Minor snow today

It is the old story, the temperatures are marginal for snow near sea level around western Washington.

 At 10 AM, some locations around Puget Sound were reporting mixed rain and snow, and some higher elevations (like Paine Field in Everett) were all snow.    However, the temperatures aloft are relatively warm and the road surfaces have warmed after our relatively balmy weather.   So not much is sticking.  But you can see flakes on some web cams (see one near Paine Field below), with some whitening on grass.

 The issue:  warm temperatures above.   A plot of temperature with height at 9:30 AM shows a freezing level of 1750 ft, which implies a snow level of 750 ft.   Yes....the higher hills could get some accumulation, but not much near sea level.

A plot of temperatures aloft (over Seattle) in time, shows -2C air at 850 hPa (around 5000 ft).  That is extremely marginal for snow, particularly when one does not have cold air in place at low levels.

The forecast pressure pattern is also not favorable, with a low center right over us and no feed of cold air from the Fraser River Valley (see forecasts of pressure and temperatures for 10 AM below).

The latest National Weather Service HRRR forecast (made every hour for 18 h) suggests some very light snow north of Seattle...and remember that is NOT snow on the ground, but what falls out of the sky. (see example of snowfall ending 11 AM)

Bottom line:  if you are near sea level, you will not see much and there is very little risk of significant snow.  If you are above 500 ft, you will see some very light accumulations. More over Whatcom county.

Sorry for folks wanted a white Christmas at sea level.   But there is plenty of snow in the mountains.

Where to go for a dry vacation?

The holiday break period is looming and folks want to know:  where will it be dry?    Well, to answer that question, below is the 1-week precipitation total from the National Weather Service GFS model.

Western WA and British Columbia:  wet.  In fact, wet along the entire West Coast, including California.  Northeast and central U.S.: wet.

You want to be dry in the lower-48 states?  Eastern Colorado is a good bet as the Florida panhandle. For completely dry conditions, head to Mexico:  Cabo San Lucas and the central/southern Mexican coast looks good.

Here in the NW, wet is the word.  The forecast for the next 3 days, indicates several inches for western Oregon and northern California.

The next 72 hr moves the focus of the rain back to the Northwest and southwest BC.

Finally,  let's take a look at our latest snowpack numbers--and they look good. The Olympics and western Cascade slopes are generally at 120-150%, with eastern WA roughly 75-90%.  With a good snowpack and all the regional reservoirs above normal, water resources for next summer looks good.

Why is Climate Research Important?

The media is full of headlines regarding the potential elimination or reduction of U.S. climate research by the Trump administration.

There are two groups that question the necessity of climate research and they are, strangely enough, on opposite sides of the political/environmental spectrum.   On one hand, there is the "climate hoax" contingent who believes that climate change is a Chinese invention to undermine the U.S. economy or a liberal plot to increase government and take control of our lives.   On the other hand, there are those who suggest that climate change is "settled science" and society has all the information it needs to act.  That "97% of climate scientists" agree on what will occur as greenhouse gases increase.  The dangers of the "settled science" group was made clear in Australia, where the conservative government fired climate scientists in CSIRO with the claim that the science issues were now clear.

I will suggest that both are profoundly wrong and that research is acutely needed to understand and project climate change forced by natural processes AND human-enhanced greenhouse gases.  In this blog I will describe the importance of climate research and will discuss weaknesses in our understanding of human-caused climate change that are rarely admitted by scientists or discussed in the press.  Weaknesses that must be addressed.

So why is climate research so important?  Let me give you a few reasons.

Reason #1:   The is Still Lots of Uncertainty of What Climate Change will Bring both Globally and Locally.

Both basic scientific principles (e.g., the physics of radiation) and our most comprehensive climate models strongly suggest the earth will warm as greenhouse gases increase.  Importantly, as our global climate models get more and more complex, the uncertainty in their projections (the range of potential outcomes they suggest) has NOT CHANGED IN DECADES.    Our best estimate are that a doubling of CO2 results in a range of roughly 1.5 to 4°C iincrease n global temperatures.  We would have said the same thing 30 years ago.

