Observation: Oquirrh Mountains

Observation Date
1/13/2019
Observer Name
Dana
Region
Salt Lake » Oquirrh Mountains
Location Name or Route
Oquirrh Mountains
Red Flags
Red Flags
Recent Avalanches
Collapsing
Poor Snowpack Structure
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Same
Problem #1 Comments
Felt numerous small collapses on shady aspects on the approach. Dug a pit at 8900 feet NW facing ascending Picnic Canyon early in the day. 100cm total snow depth, which was representative of the total pack on most slopes the shady side of the compass. ECTP27, full propagation on a thick facet layer 45cm down sitting on a decomposing crust. Pole probing led us to believe this layer was widespread and it appeared to be the culprit in numerous large, destructive avalanches. Facet layer was ~10cm thick, and while rounding to some extent, I would think it will persist in this range until/unless considerable depth is added to the snowpack. No basal facets present in any of the areas we poked around.
Comments
Running hypothesis at the start of the day was that the snowpack would be A) thinner and therefore quite a bit weaker than the Wasatch on the shady aspects (it was) B) basically non-existant on the solar aspects (it's thin but actually shaping up nicely all things considered) and C) that the snow surface on shady aspects might have decomposed enough to make slab avalanches a non-issue (it hadn't). The top few CM of the snowpack had indeed decomposed into some classic square pow, but just below that was a thin but strong 1F slab sitting on a facet layer.
We were a bit taken aback by just how large and widespread the most recent avalanche cycle had been, with numerous slides running full track, onto the flats, and uphill over small terrain features. Always amazing to see how such a short drive can get you to an area wich such different weather conditions, snow conditions, and avalanche conditions. These slides had occured on East through Northwest facing slopes. They looked to have occurred early last week during a wind loading event. I do think it would have been unlikely to trigger a slide of this magnitude yesterday with just the weight of a skier, but collapses and pit test indicated probably not impossible. So, we opted to ski more manageable terrain.
Solar aspects had about 30-60cm of crusty consolidated snow above 8000' and mostly bushes below that.
Today's Observed Danger Rating
None
Tomorrows Estimated Danger Rating
None