Observation: Cardiff Fork

Observation Date
3/24/2018
Observer Name
Brett Carroll
Region
Salt Lake » Big Cottonwood Canyon » Cardiff Fork
Location Name or Route
Cardiff Fork
Weather
Sky
Broken
Wind Direction
Southwest
Wind Speed
Strong
Weather Comments
Hot, cool, hot, cool. When the sun came out and the wind died it got hot quickly. But there was pretty even sun and cloud cover through the morning, and the clouds combined with the wind stopped the snow from heating up too much on the east facing terrain in upper Cardiff Fork. There was lots of wind loading happening, with consistent strong winds from the south and southwest along exposed ridgelines, and light to moderate winds with strong gusts in less exposed terrain.
Snow Characteristics
New Snow Depth
8"
New Snow Density
High
Snow Surface Conditions
Dense Loose
Wind Crust
Rain-Rime Crust
Damp
Snow Characteristics Comments
A fair amount of complexity in the aftermath of such a warm storm. It seems like the top of the current snowpack can be categorized fairly well in three different elevation zones. Below 9,000': It seems like terrain below 9k saw mostly or entirely rain. There was a pretty stout refreeze crust (supportable for skis and boots) at this elevation above Alta Central this morning, with wet snow underneath. I think that this elevation will become very stable once it has a chance to thoroughly drain and freeze. 9 to 10,000': Things are a bit funky in this elevation range. There were a few inches of graupel on the snow surface, on top of a rain crust (generally supportable for both skis and boots), on top of another few inches of graupel, on top of the old snow. The graupel on the surface got quite warm, and seemed to be consolidating/bonding to itself. The graupel below the rain crust was fist hardness and very poorly bonded, still very "ball bearing"esque. I don't think this is a concern for now, but I will be interested to see if this layer becomes reactive the first time that it warms and becomes saturated. Above 10,000': It seems that nearly all precip above 10k fell as graupel. Wind loaded snow on top of this graupel layer was touchy, the graupel here was also poorly bonded and acting as a weak layer.
Red Flags
Red Flags
Recent Avalanches
Wind Loading
Cracking
Red Flags Comments
I did observe a skier remotely trigger an small wind slab avalanche from a ridgeline (or maybe they dropped a small cornice on the slope? I was a little too far away to tell for sure). The avalanche happened in a steep, rocky, north facing chute at just over 10,000' at the top of Cardiff Fork, on a run called Power Outage. The initial slide broke out about 12" deep, 30' wide, and ran a few hundred feet. It also sympathetically triggered two smaller wind slabs in adjacent steep rocky chutes. While this sounds like it must have been super scary/touchy out there today, this terrain is oriented in a way that it was getting nuked by wind all morning. Outside of steep, upper elevation, north facing terrain I found a number of wind slabs 1 to 4" deep that would crack under my weight, but not much more than that.
Avalanche Problem #1
Problem
Wind Drifted Snow
Trend
Increasing Danger
Problem #1 Comments
The wind was loading exposed, north facing terrain all day today, and cross loading other features to a significantly lesser extent. The graupel on the snow surface is quite weak, and any wind slabs that form on top of this graupel will probably be touchy. With some more snow and wind in the forecast for tomorrow I would expect this danger to increase, we'll have to see how much snow and wind this next wave brings.
Avalanche Problem #2
Problem
Persistent Weak Layer
Trend
Same
Problem #2 Comments
I spot probed a number of locations in upper Cardiff today and found consistent snow depths of 200 to 230cm, and I think the odds of a deep slab in these areas with deeper snowpack are very low to none. Slopes with shallower snowpack (that have avalanched this season or on the periphery of the Cottonwoods) still have questionable structure and are still adjusting to a significant new load.
Today's Observed Danger Rating
Moderate
Tomorrows Estimated Danger Rating
Moderate