Will winter bring cold and snow, warm rain, or some combination of these to the Central Sierra Nevada Mountains and Lake Tahoe? Will the timing of cold and wet air masses moving into the region match up in such a way that snow results?
So what can the Central Sierras 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 region calls for an equal chance of above-normal, normal, and below-normal precipitation and temperatures.
The region is, to say the least, a snow lover's dream. Mount Shasta, way to the north, has an average annual snowfall of 105 inches. Lake Tahoe resorts saw 293 inches of snow fall last winter at the 6,200 foot level; at 8,200 feet, the amount was 480 inches. This trend holds true across the region, where the higher the elevation, the greater the snowfall, until one is above 8,000 feet and average annual snowfall is well over 30 feet. Non-Tahoe, but still in the region, ski areas such as Bear Valley, hits that average, while Dodge Ridge plumbs annual depths of 33 feet.
That's good for skiers and riders, and for the region's thirsty urban centers as well, where people depend on the annual snowfall to replenish their drinking water supplies.
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."