La Nina To Impact Winter Conditions?

Keep track of soil moisture this spring.

Compiled by staff

Published: Jan 24, 2011

While dry conditions resulted in an early harvest last year, it's important farmers monitor soil moisture this spring as dry weather could spell trouble for the 2011 planting season.

Al Dutcher, University of Nebraska-Lincoln state climatologist, says he isn't predicting the state will fall back into a drought, but people should be aware of the potential. The state is already about 2 inches below normal on average precipitation this fall and winter.

However, one piece of good news: the state's reservoir situation is excellent.

"With winter storm activity across the western U.S., we've seen some very encouraging snowfall totals, including north central Colorado and within the Platte River Valley of south central Wyoming," Dutcher adds.

The Seminole Reservoir within the Platte River Valley basin system in Wyoming is at 83% of capacity. Other reservoirs in the system are Pathfinder, at just under 77% full, and Glendo, at just under 70% full.

"This leaves right around 500,000 acre-feet of room available for runoff, and a normal runoff year would fill those up, and we would expect to see some downstream releases into Lake McConaughy," Dutcher says.

Lake McConaughy is at 84% of capacity, and it needs to be kept below 90% of capacity.

"So, depending on how this winter goes and if the central and northern Rockies keep getting these storms, we'll see above normal snow pack in the basin and would expect to see above normal inflows and releases on water," he explains. "We should expect to see high flows into the spring season downstream from Lake McConaughy regardless of what happens in terms of precipitation."

In addition, even though conditions have been dry this past fall, the state could still see flooding problems this spring. It will depend largely on winter and spring temperatures, ice and freeze/thaw cycles.

A major contributor to this winter's forecast is La Nina. This will enhance the northern jet stream pattern, and there is a persistent blocking of the high pressure system over the north Atlantic, called north Atlantic oscillation.

"That high pressure system is exceptionally strong this winter and as it strengthens it creates a blocking pattern for any piece of energy moving into the eastern U.S.," Dutcher says.

That is why there has been such large trough patterns in the eastern U.S., and why that region has been cold during the last 30-day period. This, coupled with a robust La Nina, means current patterns may continue this winter.

Dutcher says the good news is that conditions should not be similar to last year's heavy snowfall.

The forecasts also will vary depending on if the La Nina event continues through summer and into next year.

Half of La Nina events are multi-year, but it will take a couple more months of watching the current event to see if it will continue or have any residual effects.

If the state doesn't experience heavy spring rains, it may not be able to make soil moisture up. March is important. If March is dry, the state will need exceptional moisture to develop into April and have that carry through to summer.

Planting delays shouldn't be a problem this year as the La Nina system typically brings cool and dry conditions during February through late April.

"If we are dry during May and June, it doesn't bode well for dryland farmers and will require irrigators to put on more water," he says. However, Central Nebraska Public Power and Irrigation District indicated in October that a full allocation of 18 inches of available water is planned for its irrigation users.

Producers should try to get a good handle on their soil moisture conditions by taking soil moisture measurements across their fields. It also may be a good idea for dryland producers to adequately protect themselves with crop insurance, according to Dutcher.