JACKSON, Wyo. – A brief pattern change will occur Thursday-Saturday as a surge of monsoonal moisture arrives. A high chance of thunderstorms is expected each day with heavy downpours possible. Despite the wetter pattern, wildfire smoke will continue to be a factor.
This pattern change will also be temporary, as significant drying is expected next week. So we will have only a few days to capitalize on some much-needed rainfall.
Recent Weather
Over the past week, we have seen smoky conditions, above-average temperatures, and isolated thunderstorms with only light and spotty rainfall for most areas.
The most noteworthy weather day occurred on Saturday, when multiple rounds of thunderstorms moved through during the morning hours.
A locally heavy downpour did occur over Jackson Hole Mountain Resort with rainfall totals of 0.3 to 0.4 inches in a short period of time. Lightning from these storms also triggered a couple of wildfires in the area which were quickly suppressed by firefighters.
Wildfire Smoke
Smoke has settled into our area over the past week, and while we have seen day-to-day fluctuations in visibility and air quality, we haven’t seen any significant clear periods.
This trend looks to continue for the foreseeable future, unfortunately, due to significant wildfire activity over the Pacific Northwest and Northern California that is unlikely to slow down anytime soon.
This high-resolution smoke model for late Wednesday afternoon is a good visual that shows where the smoke is coming from.
Even with a higher potential for meaningful rainfall in our region from Thursday to Saturday, periods of smoke and reduced air quality are still expected as little to no rain is expected where the fires are actually burning.
Monsoon Moisture Surge from Thursday to Saturday
For as dry as a summer as we have had so far, we are finally going to see a chance for some meaningful rainfall.
A trough of low pressure will move across the Northern Rockies on Thursday, and increasing southwest flow on the southern end of the trough will help to draw in a more significant surge of monsoonal moisture into our area.
The result will be a chance for more numerous thunderstorms along with a greater potential for heavy downpours and meaningful rainfall amounts, as opposed to the “dry” thunderstorms we have seen lately that have only produced light and spotty rain.
The uptick in moisture could also fuel stronger storms, which have the potential to produce frequent lightning.
Grand Teton climbers will want to be extra alert during this pattern, as there will be at least a slight risk of early morning showers or thunderstorms on Thursday and Friday due to upper atmospheric disturbances expected to pass through the area.
Thursday and Friday both look like active days, with the highest chance of thunderstorms during the late afternoon and evening hours on Thursday, and during the early afternoon hours on Friday – though a storm couldn’t be ruled out at any time of day.
On Friday night and early Saturday morning, we should see a brief lull in between systems, then another low pressure trough will approach during the day on Saturday with thunderstorms likely in the afternoon and evening hours.
As for rainfall amounts, there will be some wide variations given the hit-or-miss nature of thunderstorms, even with more widespread activity expected.
Most areas in the Greater Teton-Jackson Hole region should pick up anywhere from 0.25 to 0.75 inches of rain from Thursday to Saturday, but locally higher amounts of well over an inch are possible in areas that see stronger and/or more frequent storms.
Here is a weekly rainfall projection representing the average of 50 simulations of the European weather model. Most of this rainfall is expected to fall prior to Sunday.
During this wetter pattern, we will also see cooler daytime temperatures with highs in the low 80s on Thursday and Friday, and mid to upper 70s on Saturday. Morning temperatures will be milder in the valleys given the uptick in moisture and cloud cover, with lows in the 50s expected on Thursday and Friday mornings.
Significant Drying Trend Expected Next Week
This monsoon pattern will not stick around for long, especially compared to what we have seen in recent summers.
In the wake of Saturday’s system, much drier air will move in from the west and monsoonal moisture will become shunted well to the south to near the Mexico border.
Initially, we may hang onto enough lingering moisture on Sunday for at least a chance of early to mid-afternoon thunderstorms – but these storms will likely be more isolated in nature compared to prior days.
Starting Monday and continuing through most of next week, we will head into a much drier pattern with thunderstorm chances near zero.
Temperatures will also warm up and relative humidity levels will drop over the course of the week, which may lead to an uptick in fire danger over time.
Alan Smith, Meteorologist
