Spring Skiing in January?

If you've looked at the forecast lately, you'll notice that we're expecting warmer temperatures next week.  Temperatures are forecast to be in the 40s, with even some lower 50s in places (i.e. the Palouse and Lewiston area).

Why will it be so warm?  Very strong high pressure will develop over the western US in the next few days.  But we often see that.  So what's so special about this?

The image below shows the temperatures at about 5000' above sea-level this morning.

Temperature at 5000 feet MSL on Thursday.

You'll notice that the warmest air (red shading) is over California, as well as in the lee of the Canadian Rockies.  Now here's the same image on Saturday afternoon:

Temperature forecast at 5000 feet MSL Saturday

Notice those bright red colors off the coast of northern California?  Where did that come from?  The wind will be "offshore" at this time, which means it will be blowing from the northeast, coming from Nevada and eastern Oregon, to the Pacific Ocean.  As it does this, it descends from the Sierra Nevada mountains down to sea level.  Air that descends warms due to compression.  So this warm air didn't move here from somewhere else, it was created by the wind flowing from the Sierra's (e.g. 8000 feet elevation) down to sea level.

Now here's the forecast of what will happen to that warm air on Monday:

Temperature forecast at 5000 feet MSL Monday morning

You can see that the warm air has spread northward, along the coast, and into the Inland Northwest.  

OK, so just how warm are we talking?  Well, in addition to keeping track of all of the record high and low temperatures at various cities, we also keep track of historical temperatures on our weather balloons.  So here's the January record high temperatures at 5000' MSL for various western locations, along with the computer model forecasts:

Site	Max 5000’ MSL Temperature	Model 1	Model 2	Model 3
Oakland	19°C	18.3°C	18.3°C	18.2°C
Medford	18°C	17.6°C	17.2°C	17.6°C
Salem	19°C	15.5°C	18.9°C	18.5°C
Quillayute	16.5°C	11.3°C	16.3°C	14.8°C
Spokane	14.5°C	11.2°C	12.6°C	14.1°C

The three models differ a bit in their forecast, but they all have very warm temperatures at 5000'.  Some records (going back to 1948) could be broken.  How warm are these?  The forecast of 14.1°C at Spokane, if it verifies, would be the same as what we normally see on April 6th!!!

So what does this mean?  The answer is somewhat complicated.  Here's the forecast high temperatures for Monday:

These are about 10 degree above normal for the end of January.  But this forecast could easily be very wrong.  You'll notice that much of the western Basin (i.e. Moses Lake), and the northern valleys (e.g. Omak, Colville, Bonners Ferry) are in light blue (40-45F) while the mountains (e.g. the area between Republic and Colville) are in green (45-50F).  What gives?

The northern and Cascade valleys have snow on the ground.  Any melting of snow could lead to fog and low cloud formation.  And this would keep the valley temperatures cooler (i.e. little or now sunshine).  But if that fog doesn't form, then the temperatures could easily be 10 degrees warmer than forecast.

Typically, for a mid-winter warm spell, we need wind.  The wind helps to mix the atmosphere, taking warm air aloft and mixing it with the cold air near the surface.  But in this case, there won't be much if any wind.  So we won't have any "mechanical mixing" to stir the atmosphere. The sun will have to do all the work by itself to warm up the near-surface temperatures.  With the low sun angle of late January, this is a tough task.  Not impossible, but difficult.

Meanwhile, the mountains will be above any fog formation and they should see abundant sunshine.  So confidence is high that they will be warm.   Here's the minimum temperature forecast:

Notice that the mountains are as warm as the valleys?  The mountains won't just be warm during the day, but they'll probably be above freezing during the nighttime hours as well.  And this will likely last for 3 or 4 days.  A week cold front in the middle of next week will cool things down some, but it will still be warmer than normal for late January.

So we'll get a taste of early spring next week, especially in the mountains.  There's a big bust potential for the valley temperatures, especially north of I-90.  But if you're going skiing, make sure you bring the sunscreen and don't over-dress.

How long can this stagnant weather go on?

By now, most of you may be getting tired of our boring, foggy weather.  On the positive side, you haven't had to shovel any snow, and the roads have been in decent shape, except for some occasional icy spots from freezing drizzle.  But the gray skies do tend to wear on some folks.  Here's what it looks like from space.

Visible Satellite 1/23/14

That white area in the middle of the picture is the fog and stratus that has filled in the Columbia Basin of eastern Washington and north-central Oregon.  You can see some mountains above the fog near the Washington/BC border, as well as the Washington Cascades.

