The Cold Facts About This Winter

It is not in your imagination.

 For much of the Pacific Northwest, this has been one of the coldest mid-winters in decades.

Seattle on Wednesday

Consider the daily average temperature in Seattle from January 15 to February 7 over the past thirty years (below).   This was the COLDEST year for that period.  

 I have also plotted the trend over that thirty years (brown line).   There is no trend.   

Little change from global warming or global cooling during this period.

What about in Pasco, in the Columbia Basin of eastern Washington? (see below).  This winter period was colder than normal but four other years we colder during the last thirty.  

Interestingly, the temperature trend at Pasco is DOWN....cooling... over the last thirty years.

You won't see that mentioned in certain local media outlets.😊

Considering the temperature departure from normal over the last 14 days across Washington State (below), we see the general colder-than-normal pattern, with particularly chilly temperatures over the WA coast, near Bellingham, and over the NE slopes of the Cascades.

Why have we been this cold for so long you ask?   

Because the large-scale atmospheric flow has been stuck in a very favorable pattern for NW cold, with an upper-level high-pressure ridge offshore, with troughs of lower heights/pressures on both sides.    

To illustrate, take a look at the upper-level (500 hPa pressure, about 18,000 ft) map for January 25.  This pattern puts cold northerly flow over our region.

This configuration is called an omega block, because it looks like the Greek letter omega.   It is generally a very stable pattern.

Amazingly, the best global model (European Center) is forecasting the same pattern for the next five days (see below).   I think I need to purchase some more thermal underwear.

In fact, the EC  temperature forecast IS for colder than normal weather over our region during the next week (see below).

The NOAA National Blend of Models (NBM) predicted temperatures for Seattle are very cold this week, some temps dropping into the low 20s at night.   Protect your pipes, hoses, and pets!

During this cold period, there has been a substantial increase in electrical demand for heating and because EV batteries are substantially less efficient in the cold.   As shown by the BPA statistics, renewal energy production (mainly wind, green line) has been relative low...far less than the sole nuclear plant in the region (purple).

Unfortunately this is a repeated pattern:  renewable energy like wind is least abundant when we need it the most.  Thankfully, we have the dams.  But we need to seriously think about a major expansion of nuclear.

Wet Snow "Apocalypse"

 As forecast by the models, several inches of very heavy, wet snow fell last night.

The result included damage to vegetation, downed trees, and power outages.

This morning I risked life and limb to cycle into the UW on a slushy Burke Gilman trail.  At over a dozen locations I was blocked by fallen or leaning trees or bushes (see pictures below)

Many powerlines were downed by the wet snow, with poor vegetation management by local utilities an important contributor.

Lines down

Seattle had many customers in the dark:

Even more for Puget Sound Energy:

As I will discuss in depth in a future blog, we are experiencing one of the coldest mid-winters in regional history.  

And the cold is not over.

I have some news....more lowland snow will fall over the weekend.  For example, below is the predicted 24-h snowfall ending at 4 PM on Saturday.  

Relatively light over western Washington, with far more around Portland.

California is receiving massive amounts of precipitation and their reservoirs are well above normal.   Seattle's reservoirs are near normal.  Our snowpack is above normal over the southern Cascades and modestly below normal to the north.

At this point in time, there is no reason to be concerned about water resources over the West Coast during next summer.  In fact, the seasonal prediction by the European Center is for wetter than normal conditions for the next several months from Los Angeles to the Northwest.

A More Serious Lowland Snow Threat for Later This Afternoon and Evening for Western Washington

The latest model forecasts and the recent movement of the offshore low are now more threatening for snow reaching the lowlands of western Washington.....so I wanted to provide an update.

The latest infrared satellite image shows the situation and threat for this afternoon.  A low west of the Oregon Coast is swinging bands of precipitation east and northward into western Oregon and Washington.   A first weak band went through Puget Sound early this morning leaving up to about an inch of snow near sea level (red arrow).  But it is the movement of the much stronger southern band (blue arrow) that is of more concern.  

The models have had a hard time with this band, particularly on how far north it will move,

The weather radar composite around 5 AM shows the situation in a different way.  You can see the exiting snow band north of Seattle and the more impressive snow band associated with the low over coastal Oregon.

To illustrate the effects of the first band, consider a Seattle cam located in NE Seattle.  About an inch of snow fell, but heavily traveled roads are ok.  Back roads are treacherous. 

The UW ensemble system of many high-resolution forecasts from last night shows substantial uncertainty in the forecast of snow over Seattle, but a mean prediction of about 2 inches at SeaTac.  The main snow action in Seattle will be after 4 PM this afternoon (00Z/06 in GMT/UTC time). 

What about the latest UW WRF model forecast?    Let me show you accumulated snowfall (NOT SNOW DEPTH) through the next 24 hours.

Through 1 PM. most of the snow is over NW Oregon and SW Washington

More movement to the north by 4 PM.

By 1 AM light snow will have extended through Puget Sound.

Note the end of the world, but many will see some snowflakes, except for the northwest portion of the state.

_____________________________

Steve Pool Scholarship Fund

We are now 65% to our goal of the $100K needed to create a permanent undergraduate scholarship in honor of Seattle's most well-known weather communicator,  the late Steve Pool.   

Please consider making a contribution (tax-deductible) to this University of Washington fund.   And thanks to the hundreds of folks who have already contributed.

