Wildfires are burning throughout Wyoming, consuming buildings and forcing evacuations as firefighters work to control them.
Relief from some welcome rainstorms is on the way, but it won’t get to much of Wyoming until next week. When it does arrive, it should give the Cowboy State a good soaking.
"This is probably the best-looking plume of moisture I've seen this summer," said Cowboy State Daily meteorologist Don Day. "It doesn't guarantee rain for everybody, but it'll bring a four- or five-day period to help with firefighting. So, there's help coming, but we've got to wait."
Dry Cycle Cinders
Day said the current flurry of fire activity is happening amid a well-observed seasonal cycle.
After a "wave" of moist air that manifested as thunderstorms across Wyoming, a wave of dry air descended on the Cowboy State, helping fan the flames of the ongoing and new wildfires.
"Late last week and over the weekend, there was quite a bit of shower and thunderstorm activity across the state," he said. "Many areas of Wyoming got rain. But in between these surges of subtropical moisture you have dry periods. You'll get a period of moist air coming in, then a slot of dry air behind it. That's typical for this time of year."
The windy conditions that accompany the dry air have helped the Clearwater Fire in Shoshone National Forest grow to more than 1,000 acres, threatening access to the East Entrance of Yellowstone National Park. Meanwhile, the wind-fueled flames of a grass fire in Crook County led to the temporary evacuation of Upton on Monday.
And wind help the Pleasant Valley fire near Guernsey balloon to more than 25,000 acres overnight Tuesday.
The promising plume of moisture Day is tracking will be the next wave of subtropical moisture. It will be followed by another period of dry air and blustery days, which will increase the severity of any wildfires then as well.
"Even if you get a really good rain, two or three days of hot conditions with low humidity will sap out all the moisture and things get dry very quickly. It's not surprising that we've seen this uptick in fire activity this week."
What Looks Good
The upcoming plume of subtropical moisture has potential to provide much-needed relief to firefighters. Day said the most promising aspect will be an overall increase in humidity.
"If you look at humidity readings across the state right now, they're between 10% and 30%," he said. "The air is super dry right now, but this airmass will increase that humidity. For fire-weather behavior, that's going to help."
The increased humidity will increase cloud cover, which means there's a greater chance of rain-producing thunderstorms. That's a perfect storm of much-needed relief across the Cowboy State.
It's coming, but it's not here yet. Day said signs of the coming storms could manifest over the weekend, but real relief won't get here until Monday, at least.
"Imagine a slow-moving column of moist air circulating through the area over about a four-to-five-day period," he said. "That's what will happen Monday through Friday next week."
It's Dry Out There
While the summer cycle of dry and moist air might be typical, there's no denying that it's dry across Wyoming.
According to the U.S. Drought Monitor, most of Wyoming is either abnormally dry or in moderate drought, with a few pockets of severe drought in eastern Wyoming.
Day acknowledged that this summer has been drier, even when compared to 30-year averages. The arrival of La Niña earlier this year is historically a dry signal for Wyoming, but this season is trending drier, especially in eastern Wyoming.
"We had a much above-average precipitation summer last year but a much below-average precipitation period in April and May," he said. "June wasn't a great month either, particularly in the eastern part of the state. The trend this summer, without a doubt, has been much drier than last summer, but it's nothing extraordinary."
Day added that the severity of the fire season this year is partly due to the above-average precipitation last year. The moisture fueled a flurry of plant growth, which has since died and dried out, making it a potent fuel for wildfires.
Timelines To Remember
A series of showers and thunderstorms in southeast Wyoming on Friday should be the first signs of the arrival of the next wave of subtropical moisture. From there, the column of moist air will slowly move across the state.
"It will start in western Wyoming," Day said. "The moisture plume will reach the southwest, western and northwest parts of Wyoming first on Monday and Tuesday, then the central and eastern parts of the state will be most affected Wednesday through Friday."
Any thunderstorms that develop have the potential to develop and drop more rain. However, this might not be enough to extinguish the ongoing wildfires or prevent any new ones.
"The risk isn't zero," Day said. "You can still have fires started by lightning in thunderstorms and produce rain. From what I know, some of these fires seem to have been started by lightning from last week's thunderstorms. They might have smoldered or weren't completely out, then flared up again when we hit the next wave of dry air."
Ain't Over ’Til It's Over
Even if the next wave of subtropical moisture helps extinguish Wyoming's wildfires, the season's just starting, and it has the potential to get worse.
According to historical analysis, Wyoming's wildfire season tends to be most active in late summer and early fall. At that time of year, usually from the end of August into September and October, average rainfall declines.
Day reminds Wyomingites that the fire season won't end until the first significant cold front of the year, which could happen as early as September or as late as the end of October.
"Once you leave August, you don't have nearly the number of opportunities to get wet as you would earlier in the season," he said. "To be conservative, the time from where we are now till that first strong cold front of fall is our peak fire season."
Between now and the first front of fall, Wyoming's seasonal cycle will experience several more waves of moist and dry air. Next week's column of moisture should bring some relief, but it'll be followed by another dry spell and a flare-up of fire activity across the Cowboy State.
"Let's say we get some good rains next week," Day said, and the weather helps the fire situation. We will have another dry period, and that's when we'll be susceptible to fire activity. This back-and-forth pattern between active periods of thunderstorms and dryness is continuous at this time of year."
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
