Tuesday, December 22, 2015

Alta Isn't Always King

It is unusual, but upper Little Cottonwood seems to be a dry spot in this storm, although dry spot in this sense is a relative term.

Observations from Alta-Collins show a total of about 27 inches of snow if you add up all the interval accumulations before the board is wiped back down to zero (top panel) and include the 4 inches observed so far today.  The water total is only 1.6 inches, although there may be some underdone a bit as that yields a water content of only 6%, which seems quite low compared to other locations.

Source: MesoWest
In contrast, Snowbasin has had 3.4" of water, more than double that at Alta-Collins (note scale change).

Source: MesoWest
In addition, snowfall reports from upper Big Cottonwood and Deer Valley have also topped those in upper Little Cottonwood.  I'm less sure about PCMR, but suspect they are at least close to what Alta has had so far too.  

And the latest radar shows that it continues to snow at Snowbasin, but Alta is temporarily out of the echoes.  

Factors contributing to the lower Alta snow totals in this event are multiple and include the predominantly southerly or southwesterly flow yesterday (favoring the northern Wasatch and yesterday afternoon upper BCC and Deer Valley), a tendency for the strongest precipitation features to be to our north (e.g., radar above), and just plain dumb luck (sometimes even Alta misses out on the more scattered and chaotic snow showers). 

No need to shed any tears as 27" in 48 is still just fine and eventually the law of averages will win out.  


  1. Hi Jim,

    I posted a few days ago, and forgot to get back to you. Here is the link to the NOMADs tool, which interacts with the NCEP Global Ensemble model. I apologize for the late reply, but you can guess where I was.. Solitude was epic today & yesterday. Merry Christmas!


    1. Ok I see now. NOMADS is the name of the data server. That page plots probabilities from the NCEP Global Ensemble Forecast System (which is a component of the NAEFS ensemble that we have on weather.utah.edu). The page is pretty slow and not all that useful for us in the west as the precip isn't downscaled.

    2. Ah-ha, it is primarily the absence of downscaling.. thanks for that!