Much warmer weather is expected next week after prolonged cold!

If you think this winter has a rather drastic change from the past several winters your senses are not deceiving you. When we began the month of November is seemed we would see yet another mild November, however as the calendars changed to December that notion came to an abrupt halt. The start of 2017 has continued that trend. Look at these statistics for Spokane and this will put things into perspective.

It certainly seems the mild winters of the past several years are a distant memory. This has been the snowiest winter since 2008-09 and the coldest since the early 90s. But the cold wasn't just in Spokane. Check out this list of sites that have seen their record coldest December-early January period on record (keep in mind some of these station records don't go back too far, see last column for details).

So we can see it's been cold and somewhat snowy. To see how snowy its been look at this comparison graphic of satellite pictures from early December vs. early January. 

Satellite comparison of snow cover via visible satellite. The January image suggests just about all of the Inland NW is covered with snow. 

This is quite a change. But its winter and it's not unusual to see widespread snow cover at the beginning of January across the entire Inland Northwest is it? Here is a look at the amount of water in the snow (Snow Water Equivalent- SWE) on each January 10th since 2008. 

Based on this, we actually saw the entire region covered by snow in 2016 as well. But this year and that were the only ones since 2008.  So if there is snow covering the entire region should this lead to concern? Well it depends. If we could melt all the snow at once it could cause a great concern due to runoff and potential flooding. This time of year it is improbable that we can melt all the snow over the mountains (where you can see the dark blue, purple, and red shading) as it doesn't get warm enough but we can melt some. But it is quite a bit easier to melt a significant (if not all the snow) in the valleys where we see the abundance of white and pale blue shading. Any area shaded in white has at least an inch of water tied up in the snow pack while the light blue shading represents values ranging from 2-4" of water. So what does it take to melt this? Obviously we need to see temperatures above freezing for a prolonged period. But that's not all. It also helps immensely to add wind into the equation. Warm winds and prolonged temperatures above freezing are an enemy of the snow and can cause it to quickly disappear. Imagine taking that 1 to 4" of water trapped in the snow and sending it into the rivers and streams. How about taking that same 1 to 4" of water over urban areas and sending it toward snow-clogged storm drains? That can cause quite a mess and obviously would lead to flooding issues. This scenario can be further complicated by rivers and streams choked with thick ice. 

So why are we telling you this? Well it just so happens we are looking at a dramatic change in the weather pattern early next week. Since December, we have been stuck in a persistent weather pattern featuring cold weather systems coming from our northwest. These are notoriously cold systems, and generally pose little threat from a hydrology standpoint. 

Mean 500 mb (18,000' above ground) since December. Note how the colors (or heights) buckle north into Alaska and then drop SE into the remainder of the county. This is indicative of cold NW flow. 

When we compare this weather pattern to what's normal for this time of year we see a clear signal. The blue shaded areas represent below normal heights which generally result in cold weather whereas the orange, yellow, and green shading represent warm conditions. 

500 mb height anomaly values. 

This is quite unusual. Typically we see some warmer systems invading from the southwest tied to a nice tap of relatively warm sub-tropical moisture. When these systems arrive they can bring a rapid warming in temperatures as well as significant precipitation and snow melt. Well after a long respite from such systems, we see hints of one on the horizon. Here is what many of the forecast models are hinting at for next week. 

Weather pattern for next Monday evening (500 mb heights in white, precipitable water is shaded)

What this reveals is our northwest flow of late will be replaced by southwest flow early next week. Of even more concern is the swath of green and blue shading headed into the Pacific Northwest. This indicates we will be subject to a very moist and warm air mass, which could do a very effective job of melting the low-level snow pack. Now if this feature were only going to be over us for a day it may not do much to the snow pack. However look at this map below for Wednesday. Not much difference is there?

Weather pattern for next Wednesday (500 mb heights in white, precipitable water is shaded)

So this at least indicates the potential for warm weather. Here are our forecast highs for next Wednesday. 

Forecast temperatures for next Wednesday

Notice most of the valley temperatures are above freezing. This will be good for potentially melting the snow, especially over the SE portions of Washington and NC Idaho where you see the greens (temperatures above 45°F) during the day. But what we aren't showing here is many locations across the same area will also see nighttime temperatures remaining above freezing. So its conceivable that some locations across SE Washington and NC Idaho could see temperatures above freezing anywhere from 48-72 hours. We will also see robust south to southwest winds during portions of this period. Below is the wind forecast for Tuesday. These are sustained winds. The gusts will likely range from 20-35 mph. 

