JACKSON, Wyo. — Following a stretch of higher atmospheric moisture and elevated thunderstorm activity, Northwest Wyoming will head back into a dry pattern for the next 10+ days.
Fire danger will be on the rise as well due to hotter than average temperatures, periods of gusty winds, and the potential for isolated “dry” thunderstorms that could lead to lightning-triggered fires.
Our recent influx of monsoonal moisture late last week and early this week brought localized beneficial rains, but thunderstorm activity was hit-or-miss on most days (as is usually the case) so some areas in Teton County did better than others.
The Town of Jackson saw a nice 15-20 minute deluge from a thunderstorm on Monday and managed to pick up 0.33 inches of rain total over the course of a few storms. Not bad, but it was the only meaningful rain we saw in town after missing out on thunderstorms over previous days.
Northern sections of the Jackson Hole Valley did not see much rain at all over the past week, while the Teton and Gros Ventre Mountains saw respectable amounts with rain totals ranging from about a quarter of an inch to an inch per radar estimates.
Monsoonal moisture is now shifting well south of the area, and moisture levels across Northwest Wyoming will be decreasing in the days to follow as a result.
In addition, a strong ridge of high pressure over the Intermountain West will result in hot temperatures by Jackson Hole standards. Wednesday is looking like the hottest day of the week with a high of 91 expected for the town of Jackson.
Right now, our 1,000-hour dead fuel moisture (a measure used for forested areas) is in the 11-16% range across Northwest Wyoming. Values of 10% or lower are considered critical and most likely to ignite and burn easily, so we’re not quite at the critical threshold, but we are approaching it.
However, finer fuels including sagebrush and grass are closer to the critical threshold and will burn more easily as a result.
In addition to the hot temperatures forecasted, the first of two upper atmosphere disturbances will approach on Wednesday, which will lead to an uptick in winds and a chance of isolated dry thunderstorms.
Another stronger disturbance containing little moisture will approach on Thursday, resulting in even stronger winds than Wednesday with gusts to 30 mph possible, along with a chance of dry thunderstorms, both of which will result in elevated fire danger. If there’s a silver lining, the wind forecast has actually decreased compared to how it looked a day or two ago.
A cold front will arrive sometime on Friday morning with gusty winds expected once again behind the front through Friday afternoon. Fortunately, temperatures will cool off to more seasonal levels with highs in the low 80s and relative humidity will rise some as a result. There is an outside chance of isolated, dry thunderstorms on Friday afternoon as well, but most of the activity should stay north and east of Jackson Hole.
Over the weekend, dry conditions are expected along with a warming trend as high pressure rebuilds over the area. Relative humidity will continue to trend lower, but winds will decrease as will the threat for dry thunderstorms.
However, another disturbance and associated cold front are projected to arrive on Monday, which could result in another windy day with isolated dry thunderstorms possible and elevated fire danger.
Looking farther out, most of next week is looking dry as well. Long-range models are hinting that monsoonal moisture could eventually work its way northward again during the second half of July – a “double-edged sword” that could lead to higher potential for rain, but also higher potential for lightning-triggered fires if we only see minor amounts of moisture.
Alan Smith, Meteorologist