Why so uncertain and haven't we become more confident?   The list of reasons is a long one--here are just a few:

• Uncertainty in the amount of greenhouse gases there will be emitted and retained in the atmosphere.
• Uncertainty in how the land surface will change.
• Major uncertainties in model physics, such as how clouds form or how energy is exchanged with the surface.
• Inadequate resolution of the global models, making them unable to properly deal with topoography.
• Poor handling of convection/thunderstorms.
• Many global models fail to properly simulate natural variability, like El Nino/Nina and the MJO (Madden Julian Oscillation)....to name only few.

Research is needed to reduce ALL of these and other sources of uncertainties.

The uncertainty of the local impacts of global climate change is even larger than for global changes.  Lack of resolution in global models means they don't properly handle local terrain, land-surface conditions, and land-water contrasts to name only a few factors that have huge impacts on local weather and climate.

To deal with local conditions, either the global climate models need far higher resolution or intense research/development into regional climate modeling is required, something a group of us is trying to initiate here in the Pacific Northwest.

Reason #2:   Current climate climate models are "tuned" to reproduce the current climate and thus may have serious deficiencies.  They may not be adequate for projecting future climate change.

A piece of dirty climate-change laundry is that our current climate models can not duplicate the current climate without "tuning" some parameters for which there are uncertainties.   The fact we have to do this reveals that there are still deficiencies with our knowledge and/or ability to simulate the climate.   Does this impact our ability to predict the implications of increasing greenhouse gases?  We simply don't know.

Reason #3.   There are many uncertainties in critical physical processes.

This reason is related to #1.  How will a warming climate impact sea ice?   Will large amounts of currently frozen methane be released?  How have small particles (aerosols) changed over the past 100 years and how has this impacted the climate system?   I could list dozens more of these:  important processes we don't understand well, including how they will interact with a warming planet.

The bottom line is that our current climate modeling technologies have deficiencies, both on global and local scales.  We have a lot to learn about basic physical processes that are critical for climate prediction.    There is a huge amount of work for climate scientists, earth sciences, meteorologists, and oceanographers to work on.  The science is not settled or certain other than there is little question that the planet will warm.

And society needs better answers from the scientific community for many reasons, including:

• To determine how serious the climate change threat from increasing greenhouse gases will be.
• To provide guidance on how society should adapt for future climate change, including construction of long-lived infrastructure

The U.S. will spend trillions of dollars on infrastructure (e.g., dams, roads, reservoirs, etc.), shouldn't decision makers have available the best possible information on what we expect to happen during the next century?

So  even if you have your doubts about climate change (like Trump and some Republicans), doesn't it make sense to do the research needed to strengthen the underlying science and to reduce the uncertainties?

If you are one of the environmentally committed that have no doubt about the reality of climate change, isn't it prudent to get a better answer on what we expect will happen as the concentration of greenhouse gases increase?

The U.S. has the preeminent scientific resources in the world regarding many of the basic science issues dealing with climate change.  It would be a disaster for a Trump administration or any other to dismantle a scientific capability that took a half-century to create.  Ignorance of the future is no advance for Republicans, Democrats or anyone else.

The Warm Up

Our region has endured one of the coldest periods in a few years, with teens west of the Cascade crest and single digits/below zero to the east.  And now, some light snow is falling over NW Washington.   But things are changing aloft, with warm air pushing in above us.  Normal temperatures (40s) and rain are in the forecast.

The temperature traces over the past four weeks for Seattle and Pasco are enlightening...if not chilling (red and blue lines are average highs and lows, respectively).  In Seattle, we have have been cooler than normal for the past two weeks, and the last few days were particularly frigid, with our high temperatures remaining below our normal lows.