Tuesday wind forecast

So remember earlier when we said about above freezing temperatures and good winds can result in some rapidly melting snow. It's conceivable that a good portion (if not most) of the snow over the Palouse, southern Columbia Basin, LC Valley, and even parts of the the Spokane/CdA could melt during this episode. So that's a significant chunk of the 1 to 4 inches of water tied up in the snow pack which could runoff into the area rivers. What we haven't talked about yet is how much precipitation can we expect in this upcoming weather pattern. The map below shows the GFS model forecast for precipitation amounts possible in a 48-hr period ending Wednesday afternoon. 

Tuesday-Wednesday precipitation forecast

This is a very impressive amount and is one of the wetter model runs. Locations shaded in yellow are amounts ranging from 1.50" (around Spokane) to nearly 3.00" over parts of the Idaho Panhandle. We suspect the valley precipitation will likely be overdone, but perhaps the mountains aren't showing enough precipitation. The combination of snow melt combined with ample precipitation could lead to some bad things across the region including:

• Flooding of small rivers and streams (especially over SE Washington and the southern ID Panhandle).
• Lowland flooding where the ground is frozen prohibiting infiltration into the soil. 
• Ice jams could give way and enhance the flooding potential.
• Urban flooding is a distinct possibility given snow-clogged storm drains.

But since we like to be purveyors of positivity let's not dwell on the negative and instead focus on some of the potential good:

• We will finally be able to walk on snow-free sidewalks, 
• We can drive on snow-free roads, 
• Just imagine how warm and refreshing 40s will feel compared to more single digit and teens. 
• The ice dams on snow-covered roofs may finally melt thus alleviating our worries of potential roof damage.
• Much smaller worry of frozen pipes.  
• We won't have to bundle up in countless layer of clothes just to shovel the latest dump of snow. 
• Spring is only 68 days away!!

This winter compared to last...and will we see a normal recovery?

A couple weeks ago we posted a story on our Facebook page that said, climatologically speaking the harshest part of winter is now in our rear view mirror. Here's was the post.

We stated that since the days are getting longer, sunnier (very slowly) and temperatures are on the rise that in fact, climatologically speaking the worst is over with. However, we did put a caveat in the story which said we can still get some very good winter storms during the remainder of January into February. One astute reader mentioned that we stated something similar last year in a blog entry. Last winter we had a very dry and relatively snowless beginning to the winter and wondered what the chances were of it continuing. Needless to say we recovered quite nicely in the second half of winter. This winter, things might be just a bit tougher. Just for comparison sake, here was the mountain snowpack last year on this date.

And here's how it looked this year

Not a lot of differences. All locations were seeing below normal snow water equivalent values for both years. The Okanogan Highlands and the northern Cascades are doing a little better this year, and things are a little worse elsewhere.  Also, notice how poor the snow water numbers are for the southern Washington Cascades and the Oregon Cascades.  However, these maps aren't really telling the entire story. Why is that? If we choose to just look at the amount of precipitation which has fallen since October 1st (beginning of the water year) rather than the amount of water in the snowpack the winters are completely different. Here was 2014 through January 19th. Just like the drier than normal snowpack, the precipitation was similarly dry.

Oct 1 2013-Jan 13 2014 percent of normal precipitation

Now look at the data for this water year. What a difference a year makes! All basins are seeing normal to slightly wetter than normal conditions.

So what gives, why the big difference? In one-word temperatures. Temperatures this winter and late fall have been significantly warmer temperatures than what we saw last year. Much of what's been falling has been dropping as rain as opposed to snow. Take a look at the temperature departures from normal below. They exhibit a huge difference. In the first half of winter 2013-14 temperatures were well below normal.

Oct 1-December 2013 temperature departures. Note widespread below normal temperatures

 While this year...they have been generally well above normal. The swing from last winter to this winter is around 3-6°F warmer. That may not seem like a lot, but in terms of snow it makes a big difference.

Oct 1-Jan 18 temperature departures. Note widespread warmer than normal temperatures. 

Anyway we digress. We simply wanted to demonstrate that although we have seen similar snow totals to last winter in the mountains, how we got to those totals is completely different. Last year was an ENSO neutral year which often does not foretell what sort of winter to expect. This year is an El Nino winter (albeit a weak one). Typical El Nino winters deliver warmer than normal conditions (sure enough it has been warmer), and a variable precipitation signature. So let's examine some snowfall numbers across a few valley locations including Spokane, Wenatchee and the always snowy Holden Village (on Lake Chelan). Just like the mountains, most valley locations are seeing sharp snow deficits. In fact, most locations are seeing a top-10 least snow winter since 1949. We are utilizing 1949 since that year is when the NWS began keeping track of  El Nino/La Nina data.

