June 1, 2012

As spring planting winds down and we enter the heart of the growing season, unusual early season weather patterns have created some uncertainty about the coming production season. Hopefully the next three months will bring an abundance of moisture to temper the persistent warm trend that has dominated our weather the past seven months.

State Update

Northeast Nebraska had been persistently dry since last October and was at risk of drought prior to the severe weather and heavy rainfall that occurred Memorial Day weekend. A broad swath of 2- to 4-inch rain was reported (Figure 1) from Columbus northeast toward the Nebraska-South Dakota-Iowa border. Isolated spots received almost as much moisture during this period as they had in the previous seven months. The area still carries soil moisture deficits as crops enter early growing stages.

In the Panhandle persistent dryness during the past 90 days has led to a rapid expansion of moderate drought conditions (Figure 2). This trend has intensified during the past 30 days, but it’s too early in the season to predict any long-term yield impact.

A rather disturbing trend has developed across most of northern Kansas during the past 30 days and is extending northward. Precipitation in this area through May 30 was less than 25% of normal (Figure 3) and now most of the southern tier of Nebraska border counties are considered to be abnormally dry.

Unless major moisture arrives before Tuesday morning, the U.S. Drought Monitor is likely to extend these abnormally dry conditions northward to include most of the Sandhills. An eastward expansion of the Panhandle drought area also is possible, along with the introduction of drought designations in pockets along the Kansas-Nebraska border.

Southern Nebraska experienced a relatively wet two-week period at the end of April, only to see that surplus moisture disappear in three weeks with precipitation averaging less than 25% of normal. This is why repeated events are critical for the northeast, as a short dry stretch will undo recent precipitation gains.

Looking to the Summer

The Climate Prediction Center is indicating normal temperatures for the western half of Nebraska in June, a change from what we’ve seen this year. Nebraska has had above normal temperatures for the past seven months and 10 of the last 11. At this point, I would venture to say the current trend is like to persist and there is no indication from the behavior of the jet stream that this pattern is about to shift to a sustained cool pattern. During the past couple months, brief periods of cooler temperatures were just enough to bring us back to normal or slightly below normal temperatures.

Lincoln climate records since January 1 show just how unusual these warm temperatures have been. As of May 30, 2012 there had been

• 59 days with a maximum temperature of at least 70°F,
• 31 days when the temperature reached 80°F, and
• 11 days when the temperature reached 90°F.

The next closest record for 70°F days was in 1910 with 56 days. The average for this period is 35 days. The number of 80°F days this year is second behind 1939 with 32, while the long-term average is 13. For 90-degree days this year is second behind 1934, which had 12 days. Compare this to the long-term average for 90°F days of 2.6 days.

What does all this temperature data mean? If this trend continues, crop water use demands will be well above normal and irrigators will likely face considerable higher water applications than the past few growing seasons. For dryland producers, timely and generous moisture will be necessary to meet trendline yields. We can ill afford to go over two weeks at any time without.

Finally, statewide monthly average temperatures have consistently been 4-8°F above normal during 2012. Normal July maximum temperatures across northern Nebraska average 88-89°F, while southern Nebraska averages 90-92°F. If average temperatures during July continue the recent trend, expected average highs across northern Nebraska would be 92-97°F, and those across southern Nebraska would be 94-100°F.

Al Dutcher
Extension State Climatologist