Major Flooding Coming to Western Washington

With very heavy precipitation expected next week, particularly on the western side of regional mountains, major flooding is being forecast.

Over the next five days, the UW WRF model is forecasting more than ten inches over the western side of the Cascades (see below).

 

Are you sitting down?  Ready for a shock?  Below is the ten-day accumulated precipitation forecast for the region.  Some locations are expected to receive 15-20 inches in total.  

That means flooding.

The European Center model is doing the same thing, as shown by the predicted totals through next Saturday (13 December).  For all models, the wettest day is on Tuesday.

The super-heavy precipitation on Tuesday will be associated with this region being hit by one of the strongest atmospheric rivers in a long time (Tuesday at 7 PM shown):

The Gogzilla Atmospheric River.  Trained meteorologists call this a GAR.

The Northwest River Forecast Center in Portland is predicting moderate flooding on several northwest rivers (see red dots on the map below).

For example, the Snoquamie River near Carnation will get to MAJOR flood stage (purple line) on two days (10-1lth), with levels reaching all-time high river stages on two days.

The Snohomish will reach major flood stage (red line) during the same period.

And the Skagit will approach major flood stage on December 20th.

This is a serious event, and those of you in vulnerable locations should make preparations. 

A good effect of this major precipitation event is that local reservoirs will gain an enormous amounts of water.  All the western Washington reservoirs should fill to at least normal levels and a major filling of the Yakima system will occur.