Observation: Park City Ridgeline

Observation Date
12/18/2015
Observer Name
Greg Gagne with "Gunner"
Region
Salt Lake » Park City Ridgeline
Location Name or Route
PC Ridgeline/Monitors
Weather
Sky
Few
Wind Direction
West
Wind Speed
Light
Weather Comments
Much warmer today than in recent days. Wx stations were still south of 0C, but felt uncomfortably warm in the sun.
Snow Characteristics
Snow Surface Conditions
Wind Crust
Rain-Rime Crust
Damp
Snow Characteristics Comments

We were finding a 1-2 mm rain/rime crust on all aspects up to 10k along the Park City ridgeline. Snow was damp at lower elevations when exiting mid-day. On some upper elevation northerly aspects the snow that felt on top of the rain/ime crust quickly faceted leaving a very thin layer of near-surface facets atop the crust. Not a big concern and likely to be eroded with warm temps and winds in the forecast, but just cool snow-geek stuff. (Bruce Tremper's book covers this process really well.)

Red Flags
Red Flags
Recent Avalanches
Wind Loading
Collapsing
Rapid Warming
Poor Snowpack Structure
Red Flags Comments
Rapid warming is probably an issue on steep south aspects and possibly as well as lower elevations. (Where there is now a fair amount of snow; something we're not that used to in the past few seasons.) Did get one good collapse ascending ridgeline between South & West Monitor (known as "West Monitor Sneak" on Achelis map.)
Avalanche Problem #1
Problem
Persistent Weak Layer
Problem #1 Comments

Avalanche activity on Thursday about the best evidence of our persistent slab problem.

Comments

Went out in search of continued good ski conditions on low-angled slopes, and also wanted to look first-hand at the activity along the PC ridgeline. Despite a pesky rain/rime crust, lower angled slopes are still skiing well, and as the slab stiffens up with warming temps, settlement, as well as some wind drifting, it is still possible to find supportable conditions in low-angled terrain.

The slides from South Monitor are impressive, and somewhat surprising they did not connect a larger area.

Have been out the past couple of days and am noticing quite a bit of settlement with the snowpack between 9-10k now about 60-75 cms (3 - 3.5') where I was measuring up to a meter on Tuesday.

Despite the storm snow slab now stiffening a bit, still unable to get any propagation on extended columns the past two days. Compression tests and ECTs are still showing depth hoar down near the ground the weak layer with very low scores (CT1 - CT10 and ECTN1 - ECT10). Was hoping to find some wind deposits on gentle ridgeline that separates South and West Monitor to see if tests would show propagation of the slab, but no recent drifts were found in this area.

As is often the case, was finding a particularly weak snowpack along PC ridgeline with sandboxing in faceted well down off West Monitor Sneak.

Good to see people sticking to lower angled terrain. Apart from recent avalanches and only a few collapses, am thinking we are heading back to the period where the instability is not in your face, so some may opt to venture onto steeper north-facing aspects. Seems the key to doing so is diligently checking there is no cohesive slab on top, but I personally still don't trust this snowpack.

Riming on aspen branches while ascending towards PC ridgeline.

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