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.

Massive La Nina Precipitation Coming to the Northwest

Heavy rain and snow?  Check.

Skiing before the holidays?  Check.

Bring reservoirs to near normal levels?  Check.

Threaten flooding on some local rivers?  Check and check again!

The next few weeks are going to be an exciting meteorological ride, so buckle up.

A series of atmospheric rivers will make landfall over our region, resulting in bountiful precipitation, including snow in the mountains.  Let me show you.

The next week will include three atmospheric rivers (water vapor transport is shown below...the key measure of atmospheric river activity)

A modest atmospheric river on Thursday,

A strong one next Monday.

And a GODZILLA atmospheric river next Wednesday.  Directed right towards us.  

Precipitation totals over our region?

Through Friday morning, a good wetting, with the mountains soaked by 3-5 inches.  Just the start.

By Sunday morning, very large precipitation totals will have accumulated in the mountains, with some locations receiving 5-7 inches.

But then the third, crazy-strong atmospheric river hits, and by next Friday, the totals become insane..10 inches and more in much of the mountain areas.

The above are forecasts from the UW modeling system, driven by the NOAA/NWS GFS model.

The European Center modeling system is doing the same thing, which gives us confidence that a major event is ahead.  Below are the totals through next Monday morning.  Mountains are hit very hard.

By next Friday, crazy high totals:

The rivers will rise rapidly, some to flood stage.  Consider the situation for the Snoqualmie River near Carnation (below).  The first two atmospheric rivers will bring the level up to flood stage (see below).  The third, stronger river will cause substantial flooding (not shown below).

Snow in the mountains?  Huge amounts will fall.  Here is the forecast through mid-December by the European Center model.  Yards of snow in some locations.  

The ski season will begin.  Our water resources will be greatly enhanced.  Winter recreation will beckon.