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.  

Hard Freeze This Morning

 Much of the region dropped below freezing this morning, with the main exceptions being locations close to large bodies of water.

Even my neighborhood in Seattle, not far from the water, awoke to glazed cars and icy roofs (see below).

The patterns of the frost were intricate and quite beautiful:

So how cold did it get?   The map below shows the low temperatures this morning.  Below freezing over much of western Washington, while eastern Washington was in the teens or low 20s, with a few single-digit temperatures over northeast Washington.

If you like cold, the Methow Valley did not disappoint, with most stations in the teens.

Keep in mind that the above temperatures are NOT at ground level, but at 2 meters (about 6 feet) above the surface, which is the standard height for surface air temperature.  

On cold, nearly clear nights, like last night, the ground temperatures are considerably cooler than at 6 feet.

I checked that out this morning with a research-quality thermometer over a grassy area.

Frost was evident, and the ground temperature was 29.4°F.

At 6 feet, the temperature was 33°F. An inversion (temperature increasing with height) was evident.

Tomorrow morning should be icy as well....so be careful...

La Nina Strengthens: What are the Implications for this Winter?

La Niña, associated with cool water over the tropical Pacific, has a significant impact on Northwest weather, influencing temperature, precipitation, and snowfall.  

As described below, La Niña has strengthened recently, and some decidedly La Niña weather is now in the forecasts.

As noted in previous blogs, La Niña is associated with cooler-than-normal ocean temperatures over the central tropical Pacific, known as the Nino 3.4 area (see below)

According to the latest observations, we are about to transition from a weak to a moderate La Niña (see figure below).   This figure shows the difference from normal of the temperatures in the Nino 3.4 area, with blue colors indicating below-normal temperatures.   A moderate La Nina is associated with a cool temperature anomaly larger than .9C.   

We are now crossing this threshold to moderate La Niña conditions (see below).

The recent NOAA El Nino/La Niña forecast indicates continued La Niña conditions into mid-winter.  If anything, it's erring on the warm side.

La Niña winters tend to be associated with an upper-level ridge of high pressure over the Gulf of Alaska and associated cold northerly flow over the Northwest (see below).  La Niña winters tend to be cooler than normal over the Northwest, generally with more snow than typical.

Occasionally, the jet stream breaks through underneath the ridge with a strong cyclone/wind event.

Now, let's look ahead over the next week or so, considering forecast models' predictions.

The forecast of the upper level (500 hPa, about 18,000 ft) heights/pressures for Saturday afternoon shows a big ridge offshore and northwesterly flow over Washington.  Classic La Niña pattern.

Tuesday morning?    Very similar.  La Niña upper air pattern

With a La Niña pattern with northerly flow from Alaska in place, temperatures should be a bit colder than normal over the Northwest, as illustrated by the forecast temperatures at SeaTac over the next few days.  Normal is around 50F.... predicted temperatures are several degrees cooler.

The forecast surface (2-m above the ground) temperatures on Sunday at 7 AM indicate that much of the state will be below freezing, with most of the Cascades and eastern Washington in the 20s. (see below)

Below-freezing temperatures will also occur over the eastern part of Puget Sound country.    Keep in mind that temperatures could be even cooler at the surface.  

So be ready for the first frost of the season!

The latest forecast of temperature (actually the difference of temperature from normal) from the highly skillful European Center extended forecasting system through January 13th, suggests colder than normal temperatures for the next month and a half. 

And the latest NOAA seasonal outlook is for cooler-than-normal conditions over Washington State.

Get your skis ready!

Snow in the Passes and Eastern Slopes of the Cascades

 I have received several inquiries about snow in the Cascade passes from folks who will be traveling over Thanksgiving, and for others looking for some snowy recreation this week.

So let's take a look at the latest forecasts.   

A weather system is off our coast right now and has our name on it.  It will move in on Tuesday afternoon, with precipitation into Wednesday.

The UW ultra-high resolution model predictions of snowfall totals through 1 PM on Wednesday (below) show up to about a foot in the Cascades, with about half that amount in the passes. 

Much more snow on the eastern slopes of the Cascades than to the west.  Substantial snows on the southwest side of the Olympics as well.

