JACKSON, Wyo. — October has been unseasonably mild so far and we will see a continuation of dry and sunny weather over the next several days. However, big changes are coming this weekend as an abrupt pattern transition occurs with much colder temperatures along with our first significant snowfall of the season.
October 11-17 Recap
High pressure dominated the weather pattern over the previous week with dry and sunny conditions along with above-average temperatures. It’s been a beautiful fall season for an extension of summertime outdoor recreation.
High temperatures over the past week ranged from 63ºF on October 11 to 71ºF on October 17, while low temperatures ranged from 20ºF on October 16 to 30ºF on October 12.
Last week’s high temperatures were about 10 degrees above average for mid-October, but nights were cold with lows close to average due to clear, calm conditions along with lessening daylight hours at this time of year.
No precipitation was recorded in Jackson Hole last week and we have now gone more than two weeks without any precipitation.
Forecast for Tuesday (10/18) to Monday (10/24)
Mild and dry conditions will continue from Tuesday through Friday with above-average high temperatures and chilly mornings. Highs on Tuesday and Wednesday should top out around 70ºF in the valley, and these will almost certainly be the last 70ºF days we see until next spring.
A weak cold front will sneak in on Thursday, resulting in slightly cooler daytime temperatures with highs in the upper 60s. Winds will become gusty on Friday under partly cloudy skies in advance of an approaching storm system that will signal a major pattern change.
The storm will drop in from the Gulf of Alaska sometime on Saturday, resulting in rain, snow and much colder temperatures across the area. Colder air will filter in as the day progresses with gradually lowering snow levels, while heavy snowfall will be possible across the mid to high elevations of the Tetons.
On Saturday night, snow levels will likely drop to the valley floor for the first time this season, and depending on the timing of the colder air with the lingering precipitation, slushy accumulations will be possible in the valley, including the Town of Jackson.
Travel conditions could begin to deteriorate over Teton Pass as early as Saturday afternoon and evening, with further worsening of conditions expected heading into Sunday morning as cold air settles into place, which will likely result in icing on the roadways. This is something to keep in mind if you haven’t switched over to winter tires yet.
Cold and unsettled conditions will continue on the backside of the storm system on Sunday with additional snow showers possible, especially over the higher elevations. Highs on Sunday will struggle to get out of the 30s in the valley.
Another storm system is possible early next week, potentially arriving as early as Monday. Below-average temperatures will persist into Monday as well, with additional snow possible down to the valley floor.
Extended Outlook
Next week is looking unsettled and very chilly as a colder-than-average airmass is expected to remain in place through about the end of October. Additional storm systems will be possible as well, which could produce additional snowfall in the Tetons along with a mix of snow and rain in the valley.
In other words, winter is coming…
Alan Smith, Meteorologist
Town of Jackson Climatology for October 18-24:
Average High: 56
Average Low: 22
Record High: 76 (October 20, 1921)
Record Low: 1 (October 23, 1935)
Precipitation Since Oct 1st: 0.32″ (40% of average)
