On the heels of a deep atmospheric trough that now envelops the entire Western U.S., a strong Pacific storm has formed off the coasts of Washington and Oregon and will soon drift to the south. Onshore winds will sweep copious moisture across the Pacific States, producing chilly rain in the lowlands and heavy snow in the mountains.
Over the next few days, lower elevations are expected to receive up to a foot of rain while the Sierra Nevada may be coated with five feet of snow. Of course, this precipitation is more than welcome across a landscape that has been ravaged by drought and wildfires and the heavy snowpack will help to insure an adequate water supply for regional cities. On the other hand, recent burn areas will be at risk for mudslides, lowland rivers are sure to flood and avalanches will pose a danger in the high country.
Such is the nature of Western ecosystems, where prolonged periods of drought are interrupted by brief episodes of intense precipitation. Mountain snowpack is the vital storage system for that moisture and this storm, while unleashing transient complications, will produce lasting benefits (at least for this year).
