La Niña Is Back And It Threatens To Impact Our Winter

By Chris Spears

DENVER (CBS4) - NOAA says La Niña appeared during October and there's a 65-75% chance that it will last through the winter.

La Niña is an abnormal cooling of equatorial waters in the eastern Pacific Ocean and it can have an impact on weather patterns worldwide.

During La Niña in the lower 48 U.S. states the main storm track typically favors areas to the north of Colorado, resulting in a cool, wet winter. Southern states are often warm and dry.

But for states in between, such as Colorado, things can go either way.

According to the Colorado Climate Center, La Niña tends to bring warmer-than-normal temperatures to the eastern plains.

But when it comes to winter snow, there's no specific trend in the data for Colorado.

Having said that, Colorado's northwest mountains can do well with snowfall during a La Niña winter if the jet stream orients itself from northwest to southeast over Washington, Oregon and Idaho.

When that happens northwest winds in the upper atmosphere can bring light to moderate snowfalls to the mountains along and north of Interstate 70.

If the jet sags south the whole benefits, and if it goes north, we miss out.

So far the 2017-2018 snow season is off to a slow start in Colorado and that may have some snow lovers worried, but don't panic just yet.

Recall this time last year it was warm and very dry with ski resorts pushing back their opening dates.

But then in mid-December the jet stream changed course and brought a series of soggy storm systems. In fact many places saw nearly an entire season's worth of snow in roughly 6 weeks.

For a land-locked state like Colorado, to get big snow storms, it's all about the jet stream, which is why meteorologists pay such close attention to where it is now and where it appears to be going.

And La Niña can sometimes influence the polar jet stream, especially during the winter.

Let's hope for the sake of our winter snow and water supply that the jet stream is a frequent visitor to Colorado this season!

Meteorologist Chris Spears travels weekly in the CBS4 Mobile Weather Lab reporting about Colorado's weather and climate. Check out his bio, connect with him on Facebook or follow him on Twitter @ChrisCBS4.