The Pacific Northwest is poised to close out January just as it began - soaked by heavy rainfall and bracing for flooding. A series of storms fueled by an atmospheric river will unleash over a foot of rain in parts of Washington, Oregon, and southwestern Canada before month's end, posing serious flood concerns.
An atmospheric river is a long, narrow corridor of concentrated moisture that extends from the tropics to the Pacific Northwest. Like a firehose in the sky, these moisture pipelines funnel vast amounts of rain to areas west of the Cascade Mountains. Meteorologists warn that the impending atmospheric river could be the longest and most impactful of the month.
Relentless bands of rainfall will pummel western Washington and Oregon for days, accentuated by the influx of deep tropical moisture. Rainfall totals could exceed 10-15 inches in some coastal and mountain locations by January 31st. With soils already heavily saturated, officials caution that even modest rainfall could trigger urban, small stream, and river flooding. Mudslides near recent wildfire burn scars also pose a significant risk.
While the heaviest rain will focus on the Pacific Northwest, spillover moisture will also spread into parts of southwest Canada. British Columbia's southern interior and western Vancouver Island could receive 4-8 inches of rain before month's end, raising the specter of flooding and landslides. Victoria and Vancouver will be on the edge of the heaviest moisture, but should still expect a very wet last week of January.