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Observation: Big Cottonwood Canyon

Observation Date
Observer Name
Salt Lake » Big Cottonwood Canyon
Location Name or Route
Upper Big Cottonwood
Heavy Snowfall
Wind Direction
Wind Speed
Weather Comments
OVC all day with only one period around noon when there was minimal solar with no damage incurred. Sustained S1 snowfall rates throughout the day with two distinct periods of at least S3 - S4. Total daytime snowfall 9 - 10 inches. Moderate NW Winds even down off the ridge lines with occasional Strong Gusts during the heavy PI impulses. Moderate Wind Blown observed with significant loading. Temperatures remained just cold feel like Winter above 9500 feet, yet on the mild side. The cloud cover and sustained snowfall helped maintain these cool temps.
Snow Characteristics
New Snow Depth
New Snow Density
Snow Surface Conditions
Wind Crust
Melt-Freeze Crust
Snow Characteristics Comments
Excellent riding conditions and they were able to be found on all aspects throughout the day. 8 inches overnight in Brighton, and at least 11 to 14 in the upper reaches. Settlement was significant throughout the day and the heavy PI combined with the seasonal temperatures appeared to aid in the rapid settlement. Despite all the daytime snowfall, Ski Penetration drastically lessoned, especially by mid day.
Reactive Wind Slabs up to 2 feet deep were observed.
The old snow surface from prior to yesterdays storm beginning had a texture like soft Styrofoam. Exposed upper elevation terrain still had areas of wind eroded terrain features. Fortunately these surfaces are not slick.
Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Wind Loading
Red Flags Comments
Early in the morning it was easy to identify Reactive Storm Slab layers. It appeared that the first few inches of overnight snow was very light density, and hand shears and slope cuts easily indicated this weakness. Initially this was a very Soft (Fist minus) Slab, yet as the temperatures rose and the Ski Penetration lessoned this slab became more cohesive and hard. By the end of the day this weakness appeared to settle out. At 1500 hours during the second wave of S4+ precipitation there was a widespread Natural Loose Dry Cycle. And, these stuffs ran far and fast in the upper 4 to 6 inches. 4 Finger Minus Wind Slabs were easy to trigger by the end of the day, and it was likely that this problem was much more serious on the highest ridge lines. Heavy Snowfall Rates obviously aided in initiating the Loose Dry Cycle.
Avalanche Problem #1
Wind Drifted Snow
Decreasing Danger
Problem #1 Comments
See above, and when the sun comes out on Sunday these Southerly facing Wind Slabs may become more of an issue. Besides this warming and solar issue, the polar aspects should be less Reactive on Sunday. No Natural Wind Slabs observed today, yet OVC Skies prevented good visibility. It was likely that this problem may have been an issue for other BC Travelers today.
All Solar aspect will be very likely to be reactive if the sun comes out for any sustained period of time tomorrow morning and or afternoon. Significant Natural Wet Loose avalanches may escalate the Danger Rating on Sunday to Considerable.
Avalanche Problem #2
New Snow
Decreasing Danger
Problem #2 Comments
Loose Dry in high consequence terrain will likely be an issue early tomorrow morning on steep confined terrain features.
Today's Observed Danger Rating
Tomorrows Estimated Danger Rating