Ah, it’s good to have snow on the ground, isn’t it? Six weeks of warmth and mountain biking has instantly been replaced by winter. On Friday morning, most mountains are covered in snow and temperatures are 5-15 degrees … just as things should be!

Before getting to the forecast, let’s talk about what went right and what went wrong with Thursday’s storm.

Here is the increase in SWE (snow water equivalent … the amount of liquid you’d measure when melting the snow) during Thursday’s storm. The highest amounts were in the northern mountains. With a snow ratio of roughly 15 inches to 1 inch of liquid, this map infers snowfall of about 10 inches on the high side in the northern mountains, 6-7 inches on average for the I-70 corridor, and 1-5 inches in the southern mountains.

The map above confirms my forecast that the northern mountains would get more snow than the southern mountains.

Who was the big winner? Steamboat!

I thought that the highest amounts, perhaps 10 inches, would fall along the northern divide, from Berthoud Pass to Winter Park to Eldora to Rocky Mountain National Park to Cameron Pass. That did happen (see below for Winter Park’s snow stake cam).

But why did Steamboat get 12 inches, and why didn’t I forecast this? Why did I think they would be in the 3-6 inch range? Why did we get a “Steamboat Surprise” (what I call it when Steamboat outperforms the forecast)?

I think it came down to wind direction.

During the day on Thursday, Steamboat received about 5 inches of snow at the summit. Once the sun set, I thought that maybe they would get another 1-3 inches, but instead, 7 inches fell between sunset Thursday and about 1am on Friday morning. Why 7 inches instead of 1-3 inches?

Because the wind direction was from the west or perhaps west-northwest. This is the best wind direction for Steamboat to get snow, and generally every “Steamboat Surprise” is accompanied by this wind direction.

The kicker is that I didn’t think we would see this wind direction. The high-resolution NAM model forecasted a wind from the north at Steamboat on Thursday evening. A north wind does not produce much snow for Steamboat and this is why I didn’t think they’d see a lot of snow in the evening.

The European model was forecasting a west wind at Steamboat, but I ignored this forecast because (1) it was different than other high-resolution models, including the NCAR Ensemble, and (2) because as you can see below, there was only a tiny area of westerly wind forecast around Steamboat with a northerly wind just to the north of Steamboat.

It turned out that the European model was correct, other high-resolution models were wrong, Steamboat got their wind from the west, and they outperformed the forecast. The other factor to consider is the temperature, which was correctly forecast to be 5-10F at Steamboat’s summit. This temperature is also perfect for a “Steamboat Surprise” because it produces light, fluffy snow.

Thanks for going through this analysis with me. Occasionally I’ll single out a certain mountain and look at it in detail, and Steamboat’s 12-inch report certainly qualified for further analysis.

Last thing about Steamboat – the nearest backcountry weather station (SNOTEL) called “Rabbit Ears” reported about 0.9 inches of SWE from the storm, which is in line with the snow stake camera showing 12 inches of snow. However, the usually snowier SNOTEL station called “Tower” at the top of Buff Pass only showed 0.5 inches of SWE, or about 7-8 inches of snow. That’s odd because the “Tower” station usually gets the most snow.

Ah … fun with snow forecasting!

Ok, moving on to other mountains…

Winter Park did well. They received about 4 inches by sunset and 6 inches on Thursday night. That was in line with my hope that the northern divide mountains could get to double digits.

Along the I-70 corridor, about 5-7 inches was the result for most mountains. Copper and Keystone open today (Friday) … good timing!

On the western side of I-70, Powderhorn hasn’t officially reported, but weather stations on top of the Grand Mesa show 10-12 inches. At the base of Powderhorn, their webcam shows that love is in the air.

And in Nederland on Thursday night, we were all psyched for snow! I gave a talk about the long-range outlook for December (it’s good!), and there was about 6 inches of snow on the ground with more likely up at Eldora, perhaps 8-10 inches or more.

Ok, on to the forecast…

Friday will be cloudy with flurries in the morning for the northern mountains with sun elsewhere. All areas will see the sun during the midday and afternoon hours after the clouds clear in the northern mountains. Temperatures will be cold, staying below freezing all day = good snowmaking.

Saturday and Sunday will be dry, sunny, and warmer.

Monday and Tuesday will be snowy. The next storm will arrive from the southwest on Monday and then strengthen in eastern Colorado on Tuesday. This storm track will allow the storm to bring lots of moisture, which should translate to lots of snow.

The southern mountains will be favored with perhaps 10-15 inches, and perhaps half that in the central and northern mountains (4-8 inches).

Snow will start in the southern mountains on Monday morning, fall heaviest in the south on Monday, then spread to the central and northern mountains on Monday night and Tuesday. Temperatures with this storm will be a bit on the warm side with an initial snow level of about 9,000 feet, dropping to 7,000 feet by Tuesday evening.

The best time to find powder will be Monday afternoon and Tuesday morning in the southern mountains, and on Tuesday in the central and northern mountains.

Wednesday should be dry – a good day to travel for Thanksgiving.

I have nothing but good news in the long-range outlook.

On Thursday and Friday of Thanksgiving week, a weak storm may bring light snow to northern Colorado.

The next significant storm will likely hit on Tuesday, November 29th, ish.

Then there could be a storm the following weekend, around December 3rd, ish.

And the first full week of December should be cool with another storm or two.

The pattern has shifted, snow is coming, and you should be excited.

If all of these storms materialize, there should be a decent amount of terrain open by mid-December!

Thanks for reading and happy Friday!

JOEL GRATZ

Also, follow us on Facebook at Colorado Daily Snow and findOpenSnow, and follow me personally on Twitter @gratzo and on Instagram @gratzo.

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, Abasin, Winter Park, Berthoud Pass

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

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

Southern Mountains
Telluride, Silverton, Durango, Wolf Creek (Telluride and Silverton are on the northern side of the southern mountains)