We are forecasting the hottest day ever in Spokane history

 A heat wave like no other is becoming increasingly likely.  Prepare NOW!

The biggest heat wave to ever strike the Inland NW on record is becoming increasingly likely.  What makes this event unique?

• All time record high temperatures are in jeopardy for several locations
• And this is during June (our peak heat season is late July through early August)
• 100+ degree temps will last for several days
• Mild overnight lows in the mid 60s to upper 70s will provide little to no relief at night
• Occurring during a period of severe to extreme drought
• Fire danger increasing to record levels next week and as we near the 4th of July (for this early in the season)

The Climate Prediction Center's latest Risk of Hazardous Temperatures product shows our region in a high risk of Excessive Heat through next Friday, July 2nd.  Don't be surprised by future outlooks extending this out further.

What is going to cause the excessive heat?  A very strong ridge of high pressure (record setting for late June by some model solutions).  Here is one ensemble solution showing the strong ridge centered right on top of us on Sunday.

12z GFS model of 500mb heights, winds, and temperatures valid 2 AM PDT Sunday, June 27th 2021

Strong high pressure in late June spells trouble!  Why?  The lower atmosphere continues to warm as the ridge persists over the region as the late June sun angle brings an abundance of solar radiation towards the Earth's surface which continues to warm things up each day.  Here is one model prediction of near surface temperature anomalies from this Thursday through the following week (June 24-July 3rd).  

Note the large area of warmth that persists into early July over the northwest US and southwest Canada.

So it looks like this heat wave will be around for awhile, but how hot will it get?  Our current forecast is calling for all time records to be threatened beginning Monday.

NWS Forecast High Temperature for Monday, June 28th (issued June 23rd) as compared to current all time records.

And if we don't break the all time records on Monday, we will probably have another shot on Tuesday and Wednesday!  Here is our current forecast as of June 23rd for Tuesday.

NWS Forecast High Temperature for Tuesday, June 29th (issued June 23rd) 

It is worth noting that a few models (especially the GFS) want to take the heat up another notch, suggesting temps near or above 110F for Spokane and near 120F for Moses Lake.

Spokane

Meteogram of forecast raw model temperatures for GEG (Spokane International Airport) through Wednesday, June 30th, 2021

Moses Lake

Meteogram of forecast raw model temperatures for Moses Lake through Wednesday, June 30th, 2021

While these values are not currently forecast, it does have our attention.  The record for the state of Washington and Idaho is 118 degrees at Ice Harbor Dam, WA and Orofino, ID so we will be watching for this potential closely.

What other impacts are expected?  As mentioned in a previous blog post, here, our region is currently experiencing severe to extreme drought over much of Eastern Washington into the Idaho Panhandle.  The unprecedented heat is not good news for the region.  Wheat and hay crops are already starving for soil moisture, and this upcoming heat will only make the soils drier than they currently are.

And what about fire danger?  Fuel moisture is expected to dry out considerably, reaching record low values for late June.  Fuel moisture comes in different sizes, but all are measures of how dry the grass, twigs, branches, and timber are.  

Forecast 100 hour (branch size) dead fuel moistures based off model data from the NWCC (Northwest Interagency Coordination Center) are shown below.  Red is observed, while blue is the forecast.   The bottom gray line is the minimum value on record.  The plot below is for NE Washington but the same idea applies to other areas of Central and Eastern Washington into the ID Panhandle.  As you can see the red line has dipped near the minimum value several times since mid-May (likely due to the drought).  The blue forecast line is expected to drop fuel moisture to record lows for this time of year.

100 hour fuel moisture (%) for NE Washington.  Red is observed, Blue is forecast from model data

Safety tips

So what can you do to stay safe during this heat wave?  Here are some suggestions

• Drink plenty of fluids and wear light colored clothes
• Check on and take care of those vulnerable to heat (children, those with chronic medical conditions, elderly, pets)
• Stay inside during the hottest times of the day (afternoon and early evening)

Heat is On The Way!

