Thursday, May 28, 2015

The Advantages of Altitude

Amongst the more interesting aspects of this past winter and spring is the contrast in snowpack evolution between the mid and upper elevations.  It's a great example of why, in a warming climate, high-elevation ski terrain and resorts are likely to have an increasing "competitive advantage" with regards to natural snowpack compared to low-elevation ski terrain and resorts.   

We begin at the Mill-D North SNOTEL at 8967 ft in Big Cottonwood Canyon.  Here the snowpack crested well below median, but it also melted out from mid-March to late April.  With the wet weather this month, there have been a couple of events that have laid down some snow, but there's been no recovery in the snowpack at all.  

If we go a little higher to the 9640 ft SNOTEL at Snowbird, we see that the melt out began later (this is a result of not only altitude but also aspect as the Mill D SNOTEL has more sun exposure) and that over the past month the snowpack has been able to survive with minimal net loss.  

There are no higher SNOTELs in the central Wasatch, so we now jump eastward to the Uinta Mountains.  At the 9992 ft Trial Lake SNOTEL just off the Mirror Lake Highway, the melt begins in late April, but it abruptly stops in early May, after which there is a net gain in snowpack of about 2.5 inches.  

Finally, if we go even higher to the 10,966 ft Lakefork Basin SNOTEL, we find minimal loss of snowpack in late April and a complete recovery in May with an increase in snowpack snow water equivalent (SWE) of about 4 inches.  The current snowpack SWE of 13.8 inches is just a shade lower than the peak of 14.2 inches in mid April.  

The bottom line here is that the snowpack at warmer, lower elevations is more sensitive to an increase in temperature than at colder, higher elevations.  It's a double whammy at lower elevation.  When it warms, your not only dealing with an earlier, faster snowmelt, but also a much greater fraction of cool-season precipitation falling as rain instead of snow.  

We had an especially warm, dry winter this year and in contrast to what you may hear on the news, it is not yet the new normal.  Good snow years will return, but over the coming decades as global warming amplifies, the competitive advantages of high elevation terrain will increase as the lower elevations take a greater proportional hit to snowfall and snowpack.  If you think the pressure is on in the central Wasatch now, wait a few more decades.   

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