The following graph shows average precipitation for approximately 1/3 month periods for Dodge City (blue bars with scale on the left axis) and the number of precipitation events 2" or greater (Red curve with scale on the right axis). Of course the winter months are the driest when the air tends to be very dry across southwest Kansas. Average precipitation and the number of 2" or greater events increase in the spring with a peak in late-May and early-June, which happens to correspond to the peak in severe thunderstorm activity for southwestern and central Kansas. After a dropoff in late-June and early-July, there is another peak in average rainfall and number of 2" or greater precipitation events in late-July into early-August, with the very highest in late-July. While some severe weather occurs during this time, most of the rain events during mid-summer occur with non-severe or marginally severe thunderstorm clusters. There tends to be a deeper layer of moisture this time of year, partly as a result of the monsoonal flow from the subtropics. This increases precipitation efficiency of rain producing thunderstorms. Since the mid to upper-level jet is typically very weak in mid-summer, storm clusters tend to move very slow. These mid-summer heavy rain events tend to occur when an upper-level ridge is in place over the southwestern United States, with upper-level troughing over the upper-Midwest or Great Lakes regions, resulting in weak west-northwesterly mid to upper level flow over the central plains. Oftentimes, these storm clusters occur on the cool side of a frontal boundary with moist upslope flow reaching as far west as the Raton Mesa and Palmer Divide in Colorado and New Mexico. Typically, isolated thunderstorms develop near topographic features in the afternoon and then progress eastward and southeastward ovenight into the adjacent plains while expanding in coverage.The past two summers have been very dry and storm clusters have been few and far between.
Later this week the ingredients described above for heavy mid-summer rainfall will be in place across the high plains region. Although there are chances of showers and thunderstorms just about every day through the weekend, the best chance of heavier rainfall appears to be Wednesday night through Thursday night. Keep in mind that the exact placement of the heavier clusters of thunderstorms is very difficult to forecast far in advance. Therefore, although there is a chance of thunderstorms across southwestern and central Kansas, the heavier amounts of rain could occur anywhere across the central plains.