 This week it will be hot and dry for most of the Inland Northwest and the Pacific Northwest. Seeing some of the model guidance and predicted temperatures for this week and next weekend reminded us of the June 27-28 heatwave of 2015 (you can read our blog post here). Let's dive into the comparisons of this heatwave vs 2015 and lay out the expected forecast for this week.

We talked earlier this month about our record dry spring, and in the last 30 days the story of very dry conditions continues. Many locations did receive some good rain from the thunderstorms of June 15th. But the total amount of precipitation in the Inland Northwest has been very low. For many places, around 25% of average or lower.

Here’s a look at our normal precipitation for May and June (since June isn’t complete yet, we went back into May) shown by the brown line, what we have accumulated on the green line, and compared this to 2015 since we know that year saw a hot spell in June. We can see that compared to 2015, this year (2021) is drier for the May - June period.

Taking into consideration the very dry spring and now start to summer, along comes a strong ridge of high pressure that will continue to strengthen and settle over the northwest. Below is a loop of the 500mb heights and anomaly from the GFS model, Thursday through next Monday.  For this weekend and early next week, extremely strong high pressure will dominate southwest Canada and the northwest US.

For June in eastern Washington (we’ll use Spokane International Airport as a point of reference), the normal high temperature is 74F. This week, we’re looking at temperatures 10 to 25F degrees above normal, or higher. Yes, higher. By next weekend, daytime temperatures in the 100-105F range are possible. This kind of heat hasn’t been seen since 2015, and thus why we look back to 2015 to see what kind of conditions were going on and what the models were saying then, giving us an idea of what might be to come this week and weekend.

Putting this into perspective, the record hottest temperature ever for Spokane is 108F set on Aug 4, 1961.

Going back to the comparison of 2015, June 27-28 saw temperatures of 102F (27th) and 105 (28th), with upper 90s on days leading up to and after that heat wave. The afternoon of June 28th, the 850mb temperature was 29.6C giving us that max temperature of 105F. What do the models say for our 850mb temps this week and next weekend? Below is the sounding climatology from SPC for Spokane (OTX) for 850mb temperatures. The all-time max 850mb temperature is 31.5C from early August.

Current deterministic model guidance for 850mb temperatures are quite jaw-dropping:

ECMWF:

Saturday - 28.85C

Sunday - 30.85C

Monday - 33.85C

Tuesday - 35.3C

Wednesday - 32.0C

GFS:

Saturday - 28.3C

Sunday - 29.7C

Monday - 33.2C

Tuesday - 34.5C

Wednesday - 33.3C

So all around very hot temperatures for this weekend and into early next week. Leading up to Sunday, the ridge strengthens Friday through Sunday with Sunday looking like the hottest in the next 7 days, which is as far as our forecast goes out at this time.

What about beyond Sunday? Forecast model guidance gets tricky the farther out in time, however strong high pressure patterns are ones that have a tendency to be more persistent, so confidence isn’t completely out the window with the idea that this heat could last into the middle part of next week. Ensemble guidance has also been very consistent in highlighting this strong ridge through early next week. The suite of models are showing 850mb forecast temperatures next Tuesday of 33C - 35C. We have many days between now and then, so these numbers may fluctuate a bit but this is something to keep in mind.

In 2015, we observed 4 days of maximum temperatures 100+F, and in 2020 we observed 3 days (the most is 6 days set in 1928).

The Climate Prediction Center is highlighting a high percentage of excessive heat for June 29-30, next Tuesday and Wednesday. This would suggest our ridge has lower chances of breaking down and better chances of this heat to persist into the middle part of next week.

Other factors we have to take into consideration are the overnight low temperatures. With such strong heat during the day, the overnight relief may become less of a relief. Together, this will increase our heat risk for various populations in our region. Currently, here is a snapshot of our heat risk forecast.

Our confidence is fairly high that we will see this prolonged heat last into early next week with this upcoming weekend seeing the hottest temperatures of the year, the hottest since 2015, and the hottest in the next 7 days. After that, it’s possible we will see continued hot temperatures and perhaps slightly hotter?

