Observation: Willows

Observation Date
12/24/2016
Observer Name
B
Region
Salt Lake » Big Cottonwood Canyon » Willows
Location Name or Route
Willow Heights, West Willow, Mule Hollow
Weather
Sky
Obscured
Precipitation
Moderate Snowfall
Wind Direction
Southeast
Wind Speed
Moderate
Weather Comments
Sustained Moderate Wind Speeds predominently out of the SE with Strong Gusts. Wind Transport and or Wind Blown mostly Moderate with occasional periods of Intense. Temperatures remained in the upper 20's at 8000 and Mid to Lower 20's at the Upper Elevations.
Snow Characteristics
New Snow Depth
8"
New Snow Density
Low
Snow Surface Conditions
Powder
Wind Crust
Melt-Freeze Crust
Snow Characteristics Comments

The SE Winds were scouring many exposed Windward Slopes from 9000 and up. Breakable M/F Crust was on the surface where this scouring was occurring. Excellent riding in other areas with 6 to 10 inches of new snow. You could still feel the Crusts on all but the Shady aspects, but it was not a factor for quality riding. NW, N and NE aspects rode better. 8 inches at 8000 in Silverfork and it appeared that some areas on the Park City Ridgeline actually did not receive as much. Wind Crusts and Pencil Hard Wind Slabs were observed in the most heavily Loaded and or Wind compacted locations. Slabs of up to 18 inches were observed. Fortunately the Temperatures did not get above 31 even at 8000 feet and the snow on all aspects remained cold and dry.

Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Wind Loading
Cracking
Poor Snowpack Structure
Red Flags Comments
Poor Snowpack Structure was mainly focusing on the PreStorm Weak Snow Surfaces that were not appearing to allow for good bonding. Hand Pits were yielding easy Shears at this interface, yet the new load did not appear to be have quite enough weight to become reactive either for Propagation and or Slab Release in many locations. Visibility was very poor and basically nonexistent when on top of the Park City Ridgeline, and thus unable to detect possible Natural Slide activity on Steep Facing Northerly terrain. It is hard to believe there was not activity, and possibly others may have had better opportunities for observations of this terrain at differing times of the day. Minimal cracking was observed in the Fresh Stiff Wind Slabs that were observed.
Avalanche Problem #1
Problem
Wind Drifted Snow
Trend
Increasing Danger
Problem #1 Comments

Active Loading and ample amounts of New Snow for Transport appeared to generate this possibility today regardless of specific Observations validating this Problem.

With the Winds forecast to accelerate and shift to a more W to NW direction overnight, this Problem may show an Increasing trend into Christmas Day.

OF NOTE: Unusual Drifting and Loading was observed today with the unique SE Winds; and as they swing more out of the NW many aspects may be suspect on Christmas Day,

Avalanche Problem #2
Problem
Persistent Weak Layer
Trend
Increasing Danger
Problem #2 Comments

Whether you call it Storm Slab or Persistent Slab, the potential for Avalanche Activity with the Weak Layer of concern being the Weak Surface PreStorm Snow appears to be very possible. Poor bonding to the NSF's and Possible SH that were buried at the beginning of this Event appears to be of concern with possible Slides being up to at least 2 Feet and more in depth by mid day on Christmas. This instability may linger well into the coming week due to the nature of the these buried Persistent Weak Layers.

Regardless of no Natural Activity observed during this day of poor Visibility, the possibility that there were Naturals appears to be certain. And, after another night of Moderate to Strong Winds combined with the possibly of another Foot to Two Feet of additional Snow Fall, the Considerable Danger from Saturday may be inching towards High on Christmas Day.

Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
High