Some parts of Iowa saw up to 6 inches of rain Wednesday. But did it help drought conditions?
During the overnight hours of Tuesday into Wednesday morning, parts of Iowa received heavy rain from thunderstorms.
The heaviest rainfall fell in a narrow zone over western and southern portions of the state, roughly along a line from north of Council Bluffs, Atlantic, Creston, and Lamoni. Roughly 2 to 6 inches of rain were reported within this zone, prompting a few flash flood warnings.
So, what caused such a narrow zone of heavy rain, and was it enough to end the drought in this part of the state?
The setup that resulted in the heavy rain began late Tuesday night and lasted into the mid-morning hours of Wednesday. Our weather pattern consisted of a stalled-out frontal boundary with an attached area of low pressure draped from northern Kansas into northern Missouri. A wind that resides just above the Earth’s surface that helps facilitate the transport of heat and moisture called the low-level jet was moving atop the front. Moisture at the surface was already collecting in the vicinity of the front, but the air from the low-level jet moving over the front only added more moisture and induced rising motion in the atmosphere to form showers and storms.
The environment in which these storms formed was exceptionally moist for this time of year which led to efficient rainfall production. Precipitable water, a measurement that meteorologists use to quantify the amount of moisture in the atmosphere, was in excess of 2 inches over southeastern Nebraska, southwest Iowa, and north-central Missouri, which is roughly 200% greater than normal for this time of year.
Once the storms formed, they trained, or moved repeatedly over the same locations as the winds in the atmosphere were running parallel to the front. Think of training storms as boxcars on a train track that are oriented in a fixed direction, only able to move where the tracks are laid out. Training thunderstorms in an excessively moist environment led to very heavy rainfall amounts in southwest Iowa.
Despite this event being beneficial for parts of southwest Iowa, only small drought improvements are expected over the next week.
The healthiest way for substantial drought removal is consistent rainfall distributed over a large area for a long period of time. Heavy rain events like this can provide some temporary relief but are not a feasible long-term solution.
The Des Moines metro area continues to suffer with six months of rainfall deficit, and much of north, east, southeast and northwest Iowa faces some form of a deficit over the last 30 days.