JACKSON, Wyo. – Following a week of mild weather, a storm will move through the area on Friday, with rain changing to snow on Teton Pass while areas below about 7,500 feet will remain all-rain.
Recent Weather Pattern
Over the past week, we have enjoyed another stretch of beautiful fall weather in the wake of a storm system that brought significant precipitation from October 10-13.
From October 14 to 21, the pattern has mostly been dry and sunny with cold mornings in the valley and sunny and pleasant afternoons. On most days, lows have been dipping into the low 20s, but afternoon highs have been rebounding well into the 60s.
The pattern has turned slightly unsettled for the middle part of this week in response to a low-pressure system that has stalled off the coast of California.
Ahead of this low, we have seen just a few pulses of moisture and energy arrive, resulting in brief rounds of showers on Tuesday and Wednesday mornings. A few showers have also developed across the area on Wednesday afternoon, mainly over the Tetons and in Teton Valley.
Snow levels (the rain/snow line) have been high on Tuesday and Wednesday, around 11,000 feet.
Here is the 7-day weather summary for the town of Jackson:
For perspective, the average high and low temperatures in Jackson on October 21 are 55º and 25º.
Upcoming Weather Pattern
The low-pressure system located just off the California coast will move inland late this week, bringing widespread precipitation to our area from Thursday night to Friday night.
Snow levels will start out around 10,000 to 11,000 feet initially on Thursday night, but a cold front will arrive in the predawn hours, with snow levels gradually dropping for the remainder of the event.
By first thing on Friday morning, snow levels will dip to 8,500 to 9,000 feet, and by mid-morning, we could see wet snow or a rain/snow mix develop near the top of Teton Pass.
As the day progresses, snow levels will continue to gradually lower, with snow likely over Teton Pass during the afternoon and evening hours. By the time the storm comes to an end on Friday night, snow levels are projected to dip to around 7,500 feet.
Temperatures may be warm enough to avoid significant winter travel impacts over Teton Pass, but some slushy accumulations on pavement still couldn’t be ruled out, especially if snowfall rates become heavy enough, so be prepared for a possible slow PM commute, especially since not everyone has winter tires on their vehicles yet at this time of year.
Light snow accumulations on grassy surfaces can be expected in the 7,500 to 8,500 foot range, while several inches (or more) is possible above 8,500 feet, which includes most of Grand Targhee and the upper half of Jackson Hole Mountain Resort.
In the Jackson Hole Valley, rain totals are projected to range from a quarter-inch to a half-inch, while rain totals in Teton Valley may be a bit higher since they’ll be closer to the center of low pressure that tracks across Eastern Idaho.
Ahead of the system on Thursday, highs will reach the 60s in the valley again though a few late-day showers couldn’t be ruled out. Friday will be much colder with highs only in the 40s in the valley, and the wet conditions will add to the chill factor.
Over the weekend, conditions will dry out with decreasing clouds and highs in the 50s on Saturday and Sunday.
Heading into next week, the pattern turns uncertain, but we will at least be in play for some more moisture as additional storm systems reach the Western U.S.
Early in the week, a storm is projected to move into the Pacific Northwest, but it’s unclear whether or not this system will impact our area. At the very least, there is a chance of raim/snow showers, but it’s also possible we miss out on this.
The 7-day precipitation projection from the European Ensemble Model represents the average of 50 simulations of this model. While we will get some moisture with this system on Friday, notice how wet the Southwest will be, as this area will be taking the brunt of this storm.
Heading into the final few days of October later next week, and into the beginning of November, the pattern remains uncertain.
Big picture, confidence is growing that a strong subtropical jet stream will set up across the southern tier of the U.S., and this will support a storm track that favors the Southwest and Southern Rockies.
We may catch some action on the northern fringe of this favored storm track from time to time, and that could mean snow for the mountains, and maybe even a shot at our first snow in the valley. But the details are uncertain with this being more than a week out.
For what it’s worth, NOAA’s 8-14 Day Outlook favors above-normal precipitation across Western Wyoming and Eastern Idaho and near-normal temperatures.
Alan Smith, Meteorologist
