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Observation: Porter Fork

Observation Date
1/6/2019
Observer Name
Grainger
Region
Salt Lake » Mill Creek Canyon » Porter Fork
Location Name or Route
Bowman Fork/Pole Canyon
Weather
Sky
Obscured
Precipitation
Moderate Snowfall
Wind Direction
Southwest
Wind Speed
Light
Weather Comments
The day was divided into 2 periods of precipitation, one overnight into Sunday morning and the other beginning with high PI rates and lower snow levels along the SLC bench and lower areas in the canyons. Snowfall in Millcreek around 1300 was ~2 in/hr at times and tapered off to clearing skies by 1530. This second mid-day pulse set up a density change in the new snow that was very easily triggered by skis and caused a (small & very soft) cycle of natural slides on slopes mid-30 degrees and steeper.
Snow Characteristics
New Snow Depth
9"
New Snow Density
Low
Snow Surface Conditions
Powder
Snow Characteristics Comments
Right-side-up new snow (6-10" above 8000') with light to moderate evidence of WSW wind effect. Most interesting was the density change that this and temperature change created between the morning and afternoon pulses of snow.
This interface was 2-5" below the surface and sensitive to skis on westerly aspects, propagating surprisingly wide soft slabs for how thin and soft they were. This layering also created a miniature natural cycle, examples on north through easterly aspects along ridgetops and over steep rollovers.
Many southeast through west slopes in this area also have a (generally pencil hard) thermal crust underneath the storm snow from this last week.
Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Avalanche Problem #1
Problem
New Snow
Trend
Decreasing Danger
Problem #1 Comments
-Crusts on thermal aspects from this last week may create a smooth sliding surface for new snow as it continues into tomorrow.
-Sensitivity in the interface between the day's 2 pulses of snow. Mini soft slabs midway through storm snow. Many steeper areas naturaled and I would expect the layer to remain sensitive for a short time but possible failures in the very near future.
Avalanche Problem #2
Problem
Wind Drifted Snow
Trend
Same
Problem #2 Comments
Isolated but still sensitive areas of hard wind-slab from this last high pressure's winds.
Thin naturals widespread near ridgetops, E-facing.
Mid-slope naturals on density change on steep rollovers.
Many areas where skis easily triggered top few inches with skis on angles over mid-30s. Mini SS on density change.
Today's Observed Danger Rating
Moderate
Tomorrows Estimated Danger Rating
Considerable
Coordinates