JACKSON, Wyo. – An active early summer pattern has taken hold across Northwest Wyoming over the past 10 days with showers and thunderstorms developing on a daily basis. This pattern is expected to continue for the foreseeable future as we head into June.
The large-scale pattern currently features a strong ridge of high pressure over the Great Plains that extends up into Canada. Meanwhile, weakening areas of low pressure have been slowly moving into the Western U.S. from the Pacific, tapping into subtropical moisture.
The amount of water vapor in the atmosphere working its way into the Central and Northern Rockies has been above average for this time of year. The uptick in moisture combined with strong solar radiation and relatively warm temperatures have allowed the atmosphere to destabilize each day, contributing to an uptick in thunderstorm activity.
We will essentially be on a rinse-and-repeat pattern for at least the next week (and likely beyond) with subtle day-to-day variations in shower/thunderstorm chances, coverage, lightning frequency and rainfall amounts. But overall, lightning activity and rainfall will be greater than usual through the first one to two weeks of June.
While showers and thunderstorms are likely to develop each day, the most active period is expected to be from Friday through Sunday (sorry weekend warriors) with elevated moisture levels expected to contribute to more widespread showers and thunderstorms.
Generally speaking, showers and thunderstorms will be most likely during the afternoon and early evening hours over the next week. However, showers (and a slight chance of thunderstorms) will also be possible at times during the overnight and morning hours, with the best chance of this “off-hour” activity expected over the weekend.
Rainfall amounts will be hit or miss each day in this type of pattern, but significant rain amounts are expected to add up over time during the next week with generally wetter-than-average conditions for early June.
Despite the frequent shots of rain and thunderstorms, no significant cold fronts are expected to move through over the next week. At the same time, increased cloud cover will have a moderating effect on temperatures, both in terms of daytime highs and overnight valley lows.
Highs on Wednesday have reached the low 70s in the valley with similar temperatures expected on Thursday. From Friday through Sunday, highs will be in the 60s given the increase in cloud cover. Lows will typically range from the upper 30s to low 40s.
During the first half of next week, temperatures may warm slightly with highs in the upper 60s to low 70s.
For perspective, average highs during the first week of June are around 70 and average lows are in the mid 30s, so we will not be too far from average on any given day.
May Recap and Snowpack/Fire Season Update
May broke our six-month streak of below-average temperatures, and featured a rapid shift to mild conditions following a long and cold winter. Temperatures ended up 2.3ºF warmer than the long-term average, with an average high (during May 2023) of 65.8ºF and an average low of 34.1ºF.
The highest temperature of the month was 79ºF on May 21 and the lowest temperature of the month was 25ºF on May 1. The high temperature in Jackson reached 70ºF on 11 occasions.
Our average high in May 2023 was 19.1 degrees warmer than the average high in April 2023. Typically the difference in average highs in April and May is 10 degrees, which indicates just how rapid of a shift we had from late winter conditions to spring conditions.
May ended up drier than average as well throughout Teton County, despite the active finish to the month. Frequent showers and thunderstorms resulted in wet conditions late in the month, while the first three weeks of the month were mild and dry with only occasional light showers.
One thing we did not see this May that we typically see at least once are strong frontal systems that produce more widespread and steady precipitation, along with chilly temperatures and mountain snow. The Rendezvous Bowl Plot at 9,580 feet only received 2 inches of snow this May, compared to a 15-year average of 32 inches.
Believe it or not, snow depth at the Rendezvous Bowl Plot and Grand Targhee Snotel is actually below average for the end of May based on data from the previous 15 years. So while this was a big year for snowfall, mild conditions in May have contributed to higher than usual snowmelt rates, though snowmelt flooding has not been a widespread issue at least.
As we head into the summer, moisture from abundant winter snowfall along with an upcoming outlook for consistent showers and overall wet conditions should help us out in terms of wildfire potential. Of course, this also hinges on the actual weather we experience mid-summer as hot and dry conditions in July and August could theoretically lead to a more active late summer fire season.
What about smoke? We already saw a brief shot of smoke from Northern Alberta wildfires about a couple of weeks ago. Fortunately, Northern Alberta typically sees its wet season during the summer months following its spring fire season.
For the rest of the summer, if we do see smoke it’s more likely to come from the Pacific Northwest and British Columbia. This region experienced near to below-average winter snowfall, and recently experienced one of its hottest Mays on record with above-average temperatures expected to continue into June.
California, on the other hand, is coming off of a record snow year and spring temperatures have been near to below average with frequent showers also impacting the Sierra Nevada Range and Northern California recently. So if we do see smoke this summer, it’s more likely to come from the Northwest and less likely to come from California.
Alan Smith, Meteorologist
