JACKSON, Wyo. – Two long-duration storms produced snowfall totals of 70 inches at Jackson Hole Mountain Resort and 55 inches at Grand Targhee during a six-day stretch from February 13-19. A warm-up is coming this weekend with more snow for the Tetons and a rain/snow mix for the valley.
The First Storm (February 13-15)
Ski resorts have enjoyed their best conditions of the season during the past week thanks to six straight days of consistent heavy snowfall.
The first of two storms impacted the area from Thursday night through Saturday morning, bringing heavy snowfall to the Jackson Hole Valley in addition to the Tetons.
The storm arrived on Thursday night with south to southwest winds, which negated the shadowing effect of the Tetons and allowed more moisture to reach the valley.
Also, there was a significant airmass collision that created substantial vertical lift with this first storm as milder Pacific air encountered an arctic airmass in place, which did not erode easily over the Jackson Hole Valley.
Cold air is denser than warm air, so when this warmer Pacific air reached our area, it moved up and over the colder air as if it were on a ramp, leading to enhanced vertical lift that produced heavy snowfall rates in the valley.
Temperatures were in the single digits to low teens in the Jackson Hole Valley on Thursday night and Friday morning during the early part of this storm, while temperatures rose into the upper teens to low 20s in the Tetons.
It’s not often that an inversion holds in place well into a significant storm like this, but sometimes shallow arctic air trapped in the valley can be very stubborn to erode.
Eventually, the inversion did erode with warmer valley temperatures during the day on Friday and into Saturday.
From Thursday night into Friday morning, the town of Jackson actually received more snowfall (8 inches) than Jackson Hole Mountain Resort’s Rendezvous Bowl Plot (7 inches) which doesn’t happen very often! Snow King also received 9 inches.
From Friday to Saturday, the storm took on more of a typical terrain-driven snowfall distribution with heavy snow falling across the Tetons.
Storm total snowfall from Thursday night to Saturday morning ranged from 8 to 21 inches in the Tetons above 8,000 feet while the town of Jackson ended up with a storm total of 9.7 inches.
The Second Storm (February 15-19)
There was only a little break on Saturday afternoon before the next storm arrived on Saturday night. This second storm proved to be a longer-duration event than the first one, with snow falling consistently over the Tetons from Saturday night through Tuesday night.
This storm featured moderate west to west/southwest winds aloft which created more of a Teton shadowing effect in terms of mountain snowfall versus valley snowfall.
Four-day snow totals from this storm were substantial with Jackson Hole Mountain Resort’s Rendezvous Bowl Plot and Grand Targhee both receiving a total of 47 inches (about 4 feet)!
During the early part of the storm on Saturday night and Sunday, the town of Jackson picked up 3.9 inches of snow and Snow King 5 inches, while Targhee picked up 25 inches and Jackson Hole Mountain Resort 17-20 inches.
However, during the second part of this storm cycle on Monday and Tuesday, we saw one of the most extreme Teton shadow effects I’ve ever seen here.
From Monday morning through Wednesday morning, Jackson Hole’s Rendezvous Bowl Plot at 9,580 feet received 30 inches of snow and the Raymer Plot 31 inches of snow, while the base of the ski area only received 6 inches of snow and the town of Jackson received less than an inch of snow (0.8 inches).
Even Jackson Hole’s mid-mountain (8,180 feet) saw 20 inches of snow, which is a lot of snow, but only two-thirds of what the upper mountain received.
We often see large differences in snowfall between the top of Jackson Hole Mountain Resort and the valley, but a 30-inch versus less than 1-inch difference between the top of Jackson Hole Mountain Resort and the town of Jackson is a remarkable difference.
The snowfall on Monday and Tuesday was almost entirely orographically driven, meaning that winds and moisture encountering the Tetons at a perpendicular angle were forced to rise due to the terrain barrier and condense into precipitation.
The shadow effect occurs when winds move down a mountain slope at a roughly perpendicular angle. These downslope winds have a warming and drying effect with much of the moisture evaporating by the time it reaches the base of a mountain range (hence the much lighter snowfall totals).
Total Snowfall and Snowpack Update
Total snowfall spanning the six-day period from February 13 to 19 includes the following…
- 70 inches – JHMR Rendezvous Bowl
- 68 inches – JHMR Raymer Plot
- 58 inches – Surprise Meadow (GTNP)
- 55 inches – Grand Targhee
- 54 inches – JHMR Mid-Mountain
- 36 inches – Teton Pass (west side)
- 26 inches – Snake River Canyon
- 25 inches – Togwotee Pass
- 23 inches – JHMR Base Area
- 19 inches – Snow King
- 14.4 inches – Jackson
- 11.9 inches – Driggs
This was a substantial storm cycle in the Tetons, and snowfall totals for the month of February now include 130 inches at Jackson Hole’s Raymer Plot, 105 inches at Targhee, 49 inches at Snow King, and 30.7 inches in the town of Jackson.
Snow depth (the height of the snowpack) in the Tetons now ranges from 117 to 133 inches above 9,000 feet which is above average for this time of year.
In terms of snow water equivalent (the water content in the snowpack), the Snake River Headwaters Basin, which includes the Tetons and surrounding ranges, is now 111% of average.
The graph below shows just how much snowpack has improved during the month of February.
Upcoming Weather Pattern
The pattern for the rest of February looks warmer and somewhat less active, but we still have some more snow chances ahead.
A weaker storm on Wednesday night will bring light accumulations to the area, followed by a break in the pattern on Friday and Saturday with partly cloudy skies and milder temperatures.
On Sunday, a plume of subtropical moisture known as an atmospheric river will impact the Pacific Northwest with heavy rain and snow, and we will catch just enough moisture on the southern fringe of this system to see some precipitation as well along with strong winds.
Warm air will be pushing into our area and a rain/snow mix is likely in the valley with snow levels (the rain/snow line) potentially rising as high as 7,000-8,000 feet on Sunday night and into early Monday.
This is reminiscent of the storm cycle we saw early in February in terms of low-elevation rain, high-elevation wet snow, and strong winds. However, this storm does not look as strong as the early month storm with more modest precipitation amounts currently expected.
Another storm is possible later on Monday and into Tuesday with rain also possible in the valley at the onset, with a changeover back to snow (at least briefly) as a cold front moves through toward the end of the storm. Confidence in this possible storm is lower, however, as this is still the better part of a week away.
The map below shows the projected 7-day snowfall and represents the average of 50 simulations of the European Model:
Looking further out, we will likely see warmer and drier conditions during the second half of next week (highs well into the 40s in the valley), with the potential for colder and more unsettled weather to return in early March.
Alan Smith, Meteorologist
