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Just how much snow Colorado could get this weekend, and why it's tough to predict

March 11 2021 look at upcoming snowstorm
Mike Nelson_March 2021 snowstorm explainer
Posted at 9:41 PM, Mar 09, 2021
and last updated 2021-03-11 10:27:17-05

DENVER — Models for the upcoming snow show everything from a few inches to several feet, but there's a reason there's so many different forecasts out there about the storm coming in, according to Denver7 Chief Meteorologist Mike Nelson.

As of Tuesday evening, the storm was about 1,000 miles away, just coming in to the west coast — it has to cross the Sierra Nevada, the Wasatch and then the Rocky Mountains of Colorado before it even gets to the Eastern Plains and impacts the Denver area.

A lot of things can change over a few days, but we know big changes are coming. We're going to get a little snow in the next 24 hours, and then the heavy snow comes in for the weekend — and it could be one of the biggest snow storms in years.

But forecasting big storms isn't simple.

We use computer models that are very complicated and run on a supercomputer. They simulate how storm systems are going to move across the United States and around the world.

That mathematical model takes all kinds of different layers in the atmosphere and divides it up into little tiny boxes, and then tries to make it go from one time period to the next and then to the next and the next.

That's one way we can figure out how the storms are going to move.

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Different weather models give different snow totals.

Now to make it more interesting. There's not just one computer model out there. There are several different models.

There's a global forecast model, there's a European model that works in both Europe and in North America, the Canadian model, the North American model and each one of these computer models has a different set of physics, different equations, different assumptions about how the atmosphere is going to move and change with time.

So, you stick the same data into four different models. Typically, we don't get exactly the same output, so we come up with a variety of snowfall amounts for a given storm.

Here's basically what looks like is going to happen over the next couple of days.

By late Wednesday, we're expecting rain and snow showers over the West. It'll be windy and dry over the southeast by Thursday. As the storm begins to move across the Great Basin, moving across Nevada and eventually into Utah, snow increases.

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By the time we get to Friday, that low is down over the four corners area. For folks who have watched weather in Colorado for a long time, that four corners low is the most interesting one for a big heavy snow. That's because it will wind its way down over southeast Colorado, pulling a ton of moisture into the Gulf of Mexico, spinning it around up over the higher terrain to the west — that's upslope swirling around the low pressure system. That focuses the heavy snows right along the Front Range and the Continental Divide.

Again, this storm is still hundreds of miles away. As it moves closer and closer, we'll be able to pin that down a little bit better.

But it looks like the San Juans could see a foot or two of snow. Northeast Colorado could see up to a foot and rain down over the southeast with very little, if any, snow. Farther to the north and west could see 6 to 12 inches.

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Mike Nelson forecasts a potentially big weekend snow storm for Colorado.

For the Denver Front Range area, more than two feet of snow could be in store for some areas, especially just east of the Continental Divide – parts of Clear Creek, Gilpin County, Boulder County and up in Larimer County could see 48 inches of snow and locally, maybe a little bit more.

March is our biggest snow month of the year, and these big front rain snows are great for our water supply. It'll certainly be a hassle for Friday night, Saturday and Sunday, but we'll take the moisture because we really need it with the drought conditions that we've had.

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