The weather over the past week in Jackson Hole featured the first stretch of cool and wet weather this fall, followed by a beautiful and warm weekend.

Last week started out mostly cloudy and chilly with highs only in the 50s in the valley on Tuesday and Wednesday. A total of 0.52″ of rain fell on Tuesday and Wednesday, before drier conditions arrived Thursday.

Over the weekend, we temperatures in the Jackson Hole Valley warmed up quite a bit with a high of 82 on Sunday. It was a beautiful weekend to get outdoors.

For the upcoming week, we’re going to see a return to cooler and unsettled weather. Another reminder that the seasons are changing!

Take a look at the temperatures and rainfall recorded in Jackson over the past 7 days. Quite the roller coaster:

Sept 964450.09″
Sept 1059420.22″
Sept 11 52440.30″
Sept 12 63360.01″
Sept 1370300.00″
Sept 1477370.00″
Sept 1582330.00″

Warm with isolated thunderstorms on Monday afternoon

We are already starting to see changes to the weather pattern today (Monday). Currently, there is a trough of low pressure moving across the Northwest U.S., with scattered clouds and gusty winds spreading into NW Wyoming this afternoon (image source: College of DuPage).

500 millibar heights and winds showing the trough of low pressure over the Pacific Northwest at noon MST on Monday September 16

The atmosphere has become unstable across the Tetons ahead of this trough. As a result, scattered thunderstorms have developed across the Tetons and Yellowstone as of 2:30pm Monday.

Additional thunderstorms will be possible through early evening. Heads up if you have any after work hikes or mountain bike rides planned for this afternoon.

Radar image at 2:28pm Monday shows thunderstorms across Jackson Hole and the Tetons

Cold front arrives Tuesday morning with rain showers developing

The trough of low pressure will sweep across NW Wyoming tonight and Tuesday, and cold front associated with trough will arrive Tuesday morning. As a result, we can expect a wet day with much cooler temperatures across the Tetons and Yellowstone.

700-millibar relative humidity (about 10,000ft elevation) projected for 6am Tuesday morning (source: Colorado Avalanche Information Center)

Rain showers will arrive a couple of hours before sunrise Tuesday ahead of the approaching cold front. Look for the most widespread showers to occur through early afternoon, before clearing out late in the day.

Temperatures are going to be much colder on Tuesday behind this cold front with highs only in the low 50s in the Jackson Hole Valley.

As the precipitation arrives, snow levels will fall to as low as 7,500′ Tuesday morning. Light snow accumulations can be expected above these elevations, but this isn’t expected to be a heavy event.

A break in the pattern on Wednesday

Jackson Hole will be in between systems on Wednesday, so look for dry conditions, warmer temperatures, and more sunshine. Highs are expected to peak in the upper 60s in the Jackson Hole valley.

Any remaining high elevation snow cover should quickly melt off Wednesday afternoon. Overall, this looks like a good day to get outside.

Cold system with more significant precipitation arrives late this week

A more powerful trough of low pressure will arrive late this week, bringing valley rain and high elevation snow from roughly Thursday night through Saturday morning (image source:

GFS Model projected upper level trough position for 6am Friday

Thursday will initially start out dry, but a cold front will arrive in the afternoon with high temperatures about 5-10 degrees cooler than Wednesday (upper 50s/low 60s in the valley).

For outdoor activities, Thursday morning looks like the best time to get out ahead of the front. On Thursday afternoon, scattered showers and thunderstorms will develop as the cold front moves through.

More widespread precipitation will then develop Thursday night with periods of rain (and high elevation snow) expected throughout the day Friday.

Temperatures will be even colder with this system than Tuesday’s system. As a result, we could see snow levels drop down to 7,000 feet or lower at times. At the higher elevations, we could easily see some 6″+ snowfall totals from this system.

Cool and unsettled weekend expected

Model discrepancies arise over the weekend with regards to when the late week system exits and when the next system arrives.

The American GFS Model points toward precipitation ending late Friday night, while the European Model keeps moisture around through Saturday afternoon.

The best way to look at this for now is to expect rain/snow chances to linger through Saturday morning with decreasing chances of precipitation by Saturday afternoon. Mostly cloudy skies and chilly temperatures are likely to persist, though.

On Sunday, we should start out dry with perhaps some sunny skies. However, the next storm system will be approaching from the northwest late Sunday.

As a result, we could see rain chances return as early as late Sunday afternoon or early evening. This is a ways out, though, so keep an eye on the forecast for inevitable changes to timing.

Long Range Outlook – September 23 and Beyond

An active pattern with colder than normal temperatures is expected to continue next week, along with frequent precipitation chances. I’m not seeing any signs of nice “Indian summer” weather.

It’s looking like we are going to end up with well above normal precipitation for September this year. Unfortunately for mountaineers and high elevation hikers, the pattern could become quite snowy across the higher terrain.

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