Observation: Brighton Perimeter

Observation Date

1/6/2018

Observer Name

Region

Salt Lake » Big Cottonwood Canyon » Brighton Perimeter

Location Name or Route

Brighton Perimeter

Weather

Sky

Obscured

Precipitation

Light Snowfall

Wind Direction

West

Weather Comments

Dense fog and obscured skies prevented good visibility and the possibility of seeing any avalanche activity. Snowfall rate was sustained at S minus 1 thoughout the day with daytime totals at 9000 feet at 5 cm / 2 inches. Snowfall rates appeared higher at the upper elevations. The rain/snow line appeared to hover between 7500 and 8000 feet throughout the day. Winds were in the light range initially out of the SW and veering to the NW in the late afternoon hours, and no transport and or wind blown was observed. Yet, areas traveled were sheltered and protected.

Snow Characteristics

New Snow Depth

New Snow Density

High

Snow Surface Conditions

Faceted Loose

Damp

Snow Characteristics Comments

Snowfall began at 0730 and prior to any new snow coming in the surface snow conditions were covered in a deep coating of NSF's. Early morning temperatures were barely below freezing, and as a result the new snow came in damp. Because of this, the new snow at these mid elevations appeared to bond well to the old snow surfaces. In steeper terrain, the depth of the prestorm NSF's allowed for loose snow avalanches initiating in the NSF's that were down 2 to 3 inches .

Red Flags

Recent Avalanches

Wind Loading

Poor Snowpack Structure

Red Flags Comments

Early reports of avalanches from the upper elevation zones of the Brighton perimeter appear to indicate the poor snowpack structure may have been receiving enough loading by late afternoon to tip the scales towards instability. Winds at the upper elevations appear to be contributing to this critical loading potential.

Avalanche Problem #1

Problem

Persistent Weak Layer

Trend

Increasing Danger

Problem #1 Comments

At 1900 hours snow is still falling in the Cottonwoods, and it appears there is a tight band of Lake Effect that may be in play for at least another hour or two. Water content is now approaching 1/2 inch. With the moderate wind speeds in the highest elevations, and ample light speeds at the lower ridgelines, enough significant loading appears to be in place to initiate at least an isolated avalanche cycle overnight. Remote triggering appears to be possible on Sunday.. As cited above, the winds may also be contributing to this problem, and slab development may be enhanced because of this factor.

Avalanche Problem #2

Problem

Wet Snow

Trend

Increasing Danger

Problem #2 Comments

Both loose wet and shallow wet slabs may be a concern on Sunday with the forecast for clear skies and daytime highs at 9000 feet expected to be at and or near 40 degrees.

Any slides have the potential to dig down into the deeper faceted layers.

With the continued threat and the possibility of natural activity, either from overnight precip/loading, and or solar radiation during the day, a Considerable danger on Sunday appears likely on all the previously cited terrain aspects and elevations. Northeast and East aspects may be the worse.

Today's Observed Danger Rating

Moderate

Tomorrows Estimated Danger Rating

Considerable

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