Wednesday, December 29, 2010

Remarkable LCC Hourly Snowfall

To put it scientifically, it absolutely puked snow in upper Little Cottonwood Canyon during frontal passage.  Check out these observations from the Alta-Collins (CLN) MesoWest site.

Note the observation between 1600 and 1900 MST.  The snow interval board was wiped clean at some point after 1600 MST, with 5 inches falling by 1900 MST.  Thus, we know a5 inches fell in at most 3 hours.  Further, assuming the precip guage is working correctly, only .06 inches of SWE fell from 1800-1900 MST, so much of that snow probably fell during the previous 2 hours.  

We can, however, better pinpoint the snowfall using the Snowbird snowstake.  Check it out.  The snow depth goes up 4 inches between 4:12 PM (1612 MST, 2312 UTC) and 5:12 PM (1712 MST, 0012 UTC).  Four inches an hour.  Impressive!!!

This incredible hourly snowfall occurred as the cold front moved across the Cottonwoods.  Check out the radar loop.  You can see the band of enhanced radar reflectivity associated with the cold front move into the Salt Lake Valley.  Although it becomes more difficult to follow as it approaches the Wasatch, you can clearly see a band of higher reflectivity continuing toward the southeast, especially near the Wasatch Crest.  Thus, there must have been a heck of a pulse of heavy snow not only in the Cottonwoods, but also moving down the Wasatch to at least Mount Timpanogos.  The band appears to move across the Cottonwoods between about 2300 and 0000 UTC, roughly the period when it was puking snow. 

All of this happened just after the close of skiing for the day on a holiday weekend.  Must have been a nightmare getting out of the canyon today.  

1 comment:

  1. What do you make of this persistent N-S band between Ogden and SLC that looks to run parallel to the Crest (observed between about 7:30 and 8:30 PM)?