Why are we stuck in this pattern?  High pressure over the western US is steering storms away from our area.  As we've discussed in past blogs, this is causing a severe drought in the western US.  But for many in the West, they're enjoying sunshine and warmth.  Take a look at this satellite image to see what we mean:

Western US Visible Satellite picture 1/23/14

So why are we so cloudy while the rest of the West is sunny?  Professor Cliff Mass of the University of Washington wrote about this in his blog.  You can find it at:  http://cliffmass.blogspot.com/2014/01/cloud-bowl-of-eastern-washington.html  We highly recommend it.

But in short, the reason is three-fold.  First, the Columbia Basin acts as a topographic bowl.

 The Columbia Basin is bordered by the Cascades to the west, the Selkirks to the north, the Panhandle mountains to the east, and the central-Oregon mountains to the south.    A perfect bowl.  Note in the above picture of the western US, the Central Valley of California also provides a nice elongated topographic bowl.

Second, you need moisture in order to form fog.  And while we have been very dry, we still have had weather systems providing some moisture.  Coupled with the cold nights, and you get fog and stratus to form.  The Central Valley of California has been so dry this winter, they can't even produce fog! 

The third ingredient is a lid to put on the bowl of fog, to prevent it from going anywhere.  This is provided by the ridge of high pressure.  High pressure results in sinking air.  Sinking air warms. So while at the surface we're stuck in cold, sub-freezing temperatures, the air above us is much warmer.  Locations in the mountains as high as 5000-6500'' have been reaching the mid-40s each day.   The high pressure also keeps storms away from our area.  Storms mean wind, and wind mixes the air which dissipates fog. Below is a temperature and moisture sounding or profile taken at our office on 1/23 at 3 pm. There are two pink lines on this chart, the one on the right denotes how the temperature changes with height. The line on the left is the moisture profile. The farther away the two lines are from one another, the drier the air.  So on this sounding, most of the atmosphere is clear and dry. The exception is near the ground where our temperatures have been stuck in the mid 20s to lower 30s for days and the sun has been a rather rare site. Notice how the temperature increases with height and peaks at 47° at an elevation around 6500'. So if you seeking sun and warmth, the mountains are the place to go. 

Spokane temperature sounding 3pm Thursday. Light pink line or right denotes the temperature profile. 

One positive of this weather has been the beautiful natural flocking which has adorned most of the objects stuck in fog for the past week. This flocking is being produced from the deposition of small sub-freezing water droplets on objects resulting in riming. The rime in this event is covering everything from trees, fences and power lines.  We wrote about this back in December.  You can read about it at: http://inlandnorthwestweather.blogspot.com/2013/12/another-kind-of-white-weather.html  

Here's some pictures from our office:

So this kind of weather can't last forever, can it?  No, but it can last for a few weeks.  This episode started on January 16th, and today is the 24th.  Yep, it's only been going on for a week.  Seems like a month though.  Have we seen longer episodes in the past?  Of course.  One of them occurred during the 1976/77 drought.  After a few storms brought rain and snow to the area in the middle of January 1977, a huge area of high pressure developed over the area, just like our current episode.  Spokane and the Inland NW were stuck in the fog from the 19th of January through February 10th.  That's 22 days!  Although there were a few peaks of bright sunshine during that streak they quite brief.  A weak weather system moved through at the start of February, but it was too weak to get rid of the fog.  Instead, they had some freezing rain.

How long will our current episode last?  Aside from a few possible sun breaks, we're likely stuck in the fog through the weekend and into early next week.  There's a outside chance that some locations in the Panhandle and northeast Washington will see more sun on Monday.  This is due to an arctic high pressure system centered over eastern Montana and the Dakotas that may push a bit of drier air into our area from the east.

7am 1/27/14 precipitation and sea-level pressure forecast from GFS model. 

Despite the presence of the weak system notice the 500 mb ridge (below) remains very amplified and basically centered over the Pacific Northwest. 

500 mb pattern for 7am 1/27/14  GFS model.

Starting on Tuesday, some very weak Pacific weather fronts might be able to break up the low clouds as well as bring us a dusting of snow as the ridge gets progressively weaker each day.   By the end of next week, there is more confidence that the weather pattern will have changed and we can get a respite from the fog and low clouds.

4am 1/28/14 500 mb map from GFS.
Ridge gets flattened a little by weak front. 

7am 1/30/14 500 mb map from GFS.
Ridge is virtually gone now over PacNW and is replaced by a trough off the coast. 

And this ridge breakdown could actually persist for more than a couple days. The map below is the mean 500 mb pattern projected for the period from January 30th-February 3rd. Notice the ridge has generally shifted into western Alaska and has left a broader trough over most of the US, including our area. The 8-14 day outlook (bottom image) through February 7th looks similar as well. 

6-10 day outlook. Mean 500 mb map. 

8-14 day outlook., Mean 500 mb map