Observation: Mineral Fork

Observation Date
12/20/2020
Observer Name
R. Kosinski
Region
Salt Lake » Big Cottonwood Canyon » Mineral Fork
Location Name or Route
Mineral Fork
Red Flags
Red Flags
Recent Avalanches
Cracking
Collapsing
Rapid Warming
Poor Snowpack Structure
Avalanche Problem #1
Problem
New Snow
Trend
Same
Problem #1 Comments
The last two storms we had in the past week have created a layer ~1' thick that is cohesive. The problem is that this sits on a melt/freeze crust or on facets. Cracks were propagating up to 50 feet within this layer and we had many areas where this slab broke and ran a couple inches. In higher angle terrain this will likely run long and break wide.
Avalanche Problem #2
Problem
Persistent Weak Layer
Trend
Same
Problem #2 Comments
The persistant weak layer varies from aspect to aspect with north and shaded aspects holding around 6" of facets and more east facing slopes and areas that receive sunlight typically having a melt/freeze crust on top of facets. Either way, this is not a good set up having a weak layer at ground level. Avalanches we saw today were starting in the new snow and then quickly stepping down into the facets.
Comments
We started our tour into Mineral Fork around 0845 this morning under partly cloudy skies and temps in the high teens. The skintrack is pretty boney and we saw few signs of instability until we got off the trail and into the trees. At around 8000' in the Low/Mid East Facing area, where trees are more intermittent and shrubs prove an anchor, there was widespread crackin and collapsing everywhere except low angle slopes. We got a number of spots to slide a few inches and just about every step produced collapsing and cracking. As we got up to the ridgeline, we saw that the top bowl section of every run from Low East Facing to Moonlight had avalanched (this will be submitted separately). Once on the ridge, there were a couple gusts of wind but it was generally calm with a cloud ceiling around 10,000' and very light precip. The humidity was high and made the snow damp. On the way out, the temps were above freezing with the trailhead reading 39 degrees at 1430 and rollerballs beginning to come down.
A big thank you to all the forecasters for all your hard work as we get into the depths of winter!
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
Considerable
Coordinates