JACKSON, Wyo. — Pre-existing drought conditions, low snowpack, and an unseasonably hot June are all factors that will likely result in a rough fire season ahead, not only for Western Wyoming but for much of the Western U.S. as a whole.

Let’s take a deeper look into some of these factors that will influence fire danger:

Below Average Snowpack

Snowfall was actually above average in the Tetons through the end of February thanks to heavy mid-winter snowfall. However, the pattern completely flipped at the beginning of March and the Tetons experienced one of its driest/least snowy March and April periods on record.

As a result, snow depth peaked about six weeks earlier than average and has been melting well ahead of schedule. The Grand Targhee Snotel station at 9,200 feet is valuable for measuring late-season snowpack in the Tetons. This station has only been around since 2006-2007, but June snowpack in 2021 has been the lowest in its 15-year history.

The rate of snowmelt and snowpack decline in the spring is a major contributing factor to summer fire danger, even if the amount of snow that fell during the winter was healthy.

Worsening Drought Conditions

Drought conditions officially reached Teton County on April 13 for the first time since October of 2016, ending a 4.5-year drought-free run.

Drought conditions have expanded across Northwest Wyoming since that time, though we did see some brief improvement after the one wet week we had in late May. Currently, Teton County is in a moderate drought, but given the hot and dry start to June, drought conditions are expected to worsen in the near future.

While drought is just beginning to expand in Western Wyoming, extreme to exceptional drought has been ongoing for quite a while now across the Southwest U.S. and this area is already experiencing several large wildfires as of mid-June.

 

 

Dry conditions in Teton County and Western Wyoming are resulting in low fuel moisture and an earlier than usual drying out of vegetation fuels, with our traditional dry season still to come in July and August. Not a good trend for fire danger.

Hot and Dry June

Temperatures running well above average during the month of June with well-below-average precipitation often portend a bad fire season in the Greater Yellowstone-Teton region, especially on top of pre-existing fire seasons.

June of 2021 has been unseasonably hot and dry so far and that trend largely looks to continue through the end of the month. This June is already on pace to be one of the hottest on record in Jackson Hole and could challenge 1988 for the record. Of course, the hot and dry June of 1988 was followed by the devastating Yellowstone wildfires of July and August of that year.

More recently, the bad fire season of 2016 was also preceded by well-above-average warmth in June.

Human Activity

While the main focus of this article is on weather and climate trends that influence fire danger, the human factor cannot be ignored either. Weather and climate set the preceding conditions for fire potential, but humans are the cause for the majority of wildfires in our current era, whereas natural triggers such as lightning account for a smaller portion of fire starts.

The fact that visitation is already setting early-season records in the Tetons and Yellowstone and the summer of 2021 is on pace to be the busiest summer on record only adds to the fire concerns, as more people on top of already dry conditions results in higher potential for human-caused fires.

Weather Factors That Affect Day-to-Day Fire Danger

Lightning is the obvious weather factor that can lead to natural fire starts. The mid-summer months of July and August are considered Jackson’s dry season when less precipitation is recorded than other months.

In some luckier years, we can see more persistent fetches of monsoon moisture arrive from the southwest, which can lead to thunderstorms with wetting rains. However, it’s also common for fringe-level monsoon moisture to make it into Jackson Hole – enough to trigger thunderstorms with light rain, gusty winds, and cloud-to-ground lightning that is more likely to cause fires.

“Dry” thunderstorms are the most common cause of natural-triggered wildfires. Moisture is confined to the upper levels of the atmosphere in these instances with dry levels at the low levels resulting in most of the rain evaporating before it reaches the surface. The downward momentum of these downdrafts results in gusty winds, which in combination with lightning strikes, can foster new rapidly spreading fires.

Wind is another major factor to consider with wildfires. Dry and windy days with low relative humidity can result in rapidly spreading fires and extreme fire behavior. Campfires left unattended or even more obscure occurrences such as items causing power lines to spark can quickly ignite and spread new fires when winds are strong.

Seasonal Outlook from the National Interagency Fire Center

June:

The most recent seasonal outlook issued at the beginning of June highlighted the Southwest U.S. and portions of the interior Great Basin for elevated fire potential. So far, this is turning out to be true as numerous wildfires are ongoing in the drought-stricken regions of Arizona and Utah.

July:

Above normal fire potential will spread into the Tetons, Jackson Hole, Gros Ventre, and Wind River regions as well as much of Idaho in July.

August:

Above-normal fire danger is expected across nearly all of Wyoming, Idaho, and Montana in August as well as California. Fire danger is expected to ease across the Southwest as the North American Monsoon takes hold (which typically brings subtropical moisture and thunderstorms with wetting rains to the Four Corners states).

September:

Above-normal fire danger is expected to persist across Teton County and Western Wyoming as well as portions of Idaho and the western-most states. We typically see our first widespread wetting rains and high elevation snows in September, but until this happens elevated fire danger is likely to continue.

At this point, about all we can do is hope for the best as our dry season has clearly started well ahead of schedule this year. Preceding conditions are one thing, but perhaps we’ll get lucky and have a limited number of natural and human “triggers” that could start wildfires. However, given what we know, it would be a good idea to prepare ahead of time for possible wildfires, smoky conditions, and poor air quality.

Alan Smith, Meteorologist

Alan is a professional meteorologist who holds a degree from MSU Denver and writes weather forecasts for Buckrail. He has lived in Jackson full-time since 2015. He is currently a Meteorologist and Operations Manager for OpenSnow, which is a weather forecasting service for skiing and outdoor adventures. At OpenSnow, Alan writes forecasts for the Tetons, Pacific Northwest, British Columbia, and North America as a whole.