A cold storm system impacted Western Wyoming at the end of last week, bringing the first significant snowfall to the higher elevations. The Grand Targhee Snotel recorded 9″ of snow on Friday, and it’s likely that areas above 10,000 feet received even more.

So far, this has been a much wetter than average (and also cooler than average) September. We are now enjoying a nice break in the pattern before another stretch of cold, wet, and snowy weather arrives this weekend.

Today (Monday), we are in between weather features with the polar jet stream located up in Canada, and a trough of low pressure located farther south in Arizona. The latter is resulting in heavy rainfall and even severe thunderstorms in Arizona today.

Jet stream level winds as of Monday afternoon (source: College of DuPage)

Mostly sunny and dry weather through Thursday

The jet stream will remain north of Jackson Hole through midweek, resulting in very pleasant conditions. Temperatures will be chilly in the mornings and warm in the afternoons with highs in the mid 60s to near 70 each day through Thursday.

We will be close enough to the southern fringe of the jet stream to result in some breezy winds each day. This is especially true across the higher elevations.

Speaking of higher elevations, we still have pretty good snow cover above 9,500 feet. See the webcam images from the top of Grand Targhee and from Driggs, ID looking at the west side of the Tetons this afternoon.

Top of Grand Targhee, Monday September 23
View of the Tetons from the west side, Monday afternoon September 23

There should be good snow melt up high throughout the week, though some of the higher peaks and even some of the higher passes will likely hang onto some snow and ice before our next system arrives.

Cold, wet, and snowy pattern arrives this weekend

A slow-moving trough of low pressure is projected to bring significant precipitation and well-below average temperatures this weekend.

Thursday night, an initial upper level disturbance will arrive, resulting in some scattered rain showers late Thursday night and also on Friday. This is not expected to be a significant event, but will be a sign of things to come.

High temperatures will also be about 10 degrees cooler on Friday with valley highs only in the mid to upper 50s.

Saturday through Monday looks the wettest period of weather as a deep trough of low pressure impacts the region.

GFS Model projected 500-millibar height anomalies for Saturday evening show the position of the low pressure system that will impact Jackson Hole

Although we are still 5-7 days out, it appears that we could see significant precipitation out of this event. This includes the potential for significant high elevation snow.

On Sunday and Monday, colder air arrive with high temperatures likely remaining in the 40s in the valley. It’s also very possible we could see snow levels drop to the valley floor at times as the colder air settles in.

Again, this system is still the better part of a week out so the details are sure to change. However, a cold and wet weekend looks like a good bet for Jackson Hole and Yellowstone from Saturday through Monday.

Long Range Outlook – October 1 and Beyond

Looking ahead to next week – we should see lingering precipitation chances and well below average temperatures through about Tuesday October 1st.

Beyond Tuesday, the long range models are trending toward drier conditions through the latter part of the work week. Temperatures will likely start out well below average as conditions first clear out, before a gradual warming trend ensues.

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