Least 10 snowy Spokane winters through 1/19 since 1949

Least 10 snowy Wenatchee winters through 1/19 since 1949

Least 10 snowy Holden Village winters through 1/19 since 1949

So of those three sites, this year ranks as either the 5th or 6th least snowy winter through 1/19. But more importantly how did the rest of the winter fare and could the snowfall deficit be made up. The answer is an overwhelming no. In Spokane, none of the 10 least snowy years through 1/19 was able to recover to normal. The winter of 1989-90 was close. Last year was also somewhat close as much of the region saw a record or near record snows in February. However, those were not El Nino years. Of the El Nino years, three of them, the remainder of the winter failed to deliver more than 6 inches of snow.

For Wenatchee, two of the winters were able to recover to above normal levels after such a slow start to the snow season.  Both of those years were ENSO neutral years. During the El Nino years, the numbers were quite meager. The two El Nino winters on the list experienced snowfall of less than an inch through the remainder of the season. On average, less than 5" of snow typically falls during the remainder of the season. 

Now onto the ever snowy Holden Village area. The numbers for here spell bad news for heavy snow lovers. Of the 10 least snowy winters through 1/19, none were able to get back to normal. Last year was close (after an astounding and record breaking 142" of snow in February) as was 1989-90. Both of those years were ENSO neutral ones. The trends during an El Nino year are much less promising. Of the 4 El Nino years on the list, none were able to recover to normal levels. Additionally, 3 of the 4 El Nino years saw significantly less snow than normal through the remainder of the winter.

So climotology tells us the odds of recovering from such a slow start to the winter are slim and given our weak El Nino conditions the chances are even slimmer. However, keep in mind that long-term weather forecasting can prove a futile endeavor and ultimately anything can happen. 

Through the remainder of the month the weather pattern will not be conducive to adding significant amounts to our  snow totals. Although wet weather will likely return by the end of the week, this moisture will be accompanied by unusually warm temperatures at least over the mountains. The 6-10 and 8-14 day outlooks are calling for a good chance of warmer than normal temperatures and average or slightly wetter than normal conditions. 

8-14 day precipitation outlook

8-14 day temperature outlook

Snowfall opportunities in the coming days

With an Arctic air mass solidly entrenched over the northwest US, we're looking at the potential for snow for the Inland Northwest in the coming days.  As usual, these forecasts are going to be tricky.  So keep checking the forecast to stay up to date.

First, we'll start off with a look at this morning's minimum temperatures in the Pacific Northwest.

Low Temperatures Thursday 6 February 2014

Sub-zero temperatures were widespread in eastern Washington and northern Idaho. There were several locations which reported readings of -20°F, the coldest readings this winter.   Western Montana saw temperatures as cold as -40 degrees!  But notice that it was quite cold in western Washington and Oregon as well.

The first storm is already moving onshore today (Thursday).  Snow is falling over western Oregon, all the way to the coast.  Here's the webcam capture from the Oregon coast in the town of Pacific City.

Web camera showing snow at Pacific City Oregon, 6 Feb 2014

However, this storm will track across northern Oregon into southwest Montana.  This will leave most of the Inland Northwest on the northern fringe of the snowfall.  Below is the current forecast of snow for Thursday night through Friday:

Snowfall forecast for Thursday night and Friday morning (Feb 6-7 2014)

As you can see, those folks near the Canadian border will see the least amount of snow, while locations in southeast Washington the southern Idaho Panhandle will see the most.  The Spokane metro area is looking to get around 1".  The very cold temperatures will result in a light fluffy snow.  That coupled with the cold dry roads means that driving conditions shouldn't be too bad on Friday. However, there is some potential for blowing and drifting snow, especially over the Palouse and southeast Columbia Basin where northeast winds of 10-15 mph could stir things up considerably.  

The next storm will follow a similar track, and will move through the region on Friday night and Saturday.  The chart below shows the expected snow fall from this storm.

Snowfall forecast for late Friday night through  Sunday (Feb 8-9 2014)

After a break on Sunday, a weak front will bring light snow to most of the area on Monday.  At this point, this doesn't look like a big snow event.

Storm number four looks like it will move through the area by the middle of the week.  The computer models don't have great agreement on this system, so our confidence is low.

Throughout all of this, our temperatures will gradually be warming.  The image below gives you an idea of what we're looking at for Spokane.

