JACKSON, Wyo. – A weak storm brought snow to the area on Sunday-Monday, but overall it has been a very quiet start to December. A stronger storm will arrive this weekend, however, with moderate to heavy snow possible.
Recent Weather Conditions
We’ve had one storm in the first 10 days of December. It was a weaker storm that produced snow showers last Sunday and Monday (December 8-9) with highly variable snowfall totals.
Snowfall in the Tetons ranged from 3 to 10 inches, with the Rendezvous Bowl Plot at 9,580 feet at Jackson Hole Mountain Resort receiving 10 inches over 2 days. Snowfall in the valleys ranged from a trace to 2 inches, with the town of Jackson picking up 0.9 inches.
Temperatures so far in December have been slightly above average. Highs have generally been in the 20s and the 30s and lows in the single digits in the valley, but we have not had any significant cold snaps yet.
Snowpack in the Tetons and Upper Snake River Basin is only 51% of average, and among the lightest we have ever seen on this date in the past 45 years.
Current snow depths in the Tetons (i.e. the height of the snowpack) range from 23 to 32 inches above 9,000 feet and 15 to 19 inches at 8,000 feet.
Upcoming Weather Pattern
From Wednesday to Friday, we will see mostly cloudy skies and seasonally cool temperatures, but otherwise, the weather pattern will remain quiet. Friday will be a little more unsettled as a weak disturbance moves through with heavier cloud cover and flurries possible, but meaningful accumulations are not expected.
A stronger storm will move through over the weekend with moderate to heavy snowfall possible.
Snow could begin as early as Saturday afternoon, but most of the snowfall is expected to occur from Saturday night through the daytime period on Sunday, with lighter lingering snow showers on Sunday night.
This storm will arrive with southwest winds, with Pacific moisture streaming from southwest to northeast through the Sierra Nevada Range before reaching the Tetons. This is often a favorable trajectory for significant snowfall.
Temperatures will start out warm during this storm on Saturday evening and will gradually trend colder over time through Sunday. Snowfall on Saturday night will likely be wet/dense but should trend drier and more powdery on Sunday.
There are some model differences in the extent of the warmth on Saturday. If any of the warmer model solutions come to fruition, then rain couldn’t be ruled out in the valley on Saturday night. But the majority of models keep temperatures cold enough for all snow at this time.
Travel impacts will be highest from Saturday night through Sunday night, and once colder air arrives, icing on the roads will also be possible from Sunday night into Monday morning.
Following a lull in the pattern on Monday, a weaker storm is possible next Tuesday which could bring another shot of snow. Confidence is low, however, as not all weather models are on board with this yet.
The snowfall projection for the next 7 days represents the average of 50 simulations of the European weather model:
Looking further out, a ridge of high pressure is projected to build over the Western U.S. after December 17, with a trend toward drier conditions heading into the weekend of December 21-22 and possibly lasting through Christmas.
Temperatures will also warm up in this pattern, at least in the mountains, while inversions could lead to colder temperatures in the Jackson Hole Valley.
Storms are projected to pass over the northern periphery of the high pressure ridge into British Columbia in this pattern, and it’s possible we could see an occasional storm pass far enough south to bring us a chance of snow.
But overall, the pattern doesn’t look favorable for significant snow from about December 18 to 25.
Alan Smith, Meteorologist
