Mild, sunny weather coming to an end as a cool and wet pattern emerges

JACKSON, Wyo. — Tuesday will be our last nice day before a significant pattern change occurs during the second half of the week. Skies will be mostly sunny to partly cloudy through Tuesday afternoon with highs reaching the low 70s in the valley. This will likely be the last 70-degree day in Jackson until next spring.

Let’s dive into the details…

Tuesday Night through Wednesday Night

On Tuesday night, a weak storm system will approach from the southwest with scattered showers developing after midnight and continuing through the early morning hours on Wednesday.

Scattered showers can then be expected at times throughout the day on Wednesday, and thunderstorms are also possible since the atmosphere will be unstable. Temperatures will be cooler with highs in the low to mid 60s in the valley, but snow levels will be rather high, ranging from 10,500-11,500 feet.

Thursday Morning through Friday Evening

There won’t be much of a break behind Wednesday’s system with isolated showers remaining possible through Wednesday night, and more widespread showers developing on Thursday as the next system arrives. A few embedded thunderstorms are possible as well.

Temperatures will continue to trend cooler on Thursday with highs in the upper 50s in the valley, and snow levels will range from 9,500-10,500 feet.

Periods of rain will continue through Friday as the main part of the system approaches with some of the heaviest rainfall rates expected on Friday evening/Friday night as a cold front arrives.

Ahead of the cold front, snow levels will range from 9,000-10,000 feet during the day on Friday with highs in the mid 50s in the valley.

Friday Night through Saturday Afternoon

Behind the cold front on Friday night, snow levels will fall to 7,500 feet overnight and into Saturday morning.

As a result, drivers over Teton Pass and even up in Yellowstone could encounter snow on Saturday morning, though travel impacts are likely to be minimal. Roads could become snow-packed or icy over Togwotee Pass, however, since it sits at a higher elevation.

Showers will become more terrain-driven on the backside of the system on Saturday as winds transition from southwest (in the days prior) to west/northwest behind the cold front. Rain and snow showers will continue over the Tetons and surrounding through the day on Saturday with lighter and more intermittent rain showers over the valley.

This wet pattern from Wednesday through Saturday will impact all of Northwest Wyoming along and west of the Continental Divide (including the Wind River Range, Salt River Range, Yellowstone, etc.) with drier conditions east of the Divide.

Total liquid precipitation amounts with this system from Wednesday through Saturday will range from 1.5-2.5 inches over the Tetons and higher elevations of Western Wyoming and 0.75-1.5 inches over the Jackson Hole Valley and Star Valley.

5-Day Temperature and Precipitation Outlook for Teton County from Tuesday through Saturday

Extended Range Outlook

We should see a lull in the action on Saturday night and Sunday with dry conditions and intermittent sunshine during the day on Sunday. Temperatures will remain chilly, however, with highs only in the low 50s in the valley.

This break looks to be short-lived, however. As we head into next week, there is high confidence that we will see below-average temperatures and wetter than average conditions. NOAA’s 6-10 Day Outlook highlights this pattern well…

The next storm system will approach early next week, around the Monday/Tuesday timeframe (October 11-12). This system could be on the stronger side, but where the center of low pressure sets up and the ensuing movement and wind patterns will determine the impacts for Jackson Hole.

This system could influence our weather to some extent for most of next week, and this includes the potential for a significant cool-down around the middle of next week that could result in snow levels falling to the valley floor.

Given the upcoming pattern change over the next two weeks, if you have time for one more mountain bike ride or one last float trip on Tuesday afternoon, then do so while you can!

Alan Smith, Meteorologist