OMAHA (DTN) -- Despite a lack of snow cover and milder temperatures in the Northern Plains, weather and climate experts shied away from making "definitive statements" about the flood potential for the Missouri River basin next spring during a flood outlook webinar Friday.

"Conditions are certainly less favorable for flooding so far compared to last year," said Doug Kluck, NOAA central region climate services director. The Central Region boundaries include the Missouri basin.

Included in Kluck's assessment of early-winter conditions that point to a reduced risk of flooding next spring are: lower soil moisture in the upper Missouri River basin compared to a year ago; much less snow-water equivalent than the same time in 2010; much less precipitation in the water year which began in October vs. last year in the upper basin; warmer-than-normal conditions this year so far; and no flooding in the entire Missouri River basin at this time except for a portion of the James River valley in South Dakota. "And the James flooding actually reflects long-term wet conditions," Kluck said.

However, there is still a long way to go before spring, and forecasts for January through June tend to feature below-normal temperatures and above-normal precipitation in the Northern Plains, which encompass the upper Missouri River basin. Much of that forecast leaning is due to the re-occurrence of La Nina in the Pacific Ocean -- a feature which includes below-normal temperatures in the equatorial Pacific Ocean along with an atmospheric pattern that highlights the potential for a stronger storm track in the northwestern U.S. "The January through March period is pegged to show the greatest La Nina influence," Kluck said.

There is plenty of wiggle room in those outlooks. One reason for variance is that the La Nina of winter 2011-12 is much weaker than the La Nina of winter 2010-11. "The stronger La Nina is, the greater the confidence about the cold (forecast) over the Northern Plains," said Dennis Todey, South Dakota state climatologist. "The weaker La Nina is, the less strong the signal for those colder temperatures to occur."

Besides some uncertainty with La Nina, NOAA's Kluck also said that another key element in last winter's situation called the Arctic Oscillation has not been evident as yet. "The Arctic Oscillation kept cold air in place over the upper (Missouri River) basin, and we have not seen that yet, and the prediction for the next week or two is that it will not be showing up," Kluck said.

Caution was also expressed regarding putting too much emphasis on lower snow pack at this point in the season than a year ago, said Kevin Low, forecaster at the central region climate office. "It's still early in the season," Low said. "You can't put a lot of stock in either mountain or Plains snowpack at this point." Snowpack in the northern Rockies is about 90% of its long-term average, with the Northern Plains snow pack lower than average for this time of year.

Another feature that is much different than a year ago is the location of storm tracks. They have rarely focused on the upper Missouri River basin. "Forecasters are not seeing a tendency for that pattern to set up yet," Kluck said. "The pattern has been almost opposite of what a normal La Nina would be with a more southwest to northeast flow."

Climatologist Dennis Todey offered an explanation for that. "When you talk about La Nina, there are different La Ninas," he said. "There are La Ninas which look like this one, especially the weaker La Ninas."

Bryce Anderson can be contacted at bryce.anderson@telventdtn.com

(SK/CZ)

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