Colorado Daily Snow
By Joel Gratz, Founding Meteorologist Posted 4 years ago December 12, 2019
Let’s do this
Summary
It’s a complex forecast but the outcome is actually pretty straightforward – most mountains will see 10-20+ accumulations from Thursday through Sunday and we’ll have multiple powder days back-to-back. Friday will be the first powder day with 5-10+ inches favoring the northern mountains. Saturday will be the second powder day with 5-10+ inches favoring the northern and central mountains. And Sunday should be a third powder day with 5-10+ inches favoring the central and southern mountains (I have lower confidence in the details of Sunday’s powder). This is going to be a great storm cycle that should help to open a lot of terrain.
Short Term Forecast
The Upcoming Storm in Perspective
I am very excited about the upcoming storm because it will bring big snow amounts to mountains that do not often see high totals in a short period of time.
Thanks to a somewhat direct moisture feed from the Pacific Ocean, it’s not unusual for the southern mountains to see 1-2 feet of snow in a day or two.
However, these bigger snowfall amounts are rarer for the central and northern mountains as more factors need to come together to make it happen.
In the upcoming storm, most of the factors look favorable to bring a lot of snow to the northern and central mountains in 1-2 days, and that is noteworthy. Plus, the southern mountains should see decent (or even significant) snow as well, so all areas of the state should be feeling pretty darn happy by the end of the weekend.
Don’t Overthink It
With an incoming system like we’re about to see, with 10-20+ inches of snow across multiple days, there can be a tendency among us powder seekers to optimize.
Exactly which day will be deeper? Will the snow quality on one day be much better than another? Will one mountain offer more snow than a close-by mountain?
These are useful questions to ask, and I will try to answer them. However, don’t fret too much about the details. There is a lot of snow on the way, most of the state will have fun powder days coming up, and the most important thing we can all do is to get out and enjoy the powder. If we over-think storms like this and try to optimize too much and try to ski just the deepest day, you might miss out on surprises on other days, like new terrain opening or more snow than expected from an intense squall.
This is going to be fun.
Be Mindful
I am getting powder fever. You’re probably getting a case of it as well. So just a note to remind all of us to take a breath and remember…
* It is early season and the base is still somewhat thin. You could hit things under the snow. Speaking of which, best wishes to OpenSnow fan Mr. Baker for a speedy recovery!
* Avalanche risk in the backcountry will likely increase. Lots of new snow and a change in the weather usually means a higher avalanche risk. Check in with the CAIC before you head out: https://avalanche.state.co.us/
Thursday
The northern mountains saw a dusting on Wednesday night. Now on Thursday morning, the forecast models have sped up the onset of the snow and the northern mountains could see snow showers and light accumulations (a few inches) throughout the day.
Thursday Night & Friday Morning
The northern mountains should see 5-10+ inches with about half or more of this falling on Thursday night and more falling on Friday morning. The snow should extend to the Aspen area with maybe 3-6 inches. Friday morning should be fun.
Friday Afternoon
We’ll likely see a short break in the snow. Light snow or snow squalls may continue, but accumulations should be light.
Friday Night & Saturday
Game on. A second and stronger wave of snow will bring 5-10+ inches to the northern, central, and the north-side of the southern mountains. The combination of strong energy, the jet stream, and plentiful moisture is a setup for the atmosphere to over-deliver.
I have three caveats to the forecast.
First, temperatures will be on the warmer side which means that the snow could be a bit thicker and higher elevations (like Summit County) can score more and better quality snow. However, I remember past situations like this where the snow quality was better than expected, even with warmer air near the ground, due to the jet stream helping to create snowflakes much higher up in the sky where temperatures were optimal for dendrites (big, beautiful flakes).
Second, the wind direction on Friday night into Saturday morning will be generally from the west-southwest. This will favor Crested Butte, Monarch, and the Aspen area to some extent. Usually with a wind from the WSW I would be less excited about snow outside of these areas, but the other factors (energy, jet stream) should overwhelm the not-so-perfect wind direction elsewhere and still bring good snow.
Third, thanks to the jet stream, there will be narrow bands of snow that form. It’s impossible to know exactly where these bands will form over the northern and central mountains. Any band could produce 1-3 inch-per-hour snowfall rates (dumpage) and snow totals could go over the high side of the forecast.
Saturday Night & Sunday
I have low confidence in this forecast. Most models agree that snow will wind down in the northern mountains, maybe continue in the central mountains, and ramp-up in the southern mountains. That sounds reasonable, but I want another day to see new model data before offering a more confident forecast.
Graphics
The general timing for snow in the northern mountains looks about like this forecast from the CAIC WRF 2km model for Arapahoe Basin. Snow Thursday night into Friday with 5-10 inches, a break on Friday afternoon, then snow Friday night into Saturday with 5-10 inches.
The CAIC WRF 2km model is bullish for 10-20+ inches in the northern and central mountains from Thursday through Saturday night. Sometimes this model can err too high, but in this case, I think the general 10-20 inch forecast is reasonable based on other models and the positive factors of this storm (jet stream, energy, moisture).
Last Word
I love the timing of this storm because it comes just when most mountains need another big shot of snow to get a lot of terrain open. If we can get 1-2 feet out of this storm, there should be a lot of rope drops over the next few days.
Extended Forecast
Next week, Monday, December 16 – Friday, December 20, looks mostly or completely dry.
After that and as we get closer to Christmas, all models agree that there will be storminess along the west coast, and this storminess should head into Colorado within a day or two December 25th.
Thanks for reading!
My next update will be on Friday morning.
JOEL GRATZ
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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