Snow day storm: ‘Not surprising, still impressive’

 

Wednesday’s sudden snowstorm that closed Colorado State University and dumped heavy, wet snow throughout the Denver metro area was a “classic” for this time of year, says Colorado State Climatologist Nolan Doesken.

To get just a little technical, the Front Range and western High Plains is an area known for cyclogenesis – a place for storms to form. Rapidly developing low pressure centers “spin up” when a few factors align: colder air to the north and northwest, warmer air to the south and southeast, sufficient moisture in the atmosphere, and a strong jet stream overhead, dipping southward.

This swirl of factors happens most often from late autumn into late spring, when the atmosphere is warming and carrying more water vapor, but the air is still cold, Doesken said. “Today’s storm was a classic example of something we expect a few times each year.”

These spring storms sometimes spin like a top in about the same location for a few hours to a day or longer, he added. These longer-lasting storms (think March 17-19, 2003) can “really dump on the Front Range.”

Some people were caught off guard by the return of winter three days after the beginning of spring this year, but in fact, this particular storm was anticipated at least a week ago.

“Thirty years ago, we might have had only about a one- or two-day advance warning,” according to Doesken, who is also a member of CSU’s atmospheric science faculty. “But that being said, the exact behavior of rapidly developing storms is still hard to nail down until it happens.”

For the uninitiated, Doesken points out that along the Front Range urban corridor, March has the highest average monthly snowfalls. Which means this storm was right on schedule, in the climatological sense.

“If we’re going to get a foot or more of snow in a day, this is the most likely time of year for that to happen in this part of the country. In terms of intensity – most of the snow fell in about seven hours here – it was not surprising, but still very impressive.”

Doesken says this will be a record snowfall for March 23, most likely  around 14 inches in just 7 hours, although the official storm total for the CSU campus station won’t be available until Wednesday evening.  

“Fort Collins may be on the lower end of the snow stick compared to Boulder, Broomfield, Loveland, and other places,” Doesken said at mid-afternoon. “I’ve got several preliminary CoCoRaHS totals from those areas coming in at 20 to 25 inches.”

Whatever the final total, there are many other even larger storms in the record books for March, April and even May.

“We were plastered here in May 1978 with over 2 feet of snow. And then a similar type of storm developed rapidly back in mid-May of 1983 – also on the heels of a strong El Nino.”

This El Nino has produced storms that have closed campus twice in two months – a legendarily rare occurrence.