Skiers and snowboarders scan for signs each year as fall spins into winter to glean some inkling of what lies ahead. Will winter bring cold and snow, warm rain, some combination? Will the timing of cold arctic air masses moving into the region from the north match up with the arrival of moisture from the coast in such a way that snow results?
So what can Oregon expect this coming winter, according to the Lords of Climate at the National Weather Service? Short and sweet: The NWS long-range forecast for the Pacific Northwest for December, January, and February calls for above-normal temperatures and below-normal precipitation, a witches' brew from the viewpoint of skiers and riders.
Location is a key factor in snowfall in this ocean-dominated region, with inland areas more prone to snow and cold than coastal cities. Portland, Ore., has an average annual snowfall of 6.5 inches, while Sexton Summit gets 98 inches.
The National Weather Service puts out long-range forecasts for the entire country. These prognostications are based on historic weather patterns, temperature and precipitation records, and other climate indicators from around the globe. They sometimes hit the nail on the head, but often do not.
Some seek counsel elsewhere. Do woolly bear caterpillars have thicker coats than normal? Are there more nuts falling, and are squirrels scampering even more madly than usual to store up winter food? It's a mystery why people ascribe powers of foreknowledge to insects, rodents, and nuts, but some do. After comparing long-range predictions with what actually happens, some conclude the critters and acorns are just as reliable as the scientists.
Jeremy Davis, senior meteorologist with Weather Routing Inc., a weather service in upstate New York, questions the wisdom of over-reliance on long-range forecasts. Davis suggests that the devil in forecasting lies in the little details of timing that determine the shape of the weather.
"Whether you have snow or rain depends on exactly when the precipitation falls," Davis said. "It can be warm and dry, or cold and precipitating. The long-range forecasts missed the cold snap in January, and the rainy June."