Powder advisory: La Niña favors Colorado this winter

“La Niña means good, good things”

Does La Niña equal “The Big One?” Are we headed for another epic winter? The forecasters are predicting, at the very least, that we won’t get skunked. According to the National Oceanic and Atmospheric Administration (NOAA), La Niña is in full effect, and in the northern hemisphere is expected to last into spring 2011—possibly one of the strongest La Niñas in 50 years. Not to get everyone’s hopes up, but the last La Niña winter was 2007-08, a record-breaking winter in the valley.

And NOAA’s Climate Prediction Center’s November La Niña advisory stated: “La Niña continued during October 2010, as indicated by below-average sea surface temperatures (SSTs) across most of the equatorial Pacific Ocean.”
Likely impacts in the United States include an enhanced chance of above-average precipitation in the Pacific Northwest, Northern Rockies (along with a concomitant increase in snowfall), and Ohio Valley, while below-average precipitation is most likely across the south-central and southeastern states.

Powder Forecast
As for the outlook in Colorado, Joel Gratz, founder of Coloradopowderforecast.com, said to expect a solid winter. “La Niña means good, good things for Colorado. From about Crested Butte and north, this season’s snowfall should total 100 percent to 125 percent of average.
“For Colorado and the United States in general, La Niña favors areas that are farther north. I would expect Steamboat to do very well this year, as well as states north of Colorado.”
In the central mountains, we’re right on the edge—and hopefully inside of the storm track. So far, so good. Early-season storms, according to Gratz, “are 100 percent typical. It’s actually uncanny how these individual early-season storms epitomize the average La Niña pattern. Most La Niña-type storms will provide good snow to the central and northern Colorado Mountains, with slightly lower amounts for the San Juans.
“The [Elk Mountains] should do well and are a part of my ‘100 to 125 percent’ of average snowfall zone on the season. During the last La Niña winter [2007-2008], Irwin recorded over 1,000 inches of snow. Heck yeah!”

La Niña’s impact on avalanche hazard
Something to keep in mind if this winter does bring heavy, consistent snowfall—with more frequent and larger storms comes higher avalanche risk. An article in the December 2010 issue of the Avalanche Review explored the possible correlation between La Niña years and increased avalanche fatalities.
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The Pacific Northwest often benefits most from a snowfall perspective; however during the last La Niña winter, there was a record number of avalanche fatalities in Washington State. And in North America, there were 14 fatalities during the month of December alone.
Author Mark Moore writes, “While the state-by-state chart does show a decrease in fatalities for a few areas during La Niña winters (i.e., Idaho, Montana, and Utah), these are in the minority. In all other areas studied, including the United States and Canada as a whole, the changes in annual fatalities range from subtle increases to rather significant ones. Though the data is still too sparse to be statistically significant, even the possibility of such a correlation should set off cautionary flags for anyone venturing into the backcountry.”
Keep an eye on the snowpack, and check in at cbavalanchecenter.org for the daily avalanche forecast. Forecaster John MacKinnon said there are deep, persistent weak layers on North and East aspects in particular. On Tuesday, November 30, the forecast reported: “Pockets of CONSIDERABLE (Level 3) danger remain near and above treeline on North through Southeast aspects. The danger is MODERATE (Level 2) on all other aspects.”