I hate when people comment that the weather is unpredictable, because that’s a lie. Perhaps 50 to 100 years ago, there were few credible predictions of weather. But now, almost every storm, hurricane, tornado and snowflake is predicted hours, days or even a week in advance. 

Meteorology is actually a massive technological success story of the last 50 years, one that we often take for granted. Just look at our satellite imagery, which gives us new pictures of the weather every five minutes from a satellite that’s 22,500 miles above the earth. And all of this is reliable and free to the general public—simply amazing.

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You knew there would be a “but” though, and here it is. Despite the incredible advances in meteorology and our vast knowledge of the atmosphere, there are still small elements of the weather that remain random, or “somewhat” unpredictable. Rarely do forecasters fail to predict a big storm, but the local weather effects of each storm can remain elusive and outside the realm of predictability. And this is exactly what happened at Steamboat Ski Area on Sunday night, Feb. 19, 2012.

Looking at the picture above from Monday morning, February 20, it’s evident that Steamboat measured a lot of fresh powder. How much? From 5 p.m. on Sunday night through 5 a.m. on Monday morning, 23 inches of snow fell. That’s nearly two inches per hour for 12 hours—a massive amount of snow no matter the location. And over 24 hours, Steamboat set a new record— receiving 34 inches of snow. This leads to the next question, which is “Was this amount of snow in the forecast?” And of course the answer is “no.” 

I call this the “Steamboat Surprise” because there’s usually one storm every year that dumps a LOT more snow on Steamboat than anyone (including myself) would have forecast. In fact, it was one of these Steamboat Surprises back on Nov. 27, 2005 that motivated me to start a weather forecasting company devoted specifically to skiers and riders. The most amazing part of this storm, however, was not the massive amount of snow. It was the difference in snow totals across a very small area.

SteamboatSurprise

Snow totals varied widely over just a few miles, making the Steamboat Surprise even more difficult to predict.

After seeing this phenomenon for seven years, I’ve found that there are some weather factors that contribute to exceptionally deep (and fluffy) snowstorms at Steamboat:

  • A very moist atmosphere from the surface up to 20,000 feet.
  • A wind direction from the west-northwest (290 degrees).
  • A mountaintop temperature of about 5 degrees Fahrenheit.

The best snowflakes for powder skiing are big dendrites, which look like the “typical” snowflake that you’d see in movies or cartoons. To create these snowflakes, we need lots of moisture and temperatures between 0 and 10 degrees Fahrenheit at the top of the mountain. Also, a wind from the west-northwest is perfect for Steamboat because it funnels right up the valley and hits the ski area without having to cross other big mountains and therefore prematurely dump out snow.

Now, I bet you’re thinking that predicting the Steamboat Surprise isn’t that hard to predict after all. In fact, all we need to do is look for those three factors—a certain amount of moisture, the right wind direction and the correct temperature—and we’ll know that a Steamboat Surprise is on its way. However, these factors usually occur many times over the course of a winter, but they only create a Steamboat Surprise once (or maybe twice). 

Which leaves me no closer to figuring this out than back in November of 2005. But there is a silver lining on two fronts. First, there can still be hope of surprise powder days, and nobody will complain about that. And second, as weather technology continues to improve over the next few decades, I think we’ll finally be able to solve the mystery of the Steamboat Surprise. Until then, though, I’ll be forced to admit that certain aspects of snowstorms are still—gulp—unpredictable.

Meteorologist Joel Gratz is the creator of opensnow.com and is based in Boulder, Colo.

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