La Niña update

The CPC has issued it's December El Niño/Southern Oscillation (ENSO) diagnostic discussion, which for this winter concentrates on the ongoing La Niña.  La Niña conditions are expected to peak during Nov-Jan and persist until spring.  Consistent with La Niña, current sea-surface temperatures are well below average across the eastern and central equatorial pacific.

Source: NOAA/CPC

Winters during La Niña years tend to be snowier in the Pacific Northwest and British Columbia.  It's not guaranteed, but the dice are loaded.  Northern Utah sits just on the southern fringe of the positive snow anomaly region for the Jan-Mar period.

Source: NOAA/CPC

The National Weather Service has examined the snowfall at Alta during La Niña, El Niño, and "No Niña" years (typically called ENSO neutral by the science community, but No Niña is catchier so I'll go with it).   The 55-year average ski season (Nov-Apr) snowfall Alta is 500 inches.  During La Niña years it is 509 inches, El Niño years 517 inches, and No Niña years 489 inches.  These differences are small and likely not statistically significant given the modest sample size.  In other words, any loading of the dice at Alta is pretty weak.

If we look specifically at snowfall during past La Niña ski seasons and classify four as near average (they use normal, but as discussed in an earlier post, I don't like that term), four as snowy, and 2 as low snow years.

Source: National Weather Service Salt Lake Forecast Office

The distinction between these 3 categories is, however, relatively subtle and a look at the histogram shows relatively even scatter about the mean.  The bottom line is that for the Wasatch Mountains, the existence of La Niña provides little predictive skill for what the upcoming winter will be like.  Fortunately, at least in the Cottonwood Canyons, even a bad year is better than a good year most anywhere else, so my advice is to get out and enjoy it every time mother nature brings the goods.