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Spokane, Washington  Est. May 19, 1883
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Weathercatch: Forecasts are vital guide posts, not absolutes

It was a treacherous commute to work on Feb. 21 in Spokane.  (Jesse Tinsley/The Spokesman-Review)
It was a treacherous commute to work on Feb. 21 in Spokane. (Jesse Tinsley/The Spokesman-Review)
By Nic Loyd and Linda Weiford For The Spokesman-Review

Above-average temperatures during the first half of February lured us into thinking that winter might be over. The latter part of the month, however, was a totally different story. Billowing clouds. Wind-driven snow. A severe blast of cold. Although meteorologists had expected the weather to turn more wintry, they hadn’t planned on it being to such an extreme degree.

From California and Colorado to Washington state and beyond, early computer models were in agreement that a pattern change during the latter part of the month would be more of a blip than a bang. Ten days out, little more than cooler temperatures and occasional spurts of snow and rain were forecast. Even Canada’s two leading weather agencies predicted only weak weather disturbances in its western provinces.

Then, six days before the projected weather change, it was clear that a much more dramatic pattern shakeup was in store and forecasts were revised to reflect this.

Sure enough, as residents began the workweek on the morning of Feb. 21, a storm moved through parts of Oregon and Eastern Washington that dropped 3.7 inches of blowing snow in Spokane. The next day, a disruptive surge of arctic air intensified by wind gusts poured through the region. The coldest temperatures fell during the early hours of Feb. 23, when Spokane recorded a low of 3 degrees, Deer Park hit minus 3 and Coeur d’Alene dipped to minus 1. Meanwhile, daytime highs ran in the teens. (Spokane’s normal high temperature for that date is 41 degrees and the normal low is 27.)

We had six days’ advance notice that there would be snowfall followed by a cold snap, and the National Weather Service did a terrific job of alerting the public. Why weren’t these conditions obvious 10 days in advance? Because weather forecasts are a look into the future and the farther away in time, the higher the likelihood that conditions will shift. After all, the atmosphere is enormously complex. A few small changes in one location can yield big consequences elsewhere.

Take, for instance, the large high-pressure ridge off the West Coast that blocked winter storms during the first half of February. Thanks to that ridge, we experienced sunshine and mild temperatures during that period. But the ridge began dissipating, allowing a storm system followed by a whoosh of arctic air to funnel through British Columbia and into the western United States and eventually into the Midwest. Because of the atmosphere’s complexity and the limits of forecasting technology, it was nearly impossible to predict how significantly that ridge of high pressure would break down.

A five-day forecast accurately predicts the weather 90% of the time, according to the National Oceanic and Atmospheric Administration. It drops to 80% for a seven-day forecast and down to 50% when forecasting 10 days out, the agency states.

Put simply, weather can behave in unexpected ways. Although forecasting has improved by leaps and bounds during the past few decades, in the end, it’s not sophisticated computer models, glitzy satellites and radar technology that have the final say. It’s Mother Nature.

Nic Loyd is a meteorologist in Washington state. Linda Weiford is a writer in Moscow, Idaho, who’s also a weather geek. Contact: ldweiford@gmail.com.

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