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Observation: Snowbird periphery

Observation Date
2/10/2018
Observer Name
B
Region
Salt Lake » Little Cottonwood Canyon » Snowbird periphery
Location Name or Route
Gad Valley LCC
Weather
Sky
Obscured
Precipitation
Moderate Snowfall
Wind Direction
Northwest
Wind Speed
Moderate
Weather Comments
One inch overnight and into the early morning hours. Light N winds at 1200 and increasing during the afternoon hours. Wind blown and or transport moderate. Temperatures falling throughout the day and barely climbing into the lower 20's at 9000. Snow fall rates averaging S2 after noon, with at least 5 inches during this time period.
Snow Characteristics
New Snow Depth
6"
New Snow Density
Low
Snow Surface Conditions
Powder
Wind Crust
Snow Characteristics Comments

Improved riding condition with the new snow. Winds not much of a factor at mid elevations. Speculations and confidence high that the upper elevations were experiencing strong winds and intense loading on E and S facing slopes, as well as cross loading on terrain features.

Red Flags
Red Flags
Wind Loading
Poor Snowpack Structure
Red Flags Comments
See above for wind loading details. Poor visibility only allowed for sporadic visual confirmation of wind loading, yet remote weather stations provided strong evidence of significant and widespread wind slab development at the upper elevations. Poor snowpack structure confirmed in protected mid elevation terrain on NW and NE aspects. ECTP 21 and 24 at 35 cm up on NW and NE aspects at 9000. Fist hard basal facets weak layer. HS in these locations: 75 cm on NW, and 110 cm on NE aspects respectively.
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Same
Problem #1 Comments

Poor snowpack structure described above indicating some of the weakest and most reactive structure observed in past 10 days. May be due to the location which houses cooler than typical temperatures due to pooling of cold air in localized basin. Regardless, this is not an isolated and or unique structure as indicated by previous observations from various locations.

Avalanche Problem #2
Problem
Wind Drifted Snow
Trend
Increasing Danger
Problem #2 Comments

See above, and with the winds still at moderate to strong speeds still at 2000 hours and forecast to continue through the evening and early morning hours, this danger/hazard appears to be increasing at upper elevations.

Of note: The first few inches of new snow were very light density and during the day on Saturday the densities increased slightly with mixed forms and graupel constituting the remaining 5 inches of accumulations. As a result there may be a reactive weak layer at the new snow/old snow interface; and this may be exacerbated due to the strong likelihood that there were NSF's on the prestorm snow surface on shady aspects. Steep terrain was exhibiting minimal Loose Snow Dry avalanching late in the day on steep terrain features. And finally, Sundays forecast for 32 degrees and sunny at 9300 feet should help initiate a wet loose avalanche cycle in the new snow. Along with this, the southerly facing steep slopes have firm m/f crusts in place that should allow for these slides to run easily and possibly long.

Moderate overall today for wind slabs and lingering persistent slab possibilities. Mostly moderate on Sunday for reasons described above with natural wet loose with solar effects and daytime heating.

Today's Observed Danger Rating
Moderate
Tomorrows Estimated Danger Rating
Moderate