If you are planning to attend my talk on Friday, December 6 in Breckenridge or Thursday, December 12 in Basalt, please see the “Announcements” section at the bottom for important changes!

Thursday Snowfall Recap

The storm delivered about what we expected between Wednesday night and Thursday afternoon. The system had weak energy but made up for some of this weakness with abundant moisture. My forecast was for an average of 2-6 inches with up to 10 inches in a few southern areas. This is about what happened, which means that my inbox should remain free of hatemail through today:-)

Purgatory: 9”
Wolf Creek: 9”
Irwin Catskiing: 7”
Aspen Highlands: 6”
Snowmass: 6”
Steamboat: 6”
Crested Butte: 5”
Silverton: 5-6” (estimate)
Telluride: 5”
Winter Park: 5”
Aspen Mountain: 4”
Sunlight: 4”
Arapahoe Basin: 3”
Eldora: 3”
Keystone: 3”
Loveland: 3”
Beaver Creek: 2”
Cooper: 2”
Copper Mountain: 2”
Vail: 2”
Breckenridge: 1”

Thursday’s temperatures were warm (in the 20s), so this new snow was pretty thick and dense. Not every day can be a blower powder day, and thicker snow is a good thing to soften and eventually build the base.

Friday and Saturday

We’ll see dry weather as the previous storm has moved well to the east and is bringing precipitation to the eastern half of the United States.

In the wake of Thursday’s storm, moisture is lingering over the northern mountains now on Friday morning. We can see the low clouds over the northern mountains, shown in blue in this satellite animation. The animation also superimposes the nighttime lights of the Denver metro area and other towns across the region.

Friday morning’s low clouds should eventually dissipate by late morning or midday, and then we should see a lot of sunshine across the state for Friday afternoon and Saturday with comfortable high temperatures in the upper 20s to low 30s.

The state of our snowpack (more specifically, the amount of water that is in our snowpack) is about or just above average for this time of the season. Yes, we always want more snow to open more terrain, but we’re in pretty good shape despite the three weeks of dry weather in early-and-mid November.

Next storm Sunday & Monday

My previous forecast was for 4-10 inches. The latest models confirm that this is a reasonable estimate and that a few spots might hit the one-foot mark.

Snow will begin on Sunday morning and continue through Monday afternoon.

The Sunday snowfall should favor the southern and central mountains as we’ll see winds from the southwest and west-southwest. Temperatures will be warm (in the 20s) on Sunday so the snow will likely be thicker and denser with a rain/snow line around 7,000 feet (which means that most mountains will see all snow).

Then on Sunday night and Monday, colder air will arrive as the wind changes to blow from the northwest, and this should favor the most snow in the northern mountains. Temperatures will cool into the mid-teens by Monday morning, which is cold enough for the atmosphere to create fluffy snow, but these temperatures are also warm enough to allow enough moisture to remain which can lead to moderate-to-significant accumulations in northwest flow.

The University of Utah's multi-model forecast, which adjusts for terrain that these lower-resolution models do not adequately model, shows the promise of the storm.

Steamboat and a few other northern mountains could see 10+ inch totals with the best snow likely on Monday morning through midday.

Thanks to a period of winds from the west-southwest on Sunday midday through Sunday evening, Crested Butte, Monarch, and other central mountains could see 7-10+ inches. A west-southwest is the best wind direction for Crested Butte and works OK at Monarch, Snowmass, and Sunlight. The other Aspen-area mountains prefer a west or northwest wind.

And the southern mountains will not be left out with the best snow likely falling on Sunday and Sunday early evening while the wind direction blows from the southwest and west-southwest. Coal Bank Pass is between Purgatory and Silverton with projections for around 10 inches.

Again, I’ll go with a 4-10 inch forecast with a few spots hitting one foot. The Sunday snow will be denser, followed by fluffier snow on Sunday night into Monday. The best turns will be on Sunday last chair and more likely on Monday morning.

The outlook through mid-December is still “meh”. It could go in any direction. Storms could just miss us, leaving just light snow. We may get a few moderate systems. Or maybe we’ll get lucky and a stronger storm could bring big totals. I just don’t know.

Our next chance for snow following the Sunday/Monday storm will be late in the week around Friday, December 13th. I have low expectations for snow totals but maybe we’ll sneak out a few inches.

Then another system could bring snow sometime around Sunday, December 15 – Monday, December 16th. This storm has more potential than the “Friday the 13th” storm, though it’s still too far away to get super excited.

One way to look at the longer-range forecast is to follow the Pacific North American Pattern (PNA). A negative number generally trends toward stormy weather for the western United States. After about December 15th, the average forecast from most models (the green line) shows the PNA trending toward zero or negative. This is good but is no guarantee of big snow. Also, the blue bars show the range of model forecasts, which is anything from very negative (good) to pretty positive (not so good).

In sum, this is a typical 10+ day forecast, which is to say that most of the time we just don’t know.

Thanks for reading!

My next update will be on Saturday morning.

JOEL GRATZ

PS – There are changes to my upcoming talks in Breckenridge (now Silverthorne) and Basalt. Please look below for details!

Upcoming talks

These talks are usually 45 minutes and allow me to show a little of the science behind snow forecasting, have some fun, and answer lots of questions.

NEW LOCATION
Silverthorne: Friday, December 6
* Talk is from 600-645 at Angry James Brewery (421 Adams Ave, Silverthorne, CO)
* Free event, no tickets required
* More details

SOLD OUT
Basalt: Thursday, December 12
* Tickets are sold out (thank you!) and there is now a waitlist
* More details

Geography Key

Northern Mountains
Steamboat, Granby, Beaver Creek, Vail, Ski Cooper, Copper, Breckenridge, Keystone, Loveland, Abasin, Winter Park, Berthoud Pass, Eldora, Rocky Mountain National Park, Cameron Pass

Along the Divide
Loveland, Arapahoe Basin, Winter Park, Berthoud Pass

East of the Divide
Eldora, Echo, Rocky Mountain National Park, Cameron Pass

Central Mountains
Aspen, Sunlight, Monarch, Crested Butte, Irwin, Powderhorn

Southern Mountains
Telluride, Silverton – north side of the southern mountains | Purgatory, Wolf Creek – south side of the southern mountains