What we are experiencing is an atmospheric river, otherwise known as “the pineapple express” of a weather system coming from Hawaii in the form of very warm temperatures and lots of rain. If it occurs later in November, it can be very bad everywhere due to rain falling on snow in the mountains and extreme river flooding.
However, the northern part of Washington and British Columbia is getting hammered with river flooding, surface water flooding and the consequential damages that come from such events such as bridge and road washouts.
The other big threat is landslides. This latest storm is a culminating event for about seven inches of rain that I have recorded at my house. There are many hilly and mountainous areas in the state and when that much water percolates down and hits a layer of clay, slides can happen. These can be shallow or deep-seated slides that take out whole sections of a hillside, which can impact roads and homes.
Another “worst case scenario” would be an earthquake, even a somewhat minor one, say around a 5.0, that would unleash hundreds of slides due to the extremely wet soil conditions. Back in 2001 when the Nisqually earthquake happened we had slides, but it was one of the driest winters on record.
