The headlines in the Seattle Times and elsewhere are ominous: a low snowpack over Washington State means more wildfires this summer.
Some politicians and state agencies make the same claims. Less snowpack and earlier melt-out produce a drier environment that brings earlier and greater wildfires.
Sounds reasonable, right?
There is a problem with this claim: it is not true.
And there are good reasons why it is not true.
Let's look at the data!
Last night, I plotted the Washington State wildfire area burned (orange) and the WA April 1 snowpack (based on USDA Snotel sites)--blue line-- for 2002-2024. The latter was provided by Mark Albright, past Washington State Climatologist. April 1 snowpack is the classic measure of snow amount before the summer season.
You will notice a few things. First, there are lots of ups and downs in the snowpack and burned area, but very little correlation between the two.
There WOULD be a correlation if snowpack were an important modulator of wildfires.
There is only one year in which there seems to be a connection: 2015. This was a year with an extremely low snowpack and record-breaking wildfires.
But correlation is not causation. It turns out that 2015 had an unbelievably strong and persistent ridge of high pressure that extended from winter into summer. THAT feature resulted in low snowpack during winter and warm/dry conditions over summer. Warm/dry conditions that enhanced wildfire risk
Allow me to prove this to you.
Below is a map of the difference from normal of the 500 hPa heights (think of pressure at 18,000 ft) for January to April 2015. The red colors indicate much higher pressure than normal at this elevation. Such high pressure works powerfully to dry and warm, reducing precipitation and snowfall.
But now the essential point. The ridge stayed very, very strong and shifted a bit to the west during May through July (see below). This is a VERY, VERY warm, dry pattern for the Northwest and is optimal to promote fires.
So it wasn't low snowpack that made summer 2015 a tinderbox in our region...it was the atmospheric pattern.
More attention should be given to our mismanagement of our forest lands, human ignition sources (e.g., lack of powerline maintenance), and the intrusion of flammable invasive species around our state (like cheatgrass, aka grassoline).
There is no reason to suspect this pattern has anything to do with global warming. Trust me, I know about this: I have published papers on exactly this topic.
If one thinks carefully about the issue, one would NOT expect much correlation between Northwest snowpack and wildfires.
Most of our wildfires occur at lower to middle elevations that melt out well before the fire season every year. Low snowpack years simply melt out a few days or weeks earlier.
So by the mid-summer fire season, the impact is very minimal at the elevation at which the fires are occurring.
Furthermore, a large snowpack can make the wildfire season WORSE by providing moisture longer in the spring, promoting MORE vegetation growth.
This vegetation rapidly dries out in late spring and summer, providing MORE fuel to burn.
Year after year, the Seattle Times and others have predicted a big wildfire season based on snowpack and were wrong (see below). Truth and science matter.
At this point in time, there is no reason to expect an enhanced wildfire season due to snowpack or meteorology.
In fact, the latest USDA Fuelcast predictions of herbaceous fuels over eastern WA are for less than normal (see maps below).
More attention should be given to our mismanagement of our forest lands, human ignition sources (e.g., lack of powerline maintenance), and the intrusion of flammable invasive species around our state (like cheatgrass, aka grassoline).
Per your blog post of May 20, 2015:
ReplyDelete"I have talked to my colleagues in the wildfire business and most of them feel the snowpack issue is overblown. They tell me that the key determiner of whether there will be extensive fires in the summer are:
1. Whether we are much warmer than normal in July and August
2. Whether there are a lot of thunderstorms to initiate fires.
3. Whether we are much drier than normal in July and August
Regarding the last bullet, we are normally dry during our summer, but rain can moisten the "fuels" and lessen the fire risk.”
So, will we receive substantial summer precipitation similar to last year? Will summer temperatures be warmer than normal? Will there be thunderstorms?
Those are questions which no one can answer definitively, so we’ll just have to wait see - like always.
Regarding your claim that “a large snowpack can make the wildfire season WORSE…” - can you cite an example in Washington where above normal snowpack was associated with a worse than normal wildfire season? There would seem to be some tension between this claim and claims that there is little correlation between snowpack and wildfire. According to the plot of April 1 snowpack and acres burned it does appear that there was a noticeable uptick in wildfire activity during the summer of 2006 which followed the above normal snowpack of the winter of 2005-2006. However, July and August of 2006 were exceptionally dry despite being cooler than normal. On the other hand, June-August of 2015 were not extremely dry but were much warmer than normal.
Overall, it would seem to be the case that snowpack probably does not contribute much to weighting the dice for or against wildfire except perhaps at the tails of the distribution and that temperatures and rainfall have a much greater effect. Given the trend toward warmer and drier summers that has become pronounced during the 21st century, it seems reasonable to suggest that wildfire risk should be expected to be generally enhanced independent of snowpack.
