The meteorological winter (December-January-February) temperature and precipitation outlooks were recently released by NOAA’s Climate Prediction Center (CPC). In winter, the phase of the El Niño Southern Oscillation (ENSO) climate signal typically influences temperature and precipitation behavior. The neutral phase of ENSO is currently in place and hence in the absence of an El Niño or La Niña, long-term climatology and recent trends become the dominant seasonal predictor. Other climate patterns are also considered, such as the phase of the Madden-Julian Oscillation (MJO) and Arctic Oscillation (AO). A negative phase of the AO produces shifts in the storm track into the Midwest along with colder air masses. A positive AO shifts the storm track farther north and generally keeps colder air out of the region. These patterns unfortunately are not forecastable more than a few weeks ahead of time.
Winter weather outlook
Temperature-wise, much of the Upper Midwest, including Iowa, is classified as having an “Equal Chance” (EC) of above, below or near-climatological behavior. Near-average temperatures are given slightly higher probability of occurring (34%) when EC is present with above and below-average probabilities equally split at 33%.
We have a better handle on the expectations for precipitation this winter. We are seeing a distinct signal for precipitation for the southern part of Iowa to having a slightly elevated chance of wetter-than-normal conditions with probabilities increasing into northern Iowa. The CPC does not produce a snowfall outlook as winter season systems are extremely variable and are often not predictable more than a week out. The longer range outlooks continue the above average precipitation chances into early spring.
Weather impacts on agriculture
Moving into winter, we are always mindful of agricultural impacts with a particular focus on moisture variables, including precipitation and sub-soil conditions. As we closed out October, southwestern Iowa has had anywhere from two to five inches of above average rainfall. Much of Iowa has had rainfall amounts four to eight inches above normal over the last 60 days. With recent wetness, concerns about abnormally dry and drought conditions have a vanished. Modeled sub-soil moisture is near capacity; if you think of a sponge, current conditions indicate the sponge is almost soaked. We will need to monitor snowfall in the upper Missouri basin as stream flows are near to above average; flooding could continue to be an issue for southwestern Iowa moving into Spring 2020. Early snowfall across much of the state last week added additional soil moisture and further slowed some harvest operations. The good news is, while November is likely to be colder, precipitation chances are weak and no major storm systems are showing up yet.