But if you want to be impressed, check out Pasco in the TriCities,  where the recent temperatures have gyrated down to nearly -10F.  That is cold.

 The origin of all our cold weather has been the combination of high pressure (ridging) offshore and low pressure (troughing), as illustrated by the upper level (500 hPa) map for Friday morning at 4 AM.

 The forecast map for 4 AM Monday is very different, with much more zonal (east-west flow) as a result of a weakened ridge/trough.  Back to normal.

Over Seattle right now the temperatures aloft are warming rapidly (red lines, this figure show changes above Sea Tac with time--increasing to the left on the x axis and height on the y axis)

The light snow is a sign of the warming, with the movement of warm air into the region associated with upward vertical motion.  So far it has been mainly a dusting, as suggested by the latest cam shot near Bellingham.

What is going to happen now?  The meteorologically enlightened prefer to use ensemble forecasts and a probabilistic viewpoint, so here are min and max temperatures forecast by the European Center model for Seattle.  The range of possibilities is shown by the blue brackets.  The ensembles are emphatic about a warm up (you can bet on that!), with highs reaching to near 48F in a few days.  A slow cooling follows, but there is increasing uncertainty past a week.  Enjoy the warmth...it will feel nearly tropical after what we had.

The Tri-Cities will have to wait a few days, as shown by the predicted temperatures at Hanford.  But they will enjoy some thermal relief as well.

Cold Temperatures and Light Snow on Sunday AM

For many locations in western WA, the coldest temperatures in a year or so are being experienced this morning.  As shown in plot (low temps the last 24h), many locations in western WA dropped into the low to mid 20sF, with teens in Whatcom County (near the exit of the Fraser River Gap) and in low spots near the western Cascade foothills.   Teens and single digits all around eastern WA, with a few negatives.

 As predicted, cold, continental air is entrenched over the Northwest (see surface forecast for 10 AM Friday of sea level pressure and low-level temperatures).  We are shielded from the coldest air (purple color) in the mid continent by the Rockies and Cascades.

The latest NOAA snow analysis shown plenty of lowland snow include Whatcom County and Vancouver BC, and from Olympia to Salem.

Today (Friday) will see high temperatures only reaching around freezing and Saturday morning will again slip into the 20s and teens.  But change is coming.    Saturday will be generally dry (perhaps a few errant flurries at most), but Sunday morning a Pacific weather system will approach.  With cold air in place, it will start as snow in many areas of western WA. Here is the predicted snow cover percentile for western WA at 10 AM Sunday...even Seattle gets some.

Snow depths are not impressive over the lowlands.

By late Sunday/early Monday the warmer Pacific air will be in place and the normal wet/mild weather we so love will return.

Hard Freeze Will Soon Hit West of the Cascade Crest

You think it has been colder than normal?  It has been.  But even colder air will descend over the region by this weekend, dropping temperatures below 20F for a number of western Washington locations.   And lots of below-zero temperatures east of the Cascade crest.

We are talking about the coldest temperatures in 3-5 years for many locations.  A hard freeze capable of damaging plants and freezing some exposed pipes.

And then there will be snow tomorrow over Oregon, the southern Cascades, southwest Washington, and much of eastern Washington.  

Let's "warm up" by starting with the low temperatures on Tuesday (below). Upper 20s and 30s over western Washington, teens in the mountains, and single digits of NE Washington.  A few negative temperatures in some cold pockets, generally in valleys.  Before long you will be thinking of these temperatures as subtropical.

One way to show you the changes are with forecast maps of sea level pressure (solid lines) and 925 hPa (around 2500 ft) temperatures (colors).  Blues are very cold and purples you don't want to know about.

Currently, cold air is found east of the Cascade crest with cool air over NW Washington.

 By Friday morning at 4 AM, the air has cooled and extended over all of Oregon.

 Four AM on Saturday, the entire region is locked in the ice box, with very cold air pushing into CA and Nevada.

