Sunday, January 16, 2011

Today's Ski "Glopfest"

As advertised a couple of days ago, snow levels have climbed today and as of about 2PM this afternoon sit somewhere near 8500 feet.  The Alta cam photo from this morning summarizes the day nicely.

I'm now ready to "officially" declare that this dirty ridge has reached at least NC-17 status.  I've skied some warm storms at Alta, including some with serious Cascade concrete, but don't recall ever squeezing as much water out of my gloves as I did at the end of the day today.  Dirty indeed!

Skiing at Alta today, I found the "wintery mix" of ice pellets, mist, and drizzle to be quite interesting.  Even above the freezing level, which as of 2 PM sat at about 9500 feet, I was constantly wiping my goggles to see.   The existence of liquid water above the freezing level is not uncommon in warm, shallow clouds like todays, but there were also plenty of ice pellets around and very few snowflakes.  This is speculation, but I suspect that today the the primary mechanism for precipitation growth was turbulence (a.k.a. airmass scrambling) within the orographically lifted stable layer.  This turbulence led to drizzle formation through collision and coalescence and lifted some (but not all) of the drizzle drops high enough to freeze, leading to a mixture of ice pellets, mist, and drizzle in the layer surrounding the freezing level (including above the freezing level).

Of course this is all just an educated guess, and there's a wide range of possibilities given the limited cloud microphysical data available.  If anyone knows of a good study examining similar processes, please let me know.

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