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Observation: Catherines

Observation Date
10/30/2013
Region
Salt Lake » Big Cottonwood Canyon » Catherines
Location Name or Route
Brighton to Catherine's Basin, Rocky Points, Dry Fork/Sunset Saddle, Supreme
Weather
Sky
Overcast
Precipitation
Light Snowfall
Wind Direction
Northwest
Wind Speed
Calm
Weather Comments
Temperatures cold for October: mid 20's above 9k. Overcast skies with light snowfall occurring throughout the day...after an intense burst of high PI that occurred from 9:00 am till 11:00 am. Winds remained extremely light with a suttle breeze only detected on the upper ridgelines. No visible transport observed. The sun did not appear to adversely affect the snow surface.
Snow Characteristics
New Snow Depth
12"
New Snow Density
Medium
Snow Surface Conditions
Powder
Snow Characteristics Comments

Snow totals for the storm:

13 inches in Silverfork

​15 inches at upper elevations

All areas settled out significantly due to the warm ground temperatures and initial warmth of the pre-frontal phase of the storm event.

Total Snowpack Depth:

24 to 33 inches on NNE - NNW aspects above 9800 feet

The bulk of the latest event occurred overnight on the 28th into the early morning hours of the 29th. Another 3 inches fell between 9:00 am and 11:00 am on the 30th. The event came in with moderate winds, and it was quite warm with the initial 3 inches coming in very dense and damp. From this point on the storm was right side up. Then the additional 3 inches that fell on the 30th was a bit more dense and slightly slabby creating a slight density inversion in the upper levels of the snowpack.

Riding conditions above 9800 feet were creamy on NNW - NNE aspects. Obstacles obviously are the main concern in all terrain choices with the limited/thin snowpack.

Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Cracking
Collapsing
Poor Snowpack Structure
Red Flags Comments
Widespread cracking and muffled collapsing observed on all shady aspects above 9200 feet with slope angles 33 degrees and greater. See avalanche observation for details on Pioneer Peak area activity. Heavy snowfall rates during the peak hours of the event appeared to help overload a previously poor structured/weak snowpack. The previous event (Oct. 11th) prior to the the event on the 29th has appeared to develop into moderate sized facets. The other two snow events from earlier in Sept. and Oct. have consolidated into 2 to 4 inches of dense/damp m/f crusts. The new snow initially bonded to the previous snow surface due to it's warmth, yet easy to very easy shears were observed in moderate sized facets, 1 to 2 inches down from the previous snow surface. OF NOTE: This layer will be easily detected due to a "Snirt" layer that was formed during the first part of the latest event. These shears were observed 1 to 2 inches below the "Snirt" layer.
Avalanche Problem #1
Problem
New Snow
Trend
Same
Problem #1 Comments

Technically the problem is a "Storm Slab" as it is a new slab from the latest event. Yet, due to the nature of the persistent weak layer (as previously described) it may be identified from this point on as a Persistent Slab. Though it did not appear as sensitive as observations indicated it was on the 29th, this problem is not going away, and it may possibly develop into a much thicker faceted layer if we do not get any more new snow within the next couple of weeks. All northerly and or shady aspects with any old snow are suspect. This problem was observed down to at least 9000 feet. Propagation and remote triggering may still be possible on all slopes that had old snow before this latest event on slopes with angles greater than 35 degrees. Of note, it appears that upper elevation slopes with due East and or West aspects may have gotten a significant m/f crust from the latest warm period. In some areas observed, the old snow has consolidated down to a supportable m/f crust with the basal facets not as much of an issue. Each slope should be inspected for the prevalence of these basal facets; and it is very easy to identify the loose basal facets with quick hand pits.

Snow Profile
Aspect
Northwest
Elevation
10,000'
Slope Angle
38°
Comments

Layering was as follows, top down:

Surface, Stellars

12 inches of fist (new snow)

1/2 inch of pencil (consolidated due to the warm snow from the initial phase of the latest event)

Thin "Snirt" layer

Shears 1 to 2 inches below "Snirt" layer: CT11, ECTP13, both exhibiting Q1 and SC Fracture Characteristics

8 inches of fist, moderate sized facets

2 inches of pencil to knife m/f, moderate to large sized damp grains

Ground

Coordinates