The latest European Center ensemble  and high resolution temperature forecasts suggest the HIGHS at Sea Tac airport will remain in the upper 20s on Saturday and the lows in the lower 20s.

Weather.com, which uses sophisticated statistics on top of combining a number of major weather models,  projects a high of 33 and a low of 21 on Friday.

Sea-Tac is NOT a cold spot and teens will be prevalent away from the water and particularly in low-lying locations.  Protect your pets, plants, and hoses.

And did a say something about snow?  Yes, I did!  A low pressure center will move across southern Oregon tomorrow, producing a shield of snow that will move across Oregon and SE Washington.

Here is the 24 h snow total ending 4 AM Thursday.  Eastern Oregon really gets it, with the eastern slopes of the Oregon Cascades BURIED with several feet of snow.  Folks around Mt. Batchelor will be smiling.  Portland may get a small piece of this, as might Yakima and the Tri-Cities.

But there is a bright light in all this.  Expect plenty of sun with the cold temperatures and believe it or not, sunset times are now getting later.  4:17 PM today and by Monday it will be 4:19 PM.  Unfortunately, it will still be getting darker in the morning until the winter solstice.

Freezing Rain Hits Portland and Bellingham

On Thursday evening, while Seattle was worrying about approaching snow, Portland was being hit by freezing rain:  liquid precipitation that freezes on contact with the ground or other objects. Extending from the western Columbia Gorge into the northern Willamette Valley, the Portland freezing rain lasted from 4 PM Thursday until noon on Friday, causing power outages and closing I 84 for hours.

Bellingham has also had several hours of freezing rain, mainly late Friday and Saturday, with a touch of it last night.

So why is the western Columbia Gorge, Portland, and the Bellingham region vulnerable to freezing rain, while it is an exceptional rarity here in Seattle?  How can liquid water freeze on contact?

Freezing rain is associated with supercooled water.   Strangely enough, water can be cooled to below freezing 0 C (32F) without freezing.   This is not a rarity:  much of the water in clouds is supercooled. To go from liquid water (where water molecules are moving around but are bound together) to ice (where water molecules are found in a rigid, crystalline structure) does not happen immediately when temperature drops to freezing.  Sort of like a preschool class when you tell the kids to sit down....it takes a while.   And having a template for the crystal structure from some kind of particle (such as a freezing nuclei) helps things along--and sometimes such particles are lacking in the free atmosphere.

Much of the liquid water in clouds is supercooled (below freezing).

Nearly all precipitation in the Northwest starts as snow aloft, but as it falls in our normally mild air (even in winter) it melts and turns to rain (see figure, left hand side).  And if the atmosphere is cold through depth, the snow can reach the surface (right side).   But in some situation, a shallow layer of below freezing air occurs near the surface, while warm air (above freezing) exists above.   Thus, snow aloft can melt into rain and then get supercooled just above the surface.  When it hits a cold surface it then freezes, thus freezing rain.

In the Northwest, a set up for freezing rain can occur in and downstream of gaps in our mountains. In winter, cold air is often found over eastern Oregon and Washington, with the coldest air prevented from reaching the west by the Cascades.   Yes, some air can try to get over the mountains, but it rapidly warms as it sinks on the western slopes (as it is compressed by higher pressure).    Only in and immediately downstream of sea-level gaps, such as the Columbia River Gorge or the Fraser Valley of southern BC can primo cold air get across.  This is illustrated by the temperature forecast for 1 PM Thursday from the UW WRF system for 925 hPa (about 2500 ft).  Cold temperatures are blue and white, warmer temperatures are yellow and light green.

 On Thursday, there was cold, dense air east of the Cascades crest, associated with higher pressure.   As a result, cold air accelerated westward down the Columbia Gorge, something shown by aircraft observations at Portland that day (see below).  The figure provides a time-height cross section, with time increasing to the left (from 4 AM Thursday to 4 AM Friday) and temperature (red lines) and winds shown. Heights are in pressure (850 is about 5000 ft).  Strong easterly winds are apparent at the surface, while the winds turned southerly/southwesterly aloft and the air warmed to just above freezing aloft.

