JACKSON, Wyo. — Significant rainfall from last week’s monsoonal moisture surge has lowered fire weather concerns across most of Western Wyoming and Eastern Idaho, at least temporarily.
Rainfall data during the summer months is limited across the area, but radar estimates indicate that 1-3 inches of rain fell across the Teton, Gros Ventre, Snake River, Wind River and Salt River Ranges during the one-week period from July 27 through August 3.
Of the valley locations that report rainfall, the Town of Jackson was one of the few localized areas that missed out on heavy rain with only 0.5 inches recorded during this one-week stretch. Just on the other side of the Tetons, however, Alta recorded 1.77 inches of rain. While terrain plays a role, this also highlights the “random” nature of thunderstorms and convective summertime rains.
This rainfall won’t erase the drought conditions we’re currently experiencing, but it came during a great time in the middle of fire season when we really needed some moisture. The wetting rains and seven-day streak of high moisture levels and relative humidity have resulted in a decrease in fire danger for the time being.
Fuel moisture has risen above critical levels and now ranges from 11-16% across Northwest Wyoming (10% or lower is considered critical, and indicates vegetation fuels that can burn easily). This is good news as we head into what is traditionally the most active fire month of the year.
In more good news, a Pacific storm system will move through on Friday, providing another round of wetting rains for Teton County. Early indications are that rain totals on Friday will range from 0.25-0.75 inches in the Tetons and 0.1-0.4 inches in the valley.
There will not be a heavy rain or flash flooding threat with this system since the moisture source will be from the Pacific, and not the monsoonal/subtropical moisture source from the south that we saw last week. Still, this should be a beneficial rain event by early August standards.
Heading into the weekend and early next week, a series of disturbances passing north of the area will result in drier and breezy conditions with only a slight chance of light showers.
Normally, dry and windy conditions at this time of year would be cause for concern, but thanks to last week’s rain and the fact that relative humidity values are projected to remain above 20%, significant fire weather concerns are not expected. Of course, that does not mean you should let down your guard, and remember that Stage 1 fire restrictions are still in effect.
While the fire danger has lowered in the near term, we could see fire danger rise again by late August and early September if we were to head back into a hot and dry pattern. Over the weekend and into the first half of next week, temperatures are expected to be near to slightly below average, which will help.
However, as we head into mid-August, extended-range models are projecting a return to above-average temperatures along with relatively dry conditions.
As a result, we could start to see fire danger creep higher again during the second half of August, and we’ll need to be more on-guard for wind and dry lightning events by then.
Also, despite the recent moisture, we are still dealing with smoke issues. On the one hand, rainfall significantly reduced fire activity over Idaho and portions of Eastern Oregon and Western Montana.
However, on the outer edge of last week’s monsoon moisture surge, dry thunderstorms occurred and triggered new large fires in Northern California. Currently, the largest fires are located over Northern California, Southern Oregon and British Columbia.
The Northwest (especially Washington and British Columbia) could see a reduction in fire activity thanks to rain forecasted later this week, but the Northern California wildfires aren’t going anywhere anytime soon, and will likely contribute to smoke issues in Jackson Hole from time to time for the foreseeable future.
Alan Smith, Meteorologist
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