Wednesday, January 11, 2012

"Snow Drought" and the Arctic Oscillation

(This post is a pseudo-repost from my weather blog, so the writing style is a bit different from most.)

Over the last two months, most of the United States and southern Canada have been locked into a “snow drought”, but for Vermont, at least, some significant snow may be on the way.

Snow has been hard to come by this winter in East Middlebury, and it seems that each time we pick up an inch or two, a thaw or rainstorm comes along and melts it.  The seasonably cold temperatures and lack of snow have meant ice, and lots of it, and the icy rivers and streams seem out of place flowing through the snowless forests.  The lack of snow cover has also led to solidly frozen ground, which could translate into a soggy mud season this spring.


Vermont is not alone in its lack of snow so far this winter.  Most of the “lower 48” states have picked up little or no snow thus far this winter, a dramatic difference from last year.   Oddly, southern New Mexico and western Texas have been snowy, which is great news for this drought stricken region.  California’s Sierra Nevada mountains, on the other hand, are still nearly snow-free this winter.  Most of California experiences little or no summer precipitation, and relies on Sierra snowmelt for summer water, so if significant snowfall does not occur in the next few months, the area will be in for a difficult summer.

Where is the snow?  Parts of coastal Alaska have been absolutely buried in the stuff.  The Austrian Alps have also been receiving dumpings of snow.  This winter has played out as an almost exact opposite of last winter, and the reason may be a poorly-understood jet stream phenomena known as the Arctic Oscillation.  As described in this blog post by meteorologist Jeff Masters, the “negative” phase of the Arctic Oscillation that occurred last year favored heavy snow in much of the United States, while the current “positive” phase favors warmer, dry conditions.  

The lack of snow in Vermont has been hard on snow lovers, especially those who depend on snow sports to make a living.  Not everyone is disappointed by the winter, however - a friend who works for CVPS has told me that the thus-far mild winter has been very helpful for finishing up repairs from Irene’s devastation last summer.  


Snow is finally in the forecast for Vermont - perhaps 8 or 10 inches by the weekend.  However, there is a chance of some rain and wintry mix on Thursday afternoon and Friday morning, which could cut down on snow accumulation.  As for California, some of the computer models have been indicating a switch to more stormy conditions by the end of the month, but this is a long way off.  There is still a chance for my forecast of above average snow in Vermont to come true this winter, but at this point it is not looking likely.  Maybe I should have stuck with looking at the woolly bears. As for California, always trust the oaks. Somehow they knew a dry year was coming.

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