Early winter outlook uncertain -- forecasters
The weather crystal ball is cloudier than normal heading toward winter. But, it will likely start off on a chilly note, a long-term forecast shows.
"Equal chance" is the dominant term in a recent forecast released recently by the U.S. Climate Prediction Center, leading forecasters to express uncertainty about winter's start being smooth and easy, especially considering the absence of a key weather modeling indicator.
With the exception of part of the southwest -- which will likely be drier than normal -- and the northwest -- which is projected to be wetter than normal -- the bulk of the nation will see equal chances of precipitation through the winter. That includes the entire Midwest and all but a portion of the Plains. But, the outlook's tinged with more uncertainty than normal, says director of the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center, Mike Halpert.
"It's a challenge to produce a long-term winter forecast without the climate pattern of an El Niño or a La Niña in place out in the Pacific because those climate patterns often strongly influence winter temperature and precipitation here in the United States," Halpert says. "Without this strong seasonal influence, winter weather is often affected by short-term climate patterns, such as the Arctic Oscillation, that are not predictable beyond a week or two. So it's important to pay attention to your local daily weather forecast throughout the winter."
Maps courtesy NOAA
Though the chances of below- and above-average winter precipitation and temperatures is expected to be the same in much of the nation, that doesn't necessarily mean it's going to be without distinct trends, says Nebraska state climatologist Al Dutcher.
"Nationally, the CPC December forecast is showing below normal temperatures for the northern half of Montana and North Dakota and above normal temperatures for Arizona, New Mexico, Utah, western Texas, western Oklahoma, southwest Kansas, and the southwestern two-thirds of Colorado," he says. "Over the past two months we have seen significant cold outbreaks occurring at regular intervals. Generally, the trend has been 10-14 days of below normal temperatures followed by equal lengths of above normal temperatures; however, the cold outbreaks have been slightly stronger than the warm outbreaks.
"Here in the northern Great Plains, the cold air has won out, likely due to improved surface moisture conditions limiting the runaway surface heating that was common the past two winters when soil moisture was limited. I expect the below normal temperature forecast for December is very conservative and is likely to extend much further south and east of current projections," he adds.
A big part of how sharp weather extremes unfold in the next few weeks has to do with the soil. Last winter, dry soils helped propel more volatile weather. The areas where soil moisture's short are smaller this year than a year ago, and that could keep things more stable, Dutcher says. More stable, but likely colder.
"Here in the northern Great Plains, the cold air has won out, likely due to improved surface moisture conditions limiting the runaway surface heating that was common the past two winters when soil moisture was limited," Dutcher says, adding he has "serious reservations" about the Climate Prediction Center's outlook. "I expect the below-normal temperature forecast for December is very conservative and is likely to extend much further south and east of current projections. I believe Nebraska is likely to see below normal temperatures and normal to above normal precipitation in December."