March 19, 2024

Average precipitation, wet soil could affect growing season

Three-month outlook shows little chance for severe weather

While the National Weather Service’s long-range outlooks are for Iowa to be slightly colder than normal and to receive average rainfall in the months ahead, the outlook also makes it seem as if there is a little room for adverse weather events — especially in the mid-spring.

Harry Hillaker, the State Climatologist for the Iowa Department of Agriculture and Land Stewardship, has looked over the National Weather Service’s three-month Iowa outlooks for the March-April-May period.

“As a result of very wet weather during the second one-half of the 2014 growing season (August through mid-October), currently, soil moisture levels are unusually high across much of central and southwestern Iowa,” Hillaker said. “Newton and Jasper County would be within this wetter region.”

The NWS updated its March and three-month long-term outlooks Saturday. For March, maps show slightly colder-than-normal temperatures across 13 states that make up a vertical “third” of the U.S., stretching from the Canadian border to Oklahoma, and including all of Iowa.

The three-month outlook shows Iowa temperatures have as much chance of being higher than normal as they do of being lower than usual. NWS precipitation outlooks for that same middle third of the states to receive close to average totals in March, April and May. It could be slightly warmer than usual, and with more rain, in the western third of the nation.

“All of the outlooks from March 2015 through March-April-May 2015 give equal chance for above- or below-normal precipitation across Iowa,” Hillaker said.

Jasper County averages about 2.3 inches of rain in March. The county’s historical average high temperature is 49.88 degrees, while the average low is 30.55 degrees.

Hillaker said that relatively wetter area roughly covers an area bounded by Sioux City to the northwest, Marshalltown on the northeast, Ottumwa on the southeast, Lamoni to the south and Glenwood to the southwest. The current soil moisture enhances the chances that soil moisture levels may be higher than ideal during the spring planting season.

“This does not guarantee planting delays,” Hillaker said, nevertheless, it would not take as much rain as usual to results in some delays. The positive news is that we have greater than normal moisture stored in the soil, thus providing some extra insurance in the event of any extended dry periods this growing season.”

Hillaker points out that the NWS’s April-May-June and May-June-July 90-day outlooks slightly favor warmer-than-normal weather, even though March begins in the cold pattern left over from late February. He said the models don’t indicate high probabilities for abnormal weather in Iowa for any time scale.

As for how much stock to put in these long-range models, Hillaker said there are never any guarantees attached. However, conditions in the tropical parts of the Pacific Ocean — which dictates many global weather patterns — are sending mixed messages, putting confidence in long-term outlooks even lower than usual.

Years that featured an El Niño event tended to be on the warmer side of normal for Iowa, Hillaker said, while near-normal to above-normal precipitation usually is experienced in the state during full-fledged El Niño events.

“Confidence in long-range outlooks is never high,” he said. “The tropical Pacific is in what is termed a ‘neutral’ state, meaning that neither La Niña (unusually cool) or El Niño (unusually warm) conditions are present. The current condition is a little bit toward the warm side of the historical average, but not quite warm enough to be classified as an El Niño event.”