A worsening drought over parts of eastern Washington?

   Springtime across portions of the Inland Northwest has been very dry at least compared to climatology. We can measure just how dry using various tools in our meteorological tool box. One of the conventional tools we use is simply looking at precipitation maps across the region. So how have things looked over the past 90 days? 

As you can see things are highly variable across the region. near the Cascades it has actually been quite wet, with precipitation amounts nearly twice the average amount over the past 90 days. Also near the Washington/Idaho border amounts have been close to normal (aside from the southern Palouse, LC Valley, and Blue Mountains). However one area that  stands out is a portion of central Washington in the lee of the Cascades stretching from Omak down to Moses Lake and The Tri-Cities and Yakima areas. Some of these locations have seen only a quarter of the normal precipitation during this period. 

If we add the November precipitation amounts to the mix, the resulting map doesn't look much different for the dry areas. 

So that got us thinking is this a record of some sort? Now granted these statistics are rather arbitrary, After all, who calculates records from 11/23 through 3/21? Not many people, but just for fun we will examine some of these odd records. First we will look at Yakima. 

Yakima, WA precipitation 11/23-3/21

So in fact this is a top 10 driest period for Yakima, but it was actually drier in 2018. Now how about Omak? Not quite top 10 but close. 

And finally lets look at the Ephrata:

Only in 16th place out of the last 70 years and the driest since 2014. So although this is noteworthy, it isn't really a historic dry spell. 

But precipitation alone does not tell the entire story about a dry spell of weather. Other things to take into consideration during this period include; winds, temperatures, relative humidity levels, and solar radiation. All of these parameters will impact the amount of evaporation or evapotranspiration that can take place and how quickly the soils will dry out. That is a lot of information to keep track of, however fortunately we have a relatively new and very useful tool called the  Evaporative Demand Drought Index or EDDI. This takes all the aforementioned parameters into account and states how thirsty the atmosphere is. So what is this index showing for the area? If we go back to November things look particularly bad:

Over the entire Lower 48, no area has seen  more widespread and harsh drying conditions compared to normal. The categories on the map correspond to our typical drought outlooks. In this case the shading over eastern Washington corresponds to an ED4 or an exceptional drought. Does that mean this area is now in an exceptional drought? Not necessarily. A drought is not built on four months of weather alone, but if these trends continue we will certainly be faced with worsening drought conditions over this portion of eastern Washington. Since November here is how the drought monitor has been evolving across Washington.

These images start in the middle of November and advance two weeks at a time. The last image shows the drought conditions as of the middle of March.

Specifically looking at the March 17th the outlook:

This map shows that almost 23% of Washington is in a D1 or moderate drought which just so happens to correspond closely to the first precipitation maps we showed. But what is interesting is the EDDI maps show worse conditions than what's depicted by official drought maps and sometimes this can foretell the trends. EDDI itself is not a drought prediction, but at short timescales (such as what we have shown), it indicates the potential for drought (or trends). So this area certainly bears watching.


So looking past the EDDI values what do the longer range weather forecasts tell us? That is always a tough question to answer, but lets look. The 8-14 day outlook through the beginning of April calls for near normal precipitation and cooler than normal temperatures. Near normal precipitation amounts would certainly help. The cooler than normal readings should also temper the thirstiness of the atmosphere however that could be overcome by having unusually dry air masses in place or prolonged windy conditions.

As for the April outlook, things don't look terrific for a dramatic improvement at this point with below normal precipitation favored at this time with an equal chance of normal temperatures.

And finally, if we want to peer even farther into the future (April-June) the prognostication right now would suggest worsening drought conditions. But we will just have to wait and see.

So what are the ramifications of a drought over the Columbia Basin? While much of the area is irrigated for agriculture, there are areas which also have a considerable amount of sagebrush which could eventually lead to quick burning fires this spring. It could also lead to more blowing dust than normal on a windy day.  Part of this dry area also encompasses some denser fuels both east and west of Omak. Right now the nearest snotels (snow measuring sensors) depict a snowpack around 65%. It's too early to say if this will lead to a busier than normal fire season in these areas as we have found the leading cause of a big fire season is a hot and dry summer.

We will revisit this topic later this Spring to see how things panned out.

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!!