Observation: Mary Ellen Gulch

Observation Date
1/29/2023
Observer Name
Zimmerman-Wall/AIARE PRO 2 Students
Region
Provo » American Fork » Mary Ellen Gulch
Location Name or Route
Sinner's Pass/Mary Ellen Gulch
Weather
Sky
Overcast
Precipitation
Light Snowfall
Wind Direction
Southwest
Wind Speed
Light
Weather Comments
Travel from 11am to 3pm. Mostly cloudy with only a few brief windows of illumination. No clear skies, no green housing. Snowfall rates remained light throughout the day. The forecasted rates of 2" an hour never came to pass in upper LCC or upper American Fork. The winds were generally light in the area traveled, and even on Hidden Peak on our way home at 3 they were only gusting in the low teens. Temperatures remained cold, with an air temp measured at 9900' of -10c at 2pm.
Snow Characteristics
New Snow Depth
12"
New Snow Density
Low
Snow Surface Conditions
Powder
Snow Characteristics Comments
Greatest snow on earth. The license plates don't lie, today was it.
Red Flags
Red Flags
Recent Avalanches
Wind Loading
Poor Snowpack Structure
Red Flags Comments
Poor snowpack structure is just coming back into the mix this week.
Avalanche Problem #1
Problem
New Snow
Trend
Increasing Danger
Problem #1 Comments
Loose dry avalanches and soft cornice breaking at skis was our only direct action avalanche activity noted. We did not see any naturals in the area we visited.
Based on other obs and our snowpack tests, wind effected storm slabs seem to be the name of the game when it comes to getting propagation, and especially when associated with a crust.
1. On a Northeasterly facing slope (9,900') where we dug, the light and dry snow that fell during last week's cold northerly flow has decomposed slightly and also faceted before becoming buried by the last three-day storm event. These are very small (<1mm) and hard to detect in the profile wall, and even looking under a 18x loupe it is hard to see the development of facets on the crystals clearly. We located these with multiple compression tests and observed sudden fractures but no propagation. What we noted was that the slab characteristics were so soft (Fist hard) it could not promote propagation.
2. On southerly facing, particularly the off aspects of SE/SW, we were able to find a wind effected storm slab 50cm deep overlying a crust. Sudden fractures followed by propagation in separate tests on this layer (SSW ~9800').
After some discussion with the group, and some other pros, it seems this may be related to some melt-layer recrystalization during the same weather events that allowed the facet development on the northerly slope (Jan 22nd-23rd timeframe).
This seems to be a developing problem and is corroborated by the numerous human triggered avalanches in the last 48 hours. The strength and weight of the evidence is hard to ignore. The verification of multiple trusted sources seeing the same thing in their observations leads me to believe this is worth our continued scrutiny.
Comments
Photo 1- Best visibility of the day. No observed avalanche activity in the upper Mary Ellen Gulch.
Photo 2- FCsf buried under new storm snow - Photo Edward Degitis
Photo 3- Location of profile where FCsf were found on a northeasterly facing slope
Photo 4- Cornice development along Sinner's Pass (northerly facing). The smaller ones released with skier provocation, but were somewhat stubborn.
No photos of the propagating results.
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
None
Coordinates