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The Science Behind This Week’s Weird Winter Storm

The snow that fell across the Denver metro area on Wednesday night might have caught us by surprise, but the moisture was much welcomed.

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If you were surprised to wake up on Thursday with nearly a foot of snow on your doorstep, you certainly weren’t alone. While flurries were in the forecast, the storm dumped a shocking amount of powder across much of the metro area. The weather station at Denver International Airport reported 9.6 inches of snow, and some areas downtown reported over a foot.

But how could a storm of this significance sneak up on us? What happened was something that makes Denver’s weather unique and is truly an awesome meteorological occurrence. Let’s dig in:

The Denver Convergence Zone

Maybe it’s the meteorologist in me talking, but Denver’s weather is just so cool. Because of the topography around us, some wild things—like what happened this week—can take place.

The Denver Convergence Vorticity Zone is defined by the American Meteorological Society as “A mesoscale flow feature of convergent winds, 50 to 100 km in length, usually oriented north-south, just east of Denver.” During an upslope wind event, winds coming from the east get pushed up the mountains, which creates clouds and moisture. Areas near the foothills and Palmer Divide normally perform the best in these scenarios.

What happened Wednesday night was that the upslope winds were providing the lift that we needed to create moisture, and in the lower levels of the atmosphere, Denver had winds coming from the northwest and winds coming from the southeast creating an area of convergence over the city. When you have winds that clash together like that, the air gets forced up, which creates more lift and moisture.

This week’s unique weather event was confined to Denver due to the elevation of the mountains to our west and the Palmer Ridge to our south. On top of the three to six inches of snow that was originally forecast, there was a jet enhancement, or added energy from the strong winds way up high, which created the perfect scenario for a big snow event.

Much-Needed Moisture

While the storm may have been a brief inconvenience—especially for parents who saw schools switch to remote learning or snow days—it dropped a welcome amount of moisture that should bring some relief from the dry conditions we’ve been experiencing.

One storm alone won’t cure the state’s extreme drought, but the half-inch or more of liquid that fell this week will hopefully be enough to at least make a dent in the situation. (Drought maps are updated every Thursday, so we won’t know what exactly the impact was until next week.) As we move into spring and the atmosphere warms, the air begins to hold more moisture. This is a reason why March and April are Denver’s snowiest months—there’s more moisture to work with when storms roll through.

What About the Snowpack?

As this storm was mainly confined to the Front Range, it won’t have an impact on the snowpack, but the mountains have been getting their fair share of powder throughout February. The snowpack is currently sitting at 88 percent of average, which is up from mid-January, when we were at 76 percent of normal.

Obviously, we’re still not at 100 percent of normal, so keep those snow dances coming. Luckily, our snowiest months are ahead of us: March and April tend to bring big springtime snowstorms to Colorado, and hopefully, this trend of cooler and wetter weather will continue.

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