 We've never seen a drought like this

It's well known that weather in the western US is drier than in the eastern US.  As such, droughts are more common in the West.  Most of the West is designed to accommodate this drier climate.  The mountains get heavy snow in the winter, which slowly melts off in the spring and summer.  There are numerous dams throughout the West which catch much of the snow melt, using it to irrigate our farmland (as well as generate electricity).  This enables western farmers to grow crops in some rather arid locations.  

Still, there are some areas in the West that, similar to their eastern counterparts, rely solely on the rain and snow to irrigate their croplands.  In the West we call this "dryland farming".  The biggest example of this is typically wheat and barley, but also includes a lot of hay.  The Inland Northwest is known as one of the largest producers of wheat in the US.  

These dryland crops require moisture through the spring and into the early summer.  Grains such as wheat and barley will ripen during the hot summer months and so they don't really require much if any rain at that point until they are harvested in late summer.  This matches the usual rainfall patterns we see here in the Inland Northwest.  But not this year.

Rainfall this spring hasn't just been light, it's been nearly non-existent.  We haven't seen anything like this before.  Spokane just finished it's driest February through May ever.  EVER.  Records for Spokane go back to 1881.  That means this was the driest spring in 140 years!  And it wasn't just Spokane.  The dark red area in the image below shows all of the areas that have had their driest February-May on record.

As you can see, it's been dry over much of the Northwest this spring, but the Inland Northwest has been the epicenter of this dryness.  The three month period of March through May was the driest for many other locations in the Northwest.

So the natural question is "what caused this drought?".  The answer isn't straightforward and probably incomplete given our current understanding of weather and climate.  One contributor that we are aware of is La Nina.  To which you may be saying "I thought La Nina meant wetter than normal conditions for our area", and you would be correct.  Here's a diagram showing the basic jet stream pattern for a typical La Nina that you may have seen before:

The purple and orange lines are meant to represent the variable jet stream patterns we normally see during a La Nina winter/spring.  The purple line shows a colder phase of the jet stream, diverting up into Alaska and then bringing colder but drier air into the Northwest US.  But then the jet stream will also at times follow the orange line, bringing Pacific moisture into the Northwest.  The problem is that for the spring of 2021, we've seen a LOT more of the purple jet stream, and not so much of the orange jet stream. 

Note in the image above the big H and the blocking High Pressure in the Gulf of Alaska.  Here's the air pressure anomaly at about 18,000 feet in the atmosphere from the Feb-May period this spring.

What this shows is that the air pressure in the Gulf of Alaska has been higher than normal this spring.  This compares very well with the idealized La Nina image previously shown with the Blocking High in the Gulf of Alaska.  So this looks like what we would expect for a La Nina winter/spring.

But now here's the jet stream anomaly for this past spring:

Do you see that ribbon of bright colors along the Canadian west coast?  That shows that the jet stream this year has been coming from the northwest a lot more and a lot stronger than usual.  Note that those bright colors extend all the way back to Alaska, across the north Pacifc and Kamchatka Peninsula.  In other words, the "purple" jet stream has been doing its thing during a La Nina winter like it should.

But then look at the other area of bright colors in the image above, out in the eastern Pacific.  Those show that the jet stream across the Pacific has been much weaker  and infrequent than normal.  So the "orange" jet stream that is supposed to bring the moisture, hasn't been doing its job this spring.  

The result is that we've been getting a lot more of the "purple" jet stream from the northwest (which is a dry weather pattern), and not nearly enough of the "orange" jet stream from the Pacific (which is a wet weather pattern).

Is there any hope of this pattern changing?  Officially, the Climate Prediction Center declared the 2020/21 La Nina over.  That's not to say that our weather pattern will necessarily change, especially since we are heading into the typical hot dry summer season.

Here's the computer forecast for the June-July-August season for temperature and precipitation.  They call for a warmer and drier than normal summer overall all of the western US.  

But this of course is a computer forecast.  And you may be wondering if the computer forecasts correctly predicted our record dry spring.  That's a good question, and the answer is no, the computers never saw it coming.  Here's the forecast made back in February 2021 for the Feb-Mar-Apr timeframe.  That area of light blue in the Inland Northwest shows that the computer actually expected that we would see normal or possibly wetter than normal conditions for our area, which agreed with the usual La Nina pattern.