Here is the info:

A Steve Pool memorial undergraduate scholarship has been established in his honor (see below)

Once funded by contributions, this new undergraduate scholarship will provide financial assistance to promising Atmospheric Sciences students, fostering the training of the next generation of meteorologists and atmospheric scientists.

If you want to contribute or learn more about Steve, check out the webpage below.   Thanks so much....cliff

https://together.uw.edu/Campaign/steve-pool

Snow Tonight and the the Snow Low Off Our Coast

You might call it a snow low.

Cold air is moving to the southwest across the northern BC coast and becoming unstable as it goes over warmer water, producing streaks of instability clouds that circle around the low (indicated by a red "L")

Some of the cold, Arctic air from the interior of BC is moving westward down the Fraser River Valley into Bellingham and its vicinity.   At 2 PM, it was only 25F in Bellingham and in the low 20s a few miles away.

To get a big snowstorm over western Washington, we need the low center to park just offshore of the SW Washington coast.   This pulls cold air southward over western WA and is close enough to push moisture over it.

Many of our big snow events have occurred that way.

Unfortunately, the model is moving the low too far offshore, as shown by the forecast surface map for 10 PM tonight 

There will be some snow tonight with amounts increasing with elevation.  Being at 500 or 1000 ft makes a big difference during such situations.  For example, Dr. Peter Benda measures about 5 inches of snow at around 1000 ft in Bellevue (see below).

Here is the total predicted snowfall through 4 PM Tuesday.  Mostly light amounts except where the Fraser arctic air is hitting the mountains of Vancouver Island or the north side of the Olympics. 

  

In contrast, snow depth at that time is less impressive and highly variable.

This will be one of the most sustained cold periods in years...with the cold holding out for perhaps two more weeks (see below).   Just amazingly cold.  Historic cold spell.

_____________________________

Steve Pool Scholarship Fund

We are now 65% to our goal of the $100K needed to create a permanent undergraduate scholarship in honor of Seattle's most well-known weather communicator,  the late Steve Pool.   

Please consider making a contribution (tax-deductible) to this University of Washington fund.   And thanks to the hundreds of folks who have already contributed.

Here is the info:

A Steve Pool memorial undergraduate scholarship has been established in his honor (see below)

Once funded by contributions, this new undergraduate scholarship will provide financial assistance to promising Atmospheric Sciences students, fostering the training of the next generation of meteorologists and atmospheric scientists.

If you want to contribute or learn more about Steve, check out the webpage below.   Thanks so much....cliff

https://together.uw.edu/Campaign/steve-pool

There will be some lowland snow in Western Washington

The model forecasts provided excellent over the past 24 hours, predicting the cooling and the localized snow in a Puget Sound convergence zone near Everett (see the radar image and model forecast this morning at 1 AM this morning).  Stunning.

The model forecast also suggested the potential for some snow at high elevations near Bellingham, and that occurred.

It is amazing how good the high-resolution models have become.  The same models nailed the Santa Ana winds during the recent wildfire event in LA, and the downslope winds that devastated Lahaina, Maui.  

This a very powerful technology that can save lives.  

Because of onshore flow at low levels, temperatures are marginal for lowland snow over western Washington AT THIS TIME.

Using aircraft observations coming in and out of Seattle, we know that the freezing level around 11 AM was about 1400 ft (see below).   Which means the snow level is about 400 ft.

In very heavy showers, the snow level (below which all the snow melts to rain) was able to reach sea level, which just happened here in Seattle (see below)

For local snow lovers, the problem is that the lower atmosphere is too warm a good snowfall because the air is coming over the relatively warm Pacific Ocean.  As shown below, the sea surface temperature off our coast is now about 10C--around 50 F.    A big problem if you like snow at sea level.

But something is going to happen tomorrow that will change things.  

A low-pressure center will move southward to a position off the northern Washington coast (10 PM Sunday shown).  In contrast, there is high pressure over the interior associated with very cold, Arctic air (red and white colors, blue is relatively warm).

As a result, there will be a surge of very cold air out of the Fraser River Valley and then over NW Washington.  Below are the forecast surface winds and temperatures a 4 PM Sunday and 10 AM Monday.

This has snow potential!

Now let's look at the accumulated snowfall (not snow depth) through 10 AM Monday.   

 Several inches around Bellingham and LOTS of snow on the NE side of the Olympics as the northeasterly Arctic air is lifted by the mountains.   Another band to the south where the Arctic air hits southwesterly flow coming around the southern Olympics.

But what you REALLY want to know is the predicted snow depth at this time (see below). 

 Not as impressive, but the Bellingham Area will enjoy a fairly good snow dump.  

They are used to it.  The lowlands south and east of the Olympics, where southerly air is forced upwards do well also.

Salting of some of the roads would be good and municipalities must get the homeless off the street or there will certainly be some unnecessary deaths from this event.

__________________

Steve Pool Scholarship Fund

We are now 65% to our goal of the $100K needed to create a permanent undergraduate scholarship in honor of Seattle's most well-known weather communicator,  the late Steve Pool.   

Please consider making a contribution (tax-deductible) to this University of Washington fund.   And thanks to the hundreds of folks who have already contributed.

Here is the info:

A Steve Pool memorial undergraduate scholarship has been established in his honor (see below)

Once funded by contributions, this new undergraduate scholarship will provide financial assistance to promising Atmospheric Sciences students, fostering the training of the next generation of meteorologists and atmospheric scientists.

If you want to contribute or learn more about Steve, check out the webpage below.   Thanks so much....cliff

https://together.uw.edu/Campaign/steve-pool