Observation: Main Porter

Observation Date
1/23/2021
Observer Name
Gagne/Duvernay
Region
Salt Lake » Mill Creek Canyon » Porter Fork » Main Porter
Location Name or Route
Main Porter Fork
Weather
Sky
Obscured
Precipitation
Light Snowfall
Wind Direction
Southwest
Wind Speed
Moderate
Weather Comments
Moderate gusts at the ridgetops.
Snow Characteristics
New Snow Depth
12"
New Snow Density
Medium
Snow Surface Conditions
Powder
Wind Crust
Snow Characteristics Comments
Rain/snow line may have been as high as 7500' in Millcreek, and this - combined with reduced snow totals in lower elevations - made for no avalanche activity at the lower elevations. Above about 8,000' there is a meter of settled snow wth 30-40 cms storm snow.
Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Cracking
Collapsing
Poor Snowpack Structure
Red Flags Comments
Saw at least one natural avalanche that failed at the new snow/old snow interface, and widespread cracking in wind-affected terrain above about 9,000'. Some collapsing in open meadows.
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Same
Problem #1 Comments
Rapid load with ~1"+ of water on top of a very pre-existing snowpack structure.
Comments
Was finding the storm snow to be reactive with widespread cracking in wind-loaded areas. Stepped on a wind-loaded slope on a north aspect at 9500' and pulled out a shallow, 10 cm soft slab. This in turn remotely triggered two adjacent avalanches, one that ran 150'. All three avalanches were shallow and ran within the storm snow, up to 15 cms deep.
Also saw this natural avalanche that likely failed at the new snow/old snow interface:
And plenty of spider-webbing on steep slopes
Most activity today was within storm snow (again, especially in wind-loaded terrain) and only saw one avalanche that failed at the new snow/old snow interface. (There was plenty of weak snow throughout the snowpack prior to this storm, with very weak near-surface facets and surface hoar at the old snow surface.) Although I saw nothing stepping down into older snow, this poor structure of a storm slab (containing over an inch of water) on top of a very weak snowpack will keep me on lower-angled slopes for quite some time.
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
Considerable