Rain, Wind Storms to Frequently Lash Northwest US Well Into December

By Alex Sosnowski, AccuWeather.com Senior Meteorologist

December 1,2015; 10:02PM,EST

A train of storms will slam into the Northwest United States well into next week and perhaps through much of December.
The storms, which will vary in intensity and location, will hit every one to three days with waves of drenching rain, heavy mountain snow and gusty winds.

A modest storm will affect Washington, Oregon and northern California into Wednesday. However, snow and ice may cause problems for areas east of the Cascades. Cities that can expect slippery travel for a time include Spokane and Yakima, Washington, as well as Pendleton and The Dalles, Oregon.

Storm After Storm for the Northwest

A much more potent storm will blast ashore Wednesday night and Thursday with high winds and heavy rain along the coast.
This storm has the potential to down trees and cause power outages, as well as bring the risk of flash flooding and mudslides from northern California to western Washington.

During Wednesday night and Thursday, cities that could be hit hard include Eureka and Redding, California, and Medford and Newport, Oregon.
Drenching rain will reach as far south as San Francisco with showers in Sacramento, California, on Thursday.
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A third storm is projected to roar ashore with high winds and heavy rain from northwest Oregon to coastal Washington and British Columbia during Friday night and Saturday. Major travel disruptions and the potential for power outages may include the cities of Portland, Oregon; Seattle; Bellingham, Washington; and Vancouver, British Columbia.
Storms will continue to roll in through next week.
More Storms to Blast the Northwest and Spread Farther South This Winter
The storm train will continue to bombard the Northwest well into December.
According to AccuWeather Long-Range Meteorologist Ben Noll, "Much warmer-than-average Pacific Ocean waters off the coast of Alaska and British Columbia have helped to fuel the storms." Then, the storm track became established, directing storms into the Northwest.
The jet stream over the northern Pacific has strengthened in response to El Niño.
The jet stream is a strong river of air high in the atmosphere that guides weather systems along and separates warm air to the south from cold air to the north. In essence, the jet stream acts as a storm track.
El Niño is a fairly routine warm phase of tropical Pacific waters and can last months to a couple of years.

"The evolution of the El Niño pattern should direct the jet stream and hence storms farther south late in December, but more so during January and February," Noll said.
How far south is uncertain as a pocket of very warm water near Southern California would have to cool. This warm water is creating a persistent area of high pressure over the southwest corner of the U.S.
"We expect rounds of heavy rain and mountain snow to frequent northern and central California during the middle of the winter," AccuWeather Expert Long-Range Forecaster Pastelok said. "It is still possible the heavy precipitation pushes farther south into Southern California as well."
From a drought relief standpoint, heavy rainfall in Southern California is not as critical as rain and snow farther to the north. Much of the reservoir recharge area for California is tied in with the Sierra Nevada in central and northern California. Water from melting snow in the Sierra Nevada works its way into the aquifers. The more snow there is in the winter, the more runoff there will be in the spring and summer.
As the storm train shifts farther south over time this winter, communities should prepare for the negative consequences of flooding, mudslides and coastal erosion, before the benefits of drought relief can be realized.