Livin’ La Nina loca

This Pacific Ocean phenomenon causes crazy weather swings in Colorado. But will it affect our water supply?

December 11, 2017 | By: Steve Snyder

Does it seem like something is wrong with the holiday songs this year? Like they don’t have the same feel as previous years?

“Oh the weather outside is frightful …”

Hardly! I wore shorts through most of November.

“Frosty the Snowman …”

Yeah, right! I’m supposed to make a snowman out of dried leaves and grass?

“I’m dreaming, of a white Christmas …”

That’s what it seems like right now — a dream.

Needless to say it’s been a warm, dry snow season so far. How warm and dry? Try the 10th warmest November on record, with no measurable snowfall at Denver International Airport, the official weather station for the City of Denver.

It hasn’t been much better in the mountains, which is a bit of a concern, since Denver Water gets the majority of our water supply from mountain snowmelt. Currently snowpack in the Upper South Platte River watershed and the Upper Colorado River watershed are both at 74 percent of normal.

So what’s behind this dry weather pattern? Could it be La Nina?

La Nina is the presence of cooler-than-usual sea-surface temperatures in the central Pacific Ocean. The National Oceanic and Atmospheric Administration recently updated its forecast, calling for La Nina conditions to persist in the Northern Hemisphere for most of the winter. For Colorado, that often means more snow for the northern mountains in the state, but drier conditions in the southern part as the jet stream tends to push major weather patterns further north.

And what does this all mean for Denver and the snowpack in our watershed areas?

“When it comes to forecasting La Nina patterns, you could say our area of Colorado is in no-man’s land,” said Nathan Elder, a senior water resource engineer at Denver Water. “With La Nina, we’re right in between where you typically see more snow in the north and drier conditions in the south. Many La Nina years have been dry in Denver, but we have seen a few years with significant snowfalls, too. We could go either way.”

It’s also too early to speculate on snow totals for the year because the snow season is just beginning. Remember, last year started out with a similar warm, dry pattern in November, followed by a cold and snowy December and January. And the good news is that Denver Water is currently ahead of last year with our reservoir levels, helped by several years of storing plentiful snowmelt.

While it remains dry in the city, it’s a good idea to check your landscape, and water grass, trees and shrubs once or twice a month. Colorado State University has a good fact sheet for warm winter watering.

And if you feel inclined, go ahead and sing along with those holiday favorites. Some positive weather thoughts never hurt.

Let it snow, let it snow, let it snow.”

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