Now that it’s spring in the Northern Hemisphere, I was interested in taking a look back to our winter here in Colorado. It seems like it’s been quite cold – since November! Looking at the data, indeed, this is the coldest winter we’ve had (in Denver) since 2010. Though we celebrated the start of spring on March 20, on the vernal equinox, meteorologists use the dates of December 1 – February 28 for winter recordkeeping. This means that, meteorologically speaking, winter ended on February 28.
The average temperature in Denver this (meteorological) winter was 28.5 degrees Fahrenheit (the normal is 31.8 degrees), meaning we were 3.3 degrees Fahrenheit below normal. Not only was it colder than usual, Denver also received 10 inches more of snow than normal. There was heavy snowfall across the Rocky Mountains, in general, this winter which made snow conditions dangerous and avalanche prone. However, the moisture is a welcome respite due to the drought conditions the state has been experiencing, which has impacts to the Colorado River as well.
So, what’s the cause of the cold temperatures and snowy conditions here in Colorado? It’s due to a persistent jet stream which brought more Arctic (cold) air our way, as well as moisture from the Pacific Ocean. The jet stream set up a large ridge of high pressure (associated with warmer and drier conditions) over the eastern half of the country, which had some of the warmest winters on record and very little snowfall (save for the areas near the Great Lakes, which received some big blizzards and lake-effect snowfalls), and a trough of low pressure (associated with colder and wetter conditions) across the western half of the country. This helps explain why California is experiencing record snowfall and Washington, D.C. is seeing its earliest cherry blossoms on record.
When it comes to the snowpack, the Colorado River’s headwaters are at 133% of average, compared with the 30-year climate normal between 1991 – 2020 (scientists use an average of highs and lows (temperature and precipitation) over 30 years to determine what a “normal” high and low should be for any given day, at any given location). While all this extra precipitation is helping Colorado’s drought levels in the short-term, it would take multiple years in a row (research says 5 – 6 years at 150% of average snowpack) to refill our reservoirs. That’s unlikely in a time of climate change, so resource managers still need to plan for a long-term hot and dry future and figure out the best adaptation strategies for their particular regions.