Colorado: Does El Niño bring early snow?

Historical stats don’t show big impact on date of first snow

Summit County and a small surrounding area dodged the drought bullet in late July and early August, with rainfall anywhere from 130 to 200 percent of normal, but rainfall maps show that most of the state still experienced well-below average rainfall during that span.
A similar pattern was evident for the three-month precipitation history in Colorado, with just a few pockets of above-average rainfall in the north-central mountains and the western San Juans.

SUMMIT COUNTY — Talk about living in a bubble — the latest three-month summary and outlook from the National Weather Service in Boulder shows that the rainy conditions in Summit County, and a small surrounding area, were the exception in Colorado the past 30 days. Much of the state continued to suffer through extremely dry conditions, especially the eastern plains, where precipitation was just 5 to 50 percent of normal. As a result, much of the state is still experiencing serious drought. Visit the Boulder NWS website to see the full power point presentation.


Persistent cloud cover helped keep temperatures closer to average during the 30-day period, although the trend was still toward slightly warmer than average, with no part of the state reported below-average temperatures.
Above average temps are expected across a big swath of the U.S. during the next three months.

The long-term trend toward warmer-than-average temperatures continued in late July and early August, with most parts of the state reporting readings between 2 and 4 degrees above average. According to the Climate Prediction Center, there’s a better than average chance of continued above normal temperatures for the next three months. Only the West Coast is forecast to see below average readings.

The three-month precipitation outlook for Colorado is at equal chances for either above average or below average rain and snow. There’s already been a lot of talk about an emerging El Niño and what that could mean for ski season snowfall, with some speculation that it may boost October snowfall, but that isn’t supported by a look at the dates of early snowfalls during El Niño years.

While those stats don’t speak to the quantity of early season snow, they suggest that El Niño has only a negligible effect on when the first snow falls.

El Niño doesn’t seem to have a huge impact on when the season’s first snow falls. In some locations, it seems to delay the date of the first snowfall.

Breckenridge does seem to get an early season boost from weak El Niños, when the average date of the first snow is Sept. 13. The average date for all years (1980 – 2011) is Sept. 30. The average date of Breckenridge’s first snowfall for all El Niño years is Oct. 2.

Similarly, Winter Park also seems to get snow a bit earlier in El Niño years, when the average date of the first snowfall is Sept. 26. The overall average first-snowfall date for all years between 1980 and 2011 is Oct. 4.


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