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Observation: White Rock Hollow

Observation Date
3/21/2013
Observer Name
Engelhard/McAvoy
Region
Logan
Location Name or Route
Providence Canyon up to White Rock Hollow
Weather
Sky
Overcast
Precipitation
Light Snowfall
Wind Direction
West
Wind Speed
Moderate
Weather Comments
Early morning snow showers gave way to partial clearing in the valley, yet the mountains remained overcast until 1330. Intermittent/patchy sunshine in the from the mid afternoon on, with the cloud cover remaining thick throughout. Ridgetop winds were sustained in the Moderate Range with some gusts hitting the High Range. Transport and or wind blown snow was significant throughout the day.
Snow Characteristics
New Snow Depth
8"
New Snow Density
Medium
Snow Surface Conditions
Powder
Dense Loose
Wind Crust
Melt-Freeze Crust
Snow Characteristics Comments

The East facing terrain had a consistent 8 inch blanket of moderately dense creamy new snow. A group of local celebrities showed the way up Providence Canyon to the Bear River Crest where we dropped into White Rock Hollow. We made three laps on slopes ranging from SE, E, and NE into this upper drainage. The West and NW facing upper elevation terrain had areas of wind scour intermixed with denser (but ridable) wind blown. Of note, even though there were brief periods of sunshine, and threats of greenhousing, the snow on all aspects remained cold and dry. Reports from other parts of the Bear River Range indicated that greenhousing was actually more of a factor damaging/adversely affecting the new snow. Specifically, the Steam Mill Area had much more intense sunshine and adverse affects.

HN: 6 overnight

HS taken in White Rock Hollow on S facing terrain at 8700 feet: 130 cm

HS taken in White Rock Hollow on N facing terrain at 8900 feet: 170 cm

Red Flags
Red Flags
Recent Avalanches
Wind Loading
Cracking
Red Flags Comments
Upon reaching the Ridge/Crest, we discovered a natural avalanche that had appeared to run within the past hour or two. This wind loaded East facing slope was approximately 40 degrees in steepness; and the soft slab appeared to have been triggered by building cornices that were calving off onto the steep starting zones. This slide was approximately 100 feet wide and it's crown was mostly blown in at the time of observation. This slide ran into the transition zone and was approximately 175 in vertical. The debris pile was at least 2 feet deep. We were able to intentially trigger the remainder of the gully by merely approaching the upper ridge and stomping on a 25 degree rollover that tied into the slope below. This action triggered a slab that propagated south along the ridgeline another 65 feet and the crown here was between 8 to 14 inches deep. This was a soft slab/wind slab, and it ran an equal distance down the slope. During the day we observed two more naturals in this general area. All slides were of similar depths, and all ranging from 60 to 90 feet wide. These slides did not run as far. Cracking was observed on the up track heading up to the Crest from the Providence side. Wind loading and or wind blown snow was in the Moderate Range, and plumes were observed throughout the day on many upper elevation East facing ridgelines. The winds were channeling into the lower elevation terrain below the upper ridgeline, and our skin trails and tracks were blowing in by the hour. Of note: we also observed 2 natural avalanches upon our descent of Providence Canyon. These were at about 6500 feet on North facing terrain. They ad appeared to have been a result of cross loading from the up canyon winds. Both slides were approximately 65 feet wide and ran 100 to 125 feet.
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Same
Problem #1 Comments

See above description. There were periods of intense wind activity even later in the afternoon. By the time we were heading back to Providence at 1600 the winds were still a factor. This new snow was not bonding well on the steep East and South facing terrain where the aforementioned slabs were active. As long as these winds continue to blow and remain a factor they may continue to be active in building slabs. In larger steep E, NE and SE facing terrain features, the potential for more destructive/hazardous slides may be possible.

Avalanche Problem #2
Problem
Wet Snow
Trend
Increasing Danger
Problem #2 Comments

At any point when and if the sun becomes a player with more intense sunshine, this new snow may go through a period of activity on steep E, SE and S facing terrain.