Big Snow In La Nina Winters?

October 11, 2011

We ran a story tonight; about the city getting “prepared for an early and harsh winter”.  That was paraphrased a bit, but that was the general idea.  Well, La Nina winters often start a bit slow and then get going later, so there’s no reason to think we have an “early winter”.

So does a La Nina winter mean we have a big snow year coming here in the lowlands?  I don’t think anyone knows.  Check out the last 6 La Nina winters’ snowfall accumulations.

Not very impressive is it?  Now in 2007-2008 there was a lot of snow once you got above about 500′.  And in 1995-1996 we had a huge windstorm, flood, and several close calls with snow.  But the big snow years recently?  Generally neither La Nina or El Nino.  That could be called La Nada (“the nothing” in Spanish).

This means there is no guarantee that we have a big snow winter coming up.  Of course the El Nino/Southern Oscillation (ENSO) phenomenon is only one ingredient to each winter’s weather.  There is always the Atlantic Oscillation (AO), the Pacific Decadal Oscillation (PDO) and other indices that measure global weather movements and patterns.  I feel we are only just beginning to understand how these all relate and interact with each other.  The science has a long ways to go. 

Far more likely is above average precipitation and above average snowfall in the Cascades this winter.  Last year performed well for both, although timing was a bit strange (January rain and lack of snow in the mountains).

Let’s talk more about that.  It’s another good year to pick up a season pass for ski areas.  This winter will be a moderate to strong La Nina again.  Did you know 12 of the last 13 La Ninas have dumped heavier than average snowfall in the Cascades?  Some of those have been absolutely huge snow years.  Seems like pretty good odds doesn’t it?  And no, I’m not getting a free season pass or free tickets up on Mt. Hood either; that should assure you I’m totally unbiased.  The big question will be WHEN the big snow falls.  The tendency in the past has been for the heaviest of the snowfall in the 2nd half of winter (January or beyond), but last year we had a great start, quieter mid-winter, then late winter and spring was the best.  Some of the best years have been relatively quiet until well into December, then the powder starts piling up.

Chief Meteorologist Mark Nelsen