Observation: Days Fork

Observation Date
2/5/2019
Observer Name
Gagne/Catino
Region
Salt Lake » Big Cottonwood Canyon » Days Fork
Location Name or Route
Days Fork
Weather
Sky
Obscured
Precipitation
Heavy Snowfall
Wind Direction
Southwest
Wind Speed
Moderate
Weather Comments
Periods of heavy snowfall in the morning with dense graupel. By early afternoon, the snow switched to lower-density stellars that sluffed very easily on steeper slopes.
Snow Characteristics
New Snow Depth
8"
New Snow Density
Medium
Snow Surface Conditions
Powder
Snow Characteristics Comments
Storm is switching back and forth between lower-density stellars and high-density graupel. There was a clear density inversion down 20-30 cms that was very reactive in the early afternoon with widespread cracking and 3 skier-triggered avalanches in Days Draw.
Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Wind Loading
Cracking
Poor Snowpack Structure
Red Flags Comments
Biggest red flag was avalanching.
Avalanche Problem #1
Problem
New Snow
Trend
Increasing Danger
Problem #1 Comments
Were finding two avalanche concerns with storm snow:
1 - Density inversion down 20-30 cms (perhaps now deeper with additional snow) was very reactive and we were getting widespread cracking. 3 intentional skier-triggered slides in Days Draw failing on this density inversion (photo and videos below). Largest slide was 150' wide and ran 250' vertical.
2 - Sluffing in storm snow - 10-15 cms of low-density storm snow was sluffing very easily on steeper slopes.
Avalanche Problem #2
Problem
Persistent Weak Layer
Trend
Increasing Danger
Problem #2 Comments
On Monday in Silver Fork as well as Guardsman/10,420' zone I was finding the old snow surface on aspects facing north through northeast to be quite reactive to stability tests, with most extended column tests propagating across the column, and some propagating upon isolation. The storm snow since Sunday is now 45 - 75 cms deep, so this is putting more of a load on this weak layer. The layer can be easily identified by looking for an obvious stripe as shown below (this stripe will now be much deeper in the snowpack)
This layer was much less reactive today in Days Fork, with no propagation with extended column tests. But this was mostly due to many of the slopes we were looking at had enough east in them that the weak snow at the surface likely deteriorated this past weekend. On one slope with a NE aspect at 9100' the results were ECTX, but CT21, failing in a 5 mm layer of preserved NSF buried 80 cms down.
Reports from along the Park City ridgeline today had two large avalanches failing in faceted snow down near the ground.
Comments
With more snow and wind in the forecast for the next 24 hours, avalanche danger will continue to rise.
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
High