Observation Date
2/14/2014
Observer Name
cam mackenzie
Region
Salt Lake » Big Cottonwood Canyon » 10420
Location Name or Route
10420
Weather
Sky
Obscured
Precipitation
Light Snowfall
Wind Direction
South
Wind Speed
Moderate
Weather Comments
Variable throughout the day. At ~1300, rain levels were above the spruces campeground driving up the canyon. At the top of the guardsmans pass road, Low cloudcover and LW "greenhousing" was taking its toll on the upper snowpack. Along the ridge up to peak 10420, strong South/Southwest winders were transporting large amounts of snow onto north facing shots. Later in the day, light snowfall, still very windy. Precip crystals were mostly columns/needles with some capped columns. Periods of rimed crystals but nothing I would qualify as full graupel.
Snow Characteristics
New Snow Depth
5"
New Snow Density
High
Snow Surface Conditions
Dense Loose
Damp
Snow Characteristics Comments
New snow roughly 8-10cm with a small layer of heavily rimed precip particles below it (likely from yesterdays period of high convection). Storm snow from last week is well into decomposing/destructive metamorphism phase. I wouldn't call it "new snow" anymore.
Low cloud cover and warm temps are definitely making a damp top 20cm of snow. Still not a lot of free water in the snowpack, just high densities. Today I would divide the elevations throughout the range as those who received liquid rain and have free water in the upper snowpack and elevations above the snow line with no free water. Below the line, lack of cohesion (decreased strength) in the upper snowpack was creating lots of rollerballs and some point releases along the road.
Red Flags
Red Flags
Recent Avalanches
Wind Loading
Rapid Warming
Poor Snowpack Structure
Red Flags Comments
Recent Avalacnches- Kicked one small corncie and let loose a 40' by 20' by 10" slab on a 35 degree rollover. Not enough to bury someone but definitely would have raked someone into the trees below
Wind Loading- Observed loading today on north facing slopes. New cornices/ Alta Mt Baldy data from MESOWEST leads me to believe north facing slopes have recieved consistent loading the past few days.
Rapid Warming- Periods of "greenhousing" defiitely warmed the top layers of the snowpack. With tmrws bit of warm clear air, I dont think this problem is going away
Poor snowpack Structure- Last weeks upside down snow was reactive with clean planar shears on the density change
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Increasing Danger
Problem #1 Comments
Pockets of loaded zones were reactive today, don't see it going away with more winds tonight.
Avalanche Problem #2
Problem
New Snow
Trend
Decreasing Danger
Problem #2 Comments
Last weeks storm snow doesn't seem to be propagating and creating a good slab anymore. ECTs did not propagate across any columns today.
Snow Profile
Aspect
North
Elevation
9,400'
Slope Angle
25°
Comments
One often overlooked and misunderstood characteristic of the snowpack is how test results are extremely temperature dependent. Biggest snowpilot complaint for me is that the temperature function displays only .5 degree increments. Many layers that appear to have no temperature gradient, did in fact have one present.
While instructing a course of the U, I dug this full depth pit to get a feel what snow depths are like in upper Big Cottonwood. Down low, the layers were extremely stout. No results below the K+ layer ~65cm up. Most alarming was the Q1 shears at 69cm. Although these took a lot of force to get, If a trigger is large enough to get this failure the results could be large and dangerous. Potential for smaller avalanches to step down to this layer as well.
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
Considerable
Coordinates
