How snowpack affects summer forest fires
By Benjamin Alva Polley EBS COLUMNIST
Many friends are already scheming ways to escape this summer’s possible wrath of extreme heat, excessive smoke and fire danger, and it is only mid-January. Their rationale makes sense. This year, more than half of Montana SNOTEL sites are recording lower-than-normal snowpack. Many ski resorts in Montana aren’t fully open, and the ones that are open make a lot of snow to cover a few runs from top to bottom.
Many scientists say the rationale that Montana’s summer will be hazardous for fire is too early to predict. Yes, this year’s winter is controlled by El Niño, which generally means less water and precipitation in Montana’s mountains. Yes, there is a direct correlation between snowpack and snow-water equivalent, and fire season, but it all depends.
Andrew Larson, professor of Forest Ecology and Wilderness Institute director at the University of Montana, told me over the phone that there are well-known relationships between snowpack and forest fires, especially spring snowpack.
“How much water is stored in the snowpack at a certain point in time is often a pretty good correlate of fire area burned or other measures of fire season activity,” Larson said. “It is an inverse relationship—where you get less snowpack often results in more active fire seasons.”
Low snow years usually mean snow melts off the hills and mountains sooner, vegetation potentially dries up sooner, and fire season potentially extends with low fuel moisture.
“But there’s a great big star you got to put next to that,” Larson said. “The weather during the spring, especially the summer, is a strong control of fire season activity.”
There is more to just winter and spring snowpack controlling fire activity. Many factors come into play when determining fire season, including the importance of April 1 snow water equivalent—a measure of how much water is stored in the spring snowpack. How fast snow melts and how fast plants and vegetation dry out are vital factors when considering the fire season. How much spring and summer rain falls and the severity of fire seasons has to do with temperatures.
Does the “mon-June” season happen or not? I have been in Montana for over two decades and worked a big chunk of those years as a seasonal worker in Glacier National Park on backcountry trail crews and fire lookouts, and I helped with many wildlife studies. The mon-June season used to be predictable: each May and June, the monsoon rains would come before Memorial Day and last well into mid-June. But lately, it hasn’t been as predictable.
How hot do the temperature and ground fuels get in the summer? Are there thunderstorms with lightning in addition to the hot temperatures? Is there arson activity igniting fires? Does rain happen in July and August or not? If rain comes at the right time late in summer, it can help prevent lightning ignitions from spreading.
“It was hotter than hell last year around western Montana; things were drying out, and then we had a big lightning storm that started many fires,” Larson said. “It was looking like it could be brutal all the way through August and into September. But then we got some great shots of moisture in August, which dampened things down.”
The bottom line is that predicting this summer’s fire season severity is premature.
“It’s too early to say we’re going to have a terrible fire season this year, even though our snowpack is way behind,” he said.
Benjamin Alva Polley is a place-based storyteller with stories published in Outside, Adventure Journal, Popular Science, Field & Stream, Esquire, Sierra, Audubon, Earth Island Journal, Modern Huntsman, and other publications at his website www.benjaminpolley.com/stories. He holds a master’s in Environmental Science and Natural Resource Journalism from the University of Montana.
