JACKSON, Wyo. – Following a wet June, the first few days of July featured warmer and drier conditions overall. However, thunderstorms that developed during the afternoon hours on July 1 and July 3 produced damaging winds across the Greater Teton-Yellowstone Region.
As we head later into July, we will continue to see an overall drying trend with fewer thunderstorms, and eventually, hotter temperatures.
Recent Weather Summary
June was a wet month across Teton County and the State of Wyoming as a whole. The Town of Jackson received 2.64 inches of rain in June, which is well above the historical June average of 1.50 inches. This was also the wettest June in Jackson since 2010.
Rain totals elsewhere across Teton County in June include 3.13 inches in Moran (near Jackson Lake) and 3.41 inches in Alta. Rain totals were even more impressive across Central and Eastern Wyoming where abundant Gulf of Mexico moisture was present for much of the month.
Temperatures during the month of June ended up very close to average in Jackson (0.4ºF below normal), but this is somewhat deceptive.
Average high temperatures in June were 4.7ºF below normal, but average lows were 3.9ºF above normal. This is indicative of the amount of moisture and cloud cover we experienced, which had a moderating effect on temperatures.
The first few days of July featured warmer temperatures and more sunshine, at least during the morning hours. Jackson recorded its first 80ºF days of the season after not reaching the 80ºF mark at all in June. For perspective, the average first 80ºF day in Jackson is on June 8.
While we had some great weather over Fourth of July holiday period (weekend + early this week), the two thunderstorm days we did have turned out to be rowdy thanks to two low pressure troughs that moved through.
These troughs contributed to high levels of wind shear (changes in wind with altitude) in addition to an unstable atmosphere.
On Saturday, July 1 a cluster of severe thunderstorms developed across Eastern Idaho and moved into Teton Valley, producing damaging winds from Victor to Driggs as well as along Ski Hill Road up toward Grand Targhee.
There were numerous reports of downed trees and power lines across the region with a peak wind gust of 58 mph recorded at the Driggs Airport.
As the storms moved across the Tetons in a west/northwest to east/southeast trajectory, they weakened upon reaching Jackson Hole with less lightning activity compared to the west side of the Tetons.
Winds were not as strong east of the Tetons compared to west, but they were still quite gusty with numerous limbs knocked down while sporadic trees were downed as well. The Jackson Hole Airport recorded a peak wind gust of 45 mph.
Following a one-day break in the pattern, strong to severe thunderstorms developed again on Monday, July 3. Jackson Hole and Teton Valley largely escaped the damaging winds with these storms, though a 73 mph wind gust was recorded at the Lower Saddle weather station in the Tetons at 11,600 feet.
Further north, a severe thunderstorm impacted the Lake Village area of Yellowstone National Park. The park service reports that several hundred trees were blown over by this storm, causing some damage to buildings and vehicles. Fortunately, there were no injuries.
Monday’s thunderstorms also produced severe winds (defined as wind gusts in excess of 58 mph and/or damage) on both sides of the Wind River Range across Sublette and Fremont Counties, including a 96 mph gust 10 miles northeast of Atlantic City.
Even though we had two days with strong to severe thunderstorms (on July 1 and 3), rainfall ended up being very light across most of the region with portions of Yellowstone being an exception (Yellowstone Lake received 0.40 inches of rain on July 3).
This was due to the fast-moving nature of thunderstorms as well as comparatively lower atmospheric moisture levels compared to what we experienced in June.
Fortunately, the weather pattern calmed down in time for the Fourth of July on Tuesday. A cold front also moved through the night before, resulting in very pleasant temperatures for this time of year with highs in the low to mid 70s in the Jackson Hole Valley.
Upcoming Weather Pattern
The weather pattern is looking quite nice over the next week with abundant sunshine and reduced thunderstorm activity compared to recent weeks.
Wednesday has been (and will continue to be) a dry day throughout the Tetons/Yellowstone with highs in the mid 70s. This is slightly cooler than average, as our average high for this time of year is around 80ºF.
We will see at least a slight chance of thunderstorms return late this week as a weak trough of low pressure approaches from the Pacific Northwest.
On Thursday, Yellowstone and points north and east will see scattered thunderstorms develop as moisture increases, while there is only a slight chance of a mid to late afternoon storm across the Tetons and Jackson Hole.
On Friday, thunderstorm chances will increase just slightly across the Tetons/Jackson Hole with the higher threat remaining over Yellowstone and points east.
Saturday looks like the most active thunderstorm day across the Tetons at this point as moisture increases. Storm coverage should be fairly scattered in nature with a better chance of storms north and east of Jackson Hole.
Highs will top out in the upper 70s in the valley each day from Thursday through Saturday.
On Sunday, a ridge of high pressure will start to build in from the south. It’s possible we could see enough lingering moisture for a slight chance of thunderstorms, but overall this looks like the start of a warming and drying trend. Highs will reach the low 80s in the valley.
During the first half of next week, high pressure will continue to take control, with drier and more stable air expected to shut down any thunderstorm chances altogether. It will also be noticeably hotter with highs pushing into the mid 80s.
Rainfall over the next week looks meager across Teton County, while areas north and especially east of the Tetons should see a bit more (mainly from Thursday to Saturday).
Looking further out, high pressure is expected to “flatten” somewhat during the second half of next week, which should allow a cold front to move through and cool temperatures off a little bit, at least for a couple of days.
However, no moisture is expected to arrive with this front and the overall pattern looks very dry through mid-July with minimal thunderstorm chances.
Normally at this time of year, we start to look at the North American Monsoon which is a circulation of subtropical moisture that develops seasonally across the Southwest U.S. in July and August and occasionally works its way up toward our area.
The monsoon is expected to start later than usual this year, and may only emerge across the Southwest in a weakened state heading into the second half of July. In other words, there are no hints of any monsoonal moisture reaching Western Wyoming in the next two to three weeks.
Tornado Path Visible From the Top of Sheep Mountain (Sleeping Indian)
On Tuesday, July 4, my wife and I hiked up to the top of Sheep Mountain (i.e. Sleeping Indian) just east of Jackson. From the summit, we noticed that the damage path from the June 2022 EF-2 tornado is visible to the north.
If you have any plans to hike up to the top of this mountain over the summer, keep your eyes peeled to the north for the tornado damage path – a rare sight in a high-altitude mountainous environment.
Alan Smith, Meteorologist
