Environment Blog

Normally during a La Nina winter the Northwest Coast of the U.S. experiences heavier than normal precipitation. So far this winter the stormier pattern has been conspicuously absent. Most of December and the early half of January has featured well below average rain and snow across the western U.S. This pattern is about to make an abrupt change which could last through the end of the month.

Beginning around Wednesday January 18th a stream of moisture from the Pacific will be directed at the northwestern coast of the U.S. A strong jetstream will drive a series of storms into northern California and the Pacific Northwest. Some of these storms will be accompanied by heavy coastal rain and significant higher elevation snowfall. Over a period of the next 1-2 weeks it is likely that 10-15 inches of rain will fall over western Washington and Oregon, with 5-10 inches over the northern third of California. This could lead to flooding and localized mudslides. Many feet of snow can be expected to fall in the mountains of Washington, Oregon, northern California, Idaho and northwestern Montana during this period. Some of the heavier rainfall may extend south across central California, but at this time it appears that the heaviest amounts will occur more to the north.

This abrupt pattern change could linger into the end of the month, with some relaxation in the storminess for early February. During this same time frame, the northern third of the country will see in increase in snowfall events, as multiple storms track across the northern part of the U.S.