Storm Snow and Graupel

Location Name: 
Storm Snow and Graupel
Region: 
Williams Lake Area
Date and time of observation: 
Sun, 02/23/2020 - 12:46


Red Flags: 
Recent loading by new snow, wind, or rain

Observation made by: Forecaster
Snowpit Observations
More detailed information about the snowpack: 

Very much an elevation snow storm, with 2 to 3 inches of snow from 10,500' to 8500'.  We had rain below that.  Above 10,500' we picked up 4 to 6 inches of snow. It seems like it's the year of graupel with a lot of graupel during this storm. The new snow seemed to be bonding well to old existing surface, but west winds overnight and during the day were starting to stiffen the surface snow into a cohesive slab, with lower density snow found underneath. 

Below 8500' we observed small loose wet avalanches from the rain on snow event. In snowpits on East aspects near treeline we continue to find faceted crusts with cohesive slabs on top that we are getting to fail with moderate to hard force in extended column tests.  North aspects near treeline avoided the crusts from previous high pressures but have a faceting snowpack with cohesive slabs on top.  We continue to find a high level of variability in snowpack depths due to wind transported snow earlier in the season and slopes that have been repeat offenders avalanching during the season.  In these shallow snowpacks on northerly aspects we are finding large depth hoar on the ground. 

Photo 1: Stiffening slab of the new snow with lower density snow underneath 

Snowpack photos: 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
75% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Moderate
Precipitation: 
Snow
Air temperature trend: 
Warming
Wind Direction: 
West
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

A mix of sun and clouds in the morning with light winds quickly changed by mid-day with orographic snow and winds picking up out of the West blowing in the 20 to 30 mph range. Snow was being transported near and above treeline during the day.  Snowfall was less than an inch an hour. Temperatures were warming during the day and got above freezing below 9500'