Observation: Big Cottonwood Canyon

Observation Date

4/16/2020

Observer Name

Region

Salt Lake » Big Cottonwood Canyon

Location Name or Route

Upper Big Cottonwood Canyon

Weather

Sky

Overcast

Precipitation

Light Snowfall

Wind Direction

West

Wind Speed

Moderate

Weather Comments

Skies were OVC until around 1400 when there was partial clearing at Upper Elevations and significant clearing at Mid Elevations. Accumulating Snowfall appeared to let up in the early morning hours, yet S-1 Snowfall was observed throughout the day. Moderate Westerly Winds were being channeled well down into the drainages and felt at 8000 feet and on up. More exposed areas were seeing at least Moderate Wind Blown and or Transport. Temperatures remained unseasonably cold until late morning, and rose noticeably as the cloud cover lessoned.

Snow Characteristics

New Snow Depth

New Snow Density

Medium

Snow Surface Conditions

Powder

Wind Crust

Melt-Freeze Crust

Damp

Snow Characteristics Comments

Excellent riding for mid April. As the day burned on the snow quality degraded significantly with the warming and clear skies. By 1400, all aspects except the moderately steep northerlies were getting damp and even wet from 9200 feet and down. You could still feel the bottom on many steep slopes, and this may have had something to do with the slightly inverted nature of the new snow that has accumulated over the past 4 days. Moderate angled slopes appeared to ride the best. The latest round of snow overnight consisted of at least 7 inches of graupel and rimed particles.

Red Flags

Recent Avalanches

Heavy Snowfall

Wind Loading

Cracking

Rapid Warming

Poor Snowpack Structure

Red Flags Comments

Poor snowpack structure identified as the preserved Light density snow that fell in the beginning of the snow events earlier in the week. See avalanche report regarding recent avalanches and cracking. Widespread cracking on all slopes with angles greater than 30 degrees. Slope cutting yielded reactive soft slabs that were propagating, and easily triggering avalanches on Specific terrain features like convex rollovers.

Avalanche Problem #1

Problem

New Snow

Trend

Same

Problem #1 Comments

The new snow was more dense than much of the previous snow fall events earlier in the week. And this may have had as much to do with the contributing factor of the Moderate to Strong Winds that have been active. Even in the more protected areas, the slightly inverted nature of the accumulating snow appeared to play a part in the sensitivity and reactivity observed today. In steep northerly facing terrain above 9500 feet these instabilities may linger. In the lower elevations, they most likely will have settled out with the warming and solar.

Avalanche Problem #2

Problem

Wet Snow

Trend

Increasing Danger

Problem #2 Comments

In areas that were receiving significant solar in the mid afternoon, Wet activity was likely. Fridays forecast for Sunny skies and rising temperatures will Likely increase this hazard significantly. As a result there may be a period in the afternoon when the danger rating may rise to Considerable for Wet activity.

Today's Observed Danger Rating

Moderate

Tomorrows Estimated Danger Rating

Considerable

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