2018 Summer Ag Weather Outlook

Andrew Pritchard
Meteorologist

As the 2018 planting season comes to an end in the US, it’s a good time to take a look at what the upcoming summer growing season may have in store for us.

This year we pivoted from a top 3 coldest April into the warmest May on record across much of the Corn Belt. June looks to continue very warm across the entire Central US, but there are competing factors influencing the extent of potential drought development across primary growing regions.

Most guidance suggests that at least through the middle of June a ridge of high pressure will develop through Texas, supporting extreme heat and primarily dry conditions across the Central and Southern Plains. In this scenario, high producing regions of corn and soybeans from the Dakotas into Illinois and Indiana would find themselves in prime position for the development of “ridge-riding” thunderstorm clusters.

 Above: 7-day forecast total precipitation forecast. A ridge axis over the western US favors ridge-riding thunderstorm clusters, especially within the highlighted region. (Source: NOAA)

Above: 7-day forecast total precipitation forecast. A ridge axis over the western US favors ridge-riding thunderstorm clusters, especially within the highlighted region. (Source: NOAA)

These ridge-riding thunderstorms can keep widespread drought impacts at bay, but do pose some difficulty as well. They’re often quick-moving and at times accompanied by damaging winds and large hail. The heaviest rain from these storms is often very local, so not everyone benefits. Therefore, closely monitoring recent precipitation maps will be crucial to assessing trouble spots as we move forward.

 Above: June temperature outlook. A ridge axis over the Western US as forecast would keep the Corn Belt on the periphery of the warmest temperatures, and in position for at least periodic ridge-riding clusters of thunderstorms.  (Source: NOAA)

Above: June temperature outlook. A ridge axis over the Western US as forecast would keep the Corn Belt on the periphery of the warmest temperatures, and in position for at least periodic ridge-riding clusters of thunderstorms.  (Source: NOAA)

What does this mean long-term as we head into July and August? Drought has survived May rains in the South Central and Southwestern US and historically, drought in this region has led to hotter and drier summers in the Corn Belt — especially the western Corn Belt. Drought in the Central Plains is not the only controlling factor on summer weather in the Corn Belt, but if it controls the position of the ridge in July, then warmer and drier weather is highly likely.

We also look off the coast of the US and Mexico. Heat and drought in the Corn Belt also display a strong negative correlation with sea surface temperatures off the west coast of the US and Mexico. The hottest and driest summers in the Corn Belt featured a large region of cooler than average water from the Baja of California toward the central Pacific. Today, the waters in this region are not colder than average and they are not currently forecast to become colder than average in July and August. This is a very favorable sign for agriculture across the Northern Plains into the Midwest, including much of the Corn Belt. Adding to this, the sea surface temperatures in the main development region for hurricanes are anomalously cool to start the summer which is out of phase with hot and dry summers in the Midwest.

 Above: Sea surface temperature anomalies from June 6th. Warmer than average temperatures in the highlighted region are not reflective of the hottest and driest summers in the Corn Belt historically. (Source: NOAA)

Above: Sea surface temperature anomalies from June 6th. Warmer than average temperatures in the highlighted region are not reflective of the hottest and driest summers in the Corn Belt historically. (Source: NOAA)

All of this means the forecast for July and August features a primary region of warmer than average temperatures from Texas through the Dakotas and Montana. Forecasting summer precipitation is very difficult beyond 7-10 days, so pay close attention to our forecasts week by week for updates on the position of the ridge and where we expect the highest concentration of thunderstorm activity to set up. There will be periods in July and August that the ridge migrates eastward and the entire Corn Belt experiences extreme heat and dry weather conditions, but the long-term trends plus analog and dynamical model support suggest that much of the Corn Belt does not see the worst of the summer weather this year.