The Pacific Northwest is about to get a heaping helping of rain, snow and possibly icy weather for a couple of days. Starting tomorrow, Dec. 18, a potent low-pressure system and associated cold front will crash into the region, lingering at least through Thursday, Dec. 19. Truckers having to go over mountain passes will have to chain up. Those traveling the wet I-5 corridor may run into delays too.
One to 3 feet of snow could pile up in many locations from Willamette National Forest northward to Gifford Pinchot National Forest, affecting mainly state and U.S. routes in the Cascades of Oregon and southern Washington. Significant freezing rain could develop in elevations between 3,000 and 4,500 feet in the northern Oregon Cascades and the upper Hood River valley, with total ice accumulation of one-quarter of an inch. Scattered power outages could result from the weight of the ice on utility lines. Simultaneously, the lowest slopes and valleys, as well as coastal areas, could get drenched with occasional torrential rainfall. This includes cities from Seattle to Portland and Medford, Oregon. Coastal areas could also get battered by strong winds.
Some of the worst snow and ice will likely hit the Oregon areas of Government Camp, Santiam Pass, McKenzie Pass, Parkdale and Odell, in addition to Mount St. Helens and McKenzie Pass in Washington.
Besides hazardous road conditions, short-term disruptions at the ports of Seattle and Portland are possible due to high winds and heavy rainfall. Also, air cargo may be delayed to and from Seattle-Tacoma International Airport (ICAO code: SEA). Shippers, carriers and brokers who subscribe to FreightWaves SONAR can locate these types of assets at potential risk of weather disruptions. They are color coded inside the Critical Events platform based on the anticipated level of disruption, as shown on the map above, and are updated as conditions and forecasts change.
FreightWaves Market Expert Jesse Cohen says the Seattle market’s outbound air cargo typically peaks in the summer with lower overall demand this time of year. Hence, the amount of outbound available tonnage capacity (OACT.SEA) – freighters dedicated to carrying only air cargo plus widebody passenger planes carrying belly cargo – also declines in the fall and winter. This SONAR index is updated weekly. The impending storm will not likely have a major impact on Seattle’s outbound air freight, but it may slow down delivery of air mail that includes cards and gifts for Christmas and other upcoming holidays this December.
As of this afternoon, Dec. 17, forecasts for this Pacific Northwest storm are calling for 3 to 6 inches of total rainfall for western Washington state, with the highest amounts in the Olympics and Cascades. Snow levels will begin around 3,000 feet, rising to around 5,000 feet by late Thursday, Dec. 19, into Friday, Dec. 20. The timing of this change will increase/decrease the degree of potential flooding. Nonetheless, the National Weather Service (NWS) says the rainfall will likely be sufficient enough to cause flooding impacts on several area rivers by the upcoming weekend. Some impacts could be widespread.
The northern Oregon coast range and the southern Washington Cascades appear to be the focus of precipitation. However, this type of atmospheric event is notoriously difficult to precisely predict more than 24 hours in advance. Further complicating the issue is the timing of the changing snow levels, which are difficult to pinpoint at this time. The forecast should become more fine-tuned tonight into early Wednesday. Look for updates on the FreightWaves website and social media accounts.