JACKSON, Wyo. – A storm on Tuesday produced 7-12 inches of snow in the Tetons and 3-7 inches in the valley. However, a ridge of high pressure is set to take hold over the Western U.S., resulting in a dry spell that will persist through at least early December.
Recent Weather Conditions
On Tuesday, a storm moved through the Central Rockies, bringing heavy snow to Utah and Colorado, but the Tetons also managed to pick up solid snowfall totals on the northern fringe of the storm.
Jackson Hole Mountain Resort picked up 10-12 inches of snow at its mid to upper mountain plots and Grand Targhee 8 inches.
The Jackson Hole Valley received 3-7 inches of new snow, including 6.5 inches in Wilson and 3.2 inches in Jackson.
Current snow depths include 35 inches at Grand Targhee and 28 inches at Jackson Hole Mountain Resort’s upper mountain. Snowmaking has been in full swing on Jackson Hole’s lower mountain ahead of their opening day this Friday.
In terms of snow water equivalent, snowpack is currently 71% of average in the Upper Snake River Basin which includes the Tetons and Gros Ventres.
Upcoming Weather Pattern
A ridge of high pressure will develop over the Western U.S. over the Thanksgiving holiday weekend and is expected to hold through early to mid-December with limited snowfall potential (perhaps a weak storm sneaking in every so often).
The 7-day snowfall projection representing 50 simulations of the European weather model has virtually no snow in Teton County for the next week. The jet stream will dip southward over the Eastern U.S. instead and they will have a better chance of snow than we will.
At first, we will see a cold northwest flow on the east side of the high pressure ridge from Thursday to Saturday. This will lead to cold temperatures in the mountains and in the valley with a mix of sun and clouds.
During the first week of December (starting Sunday), high pressure will strengthen and expand eastward, resulting in sunny skies, lighter winds, and a temperature inversion setting up in our area.
Temperatures will warm up in the mountains, but the stable airmass will inhibit rising vertical motion, and this will allow cold, dense pools of air to settle and remain “stuck” in the Jackson Hole Valley.
The inversion will be reinforced by the weak sun angle at this time of year along with valley snow cover which further supports the lower elevation “cold pool” as wide areas of snow cover deflect solar radiation back into the atmosphere.
Mountain temperatures will rise into the 30s in this pattern, but valley high temperatures may struggle to get out of the high teens to low 20s.
Note that weather models (and the weather apps you use) do not handle valley inversions well and are too warm on high temperature forecasts in these patterns. This is true any time you have a dry, clear, stable pattern with light winds from about late November through mid-February in our area.
How long will this dry spell last?
Some models are hinting that a storm may sneak in around December 7-8 (very low confidence this far out), but aside from that, longer-range models are projecting high pressure to remain the dominant pattern over the Western U.S. heading into mid-December.
Keep in mind that forecast confidence decreases substantially beyond 7-10 days, but there certainly aren’t any signs of a more favorable pattern for snow just yet.
Alan Smith, Meteorologist
