Looking Ahead to Spring and Summer

With the snow having melted and the road weight limit signs going up, our thoughts are naturally turning to Spring.  Will the mild temperatures and rain continue?  First, let's look at where we are on moisture.

In the Northwest, things overall are on the drier side, with pockets of above normal precipitation.

Zooming in a bit, we can see that the Columbia Basin overall has had above-normal precipitation, while much of the rest of the state has had near- or below- normal precipitation.  This makes sense.  We have had very little wind this winter (only one windy storm I can think of).  So the Cascade rain shadow hasn't been a factor this year.

Looking even closer at a few locations, we see precipitation is very close to normal for mid-February.  In fact, it's rare that it is so close to normal (I know, that sounds strange).  Here's the Spokane Airport trace since October 1st.  The green line is the actual accumulated precipitation for this winter, while the brown line is what we consider "normal".  You can see on the right side of the graph (today) that the two lines meet, meaning that Spokane Airport is right at normal for precipitation.

Looking up north at Colville, we see a similar graphic.

On the other hand, our mountain snow pack is way below normal.  Again, no surprise.  This isn't just due to the mild temperatures.  The lack of wind also means lack to orographic (terrain-forced) precipitation.  

On the map below, orange dots are observations of less than 75% normal snowpack, while red dots are less than 50% of normal.  This could have implications on the upcoming fire season.  The snowpack will melt earlier than normal, which could lead to an extra long fire season.

The snowpack up in British Columbia is about 75% of normal, which will impact the flows on the Columbia River.  All of this fits the pattern of an El Nino winter.

So going forward, how do things look?  El Nino has already started to fade and will continue to do so over the summer.  And at this point it looks like a one-hit wonder, as La Nina may emerge again next winter.  All of the computer forecasts take the equatorial Pacific ocean temperatures back down to normal and many of them predict below-normal by this autumn (i.e. La Nina). 

The long-range computer forecasts aren't very encouraging for moisture.  Here's the March-April-May outlook for rainfall.  Mostly white (near-normal) in the Northwest.

For the May-June-July time period, things are looking drier than normal in the Northwest.

And by July-August-September, the outlook is for widespread dryness throughout the West and even into the Midwest.

For temperatures, things look like they will continue to be mild, with a potential hot summer.  For March-April-May, there is good consensus for above-normal temperatures in the Northwest.

As we move into late spring and early summer (May-June-July), things continue to look warm across the country.

And for the July-August-September timeframe, there is good consensus for warmth in the West and Northeast US.

So you may be asking yourself, what was the fire season like after the last strong El Nino?  Turns out it was a quiet summer (2016), since the summer was a little on the cool side.  2015 and 2017 were very active fire summers with hot and dry conditions.  And that is what the research has shown:  the best correlation to active wildfire seasons is hot summer temperatures.  Winter snowpack, spring rains, etc all play a role, but the summer weather ultimately determines what kind of fire season we will have.