski or ride it. We did this on a W facing slope, found facets, and decided not ski it even though we suspected that the main part of the slope did not have this weak layer. We didn't want to gamble with our lives thinking that the weak layer "probably" didn't exist on the slope we wanted to ski. "Probably" isn't good enough.
Comments
We climbed up the NW ridge on Red Top Mtn in the White Pine drainage. This ridge separates the Birthday Chutes and Tri-Chutes. We looked at snow on NW facing and W facing.
  • NW facing is bad. It has an obvious layer of weak facets about a foot thick at the ground. This layer produced a massive collapse when I stepped out of my skis. This collapse shook small trees about 50 feet away. If we had been on a steeper slope we would have triggered an avalanche. 
  • We had one smaller collapse on a W facing slope near trees. This spot had weak, sugary facets at the ground because it is shaded by a line of trees.
  • Other places on a W aspect had thinner snow and no weak layer. 
  • I was very nervous about making any mistake with our terrain choices and we skied back down our skin track. Misjudging the layering in the snowpack under our feet or misjudging the aspect of a slope can have fatal consequences.
  • The safest options are skiing low angle slopes (less than 30 degrees in steepness) or skiing slopes that face south.
The GOOD NEWS - at 9400 feet there was about 4 feet of snow. This is great coverage. Hopefully it keeps snowing.
Images below are a snow profile on a NW facing slope at 9465 feet where we got the massive collapse. The second photo is the pit wall.
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
Considerable
Coordinates

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