Observation: Park City Ridgeline

Observation Date
1/31/2013
Observer Name
Bruce Tremper and Mark White
Region
Salt Lake
Location Name or Route
Park City Ridge Line from West Monitor to No-Name Bowl
Weather
Sky
Overcast
Wind Direction
West
Wind Speed
Strong
Weather Comments
Stratus clouds near ridge tops. Still quite strong winds from the west. Fairly warm temperatures.
Snow Characteristics
New Snow Depth
15"
New Snow Density
High
Snow Surface Conditions
Dense Loose
Snow Characteristics Comments

Wind blasted snow along all the ridges. But down off the ridges, the snow rides OK but it's about 8 inches of dense graupel, which is kind of punchy in places because it was deposited on top of lighter snow.

Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Wind Loading
Collapsing
Poor Snowpack Structure
Red Flags Comments
Still lots of red flags here and we avoided all slopes steeper than about 30 degrees because of all the wind, dense snow and buried layers of faceted snow.
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Decreasing Danger
Problem #1 Comments

With all the ferocious winds over the past couple days, there is no lack of wind slabs in downwind terrain. These range from soft to hard and they exist mostly on east through south facing slopes along ridge lines. As always, avoid all slopes about 34 degrees or steeper with recent wind drifts. I'm guessing the wind slabs will settle out fairly quickly and the by tomorrow, the main problem will be the persistent slabs, because they are, well, persistent.

Avalanche Problem #2
Problem
New Snow
Trend
Same
Problem #2 Comments

I can't decide whether persistent slabs or wind slabs are the most dangerous right now. The persistent slabs will break about 2-3 feet deep to a layer of faceted snow formed on the snow surface during the first part of January. This layer is quite inconsistent and spatially variable, but I can still find many areas where it's still sensitive and still propagates a fracture easily on an Extended Column Test. We saw one large avalanche today that broke on this layer.

These slabs are stubborn and inconsistent, so they will linger into the weekend. I suspect we will hear about some human triggered avalanches on this layer and I hope everyone comes home OK. They are the classic, low probability-high consequence avalanche. They may let several people jump on them before they break and take out many tracks. Persistent slabs have to be matched with equally persistent patience.

Video

Here is a quick video of the two avalanches we saw today and a snow profile showing the problem weak layer we will have to worry about through the weekend.