JACKSON, Wyo. – Hopefully you’ve been able to get out and enjoy the beautiful weather on Thursday, because big changes are on the way for the holiday weekend. A slow-moving trough of low pressure arriving from the Pacific will result in significant rainfall this weekend along with colder temperatures and a transition to snow across the higher elevations.
Ahead of this storm, Jackson enjoyed a summer-like day on Thursday with a high of 79ºF recorded in the Town of Jackson – the warmest temperature of the year so far. However, as is often the case at this time of the year, don’t get used to it just yet.
As the low pressure system approaches late this week, the weather will begin to change on Thursday night and Friday with scattered showers and thunderstorms developing. Rainfall will not be widespread during the day on Friday and showers should be brief in duration, but instability in the atmosphere will result in an elevated thunderstorm threat with dangerous cloud-to-ground lightning possible.
The highest threat for thunderstorms will be on Friday afternoon, but lightning couldn’t be ruled out on Friday morning either.
Temperatures will remain on the milder side on Friday with morning lows in the upper 40s in the valley under increased cloud cover and afternoon highs in the upper 60s to low 70s.
Late Friday night and Saturday is when the most widespread rainfall is expected across the Tetons and Jackson Hole as the low pressure system advances into the intermountain west and moisture increases from the southwest. Significant rainfall is expected throughout the day on Saturday with thunderstorms also possible in the afternoon.
Temperatures will be much cooler on Saturday with highs in the mid 50s in the valley, but snow levels will be relatively high in the 9,000-10,000 foot range.
On Sunday and Monday, colder air will arrive but precipitation will be lighter and less widespread compared to Saturday, at least across the Tetons and Jackson Hole. Yellowstone, on the other hand, will see more precipitation on Sunday and Monday compared to Jackson Hole as the focus of moisture shifts northward toward the Montana border.
Snow levels will lower to approximately 7,500-8,500 feet on Sunday and 6,500-7,500 feet on Monday with an early projection of 3-6 inches of snow for the Tetons between 8,000-10,000 feet as well as a large portion of Yellowstone National Park. The Jackson Hole Valley could potentially see some snow mix in on Monday, though accumulations are unlikely.
Highs in the Jackson Hole Valley will only reach the upper 40s to low 50s on Sunday and Monday with lows in the 30s.
As snow levels decrease in elevation, snowy conditions can be expected at times across Teton Pass, Togwotee Pass, and Yellowstone, with road closures a possibility for higher elevations of Yellowstone.
Snowfall amounts will be even heavier across the Beartooth, Absaroka, and Wind River Ranges where 6-12 inches of new snow is possible. These areas will be favored due to higher average elevations as well as northeast upslope winds along the eastern slopes of the Continental Divide late in the weekend that will enhance snowfall rates.
Liquid-equivalent precipitation amounts through Monday are generally expected to range from 1.5-2.5 inches for the Tetons above 8,000 feet as well as Yellowstone, while the Jackson Hole Valley will pick up 0.5-1.5 inches of rainfall.
Once the holiday weekend is over, we should gradually transition out of the cool and wet pattern. Tuesday will remain chilly and unsettled with highs only projected to reach the 50s along with a chance of light showers.
Warmer and drier conditions are expected over the second half of next week with highs ranging from the low 60s to low 70s, though an afternoon shower or thunderstorm couldn’t be ruled out on any given day.
By the weekend of June 4-5, the pattern could turn a bit more unsettled with slightly cooler temperatures and daily chances of showers and thunderstorms.
Alan Smith, Meteorologist
