Flooding and Mudslides across Pacific Northwest | Atmospheric River Event

An atmospheric river event continues across the pacific NW where Major flooding and mudslides prompted a state of emergency declaration to be issued for parts of Washington state Monday due to the heavy rainfall. One woman in BC has lost her life due to floodwaters while others remain missing. In Washington, state situations ensued throughout Monday and Tuesday as hundreds of individuals were rescued from flooded towns, including many by airlift from members of the Coast Guard.

Water vapor satellite imagery showed continuous moisture transport from our Atmospheric River, also known as the Pineapple Express bringing a continuous flow of moisture advection to the Pacific Northwest. This moisture transported through our atmospheric river was enhanced across the Pacific Northwest due to frontal systems and orographic lift, enhancing rainfall totals across the region on the windward side of the mountains. Over the last 72 hours near the Olympic Mountains and the Cascades, some locations saw up to 10"+ of precipitations.

Some good news is dry conditions are expected today and through tomorrow as an upper-level ridge continues to build from the west over the west coast of the lower 48, deflecting any incoming weather systems to the north towards the Vancouver Islands. However, a weak system is expected to move into the area Thursday into Friday time frame bringing additional rainfall to the region.

However, this dry weather pattern won't stay long. Cooler ocean waters continue across the equatorial Pacific. This is due to cool ocean waters continuing to be upwelled across the west coast of South America, while strong easterly trade winds are advecting the cooler ocean waters westward across the Pacific. These cooler than normal ocean waters are what we call La Nina. With a typical La Nina, we can expect ridging across the eastern Pacific and wetter conditions across the Pacific Northwest. The Climate Prediction Center (CPC) November Precipitation Outlook suggested wetter than average conditions across the Pacific Northwest and we have surely seen that already. These ocean conditions aren't going anywhere either. Current models suggest we will remain in a La Nina all winter and might not see neutral or El Nino conditions until late spring/early summer. NMME forecast model suggests similar conditions too as it keeps the Pacific Northwest wetter than average through December, January, and February.

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