With supercooled water falling on Portland, trees picked up lots of ice, causing branches to fall and power outages.  And some of the roads became dangerously slick.

Bellingham has had a lot of cold gap flow the past few days as cold northeasterly flow surged out of the Fraser River Valley (which taps cold air in the interior of BC).  This morning is no different (see surface map at 11 AM is shown).  Below freezing in the northeasterly flow north of Bellingham, result in continued snow over NW Washington.  Some of the NE flow is moving up the northern of the Olympics resulting in snow near Port Angeles.  In contrast, south of Everett the temperatures are in the low 40s.

A view of the cam at the Peace Arch near the US/Canadian border looks white with fresh snow, and the situation on Hurricane Ridge on the northern side of the Olympic Mountains shows deep fresh snow.  Northwest meteorologists must always be thinking of the gaps in our mountains when forecasting snow and freezing rain.

Nighttime Weather Cams: The Next Frontier

One of the great sources of weather information are video cams that view the sky, particularly since a number of them are now available in high-def and in near real time.    One of my favorites is the space needle pano cam, shown below, which gives you a 360 degree view of the skies of Seattle.  And there are thousands more "weather" cams around the U.S.

http://50yrcamera.spaceneedle.net/

Virtually all of these cams are daytime affairs...and clearly there is plenty of weather going on at night--as well as lots of stars, meteors, auroras, and other interesting visual elements.

With cameras and video increasingly offering low-light capabilities, why stop with daytime weather cams?   You don't have to...and someone is exploring this fascinating new dimension:  Greg Johnson of Washington's SkunkBay Weather.

Greg Johnson is our local poet-laureate/visual artist of weather cam videos and offers a website in which you can view triple-cam views of the sky from his home on the Kitsap Peninsula.   Some of his weather videos, coordinated with new age music, are moving on an emotional level.  Recently, he started producing night cam videos and the results are amazing.  Let me show you a few.

Here is one in which you can see stars (the big dipper!), clouds, aircraft, and a few meteors (click link):

http://skunkbayweather.com/Night112216.mp4

Or one during the supermoon, a few weeks ago:

Super Moon - November 2016 from SkunkBayWeather on Vimeo.

One with clouds, aurora, and meteors!
All Night - Aurora and Meteors - 12/6 - 12/7 from SkunkBayWeather on Vimeo.



Or a moonlit night in October:

Moon Lit Clouds and a Meteor - October 18, 2016 from SkunkBayWeather on Vimeo.

I think you will agree that such nighttime sky videos have a lot of promise and I look forward to the results of Greg's exploration of their potential.   With music, of course.

Thursday Snow Nowcast at 3 PM: Snow Moving in Faster Than Expected

Well, our models may have had the right idea of the threat of snow, but the recent runs clearly have a serious timing error.    The snow will arrive 4-5 hours earlier than expected.

The latest radar image  (2:27 PM) shows the story--the precipitation shield from the warm front has reached the south Sound.  Once precipitation starts aloft, it takes about an hour to reach the surface (need to humidify the layer below)

The latest visible satellite image shows an impressive cloud band with the warm front.

Let me show you some traffic cams.

It has been snowing in Portland for hours.

Vancouver

 Longview

Here is the Chehalis Airport

  Centralia.

Dupont, north of Olympia at 3:30

It should starting snowing at the surface in Olympia by 3PM.  At the current rate of progress, the snow will get to Tacoma around 4 PM and Seattle by 5-5:30 PM.

There appears to be multiple bands...the first band is producing the above snow.  It appears to be weakening over southern Puget Sound...and slowed down.  So it looks like Seattle commute will be ok.   The second band, which should arrive later (if the models are right), well be more of a threat for Seattle and points north...later in the evening.