JACKSON, Wyo. – A warm and dry pattern will briefly be interrupted this weekend when a robust disturbance arrives from the southwest, leading to multiple rounds of showers and thunderstorms on Saturday and possibly a few showers on Sunday.
Recent Weather Pattern
Dry and windy conditions have been common over the past week, thanks to a stronger and more active jet stream than is typical during the month of June.
Wyoming has been sandwiched between a strong high pressure ridge over the West Coast and an unusually persistent trough of low pressure (for this time of year) over the Upper Midwest, and a strong northwest flow aloft has been present overhead in between these two features.
Moisture has also been shunted north and east of our area in this pattern, so we have seen dry conditions over the last 7 days since picking up some light rain last Tuesday.
A series of cold fronts arrived during the middle of last week, bringing brisk and chilly conditions, including a hard freeze (27º) on the morning of June 11 and a lighter freeze on June 12.
Was this our last freeze of the season? Most likely yes, but you never know for sure. The average last freeze in Jackson (based on 2010-2025 data from the JKNW4 weather station) is June 18, while the average first freeze in the “fall” is August 27. So yes, we have a very short freeze-free season here in the Jackson Hole Valley!
Following last week’s cool weather, pleasant temperatures returned over the weekend with highs in the low 70s. We have seen a more notable warm-up since then, however, with a high of 81ºF recorded on Tuesday afternoon.
Here is the 7-day weather summary for the town of Jackson:
For perspective, the average high and low temperatures in Jackson on June 17 are 73º and 40º.
Upcoming Weather Pattern
Dry and windy conditions have prevailed on Wednesday following the passage of a weak cold front. The timing of the front along with the gusty winds prevented the typical overnight inversion from setting up, resulting in a mild morning with a low of 55º.
Dry and sunny conditions will prevail on Thursday and Friday with along with comparatively lighter (but still breezy) winds. Highs will reach the upper 70s on Thursday before heating up into the mid 80s on Friday.
Our dry spell will temporarily be interrupted this weekend. A robust shortwave trough will approach from the southwest, resulting in an active day with multiple rounds of showers and thunderstorms likely.
The timing looks to favor the afternoon and evening hours on Saturday, but some early morning activity is also possible, and that includes at least some risk for lightning during the morning, so heads up if you have outdoor plans.
This is going to be a wet thunderstorm setup with sufficient moisture levels, meaning that storms will produce meaningful rain with locally heavy downpours possible. Some storms could also be on the stronger side, with frequent lightning possible.
All areas of Teton County should pick up at least some measurable rain, and most models are projecting anywhere from 0.2 to 0.5 inches of rain over the course of the weekend, with variability likely given the nature of thunderstorms.
On Sunday, we will see a bit better of a weather window, but isolated to scattered showers and thunderstorms will be possible again during the afternoon. Coverage and rainfall should be less compared to Saturday, though.
This will be a mild southwest flow pattern so no major cooldowns are expected with highs reaching the 70s on both Saturday and Sunday.
Heading into early next week, we will head back into a dry pattern, and a warm-up is also expected, with highs getting into the 80s.
The 7-day precipitation projection, representing the average of 50 simulations of the European AIFS Ensemble Model, accounts for Saturday and Sunday’s showers and thunderstorms, while the rest of the 7-day period will be dry.
Looking further out, the rest of June looks warm and dry for the most part. Some models are hinting at a weaker disturbance with at least some low-end thunderstorm potential around June 27-28, but confidence is low.
June is almost certainly going to end up being drier than average, but long-range models are still bullish on a wetter signal for July, with monsoon moisture projected to arrive from the south.
Confidence in longer-range outlooks like this is inherently low as skill level drops substantially beyond 10-15 days, but “hints” like this are at least worth monitoring moving forward.
Alan Smith, Meteorologist