Sorry, but this seems to me to be a long winded "blame it on global warming" argument. Cliff gives ample evidence that it is not, just like other phony arguments that the Times comes up with.
DeleteSorry, but your argument is another global warming falsehood. Cliff cites time again how these arguments are more falsehoods on the part of the Times.
DeleteActually July and August of 2006 was warmer than normal besides being dry in North Central Washington, where the largest fires occurred. It was also quite dry in July and August besides being quite warm in the summer of 2015 in North Central Washington where, once again, the largest fires occurred. As mentioned, there is a good relationship between warm, dry summers and large fires in Eastern Washington and warmer, drier summers have become more common in this area so far this century.
Delete"It turns out that 2025 ..." Typo? 2015!
ReplyDeleteThanks...you are right...fixed
DeleteIt's fascinating to see how often the topic of snowpack is trotted-out by the press [even agencies] as if it's a direct driver (or harbinger) of year-round conditions. Snowpack doesn't make western Washington (or any other place) green, rain does. Some perennial bodies of water (rivers, streams) do receive some melt of mountain snow (and glaciers) at times, but for the most part it's the predominance of rain infiltrating to groundwater that makes rivers and streams flow year-round.
ReplyDeleteThat said, a few years ago an official list of "wildfires" was attached to a local drought resilience plan (ginned up by an agency in Whatcom county) that seemed poorly screened to me. A very large number of the "wildfires" on the list were insufficiently quenched BEACH and campground fires. There was hardly any attention paid to the need for preventative forestry practices (thinning, logging) or for maintaining access roads, etc. Mind you - "snow drought" was featured as a big deal (a concern), when there was (and is) absolutely no evidence suggesting lack of snow as a driver of any of this.
While the USDA fuelcast maps do indicate that Eastern Washington may fare better in the wildfire department this summer, they do suggest that a large swath of the North Cascades may have a lot of fuel to burn this year. I am surprised about this considering that the North Cascades did have a handful of impactful fires last year. Should we expect more of the same up therr this year?
ReplyDeleteOregon and Washington state governments have "It's a little fire. We'll jest let it burn." Then, the little fire becomes a big fire, and they are just "shocked, shocked" that wild fires can get so big and create so much smoke. They also believe if the fire is on Federal land, then it's not their problem, and the fire will never get on to state land. Then it's "shocked, shocked", how could that fire get so big?
ReplyDeleteState governments want the forests to burn.
Thank you for the post.
ReplyDeleteLike all things wildfire, attributing one single factor as a driver of a wildfire season is a gross oversimplification. Snowpack in the PNW is an important factor that drives wildfire seasons, essentially as the longer a snowpack persists the longer a delay until fuels are dry enough to support wildfire. Since snowpack is elevation dependent, it keeps higher elevation wildfires from occurring. But completely agreed, you cannot predict wildfire season based on snowpack. I am up in BC; 2018 we had well above normal snowpack, and a brutal wildfire season. In 2023 we had a well below normal snowpack, and a brutal wildfire season.
ReplyDeleteA much bigger predicter of wildfire season, at least up here, is June precipitation. July and August are always going to be very dry, but a dry June sets the stage for pretty severe moisture deficits that can support severe wildfire. West of the Cascades, or coastal BC, is particularly concerning when we start getting strong outflow easterly winds bringing in warm dry air. Fortunately, lightning is fairly rare in these regions, limiting ignitions (in comparison to BC interior and eastern WA).
Love the blog. Might not agree with everything you say Cliff, but I certainly agree with your commentary on massive oversimplification in the media regarding the cause and effect of wildfires and wildfire season severity.
As a Forester who started in the WA woods in 1973 I agree with Cliff. The issues that I see that create a bad fire season are the occurrence of winds and Thunderstorms in August in forests that are overly dense due to fire suppression on Government forests since the 1910 burn in N Idaho and W Montana. Also there are many more souls running around on USFS and BLM lands which increases the chance of starts. Invasive species such as cheat grass, knapweed, and scotch broom are like gasoline out on our forest lands that add to flammability.
ReplyDeleteI’ve never seen a connection between snow pack and fire season severity and I believe the graph proves it.
So no fire season? I wouldn't put money on that.
ReplyDelete100hr. dead fuel moisture correlates with acres burned much more than snow pack although the two could be linked in some cases.
ReplyDeleteWell, that chart does show a correlation. It's not year over year; it's decade over decade.
ReplyDeleteJust had the first wildfire of the season near Leavenworth. Earlier than usual.
ReplyDelete