A category 4 out of 5 atmospheric river is forecast to bring heavy rain and flooding to the Pacific Northwest the first few days of this week.
On the atmospheric river scale a category 4 is characterized as “mostly hazardous” but also “beneficial” in terms of the amount of rain expected, according to the Center for Western Water and Weather Extremes (CW3E).
The rain will mainly impact western Washington, as well as western Oregon, most of which is suffering from some level of drought. Parts of British Columbia will also get drenched and possibly flooded.
Rain totals through Wednesday could exceed 6 inches along the Interstate 5 and U.S. Highway 101 corridors, in addition to the Trans-Canada Highway. Truckers may run into delays in major metropolitan areas such as Seattle and Portland, as well as Vancouver, Canada.
The National Weather Service has issue flood watches for these U.S. locations, while Environmental Canada has rainfall warnings in British Columbia.
Excessive runoff in these areas may result in flooding of rivers, creeks, streams and other low-lying and flood-prone locations. Creeks and streams may rise out of their banks and mudslides/landslides could cause road closures. Snow melt may contribute to some of the runoff. However, some of the highest peaks in the Cascades and northern Rockies will see snow — possibly up to 24 inches — or a rain-snow mix and/or freezing rain.
Periods of high winds may impact travel, especially in coastal and high-elevation areas, with gusts of 40 mph or greater.
Major lanes of concern
• Interstate 5 from Medford, Oregon, to Seattle.
• U.S. Highway 101 from Olympia, Washington, to the Washington-Oregon border.
• Trans-Canada Highway from Vancouver to Hope, British Columbia.
Other notable weather this week
High winds will increase the risk of rollover Monday for drivers in north-central Oregon and southeastern Washington, where gusts will range from 40 to 55 mph. Gusts of 65 mph Monday will slam southeastern Wyoming and western Montana, while gusts of 40 to 55 will rock parts of Southern California, mostly in the Los Angeles area.
Click here for more FreightWaves articles by Nick Austin.
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