June 22, 2013

Figure 1. Percent of normal precipitation for June 6-29, 2013. (Source: High Plains Regional Climate Center) Figure 2. Percent of normal temperature for June 6-29, 2013. (Source: High Plains Regional Climate Center) Figure 3. Precipitation probability for July-August, 2013. EC indicates equal chance of below normal, normal, and above normal precipitation. (Source: NOAA Climate Prediction Center) Figure 4. Temperature probability for July-August, 2013. Above normal temperatures (indicated by A) are indicated at varying levels for all of Nebraska.  (Source: NOAA Climate Prediction Center)

Most of Nebraska saw a dramatic decrease in precipitation over the past two weeks as the jet stream shifted north, leading to widespread thunderstorm activity to the Dakota’s.

Nebraska has had only a few pockets of above normal moisture in the last two weeks (Figure 1). Portions of the Panhandle, northeast, south central, and east central Nebraska have benefited from recent activity, but a substantial portion of the state received below normal moisture. The northern Sandhills and areas south of I-80 have received less than 50% of normal precipitation.

Temperature trends the past two weeks have been polarized with below normal conditions in the east and above normal in the west (Figure 2). At this point, the primary concern lies with southwest, west central, and south central Nebraska where the combination of below normal moisture and above normal temperatures will likely result in a significant increase in irrigation as the corn crop enters its rapid growth stage.

Some dryland production areas, particularly in central and eastern Nebraska, may actually benefit from a dry period after a soggy April and May. Corn roots should extend deeper into the profile in search of water, which will lessen the chance for shallow rooting syndrome. (This continues to be a problem for areas of northern Iowa, southern Minnesota, and western Wisconsin plagued by excessive moisture.)

Weather models indicate widely scattered precipitation events for the next two weeks, with the driest conditions indicated for eastern Nebraska. In addition the upper air ridge is predicted to dominate the central U.S., leading to sustained above normal temperatures for Nebraska.

If this scenario verifies, pasture growth across the Sandhills and Panhandle will slow and irrigation demands will intensify. Communities that had well water issues last summer will need to be closely monitored as it is being reported that water tables in the deeper aquifers have shown little recovery during the past two months of moisture. Although irrigation is starting later than last year, water tables are considerably lower and it will not take as much irrigation pressure to impact water supplies in many of our rural communities.

There is not much information regarding precipitation to glean from the latest Climate Prediction Center (CPC) outlooks for July and July through September. CPC assigns an equal chance of below normal, normal, or above normal precipitation for both periods (Figure 3). Above normal July temperatures are assigned to western Nebraska, while all of the state is expected to experience above normal temperatures during the next three months (Figure 4).

As long as normal moisture falls during the next 60 days across eastern Nebraska, the above normal temperature prediction shouldn’t lead to significant yield declines as long as it doesn’t get blazing hot. That being said, if the moisture trends of the past two weeks continue, stress problems could appear by mid-July as the corn crop rapidly depletes soil moisture profiles. If the CPC forecast holds true, there would be an increased probability of non-stop irrigation in some areas by August.

Al Dutcher
Extension State Climatologist