JACKSON, Wyo. — A prolonged stretch of dry weather has taken hold across Jackson Hole recently. Over the past 10 days, we’ve seen only one brief stretch of snowfall on the night of November 30/morning of December 1 that produced 7 inches of snow at Jackson Hole Mountain Resort and 1.4 inches of snow in the Town of Jackson.
Snowpack is now below average thanks to the recent dry spell. At Jackson Hole Mountain Resort’s Rendezvous Bowl Plot (elevation 9,580 feet), the snow depth reported on December 7 was 35 inches, which is about 83% of average (the average snow depth for the date is 42 inches).
The culprit for our dry spell has been a blocking ridge of high pressure over Western North America that has acted as a barrier for any storms to approach from the Pacific. Jackson Hole is not the only place that has been dry recently – it’s been the entire Western U.S.
The stable atmosphere (associated with high pressure) combined with the weak December sun along with widespread snow cover have resulted in temperature inversions that have remained in place even during the afternoons, with dense cold air settled in the valley and warmer temperatures aloft in the mountains.
Here’s an example of how this inversion has looked: At the Moran weather station in the Jackson Hole Valley at an elevation of 6,800 feet, the average high and low over the past four days has been 26.5 and -0.5. At the Raymer Plot at an elevation of 9,300 feet at Jackson Hole Mountain Resort, the average high and low over the past four days has been 40 and 27.
Here is a good visual of the temperature inversion at 7 a.m. last Saturday morning (courtesy of opensnow.com) when temperatures in the valleys were near zero and temperatures in the surrounding mountains were in the 20s.
While it’s been dry lately, confidence is increasing that we will see a return to more active weather with improving snow chances – but the change will happen slowly at first.
Weather Outlook: December 7 – December 13
Sunny and dry weather will continue through Wednesday. On Thursday, a weak disturbance will arrive but little if any snowfall is expected at this point with a cool-down in the mountains (i.e. the temperature inversion erodes) being the most noticeable trend.
From Friday through Sunday, another weak disturbance or two will be possible with light snow falling at times. Models are in poor agreement on how the pattern will play out during this period, with the overall theme being that “some” snow is likely, but amounts will probably be on the lighter end.
The image below shows the projected precipitation anomalies over the next seven days, with below-average precipitation still expected in Jackson Hole and most of the Western U.S. through December 13.
Weather Outlook: December 14 – December 20
The good news for skiers and snow sports enthusiasts is that the Week 2 pattern is looking much more conducive to snowfall in Jackson Hole. The average storm track and jet stream position will be shifting farther south during this time, opening the door to more frequent storms from the Pacific.
Some models are already projecting a decent storm next Monday (December 14) and we should see additional snow opportunities next week as well.
The image below shows the projected precipitation anomalies from Days 7-14, with above-average precipitation expected in Jackson Hole and across the Northwest U.S.
Bottom line: Yes, December is off to a paltry start for snow lovers and we’ll only see subtle improvement over the next seven days, but as we head into the second half of December, confidence is increasing that the pattern will become more favorable for snow.
Alan Smith, Meteorologist
