JACKSON, Wyo. – A powerful low pressure system will impact the Tetons on Wednesday-Thursday, bringing heavy snow to the Tetons along with much colder air on Thursday and Friday. Significant travel impacts are expected over Teton Pass from Wednesday night through Friday morning.
Recent Weather Pattern
We have had the full spring variety of weather in Jackson Hole over the past week.
From last Wednesday to Friday, warm and dry conditions prevailed, and many folks were out on the trails, which had melted out and dried out much earlier than usual this year.
However, the pattern began to change on Saturday as a low pressure system approached our area.
Showers and thunderstorms developed on Saturday afternoon, including a round of strong thunderstorms that produced frequent lightning and small hail across the area. Lightning danger also forced the ski lifts to close at Jackson Hole Mountain Resort and Grand Targhee.
Showers continued across the area on Sunday and Monday, and snow levels gradually lowered as colder air arrived. On Monday, snow fell on the valley floor with a few heavier bursts moving through.
Total snowfall accumulations since Saturday have ranged from 6-12 inches in the Tetons above 8,000 feet, not factoring in melting/compaction in between snowfall events.
A heavy snow shower in the town of Jackson on Monday morning produced 1.7 inches of snow in less than an hour, and this snow proceeded to melt quickly once the snow shower ended. Jackson then picked up another 0.7 inches of snowfall on Monday night, for a 24-hour total of 2.4 inches.
Jackson has already received more snowfall in April than it did in all of March, and most locations in the Tetons have matched their March snowfall totals in the first two weeks of April, with half of the month still to go.
Below is a 7-day weather summary for the town of Jackson.
For perspective, the average high and low in Jackson on April 15 are 51º and 27º.
Upcoming Weather Pattern
A significant late-season winter storm will impact Teton County on Wednesday and Thursday, with impacts lingering into Friday as well.
Big picture, a deep trough of low pressure will approach our area from the northwest and will move across the area on Thursday. Significant moisture and upper atmospheric dynamics will accompany this trough, along with a strong cold front on Thursday morning.
Off-and-on showers during the day on Wednesday will gradually pick up in coverage and intensity on Wednesday night with periods of heavy snow in the Tetons. Strong southwest winds can also be expected through Wednesday night.
Snow levels (the rain/snow line) will range from 7,000 to 8,000 feet through most of Wednesday night, meaning rain will fall across the lower elevations.
A cold front will move through early on Thursday morning, likely around sunrise, with rain changing over to snow in the valley behind the front.
Off-and-on snow will continue throughout the day on Thursday with valley temperatures starting out in the mid 30s and eventually falling below freezing by late in the day. It will be a cold, blustery day, though snow will struggle to accumulate in the valley given the high mid-April solar angle.
Snow showers will continue through Thursday night, but will be more terrain-driven by this point with fewer/lighter snow showers in the valley. However, once the sun goes down and temperatures drop, the valleys could still pick up some light accumulations overnight.
Significant snowfall accumulations are expected to add up in the Tetons, with 10+ inch snow totals possible above 8,000 feet. Grand Targhee is still open this week and is likely looking at some late-season powder on Thursday and Friday.
This storm will lead to significant travel impacts over Teton Pass. Starting on Wednesday evening, snow will begin to accumulate on road surfaces near the top of the pass, and on Thursday morning, road conditions will continue to deteriorate as temperatures drop and snow continues to fall. Gusty winds could also lead to areas of blowing snow and low visibility.
From Thursday evening to Friday morning, icing on the roads will become a significant concern as temperatures fall into the teens and wet/slushy areas on pavement freeze up.
On Friday, we will likely see some early day breaks with the sun possibly peaking out, but temperatures will remain very chilly with valley highs only in the 30s.
On Friday afternoon, a trailing upper-level wave combined with an unstable atmosphere will lead to more snow showers developing with additional light accumulations possible, especially at mid to high elevations.
Over the weekend and into early next week, spring will return as a ridge of high pressure builds over the area. Saturday will be a transition day with a cold start to the morning (lows in the teens), followed by warmer afternoon temperatures, topping out near 50 in the valley under mostly sunny skies.
A more significant warm-up is then expected from Sunday to Tuesday with highs in the 60s.
Looking further out, cooler and more unsettled weather looks to return during the second half of next week (April 22-26) as another low-pressure trough approaches from the west.
The higher elevations will likely pick up some more snow around this time, while the valley could see both rain and snow depending on temperatures and snow levels.
Keep in mind that as we head later into April, snow tends to struggle to accumulate in the valleys, and if it does accumulate, it usually doesn’t stick around for long.
Alan Smith, Meteorologist
