Atmospheric river expected to slam West Coast(Source CBS News) Wild weather will bear down on the holiday season with a soaking atmospheric river for the West, drenching tropical downpours for the South and soaring temperatures in the East. For most, dreams of a white Christmas will remain just that. The Pacific Ocean is open for business, as a powerful Pacific jet stream will flood the U.S. with balmy air as well as some extreme weather over the next week. That includes a pseudo-subtropical storm in the Gulf of Mexico and up to foot of rain for some in the Pacific Northwest.
Atmospheric river Starting Thursday and lasting through Sunday, the Pacific Northwest will be bombarded by what is called an atmospheric river. An Atmospheric River is a fast moving, narrow ribbon of water vapor over the Pacific Ocean that transports moisture at up to 15 times the rate of the average moisture flow at the mouth of the Mississippi River. While the term has been around for some time, a team of scientists from Scripps Institution Center for Western Weather and Water Extremes, made it official this year by devising an atmospheric river scale. Like the Saffir-Simpson hurricane scale, the atmospheric river scale measures the intensity of events from Category 1 to Category 5 — 5 being exceptional. This upcoming event weighs as an AR3 for many, but as high as an AR4 for parts of Oregon, rating strong to extreme.