But this is just the beginning:  more snow will come in on late Thursday and Friday over the north Cascades (see total through 4 PM Saturday below).

There is some uncertainty in the forecasts...let me illustrate. 

 A powerful tool used by meteorologists is ensemble forecasting....running our forecast models many times with slight differences in initial conditions or physics (e.g., precipitation processes).

Below is the ensemble prediction of snow at Stampede Pass at 4000 ft on the eastern side of the Cascade crest.    

The mean forecast is for about 6 inches, with a range of 4 to 12 inches.   Snoqualmie will get less...perhaps 2-4 inches.  So, not the end of the world, as predicted by a few online sites.

Not enough snow for downhill skiing, but plenty for snowballs and perhaps snowshoeing.    The landscape will look pretty.

Enjoy.  And please drive carefully when crossing the Cascades.

The Problem With Wind Energy in the Northwest

This was a bad week for wind energy in the Northwest, but before I discuss this, let's step back for a few minutes.

There is a lot of interest in renewable energy in the Pacific Northwest that could supplement our hydropower.   

With our northern latitude and extensive clouds for much of the year, solar energy can only make a small contribution.   

To illustrate, here is the annual solar energy map for the U.S.  Western Oregon and Washington have poor solar resources.  Better in eastern Oregon and the Columbia Basin.  But even in these areas, there is very little resource from November through February.

The wind energy situation in the Northwest is better, but not particularly good.   Consider the map of annual wind energy resources in the U.S. (below).   The windy High Plains of the U.S. have terrific potential, but the western U.S., away from the coast, has very modest wind energy, at best.  Only the coastal waters from central Oregon to central CA have good wind potential.

Here in Washington State, the only decent non-coastal area for wind energy is the eastern slopes of the Cascades (see map below).   That is why nearly all of the wind turbines are there.  Constructing wind turbines offshore is very expensive and has significant environmental problems.

But there is a problem.   For much of the year, these turbines generate little power.

Consider the Bonneville Power Authority (BPA) statistics for the past week.   The total energy demand is the red line, and hydro generation is blue.

Wind energy (green) has been very small most of the week, except on one day (November 18) when a frontal system moved through.  The output from one nuclear plant (purple) has been constant and generally much higher.

The truth is that wind generation in our region is only really significant from late spring to late summer, when strong westerly flow descends the eastern slopes of the Cascades.

To see this, consider the winds at Ellensburg, surrounded by wind turbines on several sides.  Good winds from April into the middle of August.  But consistently slower (and often very weak) the remainder of the year.

In short, our region needs to maximize our hydro resources and invest in next-generation nuclear (fission) plants, which are inherently safe.

With rapidly increasing demand for electricity, expected to roughly double by mid-century (see NW Power Council estimate below),  without new generation capacity, there is a near certainty of blackouts, particularly during cold periods. 

Wet California

 This has been a very wet fall in California.    A big contrast with last year.

Los Angeles this week

Consider the differences from normal of the precipitation during the last month for the western U.S. (below).   

Wow.  Some parts of southern California have gotten 800% of normal precipitation!  The entire state is considerably wetter than normal.

Many of the rivers are running MUCH higher than normal, as shown by the latest percentages below.   Crazy high river levels over coastal southern California.

What about the levels of the all-important California reservoirs?  The answer is below.

All are at or above normal.  Over southern California, some are full.

Last year, had one of the driest Octobers through December on record in Southern California, which contributed to the LA wildfire in early January.   

Some claimed this was the result of "climate change."

The atmosphere did not get the message.   Consider the precipitation from October 1 through November 19 over the past 50 years.  This year was the second wettest of the entire record!

This wet fall has led to the suppression of wildfires.    

So far this has been a VERY low wildfire year in California....something that is being given little attention in the media. 

Below are the statistics for wildfire acres year to date.    So far in 2025, about 525,208 acres have burned compared to a fire-year average of 1,315,947.

That is only about 40% of the recent average.

So, why has California been so wet?    The answer:  a persistent trough of low pressure off its coast.

For example, here is the anomaly map (difference from normal) for the heights at 500 hPa pressure (think of pressure around 18,000 ft). 

Purple and blue indicate lower than normal values....troughs of low pressure.    Right off of California!