Looking Back

I enjoyed my ride to work this morning as there was a wonderful view of the snow-covered Wasatch capped by a lenticular cloud with the scene enhanced by fall colors in the valley.  

We are truly blessed this October as there's ski touring in the mountains and, once the trails dry a bit more, mountain biking in the valley.  Our cup runneth over. 

Let's take a quick look back at the storm.  Total snowfall based on automated observations from Alta-Collins was 14 inches with 1.98" of water.  Approximately 0.2" of that water fell as rain before snow levels dropped with the arrival of the cold front.  One aspect of the storm that I did not anticipate correctly was yesterday's snow density.  With decreasing temperatures, I thought we would see a transition to lower density snow, but the post-frontal environment was too unstable and convective.  There's an example below with four strong cells moving into or over the central Wasatch range from the northwest.  

Such cells contain strong updrafts, potentially of a few meters per second, which enables substantial riming of the snow and the formation of graupel, a styrofoam-like snow pellet.  It appears graupel was plentiful during the storm as suggested by all the pellets evident in yesterday afternoon's Alta snow-cam photo.  

Less instability and the riming would more limited and the snow lower density.  These are the tipping points that we deal with as meteorologists.  On the other hand, in such an environment, the snowfall amount might not have changed much, but the water amount would have been lower.  Right now, we want as much water in the snowfall as possible for cover and base, so all in all, yesterday was a good thing.

We're entering a break for a couple of days before the next system approaches Friday night and Saturday.  Right now, that looks like it might produce some flurries and not much more, but maybe we can get lucky again.  Continue doing whatever Pagan rituals you've been doing.