Why a Southern Plains drought could amplify Missouri’s next heat wave

While Mid-Missouri has been enjoying a stretch of comfortable, spring-like temperatures in the 60s and 70s, the meteorological engine to our west is currently being tuned for a much hotter gear. As we look ahead to the middle of May, a combination of regional drought and a shifting atmospheric pattern is setting the stage for what could be our first noticeable heat surface of the season.

To understand why next week might over-perform in the temperature department, we have to look at the soil. Usually, in early May, the ground across the Southern and Central Plains, specifically Oklahoma, Kansas, and Texas, is relatively moist from spring rains. When the sun hits moist soil, much of that solar energy is used for latent heat, or the process of evaporating water. This effectively uses up the sun's energy, keeping the air temperature from soaring too quickly.

However, as of early May, over 60% of the lower 48 states are experiencing some level of drought. In parts of the Western Plains, those conditions are categorized as extreme. Because the soil is bone-dry, there is no moisture to evaporate. Instead, 100% of that solar radiation goes into sensible heat: the energy that directly warms the air we breathe.

This creates an amplification effect. As the air heats up over the dry ground in the Plains, it dries the soil even further, creating a feedback loop that allows temperatures to spike five to ten degrees higher than standard computer models might initially suggest.

The Climate Prediction Center has already caught on to this trend. In their latest 8-14 day outlook, which covers May 15th through May 21st, a slight risk for major heat has been identified for a large swath of the Central United States.

The driver behind this is a high-pressure heat dome currently building over the Western United States. By the middle of next week, this ridge is forecast to slide eastward. As it moves toward the Mississippi Valley, it will begin to compress and trap warm air over the dry terrain of the Plains, essentially pre-heating the air before it ever reaches the Missouri border.

For those of us in Mid-Missouri, the shift will be noticeable. While we will see some scattered rain chances toward the end of this week, the long-range trend shows a dominant southerly flow taking over.

This southerly wind will act as a conveyor belt, transporting that pre-heated air from the drought-stricken Plains directly into our backyard. While it is still a week out, early indications suggest we could see afternoon highs climbing into the mid-to-upper 80s, with some areas potentially nearing the 90-degree mark by the following weekend.

Spring is often a tug-of-war between seasons, and it looks like summer is about to win its first major battle. If you have outdoor plans or early-season planting to finish, enjoy the mild temperatures through this weekend, as the thermal amplification process to our west is about to turn up the heat.