2020 Fire Weather Outlook

One of our family friends described Pacific Northwest weather as being ‘stuck in a wet sock.’ Today has certainly felt that way. We’ve had a steady drip of rain here on Whidbey Island but hardly anything in the rain gauge to show for it. For some, it’s the perfect complement to a warm cup of soup and a book, or beautiful weather to go for a hike in the woods in. For others it’s intolerable, and those who have the means quickly relocate!

But today, I’ll talk about our fire outlook for the summer; probably the furthest thing from a wet sock you could imagine. Fire weather forecasting is one of the few ‘long-range forecasts’ that bear any weight, as they incorporate not only the predicted weather outlook but current drought, soil moisture, and snowpack observations. I’ll be the first to tell you that seasonal forecasts, while not completely useless, have little skill outside of strong El Nino or La Nina events (and sometimes still fail!). And while it’s definitely not a slam dunk, it unfortunately looks like we are in for a more active-than-usual fire season this summer.

It’s no secret that the Pacific Northwest has had a string of more active-than-usual fire seasons lately. 2019 was pretty minor for the Pacific Northwest, but 2018 and 2017 were both very active seasons. August 2018 featured easterly winds that dropped smoke and ash from billowing fires over the Cascades right over the highly-populated Puget Sound megalopolis on multiple occasions, creating what must have been an apocalyptic scene for citizens enshrouded in the earthly exhaust. 2017 was capped by the Eagle Creek Fire in the Columbia River Gorge, a raging September firestorm that burned approximately 45,000 acres of timber and resulted in mandatory evacuations all the way to East Corbett. 2014 and 2015 were also extraordinarily active fire seasons for the entire Pacific Northwest. And who could forget about the devastating fires of 2017 and 2018 for California, as well as the unprecedented public safety power shutoffs during 2019?

Over the past decade, the sheer amount of Pacific Northwest wildfires hasn’t increased, but the acres burned has increased dramatically. The reasons for this are multifold; the last several summers have been some of the warmest and driest on record, and 2017 was particularly bad because it followed the wettest winter/spring on record, meaning there was a ton of fresh growth that became tinder dry in the summer and provided fuel for fires to spread. We’re also seeing more acreage burning now simply because our decades of fire mitigation have resulted in unnaturally thick forests in fire-prone locations, allowing fires to grow more easily than they otherwise would if we had just let them naturally burn out on their own accord.

The majority of Pacific Northwest fires are caused by humans, though the disparity isn’t as extreme as it is in California or east of the Rockies. However, the majority of acres burnt in the Pacific Northwest are due to fires ignited by lightning. Lightning-ignited fires often burn in remote, hard-to-reach regions and away from humans and property, so they are not only often harder to fight but take a back seat to those threatening structures. When the original ‘Smokey the Bear” campaign came out in the 40s, the standard procedure was to extinguish both lightning and human-caused fires, but since the 1980s, the standard practice has been to let lightning-caused fires burn out unless they are threatening structures as people realized (particularly after the mega-destructive Yellowstone Fire of 1988) that fire plays a natural role in the ecosystem and that mitigating natural fires only results in the buildup of fuel and an increased probability of catastrophic wildfires going forward.

Summer Fire Outlook:

Unfortunately, all indications are that we will have a more active-than-normal fire season. Our one saving grace (from a wildfire perspective) is that there may be less outdoor recreation this summer due to COVID restrictions and thus fewer opportunities for human ignitions, but the current conditions and long-range climate models suggest that we’ll have higher-than-average fire danger this summer.

Much of Oregon is now in a “moderate” or “severe” drought, and some spots even have an “extreme” designation. I believe (and I think most people would agree) that the US Drought Monitor uses hyperbolic language, but it’s the standard used by the Climate Prediction Center and, in my opinion, is the best holistic indicator of drought because it takes a wide range of variables across a wide range of timescales into account when making its designations.

According to the U.S. Drought Monitor, we are in both a short-term (<6 month) and long-term (>6 month) drought and are experiencing effects from both. With short-term droughts, finer fuels such as twigs and grasses are drier-than-average and there may be a decrease in top-level soil moisture, while long-term droughts have a greater effect on the large-scale hydrology and ecology of the affected area. With regards to fire danger, both short-term and long-term droughts dry out fuel of various sizes and, if severe enough, can kill vegetation, making them more susceptible to fires. The California drought from 2011-2016 was most severe from 2011-2014, but over half the estimated 102 million trees that died in California during the drought died in 2016 alone.

Snowpack also plays a significant role in summer fire danger. A substantial snowpack, particularly one that melts late into the spring, increases danger by keeping fuels moist and stifling the development of grass, shrubs, and other ‘fine fuels’ that inevitably dry out and burn during the summer. There are exceptions; the 2011-2012 winter was snowier-than-average and the spring was wetter and cooler-than-average, with March being the snowiest month of the entire year for many spots. Still, below-average snowpack is often a harbinger of an above-average fire season, and as the map below shows, snowpack is below-average for the eastern slopes of the Washington Cascades and nearly all of California and Nevada.

A third factor that plays a significant role in summer fire danger is the amount of ‘fine fuels,’ such as grasses and shrubs, that grow during the spring and subsequently dry out in the summer. In this manner, wetter-than-average spring weather can actually lead to increased summer fire danger, as wetter-than-average springs allow more grasses to grow. This was particularly true during the summer of 2017, as the 2016-2017 winter and spring was one of the wettest on record for many Western States, particularly the Northern Sierras. The winter single-handedly extinguished California’s drought and almost resulted in a catastrophic failure of the Oroville Dam, but the 2017 summer was one of the hottest and driest on record for many Western States and there were numerous catastrophic fires throughout the summer and autumn, capped by a series of devastating fires over Northern California in October that killed 44 and caused 14.5 billion dollars in damage. It’s rare to have above-average fine fuels and drought conditions, but according to the National Interagency Coordination Center, the Western US has above-average fine fuels at lower elevations for the third year in a row.

So with widespread short-term and long-term drought over the West, below-average snowpack, and above-average fine fuels, fuels have an above-average chance of being drier and more plentiful than average this summer. And that’s a pretty bad combo for fire danger. But at least our seasonal forecast points to cooler and wetter-than-average summer weather, right?

Sigh… I wish I could say otherwise, but the Climate Prediction Center is pretty gung-ho on us seeing warmer-than-average weather this summer, and they even have a slight chance of drier-than-average weather for the Pacific Northwest. Needless to say, hot and dry summers are associated with an increased risk of large, destructive fires.

To say seasonal weather forecasting is a bit of a crapshoot would be a criminal understatement, particularly in “Neutral” (neither El Nino or La Nina) years like we are in now. Still, climate models are in broad agreement that the West will see above-average temperatures this summer, and there actually is a bit of skill in seasonal temperature forecasts (though most of this is simply due to global warming, particularly at higher latitudes). Precipitation forecasts have almost no skill during Neutral years, which is why the CPC is so conservative with their precipitation probabilities. I’m skeptical of our chances for drier-than-average weather this summer, but I think there’s a very high probability of us being warmer-than-average – not only due to long-term warming trends but due to the anomalous ridging and warmth shown by all climate models over the West this summer.

We can’t do anything about how much rain will fall or how high temperatures will rise this summer. And lightning will ignite forest fires throughout the West this summer, just as it has done since trees first appeared nearly 400 million years ago. But we CAN do our part by preventing human-caused fires. With the world entrenched in arguably the most disruptive social and economic crisis since World War II, let’s help our first responders and fellow humans out and not burn down any forests.

Featured image credit: US Forest Service, Rim Fire of 2013