JACKSON, Wyo. – The Tetons have picked up some snow over the past week, with the most recent storm producing 10-20 inches above 8,000 ft. A warm-up will occur Thursday-Saturday and the next storm on Saturday will bring a rain/snow mix to the valley with wet snow up high.
Recent Weather and Snowfall
Two storms during the past week have helped to boost the early season snowpack in the Tetons in what has been a slow start to the season so far.
The first storm last Friday produced only 2-5 inches on the east side of the Tetons including Jackson Hole Mountain Resort, while the town of Jackson received a dusting. Snowfall was heavier on the west side with Targhee picking up 7-10 inches and Driggs 5 inches.
A stronger storm impacted the area from Sunday night through Tuesday morning, bringing heavier and more widespread snowfall with totals ranging from 10-20 inches in the Tetons and 2-6 inches in the valleys. This was the biggest storm of the season so far.
During the storm on Monday, a narrow band of locally heavy snowfall rates set up over Teton Pass and stretched into the town of Jackson for a few hours during the late afternoon. This allowed snow to quickly accumulate in town, while whiteout conditions on Teton Pass forced a temporary road closure.
A cold front had moved through earlier in the day on Monday, and behind the front, the atmosphere became very unstable due to steep lapse rates – meaning the rate of temperature decrease with altitude was greater than usual. This likely contributed to the heavy snowfall bands developing.
Snowfall became more orographic (i.e. terrain-enhanced) in nature on Monday night and Tuesday morning, favoring Grand Targhee and the west side of the range.
Storm total snowfall ranged from 10-20 inches in the Tetons above 8,000 feet, and this includes 19 inches at Grand Targhee and 13 inches at Jackson Hole Mountain Resort’s upper mountain. Snow quality was also dry and powdery due to the cold air that arrived with this storm.
The town of Jackson picked up 3.6 inches of snow, with other valley totals including 4.2 inches in Wilson, 4.7 inches in Alpine, and 1.9 inches in Driggs.
Snowpack has improved since the recent storm cycle, but is still only 65% of average for the date across the Upper Snake River Basin, which includes the Tetons, Gros Ventres, and surrounding ranges.
Snowpack is higher on the west side of the Tetons compared to the east side right now. Snow depths as of November 20 include 13 inches at Jackson Hole’s mid-mountain and 18-22 inches at Jackson Hole’s upper mountain, while Grand Targhee has a snow depth of 37 inches.
Targhee opens for the season on Friday, so the storm earlier this week came at a good time to deepen their early-season snowpack.
Upcoming Weather Pattern
An unsettled pattern will continue late this week and into next week, but there will be temperature fluctuations and storm uncertainties to deal with.
Wednesday has been a cold day with morning lows starting out near zero in town, while highs so far have been in the mid 20s (as of mid-afternoon).
A warm-up will occur from Thursday to Saturday as a ridge of high pressure builds in from the south. However, a plume of subtropical moisture will pass just north of our area on Thursday and we could see enough moisture reach our area on the southern fringe of this system for light showers to develop.
Snow levels will start out on the valley floor on Thursday morning, but will rise to 7,000 feet on Thursday afternoon and evening, meaning that any precipitation will change over to rain in the valley with wet/dense snow quality up high.
A break in the pattern is expected on Friday with temperatures continuing to trend warmer, then the next storm will arrive on Saturday. This storm will start warm with rain possible in the valleys but a cold front will move through later in the day.
A changeover to snow is possible in the valleys as the front moves through, but there is uncertainty in terms of how much moisture will trail the front and whether or not it dries out quickly once the colder air arrives.
Colder temperatures will return from Sunday into Thanksgiving Week, and the potential exists for more snow events. However, there is low confidence in terms of specific storms and timing.
For example, some weather models are projecting a storm to move in on Monday-Tuesday, while other models are keeping the storm too far south for us to see anything more than flurries. Snow is also possible around the middle of next week, but confidence is low.
Here is a 7-day snowfall projection representing the average of 50 simulations of the European weather model.
The Thanksgiving holiday period has a similar “unsettled but uncertain” outlook, though cold (below average) temperatures appear likely at this time. Chances are, we will see at least some snow around Thanksgiving, but the timing, strength, and frequency of individual storms are highly uncertain.
Alan Smith, Meteorologist
