August 27, 2009 in Washington Voices

El Niño could mean less snow this winter

Randy Mann
 

Over the past several weeks I’ve received a number of questions about what this coming winter will be like.

Well, I certainly don’t think we’re going to see record or near-record snowfall for a third year in a row, but with all these weather extremes, anything is possible.

There’s no question that the last two winters were a couple of the toughest in recorded history. The winter of 2007-’08 produced record snows across Idaho and parts of Eastern Washington. Spokane International Airport had 92.6 inches of snow, which was 0.9 inches from tying the all-time record.

When the snowfall season for 2008-’09 expired June 30, the airport had gauged an incredible 97.7 inches, smashing the record of 93.5 inches set in 1949-’50. The norm is 47.4 inches.

Last year, sea-surface temperatures along the equatorial regions were below normal levels. This cooler La Niña phenomenon likely contributed to the heavy snowfall across the Inland Northwest. This year, however, an El Niño – warmer-than-normal sea-surface temperature – developed off the west coast of South America.

During typical El Niño years, the upper-level jet-stream winds become stronger in the subtropical regions, while the northern polar jet stream becomes weaker. Much Pacific moisture that falls in our area is directed from the polar jet stream. Approximately 70 percent of the time, most of California and the southern U.S. receive above-normal moisture during an El Niño as the subtropical jet stream intensifies. The northern regions of the U.S. are usually milder and a bit drier than normal during winter.

Assuming El Niño maintains its strength, or intensifies over the next few months, this winter should be different from the past two. I expect to see widely fluctuating temperature patterns, from very mild readings to well below normal, in a relatively short period. Snowfall totals should be slightly below average as some of the moisture falls as rain. The chances of freezing rain or an ice storm will increase with a moderate to strong El Niño. Stay tuned.

In the meantime, another round of chilly and showery weather should arrive shortly after Labor Day. Our fall is expected to be cooler and wetter than normal.


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