Saturday, December 29, 2007
La NiÃ±a is still on its way; it's just a little behind schedule.
Jim Pringle, a meteorologist with the National Weather Service in Grand Junction, said he still expects the state to experience warmer and drier than normal weather this season. But it will arrive later than climatologists at the National Oceanic and Atmospheric Administration originally thought.
"The onset of the typical weather patterns experienced during a moderate to strong La NiÃ±a event were delayed by at least a month but still are expected to occur beginning later in January," Pringle said. "There are probably not many people complaining about the abundant December precipitation across the region."
The La NiÃ±a effect on climate involves fluctuations of water temperatures in the eastern Pacific Ocean off South America. It tends to produce heavier than typical precipitation in the Pacific Northwest and drier than normal conditions on the Colorado Plateau. Northwest Colorado is often rated as a toss-up in terms of winter snowfall during a La NiÃ±a event.
The early December blast of snow that blanketed the San Juan Mountains of southwest Colorado and the West Elk Mountains near Crested Butte came as a surprise to Pringle and his colleagues at NOAA. However, Pringle's original outlook for Steamboat Springs, delivered in November, wasn't far off the mark. On Nov. 22, Pringle said extreme Northwest Colorado - with an emphasis on the northwest corner of Moffat County - had a slightly stronger chance of above-average precipitation in the early winter.
Steamboat saw an unusually mild November. The opening of Steamboat Ski Area was delayed 10 days, and on Nov. 20, longtime Steamboat weather observer Art Judson recorded a daytime high of 65 degrees.
But Steamboat began to see a more typical winter weather pattern in December, a month with snowfall on 23 of its days so far.
Early in the month, a southern flow brought only moderate amounts of snow to Steamboat. Judson explained that southern storms never produce large amounts of snow in the Park Range because they don't generate enough lift. The largest snow totals are always produced by a westerly flow, Judson said. The air masses in storms that strike the west-facing slopes of the Steamboat Ski Area head-on rise faster, he said. The greater the lift, the greater the rate at which "condensate" forms, he added, and the greater the snowfall.
By mid-December, the storm track had shifted to the northwest, and the ski area began to see storm totals climbing - this month has produced more than 100 inches at mid-mountain.
Pringle believes winter will be moderate in January.
"The weather pattern for Western Colorado is still expected to transition to warmer than normal conditions for mid- to late-winter, with a trend towards drier weather," Pringle said. "The area most likely to be drier than normal during mid- to late-winter is still expected to be in the south, with equal chances of at least normal precipitation in the north."
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