7-day forecast for Spokane

As the graph shows, by the middle of next week, our temperatures will have returned to near normal for this time of year, which means highs in the upper 30s and lows in the mid 20s.

One thing to note.  Typically in these warm ups after a cold arctic intrusion, the cold air near the surface is tough to scrub out.  This can set the stage for freezing rain.  At this point it's too far in the future to predict where and when this will occur, if at all.  But most likely it would be between Monday and Wednesday of next week.

The outlook through the third week of February suggests the warming will continue with more wet weather. It's quite conceivable the weather we just experienced will be the coldest of the winter. The sun angle is getting higher by the day, while the days are steadily lengthening. By February 20th, the length of daylight will be 10 hours and 38 minutes, a gain of 47 minutes compared to today. 

  

8-14 day temperature outlook

8-14 day precipitation outlook

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 

Snow, Rain, Wind, (and Thunder?)

Yesterday's weather system brought a nice 1 to 3" of snow to many locations.  You can see an extensive list of snow reports on the National Weather Service website.  Now we have Storm #2 arriving 24 hours later.  This one will be a little different in a couple of ways.  First, this storm is a little wetter and more extensive than the first.  This means more people will see precipitation.  Here's the radar forecast from the HRRR model valid at 5pm this evening:

5pm radar forecast from the HRRR model

This is a forecast from a computer, not an actual radar image.  But it gives you an idea what the radar will look like around 5pm.  And just about everyone in the Inland NW will be seeing some sort of precipitation at this time.  Which leads us to the other difference.  While Storm #1 was all snow, this one will be more of a mixed bag of rain and snow.  The HRRR forecast for precipitation type at 5pm is shown below.

5pm precipitation type forecast from HRRR

This graph is a little hard to read, but the horizontal blue lines represent snow, while the vertical green lines are for rain.  The HRRR expects the precipitation by 5pm to be rain south of a line from Deer Park to Grand Coulee.  This includes Spokane and the Palouse.  The precipitation may initially start in the metro area as wet snow, but it won't be able to accumulate much and will change to rain later this afternoon. Also notice there are some small pockets of red scattered around the region. This represents a chance of freezing rain. If freezing rain really does occur it will be rather isolated and likely quite brief. 

Here's the storm total snow forecast from the National Weather Service.

Storm total snow ending 4pm Thursday

Most of the valleys across the north (Republic, Colville, Sandpoint) will see all snow and pick up 2-6" of snow, while the mountains will receive up to a foot.

Storm #3 will follow on Thursday afternoon/evening this will be a weaker system.  It will once again bring rain or snow to Spokane and the Palouse while the northern valleys will pick up a little more snow.

Storm #4 is still taking shape but it consistently looks like it will be the strongest of the bunch.   Today's GFS model forecast backed off a little from it's previous forecast, while some of the other models came out a little stronger today.  As a result, they're all in very good agreement at this time.  We often take this as a sign to increase our confidence in the forecast.  Even though they all agree, could they all be wrong?  Yes, but the odds are growing increasingly slim.  

Here's a breakdown of how this storm will unfold:

• Precipitation will spread over the area on Friday around or shortly after sunset.
• Spokane and the Palouse will see rain from this storm, with a possible mix of snow at the onset.
• Saturday morning will be rainy and breezy.  Spokane will be in the lower 40s by sunrise and top out in the mid 40s during the day.
• The northern valleys will start as snow and will accumulate a few inches.  They will gradually change to rain overnight.  Colville will probably change to rain before midnight, while Bonners Ferry could hold on to snow until Saturday morning.
• The cold front will move through the area during the middle of the day.  Behind the front winds will really blow.  Below is our forecast peak winds for Saturday.  Areas in white can expect gusts in excess of 50 mph.

Peak wind gusts expected on Satuday

We will likely be issuing Wind Advisories for much of the area and possibly High Wind Warnings.  You'll want to stay tuned to this forecast.

Here's a couple of other things to consider with this storm.  The rain along with the melted snow won't be able to soak into the ground since the ground is solidly frozen (from our early December cold snap).  So expect some water  ponding, even on your lawn.

The other interesting tidbit is the outside chance of a thunderstorm.  Thunder?  In early January?  Yes, it's happened before, and this is pretty much the classic set up for it:  warm moist air ahead of a strong cold front.  Below is the SREF model probability of thunderstorms. 

24 hr thunder chances ending 10pm Saturday. 

You can see a small area of 10% over southeast Washington.  If thunder does occur, we don't expect to see hundreds of lightning strikes. However a few claps of thunder are a possibility especially over southeast Washington and the southern Idaho Panhandle, including Pullman and Lewiston.