The mountains of Colorado could be in for a wetter-than-average winter this season, according to Klaus Wolter, a CU-Boulder and National Oceanic and Atmospheric Administration scientist.
"Once we get past the fall season it looks like the mountains of Colorado are in for a wet winter," said Wolter. His forecast also indicates the mountains of Utah should see above-average moisture this winter.
According to Wolter, the phenomenon known as El Niño is not expected to play a weather-making role this year. El Niño refers to the warming cycle of the tropical Pacific Ocean that influences weather patterns by affecting the jet stream above the eastern Pacific and North America. Without its influence, more storms tend to track into Colorado from the Pacific Northwest, said Wolter, who studies weather at the Cooperative Institute for Research in Environmental Science, a joint institute of CU-Boulder and NOAA.
"Indications point to a winter storm track hitting Colorado from the Northwest and when that happens, the mountains usually receive above-average moisture in the winter," said Wolter." "When I look back at 50 years of data and check out the cases where the predictions have been for a wetter-than-average winter, never have we had a dry winter. We've had a near normal winter with those kinds of situations, but the majority of the time the predictions for above-average moisture come through."
However, there is a slight downside to the forecast, Wolter said. A Pacific Northwest storm track tends to mean drier than normal conditions for the Front Range and eastern plains of Colorado.
"That storm pattern creates a downslope situation for us so we tend to get the dry Chinook-type winds sweeping down from the Continental Divide instead of moisture-laden storms," he said. "You just don't get that many wet storms along the Front Range out of that type of weather pattern."
Wolter also said it appears most likely that this winter will be mild for the western United States. The trend toward warmer winters that began more than a decade ago appears poised to continue, he said.
As for other areas of the country, Wolter expects much of the Southwest to be drier than normal while the Northeast may experience a colder than normal winter. That's because another climate feature, the North Atlantic Oscillation, which affects weather patterns in the Atlantic region, once again appears to be headed toward its "blocked phase," said Wolter. The same pattern materialized last winter, he said, and resulted in cold weather for both northern Europe and the eastern seaboard of the United States.
"The British weather service's forecast for the North Atlantic Oscillation is that they expect a similar weather pattern to happen this year," said Wolter.