Observation: 10420

Observation Date

12/27/2025

Observer Name

Gagne / Shade

Region

Salt Lake » Big Cottonwood Canyon » 10420

Location Name or Route

10,420' to PC Ridgeline

Weather

Sky

Overcast

Precipitation

Moderate Snowfall

Wind Direction

West

Wind Speed

Moderate

Weather Comments

Moderate winds from the west blowing and drifting snow along upper-elevation ridgelines. Snowfall diminished around 0900, with even some peaks of sun by late morning.

Snow Characteristics

New Snow Depth

New Snow Density

Medium

Snow Surface Conditions

Powder

Snow Characteristics Comments

Storm snow depths since 12/26 are 15-20 cms (6-8 inches). Some small, sensitive, shallow wind drifts on ridge lines.

Red Flags

Heavy Snowfall

Wind Loading

Poor Snowpack Structure

Red Flags Comments

PWL at the base of the snowpack remains reactive with full propagation where the Christmas Eve Rain Crust (CERC) is thinner (2-3 mm).

Avalanche Problem #1

Problem

New Snow

Trend

Decreasing Danger

Problem #1 Comments

The storm snow is mostly right-side up, with a few density inversions during periods of heavy precipitation which should settle out quickly. Some wind drifting with shallow soft slabs and small cornices along the ridgelines. We noted two small natural avalanches from a cornice fall.

Once the Christmas Eve Rain Crust was buried, new snow came in as dense graupel with warmer temperatures and was well-bonded to the rain crust, but the graupel could still act as a weak layer in areas with a denser slab on top, especially on slopes where the graupel has pooled and created a deeper layer.

Avalanche Problem #2

Problem

Persistent Weak Layer

Trend

Same

Problem #2 Comments

The only pit we got full propagation was at 9,600' on a N aspect near Lane's Leap. ECTP21 down 70 cms, failing in dry facets and depth hoar. The Christmas Rain Crust was 2 mm in this location. All other pits were poor quality ECTN failing in the graupel layer above the Christmas Rain Crust.

Comments

We dug several pits on northerly aspects, and found a small disparity in the thickness of the Christmas Rain Crust:

(1) 9,560' NE aspect 2-3 mm crust

(2) 9,600' N aspect 2 mm crust

(3) 9,830' N aspect 3 cm crust (photo below showing Jess Shade with the thick crust)

(4) 10,400' N aspect 1-2 mm crust

We also found mostly dry facets and depth hoar down near the ground. In areas where the crust is thinner, it is possible a wind drifted slope could create enough of a load to affect the deeper PWL.

The Christmas Rain Crust is strong and supportable and provides a nice base for travel and turns in the new snow. Fortunately, we were not finding a dust-on-crust situation as the snow from Friday and Saturday came in dense and bonded to this crust.

Today's Observed Danger Rating

Moderate

Tomorrows Estimated Danger Rating

Moderate

Coordinates

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