Say hello to La Nina
October 13, 2010
Grand County got a taste of winter weather over the weekend as two Alberta Clippers moved through the area, beginning a pattern indicative of La Nina, “The Girl,” a reverse weather pattern to her better-known brother, El Nino.
La Nina is associated with cooler-than-normal water temperatures in the equatorial Pacific Ocean while El Nino is associated with warmer water temperatures.
One of La Nina’s signatures is these cold, moist, unstable weather systems that come out of the Pacific Northwest and extend into Canada. These clippers are fast and weak, according to meteorologist Kyle Fredin at the National Weather Service in Boulder, but they tend to linger on the upslope for hours on end, dumping snow on westerly-facing mountains.
“Steamboat does really well in seasons like this,” Fredin said.
The second storm of the week arrived overnight Monday, Oct. 11, dumping 10 inches mid-mountain at Winter Park Resort, according to measurements taken by the resort.
In Fraser, a weather observer reported 2 inches of snow in town as skies began to clear Tuesday morning.
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The chain law went into effect on Berthoud Pass early Tuesday and Trail Ridge Road in Rocky Mountain National Park has been closed since Friday due to wintry weather.
The snow turned to rain below about 8,300 feet on Tuesday morning.
Temperatures were expected to rebound into the 50s starting Wednesday and lasting through Sunday, when more precipitation may move into the area.
La Nina will hang around throughout the winter, making these quick “progressive” storms the norm, Fredin said. The eastern and southern half of Colorado will tend to be drier while the Northern, western facing mountains are likely to have a snowy winter.
“La Nina is not a forecast,” Fredin added. “It’s an increased probability that the state’s northern and central mountains will be snowier west of the Continental Divide. These quick progressive storms are what you see (in La Nina years); you don’t get the big storms that wrap up the area for days.”
The last time the area saw La Nina was in the winter of 2007-2008, “and that was a weaker pattern,” Fredin said. This year, La Nina is “holding moderate and projected to maintain that intensity until it moves back to neutral in 2011/2012.”
Fredin said that a very large, strong and stable ridge was locked over the Northern Hemisphere during September, contributing to the particularly warm and dry weather we experienced last month. But, he added, it has no bearing on how the rest of the season will play out.
– Reid Armstrong can be reached at 970-887-3334 ext. 19610 or firstname.lastname@example.org.